• Docs and Samples
  • Docs
  • Samples

    • Table Of Contents

    Welcome link

    Welcome to DragonRuby Game Toolkit!

    The information contained here is all available in your the zip file at ./docs/docs.html. You can browse the docs in a local website by starting up DragonRuby and going to http://localhost:9001.

    Tips for Learning DragonRuby Game Toolkit link

    The following tips will help you learn the DragonRuby quickly.

    Tip #1: Join the Community link

    Our Discord server is extremely supportive and helpful. It's the best place to get answers to your questions. The developers of DragonRuby are also on this server if you have any feedback or bug reports.

    The Link to Our Discord Server is: http://discord.dragonruby.org.

    The News Letter will keep you in the loop with regards to current DragonRuby Events: http://dragonrubydispatch.com.

    Tip #2: Read the Book link

    Brett Chalupa (one of our community members) has written a book to help you get started: https://book.dragonriders.community/

    Tip #3: Watch the Tutorial Video link

    Here are some videos to help you get the lay of the land.

    1. Building Tetris - Part 1: https://youtu.be/xZMwRSbC4rY
    2. Building Tetris - Part 2: https://youtu.be/C3LLzDUDgz4

    Tip #4: Go Through the Sample Apps in Order link

    The sample apps are located in the ./samples directory. The samples are ordered by increasing difficulty and cover all aspects of the game engine.

    Getting Started Tutorial link

    This is a tutorial written by Ryan C Gordon (a Juggernaut in the industry who has contracted to Valve, Epic, Activision, and EA... check out his Wikipedia page: https://en.wikipedia.org/wiki/Ryan_C._Gordon).

    Introduction link

    Welcome!

    Here's just a little push to get you started if you're new to programming or game development.

    If you want to write a game, it's no different than writing any other program for any other framework: there are a few simple rules that might be new to you, but more or less programming is programming no matter what you are building.

    Did you not know that? Did you think you couldn't write a game because you're a "web guy" or you're writing Java at a desk job? Stop letting people tell you that you can't, because you already have everything you need.

    Here, we're going to be programming in a language called "Ruby." In the interest of full disclosure, I (Ryan Gordon) wrote the C parts of this toolkit and Ruby looks a little strange to me (Amir Rajan wrote the Ruby parts, discounting the parts I mangled), but I'm going to walk you through the basics because we're all learning together, and if you mostly think of yourself as someone that writes C (or C++, C#, Objective-C), PHP, or Java, then you're only a step behind me right now.

    Prerequisites link

    Here's the most important thing you should know: Ruby lets you do some complicated things really easily, and you can learn that stuff later. I'm going to show you one or two cool tricks, but that's all.

    Do you know what an if statement is? A for-loop? An array? That's all you'll need to start.

    The Game Loop link

    Ok, here are few rules with regards to game development with GTK:

    That's an entire video game in one run-on sentence.

    Here's that function. You're going to want to put this in mygame/app/main.rb, because that's where we'll look for it by default. Load it up in your favorite text editor. 

    def tick args
  args.outputs.labels << [580, 400, 'Hello World!']
end

    Now run dragonruby ...did you get a window with "Hello World!" written in it? Good, you're officially a game developer!

    Breakdown Of The tick Method link

    mygame/app/main.rb, is where the Ruby source code is located. This looks a little strange, so I'll break it down line by line. In Ruby, a '#' character starts a single-line comment, so I'll talk about this inline. 

    # This "def"ines a function, named "tick," which takes a single argument
# named "args". DragonRuby looks for this function and calls it every
# frame, 60 times a second. "args" is a magic structure with lots of
# information in it. You can set variables in there for your own game state,
# and every frame it will updated if keys are pressed, joysticks moved,
# mice clicked, etc.
def tick args

  # One of the things in "args" is the "outputs" object that your game uses
  # to draw things. Afraid of rendering APIs? No problem. In DragonRuby,
  # you use arrays to draw things and we figure out the details.
  # If you want to draw text on the screen, you give it an array (the thing
  # in the [ brackets ]), with an X and Y coordinate and the text to draw.
  # The "<<" thing says "append this hash onto the list of them at
  # args.outputs.labels)
  args.outputs.labels << { x: 580, y: 400, text: 'Hello World!' }
end

    Once your tick function finishes, we look at all the arrays you made and figure out how to draw it. You don't need to know about graphics APIs. You're just setting up some arrays! DragonRuby clears out these arrays every frame, so you just need to add what you need _right now_ each time.

    Rendering A Sprite link

    Now let's spice this up a little.

    We're going to add some graphics. Each 2D image in DragonRuby is called a "sprite," and to use them, you just make sure they exist in a reasonable file format (png, jpg, gif, bmp, etc) and specify them by filename. The first time you use one, DragonRuby will load it and keep it in video memory for fast access in the future. If you use a filename that doesn't exist, you get a fun checkerboard pattern!

    There's a "dragonruby.png" file included, just to get you started. Let's have it draw every frame with our text: 

    def tick args
  args.outputs.labels  << { x: 580, y: 400, text: 'Hello World!' }
  args.outputs.sprites << { x: 576, y: 100, w: 128, h: 101, path: 'dragonruby.png' }
end

    (Pro Tip: you don't have to restart DragonRuby to test your changes; when you save main.rb, DragonRuby will notice and reload your program.)

    That .sprites line says "add a sprite to the list of sprites we're drawing, and draw it at position (576, 100) at a size of 128x101 pixels". You can find the image to draw at dragonruby.png.

    Coordinate System and Virtual Canvas link

    Quick note about coordinates: (0, 0) is the bottom left corner of the screen, and positive numbers go up and to the right. This is more "geometrically correct," even if it's not how you remember doing 2D graphics, but we chose this for a simpler reason: when you're making Super Mario Brothers and you want Mario to jump, you should be able to add to Mario's y position as he goes up and subtract as he falls. It makes things easier to understand.

    Also: your game screen is _always_ 1280x720 pixels. If you resize the window, we will scale and letterbox everything appropriately, so you never have to worry about different resolutions.

    Ok, now we have an image on the screen, let's animate it: 

    def tick args
  args.state.rotation  ||= 0

  args.state.rotation  -= 1

  args.outputs.labels  << { x: 580, y: 400, text: 'Hello World!' }
  args.outputs.sprites << { x: 576,
                            y: 100,
                            w: 128,
                            h: 101,
                            path: 'dragonruby.png',
                            angle: args.state.rotation }
end

    Now you can see that this function is getting called a lot!

    Game State link

    Here's a fun Ruby thing: args.state.rotation ||= 0 is shorthand for "if args.state.rotation isn't initialized, set it to zero." It's a nice way to embed your initialization code right next to where you need the variable.

    args.state is a place you can hang your own data. It's an open data structure that allows you to define properties that are arbitrarily nested. You don't need to define any kind of class.

    In this case, the current rotation of our sprite, which is happily spinning at 60 frames per second. If you don't specify rotation (or alpha, or color modulation, or a source rectangle, etc), DragonRuby picks a reasonable default, and the array is ordered by the most likely things you need to tell us: position, size, name.

    There Is No Delta Time link

    One thing we decided to do in DragonRuby is not make you worry about delta time: your function runs at 60 frames per second (about 16 milliseconds) and that's that. Having to worry about framerate is something massive triple-AAA games do, but for fun little 2D games? You'd have to work really hard to not hit 60fps. All your drawing is happening on a GPU designed to run Fortnite quickly; it can definitely handle this.

    Since we didn't make you worry about delta time, you can just move the rotation by 1 every time and it works without you having to keep track of time and math. Want it to move faster? Subtract 2.

    Handling User Input link

    Now, let's move that image around. 

    def tick args
  args.state.rotation ||= 0
  args.state.x ||= 576
  args.state.y ||= 100

  if args.inputs.mouse.click
    args.state.x = args.inputs.mouse.x - 64
    args.state.y = args.inputs.mouse.y - 50
  end

  args.outputs.labels  << { x: 580, y: 400, text: 'Hello World!' }
  args.outputs.sprites << { x: args.state.x,
                            y: args.state.y,
                            w: 128,
                            h: 101,
                            path: 'dragonruby.png',
                            angle: args.state.rotation }

  args.state.rotation -= 1
end

    Everywhere you click your mouse, the image moves there. We set a default location for it with args.state.x ||= 576, and then we change those variables when we see the mouse button in action. You can get at the keyboard and game controllers in similar ways.

    Coding On A Raspberry Pi link

    We have only tested DragonRuby on a Raspberry Pi 3, Models B and B+, but we believe it _should_ work on any model with comparable specs.

    If you're running DragonRuby Game Toolkit on a Raspberry Pi, or trying to run a game made with the Toolkit on a Raspberry Pi, and it's really really slow-- like one frame every few seconds--then there's likely a simple fix.

    You're probably running a desktop environment: menus, apps, web browsers, etc. This is okay! Launch the terminal app and type: 

    sudo raspi-config

    It'll ask you for your password (if you don't know, try "raspberry"), and then give you a menu of options. Find your way to "Advanced Options", then "GL Driver", and change this to "GL (Full KMS)" ... not "fake KMS," which is also listed there. Save and reboot. In theory, this should fix the problem.

    If you're _still_ having problems and have a Raspberry Pi 2 or better, go back to raspi-config and head over to "Advanced Options", "Memory split," and give the GPU 256 megabytes. You might be able to avoid this for simple games, as this takes RAM away from the system and reserves it for graphics. You can also try 128 megabytes as a gentler option.

    Note that you can also run DragonRuby without X11 at all: if you run it from a virtual terminal it will render fullscreen and won't need the "Full KMS" option. This might be attractive if you want to use it as a game console sort of thing, or develop over ssh, or launch it from RetroPie, etc.

    Conclusion link

    There is a lot more you can do with DragonRuby, but now you've already got just about everything you need to make a simple game. After all, even the most fancy games are just creating objects and moving them around. Experiment a little. Add a few more things and have them interact in small ways. Want something to go away? Just don't add it to args.output anymore.

    Starting a New DragonRuby Project link

    The DragonRuby zip that contains the engine is a complete, self contained project structure. To create a new project, unzip the zip file again in its entirety and use that as a starting point for another game. This is the recommended approach to starting a new project.

    Considerations For Public Git Repositories link

    You can open source your game's code given the following options.

    Option 1 (Recommended) link

    Your public repository needs only to contain the contents of ./mygame. This approach is the cleanest and doesn't require your .gitignore to be polluted with DragonRuby specific files.

    Option 2 (Restrictions Apply) link

    IMPORTANT: Do NOT commit dragonruby-publish(.exe), or dragonruby-bind(.exe). 

    dragonruby
dragonruby.exe
dragonruby-publish
dragonruby-publish.exe
dragonruby-bind
dragonruby-bind.exe
/tmp/
/builds/
/logs/
/samples/
/docs/
/.dragonruby/

    If you'd like people who do not own a DragonRuby license to run your game, you may include the dragonruby(.exe) binary within the repo. This permission is granted in good-faith and can be revoked if abused.

    Considerations For Private Git Repos link

    The following .gitignore should be used for private repositories (commercial games). 

    /tmp/
/logs/

    You'll notice that everything else is committed to source control (even the ./samples, ./docs, and ./builds directory).

    The DragonRuby binary/package is designed to be committed in its entirety with your source code (it’s why we keep it small). This protects the “shelf life” for commercial games. 3 years from now, we might be on a vastly different version of the engine. But you know that the code you’ve written will definitely work with the version that was committed to source control. For private repositories, it's strongly recommended that you do NOT keep DragonRuby Game Toolkit in a shared location and instead unzip a clean copy for every game (and commit everything to source control).

    IMPORTANT: File access functions are sandoxed and assume that the dragonruby binary lives alongside the game you are building. Do not expect file access functions to return correct values if you are attempting to run the dragonruby binary from a shared location. It's recommended that the directory structure contained in the zip is not altered and games are built using that starter template.

    Deploying To Itch.io link

    Once you've built your game, you're all set to deploy! Good luck in your game dev journey and if you get stuck, come to the Discord channel!

    Creating Your Game Landing Page link

    Log into Itch.io and go to https://itch.io/game/new.

    You can fill out all the other options later.

    Update Your Game's Metadata link

    Point your text editor at mygame/metadata/game_metadata.txt and make it look like this:

    NOTE: Remove the # at the beginning of each line. 

    devid=bob
devtitle=Bob The Game Developer
gameid=mygame
gametitle=My Game
version=0.1

    The devid property is the username you use to log into Itch.io. The devtitle is your name or company name (it can contain spaces). The gameid is the Project URL value. The gametitle is the name of your game (it can contain spaces). The version can be any major.minor number format.

    Building Your Game For Distribution link

    Open up the terminal and run this from the command line: 

    ./dragonruby-publish --only-package mygame

    (if you're on Windows, don't put the "./" on the front. That's a Mac and Linux thing.)

    A directory called ./build will be created that contains your binaries. You can upload this to Itch.io manually.

    Browser Game Settings link

    For the HTML version of your game, the following configuration is required for your game to run correctly:

    For subsequent updates you can use an automated deployment to Itch.io: 

    ./dragonruby-publish mygame

    DragonRuby will package _and publish_ your game to itch.io! Tell your friends to go to your game's very own webpage and buy it!

    If you make changes to your game, just re-run dragonruby-publish and it'll update the downloads for you.

    Consider Adding Pause When Game is In Background link

    It's a good idea to pause the game if it doesn't have focus. Here's an example of how to do that 

    def tick args
  # if the keyboard doesn't have focus, and the game is in production mode, and it isn't the first tick
  if !args.inputs.keyboard.has_focus && args.gtk.production && args.state.tick_count != 0
    args.outputs.background_color = [0, 0, 0]
    args.outputs.labels << { x: 640,
                             y: 360,
                             text: "Game Paused (click to resume).",
                             alignment_enum: 1,
                             r: 255, g: 255, b: 255 }
    # consider setting all audio volume to 0.0
  else
    # perform your regular tick function
  end
end

    If you want your game to run at full speed even when it's in the background, add the following line to mygame/metadata/cvars.txt: 

    renderer.background_sleep=0

    Consider Adding a Request to Review Your Game In-Game link

    Getting reviews of your game are extremely important and it's recommended that you put an option to review within the game itself. You can use args.gtk.open_url plus a review URL. Here's an example: 

    def tick args
  # render the review button
  args.state.review_button ||= { x: 640 - 50,
                                 y: 360 - 25,
                                 w: 100,
                                 h: 50,
                                 path: :pixel,
                                 r: 0,
                                 g: 0,
                                 b: 0 }
  args.outputs.sprites << args.state.review_button
  args.outputs.labels << { x: 640, y: 360, anchor_x: 0.5, anchor_y: 0.5, text: "Review" }

  # check to see if the review button was clicked
  if args.inputs.mouse.intersect_rect? args.state.review_button
    # open platform specific review urls
    if args.gtk.platform? :ios
      # your app id is provided at Apple's Developer Portal (numeric value)
      args.gtk.openurl "itms-apps://itunes.apple.com/app/idYOURGAMEID?action=write-review"
    elsif args.gtk.platform? :android
      # your app id is the name of your android package
      args.gtk.openurl "https://play.google.com/store/apps/details?id=YOURGAMEID"
    elsif args.gtk.platform? :web
      # if they are playing the web version of the game, take them to the purchase page on itch
      args.gtk.openurl "https://amirrajan.itch.io/YOURGAMEID/purchase"
    else
      # if they are playing the desktop version of the game, take them to itch's rating page
      args.gtk.openurl "https://amirrajan.itch.io/YOURGAMEID/rate?source=game"
    end
  end
end

    Deploying To Mobile Devices link

    If you have a Pro subscription, you also have the capability to deploy to mobile devices.

    Deploying to iOS link

    To deploy to iOS, you need to have a Mac running MacOS Catalina, an iOS device, and an active/paid Developer Account with Apple. From the Console type: $wizards.ios.start and you will be guided through the deployment process.

    Deploying to Android link

    To deploy to Android, you need to have an Android emulator/device, and an environment that is able to run Android SDK. dragonruby-publish will create an APK for you. From there, you can sign the APK and install it to your device. The signing and installation procedure varies from OS to OS. Here's an example of what the command might look like: 

    # generating a keystore
keytool -genkey -v -keystore APP.keystore -alias mygame -keyalg RSA -keysize 2048 -validity 10000

# deploying to a local device/emulator
apksigner sign --ks mygame.keystore mygame-android.apk
adb install mygame-android.apk
# read logs of device
adb logcat -e mygame

# signing for Google Play
apksigner sign --min-sdk-version 21 --ks ./profiles/APP.keystore ./builds/APP-googleplay.aab

    Deploying To Steam link

    If you have a Indie or Pro subscription, you also get streamlined deployment to Steam via dragonruby-publish. Please note that games developed using the Standard license can deploy to Steam using the Steamworks toolchain https://partner.steamgames.com/doc/store/releasing.

    Testing on Your Steam Deck link

    Easy Setup link

    1. Run dragonruby-publish --only-package.
    2. Find the Linux build of your game under the ./builds directory and load it onto an SD Card.
    3. Restart the Steam Deck in Desktop Mode.
    4. Copy your game binary onto an SD card.
    5. Find the game on the SD card and double click binary.

    Advanced Setup link

    1. Restart the Steam Deck in Desktop Mode.
    2. Open up Konsole and set an admin password via passwd.
    3. Disable readonly mode: sudo steamos-readonly disable.
    4. Update pacman sudo pacman-key --populate archlinux.
    5. Update sshd_config sudo vim /etc/ssh/sshd_config and uncomment the PubkeyAuthentication yes line.
    6. Enable ssh: sudo systemctl enable sshd.
    7. Start ssh: sudo systemctl start sshd.
    8. Run dragonruby-publish --only-package.
    9. Use scp to copy the game over from your dev machine without needing an SD Card: scp -R ./builds/SOURCE.bin deck@IP_ADDRESS:/home/deck/Downloads

    Note: Steps 2 through 7 need only be done once.

    Note: scp comes pre-installed on Mac and Linux. You can download the tool for Windows from https://winscp.net/eng/index.php

    Setting up the game on the Partner Site link

    Getting your App ID link

    You'll need to create a product on Steam. This is unfortunately manual and requires identity verification for taxation purposes. Valve offers pretty robust documentation on all this, though. Eventually, you'll have an App ID for your game.

    Go to https://partner.steamgames.com/apps/view/$APPID, where $APPID is your game's App ID.

    Specifing Supported Operating Systems for your game link

    Find the "Supported Operating Systems" section and make sure these things are checked:

    Click the "Save" button below it.

    Setting up SteamPipe Depots link

    Click the "SteamPipe" tab at the top of the page, click on "depots"

    Click the "Add a new depot" button. Give it a name like "My Game Name Linux Depot" and take whatever depot ID it offers you.

    You'll see this new depot is listed on the page now. Fix its settings:

    Do this again, make a "My Game Name Windows Depot", set it to the same things, except "Operating System," which should be "Windows," of course.

    Do this again, make a "My Game Name Mac Depot", set it to the same things, except "Operating System," which should be "macOS," of course.

    Push the big green "Save" button on the page. Now we have a place to upload platform-specific builds of your game.

    Setting up Launch Options link

    Click on the "Installation" tab near the top of the page, then "General Installation".

    Under "Launch Options," click the "Add new launch option" button, edit the new section that just popped up, and set it like this:

    (Whenever you see "mygamename" in here, this should be whatever your game_metadata's "gameid" value is set to. If you see "My Game Name", it's whatever your game_metadata's "gametitle" value is set to, but you'll have to check in case we mangled it to work as a filename.)

    Click the "Update" button on that section.

    Add another launch option, as before:

    Add another launch option, as before:

    Publish Changes link

    Go to the "Publish" tab at near the top of the page. Click the "View Diffs" button and make sure it looks sane (it should just be the things we've changed in here), then click "Prepare for Publishing", then "Publish to Steam" and follow the instructions to publish these changes.

    Go to https://partner.steamgames.com/apps/associated/$APPID For each package, make sure all three depots are included.

    Configuring dragonruby-publish link

    You only have to do this part once when first setting up your game. Note that this capability is only available for Indie and Pro license tiers. If you have a Standard DragonRuby License, you'll need to use the Steamworks toolchains directly.

    Go add a text file to your game's metadata directory called steam_metadata.txt ... note that this file will be filtered out dragonruby-publish packages the game and will not be distributed with the published game. 

    steam.publish=true
steam.branch=public
steam.username=AAA
steam.appid=BBB
steam.linux_depotid=CCC
steam.windows_depotid=DDD
steam.mac_depotid=EEE

    If steam.publish is set to false then dragonruby-publish will not attempt to upload to Steam. false is the default if this file, or this setting, is missing.

    Where "AAA" is the login name on the Steamworks Partner Site to use for publishing builds, "BBB" is your game-specific AppID provided by Steam, "CCC", "DDD", and "EEE" are the DepotIDs you created for Linux, Windows, and macOS builds, respectively.

    Setting a branch live link

    Once your build is uploaded, you can assign it to a specific branch through the interface on the Partner site. You can make arbitrary branches here, like "beta" or "nightly" or "fixing-weird-bug" or whatever. The one that goes to the end users without them switching branches, is "default" and you should assume this is where paying customers live, so be careful before you set a build live there.

    You can have dragonruby-publish set the builds it publishes live on a branch immediately, if you prefer. Simply add... 

    steam.branch=XXX

    ...to steam_metadata.txt, where "XXX" is the branch name from the partner website. If this is blank or unspecified, it will _not_ set the build live on _any_ branch. Setting the value to public will push to production.

    A reasonable strategy is to create a (possibly passworded) branch called "staging" and have dragonruby-publish always push to there automatically. Then you can test from a Steam install, pushing as often as you like, and when you are satisfied, manually set the latest build live on default for the general public to download.

    If you are feeling brave, you can always just set all published builds live on default, too. After all, if you break it, you can always just push a fix right away. :) (or use the Partner Site to roll back to a known-good build, you know.)

    Publishing Build link

    Run dragonuby-publish as you normally would. When it is time to publish to Steam, it will set up any tools it needs, attempt to log you into Steam, and upload the latest version of your game.

    Steam login is handled by Valve's steamcmd command line program, not dragonruby-publish. DragonRuby does not ever have access to your login credentials. You may need to take steps to get an authorization token in place if necessary, so you don't have to deal with Steam Guard in automated build processes (documentation on how to do this is forthcoming, or read Valve's SteamCMD manual for details).

    You (currently) have to set the new build live on the partner site before users will receive it. Optionally automating this step is coming soon!

    Questions/Need Help? link

    You probably have several. Please come visit the Discord and ask questions, and we'll do our best to help, and update this document.

    DragonRuby's Philosophy link

    The following tenants of DragonRuby are what set us apart from other game engines. Given that Game Toolkit is a relatively new engine, there are definitely features that are missing. So having a big check list of "all the cool things" is not this engine's forte. This is compensated with a strong commitment to the following principles.

    Challenge The Status Quo link

    Game engines of today are in a local maximum and don't take into consideration the challenges of this day and age. Unity and GameMaker specifically rot your brain. It's not sufficient to say:

    But that's how we've always done it.

    It's a hard pill to swallow, but forget blindly accepted best practices and try to figure out the underlying motivation for a specific approach to game development. Collaborate with us.

    Continuity of Design link

    There is a programming idiom in software called "The Pit of Success". The term normalizes upfront pain as a necessity/requirement in the hopes that the investment will yield dividends "when you become successful" or "when the code becomes more complicated". This approach to development is strongly discouraged by us. It leads to over-architected and unnecessary code; creates barriers to rapid prototyping and shipping a game; and overwhelms beginners who are new to the engine or programming in general.

    DragonRuby's philosophy is to provide multiple options across the "make it fast" vs "make it right" spectrum, with incremental/intuitive transitions between the options provided. A concrete example of this philosophy would be render primitives: the spectrum of options allows renderable constructs that take the form of tuples/arrays (easy to pickup, simple, and fast to code/prototype with), hashes (a little more work, but gives you the ability to add additional properties), open and strict entities (more work than hashes, but yields cleaner apis), and finally - if you really need full power/flexibility in rendering - classes (which take the most amount of code and programming knowledge to create).

    Release Early and Often link

    The biggest mistake game devs make is spending too much time in isolation building their game. Release something, however small, and release it soon.

    Stop worrying about everything being pixel perfect. Don't wait until your game is 100% complete. Build your game publicly and iterate. Post in the #show-and-tell channel in the community Discord. You'll find a lot of support and encouragement there.

    Real artists ship. Remember that.

    Sustainable And Ethical Monetization link

    We all aspire to put food on the table doing what we love. Whether it is building games, writing tools to support game development, or anything in between.

    Charge a fair amount of money for the things you create. It's expected and encouraged within the community. Give what you create away for free to those that can't afford it.

    If you are gainfully employed, pay full price for the things you use. If you do end up getting something at a discount, pay the difference "forward" to someone else.

    Sustainable And Ethical Open Source link

    This goes hand in hand with sustainable and ethical monetization. The current state of open source is not sustainable. There is an immense amount of contributor burnout. Users of open source expect everything to be free, and few give back. This is a problem we want to fix (we're still trying to figure out the best solution).

    So, don't be "that guy" in the Discord that says "DragonRuby should be free and open source!" You will be personally flogged by Amir.

    People Over Entities link

    We prioritize the endorsement of real people over faceless entities. This game engine, and other products we create, are not insignificant line items of a large company. And you aren't a generic "commodity" or "corporate resource". So be active in the community Discord and you'll reap the benefits as more devs use DragonRuby.

    Building A Game Should Be Fun And Bring Happiness link

    We will prioritize the removal of pain. The aesthetics of Ruby make it such a joy to work with, and we want to capture that within the engine.

    Real World Application Drives Features link

    We are bombarded by marketing speak day in and day out. We don't do that here. There are things that are really great in the engine, and things that need a lot of work. Collaborate with us so we can help you reach your goals. Ask for features you actually need as opposed to anything speculative.

    We want DragonRuby to *actually* help you build the game you want to build (as opposed to sell you something piece of demoware that doesn't work).

    Frequently Asked Questions, Comments, and Concerns link

    Here are questions, comments, and concerns that frequently come up.

    Frequently Asked Questions link

    What is DragonRuby LLP? link

    DragonRuby LLP is a partnership of four devs who came together with the goal of bringing the aesthetics and joy of Ruby, everywhere possible.

    Under DragonRuby LLP, we offer a number of products (with more on the way):

    All of the products above leverage a shared core called DragonRuby.

    NOTE: From an official branding standpoint each one of the products is suffixed with "A DragonRuby LLP Product" tagline. Also, DragonRuby is _one word, title cased_.

    NOTE: We leave the "A DragonRuby LLP Product" off of this one because that just sounds really weird.

    NOTE: Devs who use DragonRuby are "Dragon Riders/Riders of Dragons". That's a bad ass identifier huh?

    What is DragonRuby? link

    The response to this question requires a few subparts. First we need to clarify some terms. Specifically _language specification_ vs _runtime_.

    Okay... so what is the difference between a language specification and a runtime?

    A runtime is an _implementation_ of a language specification. When people say "Ruby," they are usually referring to "the Ruby 3.0+ language specification implemented via the CRuby/MRI Runtime."

    But, there are many Ruby Runtimes: CRuby/MRI, JRuby, Truffle, Rubinius, Artichoke, and (last but certainly not least) DragonRuby.

    Okay... what language specification does DragonRuby use then?

    DragonRuby's goal is to be compliant with the ISO/IEC 30170:2012 standard. It's syntax is Ruby 2.x compatible, but also contains semantic changes that help it natively interface with platform specific libraries.

    So... why another runtime?

    The elevator pitch is:

    DragonRuby is a Multilevel Cross-platform Runtime. The "multiple levels" within the runtime allows us to target platforms no other Ruby can target: PC, Mac, Linux, Raspberry Pi, WASM, iOS, Android, Nintendo Switch, PS4, Xbox, and Stadia.

    What does Multilevel Cross-platform mean?

    There are complexities associated with targeting all the platforms we support. Because of this, the runtime had to be architected in such a way that new platforms could be easily added (which lead to us partitioning the runtime internally):

    Levels 1 through 3 are fairly commonplace in many runtime implementations (with level 1 being the most portable, and level 3 being the fastest). But the DragonRuby Runtime has taken things a bit further:

    These levels allow us to stay up to date with open source implementations of Ruby; provide fast, native code execution on proprietary platforms; ensure good separation between these two worlds; and provides a means to add new platforms without going insane.

    Cool cool. So given that I understand everything to this point, can we answer the original question? What is DragonRuby?

    DragonRuby is a Ruby runtime implementation that takes all the lessons we've learned from MRI/CRuby, and merges it with the latest and greatest compiler and OSS technologies.

    How is DragonRuby different than MRI? link

    DragonRuby supports a subset of MRI apis. Our target is to support all of mRuby's standard lib. There are challenges to this given the number of platforms we are trying to support (specifically console).

    Does DragonRuby support Gems?

    DragonRuby does not support gems because that requires the installation of MRI Ruby on the developer's machine (which is a non-starter given that we want DragonRuby to be a zero dependency runtime). While this seems easy for Mac and Linux, it is much harder on Windows and Raspberry Pi. mRuby has taken the approach of having a git repository for compatible gems and we will most likely follow suite: https://github.com/mruby/mgem-list.

    Does DragonRuby have a REPL/IRB?

    You can use DragonRuby's Console within the game to inspect object and execute small pieces of code. For more complex pieces of code create a file called repl.rb and put it in mygame/app/repl.rb: 

    repl do
  puts "hello world"
  puts 1 + 1
end

    4. To ignore code in repl.rb, instead of commenting it out, prefix repl with the letter x and it'll be ignored. 

    xrepl do # <------- line is prefixed with an "x"
  puts "hello world"
  puts 1 + 1
end

# This code will be executed when you save the file.
repl do
  puts "Hello"
end

repl do
  puts "This code will also be executed."
end

# use xrepl to "comment out" code
xrepl do
  puts "This code will not be executed because of the x in front of repl".
end

    Does DragonRuby support pry or have any other debugging facilities?

    pry is a gem that assumes you are using the MRI Runtime (which is incompatible with DragonRuby). Eventually DragonRuby will have a pry based experience that is compatible with a debugging infrastructure called LLDB. Take the time to read about LLDB as it shows the challenges in creating something that is compatible.

    You can use DragonRuby's replay capabilities to troubleshoot:

    1. DragonRuby is hot loaded which gives you a very fast feedback loop (if the game throws an exception, it's because of the code you just added).
    2. Use ./dragonruby mygame --record to create a game play recording that you can use to find the exception (you can replay a recording by executing ./dragonruby mygame --replay last_replay.txt or through the DragonRuby Console using $gtk.recording.start_replay "last_replay.txt".
    3. DragonRuby also ships with a unit testing facility. You can invoke the following command to run a test: ./dragonruby mygame --test tests/some_ruby_file.rb.
    4. Get into the habit of adding debugging facilities within the game itself. You can add drawing primitives to args.outputs.debug that will render on top of your game but will be ignored in a production release.
    5. Debugging something that runs at 60fps is (imo) not that helpful. The exception you are seeing could have been because of a change that occurred many frames ago.

    Frequent Comments About Ruby as a Language Choice link

    But Ruby is dead. link

    Let's check the official source for the answer to this question: isrubydead.com: https://isrubydead.com/.

    On a more serious note, Ruby's _quantity_ levels aren't what they used to be. And that's totally fine. Everyone chases the new and shiny.

    What really matters is _quality/maturity_. Here's a StackOverflow Survey sorted by highest paid developers: https://insights.stackoverflow.com/survey/2021#section-top-paying-technologies-top-paying-technologies.

    Let's stop making this comment shall we?

    But Ruby is slow. link

    That doesn't make any sense. A language specification can't be slow... it's a language spec. Sure, an _implementation/runtime_ can be slow though, but then we'd have to talk about which runtime.

    Here's a some quick demonstrations of how well DragonRuby Game Toolkit Performs:

    Dynamic languages are slow. link

    They are certainly slower than statically compiled languages. With the processing power and compiler optimizations we have today, dynamic languages like Ruby are _fast enough_.

    Unless you are writing in some form of intermediate representation by hand, your language of choice also suffers this same fallacy of slow. Like, nothing is faster than a low level assembly-like language. So unless you're writing in that, let's stop making this comment.

    NOTE: If you _are_ hand writing LLVM IR, we are always open to bringing on new partners with such a skill set. Email us ^_^.

    Frequent Concerns link

    DragonRuby is not open source. That's not right. link

    The current state of open source is unsustainable. Contributors work for free, most all open source repositories are severely under-staffed, and burnout from core members is rampant.

    We believe in open source very strongly. Parts of DragonRuby are in fact, open source. Just not all of it (for legal reasons, and because the IP we've created has value). And we promise that we are looking for (or creating) ways to _sustainably_ open source everything we do.

    If you have ideas on how we can do this, email us!

    If the reason above isn't sufficient, then definitely use something else.

    All this being said, we do have parts of the engine open sourced on GitHub: https://github.com/dragonruby/dragonruby-game-toolkit-contrib/

    DragonRuby is for pay. You should offer a free version. link

    If you can afford to pay for DragonRuby, you should (and will). We don't tell authors that they should give us their books for free, and only require payment if we read the entire thing. It's time we stop asking that of software products.

    That being said, we will _never_ put someone out financially. We have income assistance for anyone that can't afford a license to any one of our products.

    You qualify for a free, unrestricted license to DragonRuby products if any of the following items pertain to you:

    Just contact Amir at [email protected] with a short explanation of your current situation and he'll set you up. No questions asked.

    But still, you should offer a free version. So I can try it out and see if I like it. link

    You can try our web-based sandbox environment at http://fiddle.dragonruby.org. But it won't do the runtime justice. Or just come to our Discord Channel at http://discord.dragonruby.org and ask questions. We'd be happy to have a one on one video chat with you and show off all the cool stuff we're doing.

    Seriously just buy it. Get a refund if you don't like it. We make it stupid easy to do so.

    I still think you should do a free version. Think of all people who would give it a shot. link

    Free isn't a sustainable financial model. We don't want to spam your email. We don't want to collect usage data off of you either. We just want to provide quality toolchains to quality developers (as opposed to a large quantity of developers).

    The people that pay for DragonRuby and make an effort to understand it are the ones we want to build a community around, partner with, and collaborate with. So having that small monetary wall deters entitled individuals that don't value the same things we do.

    What if I build something with DragonRuby, but DragonRuby LLP becomes insolvent. link

    We want to be able to work on the stuff we love, every day of our lives. And we'll go to great lengths to make that continues.

    But, in the event that sad day comes, our partnership bylaws state that _all_ DragonRuby IP that can be legally open sourced, will be released under a permissive license.

    RECIPIES: link

    How To Determine What Frame You Are On link

    There is a property on state called tick_count that is incremented by DragonRuby every time the tick method is called. The following code renders a label that displays the current tick_count. 

    def tick args
  args.outputs.labels << [10, 670, "#{args.state.tick_count}"]
end

    How To Get Current Framerate link

    Current framerate is a top level property on the Game Toolkit Runtime and is accessible via args.gtk.current_framerate. 

    def tick args
  args.outputs.labels << [10, 710, "framerate: #{args.gtk.current_framerate.round}"]
end

    How To Render A Sprite Using An Array link

    All file paths should use the forward slash / *not* backslash . Game Toolkit includes a number of sprites in the sprites folder (everything about your game is located in the mygame directory).

    The following code renders a sprite with a width and height of 100 in the center of the screen.

    args.outputs.sprites is used to render a sprite.

    NOTE: Rendering using an Array is "quick and dirty". It's generally recommended that you render using Hashes long term. 

    def tick args
  args.outputs.sprites << [
    640 - 50,                 # X
    360 - 50,                 # Y
    100,                      # W
    100,                      # H
    'sprites/square-blue.png' # PATH
 ]
end

    Rendering a Sprite Using a Hash link

    Using ordinal positioning can get a little unruly given so many properties you have control over.

    You can represent a sprite as a Hash: 

    def tick args
  args.outputs.sprites << {
    x: 640 - 50,
    y: 360 - 50,
    w: 100,
    h: 100,

    path: 'sprites/square-blue.png',
    angle: 0,

    a: 255,
    r: 255,
    g: 255,
    b: 255,

    # source_ properties have origin of bottom left
    source_x:  0,
    source_y:  0,
    source_w: -1,
    source_h: -1,

    # tile_ properties have origin of top left
    tile_x:  0,
    tile_y:  0,
    tile_w: -1,
    tile_h: -1,

    flip_vertically: false,
    flip_horizontally: false,

    angle_anchor_x: 0.5,
    angle_anchor_y: 1.0,

    blendmode_enum: 1

    # labels anchor/alignment (default is nil)
    anchor_x: 0.5,
    anchor_y: 0.5
  }
end

    The blendmode_enum value can be set to 0 (no blending), 1 (alpha blending), 2 (additive blending), 3 (modulo blending), 4 (multiply blending).

    How To Render A Label link

    args.outputs.labels is used to render labels.

    Labels are how you display text. This code will go directly inside of the def tick args method.

    NOTE: Rendering using an Array is "quick and dirty". It's generally recommended that you render using Hashes long term.

    Here is the minimum code: 

    def tick args
  #                       X    Y    TEXT
  args.outputs.labels << [640, 360, "I am a black label."]
end

    A Colored Label link

    def tick args
  # A colored label
  #                       X    Y    TEXT,                   RED    GREEN  BLUE  ALPHA
  args.outputs.labels << [640, 360, "I am a redish label.", 255,     128,  128,   255]
end

    Extended Label Properties link

    def tick args
  # A colored label
  #                       X    Y     TEXT           SIZE  ALIGNMENT  RED  GREEN  BLUE  ALPHA  FONT FILE
  args.outputs.labels << [
    640,                   # X
    360,                   # Y
    "Hello world",         # TEXT
    0,                     # SIZE_ENUM
    1,                     # ALIGNMENT_ENUM
    0,                     # RED
    0,                     # GREEN
    0,                     # BLUE
    255,                   # ALPHA
    "fonts/coolfont.ttf"   # FONT
  ]
end

    A SIZE_ENUM of 0 represents "default size". A negative value will decrease the label size. A positive value will increase the label's size.

    An ALIGNMENT_ENUM of 0 represents "left aligned". 1 represents "center aligned". 2 represents "right aligned".

    Rendering A Label As A Hash link

    You can add additional metadata about your game within a label, which requires you to use a `Hash` instead.

    If you use a Hash to render a label, you can set the label's size using either SIZE_ENUM or SIZE_PX. If both options are provided, SIZE_PX will be used. 

    def tick args
  args.outputs.labels << {
    x:                       200,
    y:                       550,
    text:                    "dragonruby",
    # size specification can be either size_enum or size_px
    size_enum:               2,
    size_px:                 22,
    alignment_enum:          1,
    r:                       155,
    g:                       50,
    b:                       50,
    a:                       255,
    font:                    "fonts/manaspc.ttf",
    vertical_alignment_enum: 0, # 0 is bottom, 1 is middle, 2 is top
    anchor_x: 0.5,
    anchor_y: 0.5
    # You can add any properties you like (this will be ignored/won't cause errors)
    game_data_one:  "Something",
    game_data_two: {
       value_1: "value",
       value_2: "value two",
       a_number: 15
    }
  }
end

    Getting The Size Of A Piece Of Text link

    You can get the render size of any string using args.gtk.calcstringbox. 

    def tick args
  #                             TEXT           SIZE_ENUM  FONT
  w, h = args.gtk.calcstringbox("some string",         0, "font.ttf")

  # NOTE: The SIZE_ENUM and FONT are optional arguments.

  # Render a label showing the w and h of the text:
  args.outputs.labels << [
    10,
    710,
    # This string uses Ruby's string interpolation literal: #{}
    "'some string' has width: #{w}, and height: #{h}."
  ]
end

    Rendering Labels With New Line Characters And Wrapping link

    You can use a strategy like the following to create multiple labels from a String. 

    def tick args
  long_string = "Lorem ipsum dolor sit amet, consectetur adipiscing elitteger dolor velit, ultricies vitae libero vel, aliquam imperdiet enim."
  max_character_length = 30
  long_strings_split = args.string.wrapped_lines long_string, max_character_length
  args.outputs.labels << long_strings_split.map_with_index do |s, i|
    { x: 10, y: 600 - (i * 20), text: s }
  end
end

    How To Play A Sound link

    Sounds that end .wav will play once: 

    def tick args
  # Play a sound every second
  if (args.state.tick_count % 60) == 0
    args.outputs.sounds << 'something.wav'
  end
end

    Sounds that end .ogg is considered background music and will loop: 

    def tick args
  # Start a sound loop at the beginning of the game
  if args.state.tick_count == 0
    args.outputs.sounds << 'background_music.ogg'
  end
end

    If you want to play a .ogg once as if it were a sound effect, you can do: 

    def tick args
  # Play a sound every second
  if (args.state.tick_count % 60) == 0
    args.gtk.queue_sound 'some-ogg.ogg'
  end
end

    Using args.state To Store Your Game State link

    args.state is a open data structure that allows you to define properties that are arbitrarily nested. You don't need to define any kind of class.

    To initialize your game state, use the ||= operator. Any value on the right side of ||= will only be assigned _once_.

    To assign a value every frame, just use the = operator, but _make sure_ you've initialized a default value. 

    def tick args
  # initialize your game state ONCE
  args.state.player.x  ||= 0
  args.state.player.y  ||= 0
  args.state.player.hp ||= 100

  # increment the x position of the character by one every frame
  args.state.player.x += 1

  # Render a sprite with a label above the sprite
  args.outputs.sprites << [
    args.state.player.x,
    args.state.player.y,
    32, 32,
    "player.png"
  ]

  args.outputs.labels << [
    args.state.player.x,
    args.state.player.y - 50,
    args.state.player.hp
  ]
end

    Accessing files link

    DragonRuby uses a sandboxed filesystem which will automatically read from and write to a location appropriate for your platform so you don't have to worry about theses details in your code. You can just use gtk.read_file, gtk.write_file, and gtk.append_file with a relative path and the engine will take care of the rest.

    The data directories that will be written to in a production build are:

    The values in square brackets are the values you set in your app/metadata/game_metadata.txt file.

    When reading files, the engine will first look in the game's data directory and then in the game directory itself. This means that if you write a file to the data directory that already exists in your game directory, the file in the data directory will be used instead of the one that is in your game.

    When running a development build you will directly write to your game directory (and thus overwrite existing files). This can be useful for built-in development tools like level editors.

    For more details on the implementation of the sandboxed filesystem, see Ryan C. Gordon's PhysicsFS documentation: https://icculus.org/physfs/

    IMPORTANT: File access functions are sandoxed and assume that the dragonruby binary lives alongside the game you are building. Do not expect file access functions to return correct values if you are attempting to run the dragonruby binary from a shared location. It's recommended that the directory structure contained in the zip is not altered and games are built using that starter template.

    Troubleshoot Performance link

    args.state.bullets.each do |bullet|
  args.outputs.sprites << bullet.sprite
end

    do 

    args.outputs.sprites << args.state.bullets.map do |b|
  b.sprite
end

    args.state.fx_queue |fx|
  fx.count_down ||= 255
  fx.countdown -= 5
  if fx.countdown < 0
    args.state.fx_queue.delete fx
  end
end

    Do: 

    args.state.fx_queue |fx|
  fx.count_down ||= 255
  fx.countdown -= 5
end

args.state.fx_queue.reject! { |fx| fx.countdown < 0 }

    Outputs (args.outputs) link

    Outputs is how you render primitives to the screen. The minimal setup for rendering something to the screen is via a tick method defined in mygame/app/main.rb 

    def tick args
  args.outputs.solids     << { x: 0, y: 0, w: 100, h: 100 }
  args.outputs.sprites    << { x: 100, y: 100, w: 100, h: 100, path: "sprites/square/blue.png" }
  args.outputs.labels     << { x: 200, y: 200, text: "Hello World" }
  args.outputs.borders    << { x: 0, y: 0, w: 100, h: 100 }
  args.outputs.lines      << { x: 300, y: 300, x2: 400, y2: 400 }
end

    Render Order link

    Primitives are rendered first-in, first-out. The rendering order (sorted by bottom-most to top-most):

    solids link

    Add primitives to this collection to render a solid to the screen.

    Rendering a solid using an Array link

    Creates a solid black rectangle located at 100, 100. 160 pixels wide and 90 pixels tall. 

    def tick args
  #                         X    Y  WIDTH  HEIGHT
  args.outputs.solids << [100, 100,   160,     90]
end

    Rendering a solid using an Array with colors and alpha link

    The value for the color and alpha is a number between 0 and 255. The alpha property is optional and will be set to 255 if not specified.

    Creates a green solid rectangle with an opacity of 50%. 

    def tick args
  #                         X    Y  WIDTH  HEIGHT  RED  GREEN  BLUE  ALPHA
  args.outputs.solids << [100, 100,   160,     90,   0,   255,    0,   128]
end

    Rendering a solid using a Hash link

    If you want a more readable invocation. You can use the following hash to create a solid. Any parameters that are not specified will be given a default value. The keys of the hash can be provided in any order. 

    def tick args
  args.outputs.solids << {
    x:    0,
    y:    0,
    w:  100,
    h:  100,
    r:    0,
    g:  255,
    b:    0,
    a:  255,
    anchor_x: 0,
    anchor_y: 0,
    blendmode_enum: 1
  }
end

    Rendering a solid using a Class link

    You can also create a class with solid properties and render it as a primitive. ALL properties must be on the class. *Additionally*, a method called primitive_marker must be defined on the class.

    Here is an example: 

    # Create type with ALL solid properties AND primitive_marker
class Solid
  attr_accessor :x, :y, :w, :h, :r, :g, :b, :a, :anchor_x, :anchor_y, :blendmode_enum

  def primitive_marker
    :solid # or :border
  end
end

# Inherit from type
class Square < Solid
  # constructor
  def initialize x, y, size
    self.x = x
    self.y = y
    self.w = size
    self.h = size
  end
end

def tick args
  # render solid/border
  args.outputs.solids  << Square.new(10, 10, 32)
end

    borders link

    Add primitives to this collection to render an unfilled solid to the screen. Take a look at the documentation for Outputs#solids.

    The only difference between the two primitives is where they are added.

    Instead of using args.outputs.solids: 

    def tick args
  #                         X    Y  WIDTH  HEIGHT
  args.outputs.solids << [100, 100,   160,     90]
end

    You have to use args.outputs.borders: 

    def tick args
  #                           X    Y  WIDTH  HEIGHT
  args.outputs.borders << [100, 100,   160,     90]
end

    sprites link

    Add primitives to this collection to render a sprite to the screen.

    Rendering a sprite using an Array link

    Creates a sprite of a white circle located at 100, 100. 160 pixels wide and 90 pixels tall. 

    def tick args
  #                         X    Y   WIDTH   HEIGHT                      PATH
  args.outputs.sprites << [100, 100,   160,     90, "sprites/circle/white.png"]
end

    Rendering a sprite using a Hash link

    If you want a more readable (and faster) invocation, you can use the following hash to create a sprite. Any parameters that are not specified will be given a default value. The keys of the hash can be provided in any order. 

    def tick args
  args.outputs.sprites << {
    x:                             0,
    y:                             0,
    w:                           100,
    h:                           100,
    path: "sprites/circle/white.png",
    angle:                         0,
    a:                           255,
    r:                             0,
    g:                           255,
    b:                             0
  }
end

    Here are all the properties that you can set on a sprite. The only required ones are x, y, w, h, and path.

    Required properties

    Anchors and Rotations

    Here's an example of rendering a 80x80 pixel sprite in the center of the screen: 

    def tick args
  args.outputs.sprites << {
    x: 640 - 40, # the logical center of the screen horizontally is 640, minus half the width of the sprite
    y: 360 - 40, # the logical center of the screen vertically is 360, minus half the height of the sprite
    w: 80,
    h: 80,
    path: "sprites/square/blue.png"
 }
end

    Instead of computing the offset, you can use anchor_x, and anchor_y to center the sprite. The following is equivalent to the code above: 

    def tick args
  args.outputs.sprites << {
    x: 640,
    y: 360,
    w: 80,
    h: 80,
    path: "sprites/square/blue.png",
    anchor_x: 0.5, # position horizontally at 0.5 of the sprite's width
    anchor_y: 0.5  # position vertically at 0.5 of the sprite's height
 }
end

    Cropping Properties

    See the sample apps under ./samples/03_rendering_sprites for examples of how to use this properties non-trivially.

    Blending Options

    The following sample apps show how blendmode_enum can be leveraged to create coloring and lighting effects:

    Triagles (Indie, Pro Feature)

    Sprites can be rendered as triangles at the Indie and Pro License Tiers. To rendering using triangles, instead of providing a w, h property, provide x2, y2, x3, y3. This applies for positioning and cropping.

    Here is an example: 

    def tick args
  args.outputs.sprites << {
    x: 0,
    y: 0,
    x2: 80,
    y2: 0,
    x3: 0,
    y3: 80,
    source_x: 0,
    source_y: 0,
    source_x2: 80,
    source_y2: 0,
    source_x3: 0,
    source_y3: 80,
    path: "sprites/square/blue.png"
  }
end

    For more example of rendering using triangles see:

    Rendering a sprite using a Class link

    You can also create a class with solid/border properties and render it as a primitive. ALL properties must be on the class. *Additionally*, a method called primitive_marker must be defined on the class.

    Here is an example: 

    # Create type with ALL sprite properties AND primitive_marker
class Sprite
  attr_accessor :x, :y, :w, :h, :path, :angle, :a, :r, :g, :b, :tile_x,
                :tile_y, :tile_w, :tile_h, :flip_horizontally,
                :flip_vertically, :angle_anchor_x, :angle_anchor_y, :id,
                :angle_x, :angle_y, :z,
                :source_x, :source_y, :source_w, :source_h, :blendmode_enum,
                :source_x2, :source_y2, :source_x3, :source_y3, :x2, :y2, :x3, :y3,
                :anchor_x, :anchor_y

  def primitive_marker
    :sprite
  end
end

# Inherit from type
class Circle < Sprite
  # constructor
  def initialize x, y, size, path
    self.x = x
    self.y = y
    self.w = size
    self.h = size
    self.path = path
  end

  def serialize
    {x:self.x, y:self.y, w:self.w, h:self.h, path:self.path}
  end

  def inspect
    serialize.to_s
  end

  def to_s
    serialize.to_s
  end
end

def tick args
  # render circle sprite
  args.outputs.sprites  << Circle.new(10, 10, 32,"sprites/circle/white.png")
end

    attr_sprite link

    The attr_sprite class macro adds all properties needed to render a sprite to a class. This removes the need to manually define all sprites properties that DragonRuby offers for rendering.

    Instead of manually defining the properties, you can represent a sprite using the attr_sprite class macro: 

    class BlueSquare
  # invoke the helper function at the class level for
  # anything you want to represent as a sprite
  attr_sprite

  def initialize(x: 0, y: 0, w: 0, h: 0k
    @x = x
    @y = y
    @w = w
    @h = h
    @path = 'sprites/square-blue.png'
  end
end

def tick args
  args.outputs.sprites << BlueSquare.new(x: 640 - 50,
                                         y: 360 - 50,
                                         w: 50,
                                         h: 50)
end

    labels link

    Add primitives to this collection to render a label.

    Rendering a label using an Array link

    Labels represented as Arrays/Tuples: 

    def tick args
                         #        X         Y              TEXT   SIZE_ENUM
  args.outputs.labels << [175 + 150, 610 - 50, "Smaller label.",         0]
end

    Here are all the properties that you can set with a label represented as an Array. It's recommended to move over to using Hashes once you've specified a lot of properties. 

    def tick args
  args.outputs.labels << [
    640,                   # X
    360,                   # Y
    "Hello world",         # TEXT
    0,                     # SIZE_ENUM
    1,                     # ALIGNMENT_ENUM
    0,                     # RED
    0,                     # GREEN
    0,                     # BLUE
    255,                   # ALPHA
    "fonts/coolfont.ttf"   # FONT
  ]
end
d

    Rendering a label using a Hash link

    def tick args
  args.outputs.labels << {
      x:                       200,
      y:                       550,
      text:                    "dragonruby",
      size_enum:               2,
      alignment_enum:          1, # 0 = left, 1 = center, 2 = right
      r:                       155,
      g:                       50,
      b:                       50,
      a:                       255,
      font:                    "fonts/manaspc.ttf",
      vertical_alignment_enum: 0  # 0 = bottom, 1 = center, 2 = top
  }
end

    Screenshots link

    Add a hash to this collection to take a screenshot and save as png file. The keys of the hash can be provided in any order. 

    def tick args
  args.outputs.screenshots << {
    x: 0, y: 0, w: 100, h: 100,    # Which portion of the screen should be captured
    path: 'screenshot.png',        # Output path of PNG file (inside game directory)
    r: 255, g: 255, b: 255, a: 0   # Optional chroma key
  }
end

    Chroma key (Making a color transparent) link

    By specifying the r, g, b and a keys of the hash you change the transparency of a color in the resulting PNG file. This can be useful if you want to create files with transparent background like spritesheets. The transparency of the color specified by r, g, b will be set to the transparency specified by a.

    The example above sets the color white (255, 255, 255) as transparent.

    Inputs (args.inputs) link

    Access using input using args.inputs.

    last_active link

    This function returns the last active input which will be set to either :keyboard, :mouse, or :controller. The function is helpful when you need to present on screen instructions based on the input the player chose to play with. 

    def tick args
  if args.inputs.last_active == :controller
    args.outputs.labels << { x: 60, y: 60, text: "Use the D-Pad to move around." }
  else
    args.outputs.labels << { x: 60, y: 60, text: "Use the arrow keys to move around." }
  end
end

    :mouse, or :controller. The function is helpful when you need to present on screen instructions based on the input the player chose to play with.

    locale link

    Returns the ISO 639-1 two-letter langauge code based on OS preferences. Refer to the following link for locale strings: https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes).

    Defaults to "en" if locale can't be retrieved (args.inputs.locale_raw will be nil in this case).

    up link

    Returns true if: the up arrow or w key is pressed or held on the keyboard; or if up is pressed or held on controller_one; or if the left_analog on controller_one is tilted upwards.

    down link

    Returns true if: the down arrow or s key is pressed or held on the keyboard; or if down is pressed or held on controller_one; or if the left_analog on controller_one is tilted downwards.

    left link

    Returns true if: the left arrow or a key is pressed or held on the keyboard; or if left is pressed or held on controller_one; or if the left_analog on controller_one is tilted to the left.

    right link

    Returns true if: the right arrow or d key is pressed or held on the keyboard; or if right is pressed or held on controller_one; or if the left_analog on controller_one is tilted to the right.

    left_right link

    Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.left and args.inputs.right. 

    args.state.player[:x] += args.inputs.left_right * args.state.speed

    up_down link

    Returns -1 (down), 0 (neutral), or +1 (up) depending on results of args.inputs.down and args.inputs.up. 

    args.state.player[:y] += args.inputs.up_down * args.state.speed

    text link

    Returns a string that represents the last key that was pressed on the keyboard.

    Mouse (args.inputs.mouse) link

    Represents the user's mouse.

    has_focus link

    Return's true if the game has mouse focus.

    x link

    Returns the current x location of the mouse.

    y link

    Returns the current y location of the mouse.

    inside_rect? rect link

    Return. args.inputs.mouse.inside_rect? takes in any primitive that responds to x, y, w, h:

    inside_circle? center_point, radius link

    Returns true if the mouse is inside of a specified circle. args.inputs.mouse.inside_circle? takes in any primitive that responds to x, y (which represents the circle's center), and takes in a radius:

    moved link

    Returns true if the mouse has moved on the current frame.

    button_left link

    Returns true if the left mouse button is down.

    button_middle link

    Returns true if the middle mouse button is down.

    button_right link

    Returns true if the right mouse button is down.

    button_bits link

    Returns a bitmask for all buttons on the mouse: 1 for a button in the down state, 0 for a button in the up state.

    wheel link

    Represents the mouse wheel. Returns nil if no mouse wheel actions occurred. Otherwise args.inputs.mouse.wheel will return a Hash with x, and y (representing movement on each axis).

    click OR down, previous_click, up link

    The properties args.inputs.mouse.(click|down|previous_click|up) each return nil if the mouse button event didn't occur. And return an Entity that has an x, y properties along with helper functions to determine collision: inside_rect?, inside_circle. This value will be true if any of the mouse's buttons caused these events. To scope to a specific button use .button_left, .button_middle, .button_right, or .button_bits.

    Touch link

    The following touch apis are available on touch devices (iOS, Android, Mobile Web, Surface).

    args.inputs.touch link

    Returns a Hash representing all touch points on a touch device.

    args.inputs.finger_left link

    Returns a Hash with x and y denoting a touch point that is on the left side of the screen.

    args.inputs.finger_right link

    Returns a Hash with x and y denoting a touch point that is on the right side of the screen.

    Controller (args.inputs.controller_(one-four)) link

    Represents controllers connected to the usb ports.

    active link

    Returns true if any of the controller's buttons were used.

    up link

    Returns true if up is pressed or held on the directional or left analog.

    down link

    Returns true if down is pressed or held on the directional or left analog.

    left link

    Returns true if left is pressed or held on the directional or left analog.

    right link

    Returns true if right is pressed or held on the directional or left analog.

    left_right link

    Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.controller_(one-four).left and args.inputs.controller_(one-four).right.

    up_down link

    Returns -1 (down), 0 (neutral), or +1 (up) depending on results of args.inputs.controller_(one-four).up and args.inputs.controller_(one-four).down.

    (left|right)_analog_x_raw link

    Returns the raw integer value for the analog's horizontal movement (-32,000 to +32,000).

    (left|right)_analog_y_raw link

    Returns the raw integer value for the analog's vertical movement (-32,000 to +32,000).

    (left|right)_analog_x_perc link

    Returns a number between -1 and 1 which represents the percentage the analog is moved horizontally as a ratio of the maximum horizontal movement.

    (left|right)_analog_y_perc link

    Returns a number between -1 and 1 which represents the percentage the analog is moved vertically as a ratio of the maximum vertical movement.

    directional_up link

    Returns true if up is pressed or held on the directional.

    directional_down link

    Returns true if down is pressed or held on the directional.

    directional_left link

    Returns true if left is pressed or held on the directional.

    directional_right link

    Returns true if right is pressed or held on the directional.

    (a|b|x|y|l1|r1|l2|r2|l3|r3|start|select) link

    Returns true if the specific button is pressed or held.

    truthy_keys link

    Returns a collection of Symbols that represent all keys that are in the pressed or held state.

    key_down link

    Returns true if the specific button was pressed on this frame. args.inputs.controller_(one-four).key_down.BUTTON will only be true on the frame it was pressed.

    key_held link

    Returns true if the specific button is being held. args.inputs.controller_(one-four).key_held.BUTTON will be true for all frames after key_down (until released).

    key_up link

    Returns true if the specific button was released. args.inputs.controller_(one-four).key_up.BUTTON will be true only on the frame the button was released.

    Keyboard (args.inputs.keyboard) link

    Represents the user's keyboard.

    active link

    Returns Kernel.tick_count (args.state.tick_count) if any keys on the keyboard were pressed.

    has_focus link

    Returns true if the game has keyboard focus.

    up link

    Returns true if up or w is pressed or held on the keyboard.

    down link

    Returns true if down or s is pressed or held on the keyboard.

    left link

    Returns true if left or a is pressed or held on the keyboard.

    right link

    Returns true if right or d is pressed or held on the keyboard.

    left_right link

    Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.keyboard.left and args.inputs.keyboard.right.

    up_down link

    Returns -1 (left), 0 (neutral), or +1 (right) depending on results of args.inputs.keyboard.up and args.inputs.keyboard.up.

    keyboard properties link

    The following properties represent keys on the keyboard and are available on args.inputs.keyboard.KEY, args.inputs.keyboard.key_down.KEY, args.inputs.keyboard.key_held.KEY, and args.inputs.keyboard.key_up.KEY:

    char link

    Method is available under inputs.key_down, inputs.key_held, and inputs.key_up. Take note that

    args.inputs.keyboard.key_held.char will only return the ascii value of the last key that was held. Use args.inputs.keyboard.key_held.truthy_keys to get an Array of Symbols representing all keys being held.

    To get a picture of all key states args.inputs.keyboard.keys returns a Hash with the following keys: :down, :held, :down_or_held, :up.

    NOTE: args.inputs.keyboard.key_down.char will be set in line with key repeat behavior of your OS.

    This is a demonstration of the behavior (see ./samples/02_input_basics/01_keyboard for a more detailed example): 

    def tick args
  # uncomment the line below to see the value changes at a slower rate
  # $gtk.slowmo! 30

  keyboard = args.inputs.keyboard

  args.outputs.labels << { x: 30,
                           y: 720,
                           text: "use the J key to test" }

  args.outputs.labels << { x: 30,
                           y: 720 - 30,
                           text: "key_down.char: #{keyboard.key_down.char.inspect}" }

  args.outputs.labels << { x: 30,
                           y: 720 - 60,
                           text: "key_down.j:    #{keyboard.key_down.j}" }

  args.outputs.labels << { x: 30,
                           y: 720 - 30,
                           text: "key_held.char: #{keyboard.key_held.char.inspect}" }

  args.outputs.labels << { x: 30,
                           y: 720 - 60,
                           text: "key_held.j:    #{keyboard.key_held.j}" }

  args.outputs.labels << { x: 30,
                           y: 720 - 30,
                           text: "key_up.char:   #{keyboard.key_up.char.inspect}" }

  args.outputs.labels << { x: 30,
                           y: 720 - 60,
                           text: "key_up.j:      #{keyboard.key_up.j}" }
end

    keys link

    Returns a Hash with all keys on the keyboard in their respective state. The Hash contains the following keys

    Runtime (args.gtk) link

    The GTK::Runtime class is the core of DragonRuby. It is globally accessible via $gtk or inside of the tick method through args. 

    def tick args
  args.gtk # accessible like this
  $gtk # or like this
end

    Class Macros link

    The following class macros are available within DragonRuby.

    attr link

    The attr class macro is an alias to attr_accessor.

    Instead of: 

    class Player
  attr_accessor :hp, :armor
end

    You can do: 

    class Player
  attr :hp, :armor
end

    attr_gtk link

    As the size/complexity of your game increases. You may want to create classes to organize everything. The attr_gtk class macro adds DragonRuby's environment methods (such as args.state, args.inputs, args.outputs, args.audio, etc) to your class so you don't have to pass args around everwhere.

    Instead of: 

    class Game
  def tick args
    defaults args
    calc args
    render args
  end

  def defaults args
    args.state.space_pressed_at ||= 0
  end

  def calc args
    if args.inputs.keyboard.key_down.space
      args.state.space_pressed_at = args.state.tick_count
    end
  end

  def render args
    if args.state.space_pressed_at == 0
      args.outputs.labels << { x: 100, y: 100,
                               text: "press space" }
    else
      args.outputs.labels << { x: 100, y: 100,
                               text: "space was pressed at: #{args.state.space_pressed_at}" }
    end
  end
end

def tick args
  $game ||= Game.new
  $game.tick args
end

    You can do: 

    class Game
  attr_gtk # attr_gtk class macro

  def tick
    defaults
    calc
    render
  end

  def defaults
    state.space_pressed_at ||= 0
  end

  def calc
    if inputs.keyboard.key_down.space
      state.space_pressed_at = state.tick_count
    end
  end

  def render
    if state.space_pressed_at == 0
      outputs.labels << { x: 100, y: 100,
                          text: "press space" }
    else
      outputs.labels << { x: 100, y: 100,
                          text: "space was pressed at: #{state.space_pressed_at}" }
    end
  end
end

def tick args
  $game ||= Game.new
  $game.args = args # set args property on game
  $game.tick        # call tick without passing in args
end

$game = nil

    Indie and Pro Functions link

    The following functions are only available at the Indie and Pro License tiers.

    get_pixels link

    Given a file_path to a sprite, this function returns a one dimensional array of hexadecimal values representing the ARGB of each pixel in a sprite.

    See the following sample app for a full demonstration of how to use this function: ./samples/07_advanced_rendering/06_pixel_arrays_from_file

    dlopen link

    Loads a precompiled C Extension into your game.

    See the sample apps at ./samples/12_c_extensions for detailed walkthroughs of creating C extensions.

    Environment and Utility Functions link

    The following functions will help in interacting with the OS and rendering pipeline.

    calcstringbox link

    Returns the render width and render height as a tuple for a piece of text. The parameters this method takes are: 

    def tick args
  text = "a piece of text"
  size_enum = 5 # "large font size"

  # path is relative to your game directory (eg mygame/fonts/courier-new.ttf)
  font = "fonts/courier-new.ttf"

  # get the render width and height
  string_w, string_h = args.gtk.calcstringbox text, size_enum, font

  # render the label
  args.outputs.labels << {
    x: 100,
    y: 100,
    text: text,
    size_enum: size_enum,
    font: font
  }

  # render a border around the label based on the results from calcstringbox
  args.outputs.borders << {
    x: 100,
    y: 100,
    w: string_w,
    h: string_h,
    r: 0,
    g: 0,
    b: 0
  }
end

    request_quit link

    Call this function to exit your game. You will be given one additional tick if you need to perform any housekeeping before that game closes. 

    def tick args
  # exit the game after 600 frames (10 seconds)
  if args.state.tick_count == 600
    args.gtk.request_quit
  end
end

    quit_requested? link

    This function will return true if the game is about to exit (either from the user closing the game or if request_quit was invoked).

    set_window_fullscreen link

    This function takes in a single boolean parameter. true to make the game fullscreen, false to return the game back to windowed mode. 

    def tick args
  # make the game full screen after 600 frames (10 seconds)
  if args.state.tick_count == 600
    args.gtk.set_window_fullscreen true
  end

  # return the game to windowed mode after 20 seconds
  if args.state.tick_count == 1200
    args.gtk.set_window_fullscreen false
  end
end

    window_fullscreen? link

    Returns true if the window is currently in fullscreen mode.

    set_window_scale link

    This function takes in a float value and uses that to resize the game window to a percentage of 1280x720 (or 720x1280 in portrait mode). The valid scale options are 0.1, 0.25, 0.5, 0.75, 1.25, 1.5, 2.0, 2.5, 3.0, and 4.0. The float value you pass in will be floored to the nearest valid scale option.

    platform? link

    You can ask DragonRuby which platform your game is currently being run on. This can be useful if you want to perform different pieces of logic based on where the game is running.

    The raw platform string value is available via args.gtk.platform which takes in a symbol representing the platform's categorization/mapping.

    You can see all available platform categorizations via the args.gtk.platform_mappings function.

    Here's an example of how to use args.gtk.platform? category_symbol: 

    def tick args
  label_style = { x: 640, y: 360, anchor_x: 0.5, anchor_y: 0.5 }
  if    args.gtk.platform? :macos
    args.outputs.labels << { text: "I am running on MacOS.", **label_style }
  elsif args.gtk.platform? :win
    args.outputs.labels << { text: "I am running on Windows.", **label_style }
  elsif args.gtk.platform? :linux
    args.outputs.labels << { text: "I am running on Linux.", **label_style }
  elsif args.gtk.platform? :web
    args.outputs.labels << { text: "I am running on a web page.", **label_style }
  elsif args.gtk.platform? :android
    args.outputs.labels << { text: "I am running on Android.", **label_style }
  elsif args.gtk.platform? :ios
    args.outputs.labels << { text: "I am running on iOS.", **label_style }
  elsif args.gtk.platform? :touch
    args.outputs.labels << { text: "I am running on a device that supports touch (either iOS/Android native or mobile web).", **label_style }
  elsif args.gtk.platform? :steam
    args.outputs.labels << { text: "I am running via steam (covers both desktop and steamdeck).", **label_style }
  elsif args.gtk.platform? :steam_deck
    args.outputs.labels << { text: "I am running via steam on the Steam Deck (not steam desktop).", **label_style }
  elsif args.gtk.platform? :steam_desktop
    args.outputs.labels << { text: "I am running via steam on desktop (not steam deck).", **label_style }
  end
end

    production? link

    Returns true if the game is being run in a released/shipped state.

    If you want to simulate a production build. Add an empty file called DRAGONRUBY_PRODUCTION_BUILD inside of the metadata folder. This will turn of all logging and all creation of temp files used for development purposes.

    platform_mappings link

    These are the current platform categorizations (args.gtk.platform_mappings): 

    {
  "Mac OS X"   => [:desktop, :macos, :osx, :mac, :macosx], # may also include :steam and :steam_desktop run via steam
  "Windows"    => [:desktop, :windows, :win],              # may also include :steam and :steam_desktop run via steam
  "Linux"      => [:desktop, :linux, :nix],                # may also include :steam and :steam_desktop run via steam
  "Emscripten" => [:web, :wasm, :html, :emscripten],       # may also include :touch if running in the web browser on mobile
  "iOS"        => [:mobile, :ios, :touch],
  "Android"    => [:mobile, :android, :touch],
  "Steam Deck" => [:steamdeck, :steam_deck, :steam],
}

    Given the mappings above, args.gtk.platform? :desktop would return true if the game is running on a player's computer irrespective of OS (MacOS, Linux, and Windows are all categorized as :desktop platforms).

    open_url link

    Given a uri represented as a string. This fuction will open the uri in the user's default browser. 

    def tick args
  # open a url after 600 frames (10 seconds)
  if args.state.tick_count == 600
    args.gtk.open_url "http://dragonruby.org"
  end
end

    system link

    Given an OS dependent cli command represented as a string, this function executes the command and puts the results to the DragonRuby Console (returns nil). 

    def tick args
  # execute ls on the current directory in 10 seconds
  if args.state.tick_count == 600
    args.gtk.system "ls ."
  end
end

    exec link

    Given an OS dependent cli command represented as a string, this function executes the command and returns a string representing the results. 

    def tick args
  # execute ls on the current directory in 10 seconds
  if args.state.tick_count == 600
    results = args.gtk.exec "ls ."
    puts "The results of the command are:"
    puts results
  end
end

    show_cursor link

    Shows the mouse cursor.

    hide_cursor link

    Hides the mouse cursor.

    cursor_shown? link

    Returns true if the mouse cursor is visible.

    set_mouse_grab link

    Takes in a numeric parameter representing the mouse grab mode.

    set_system_cursor link

    Takes in a string value of "arrow", "ibeam", "wait", or "hand" and sets the mouse curosor to the corresponding system cursor (if available on the OS).

    set_cursor link

    Replaces the mouse cursor with a sprite. Takes in a path to the sprite, and optionally an x and y value representing the realtive positioning the sprite will have to the mouse cursor. 

    def tick args
  if args.state.tick_count == 0
    # assumes a sprite of size 80x80 and centers the sprite
    # relative to the cursor position.
    args.gtk.set_cursor "sprites/square/blue.png", 40, 40
  end
end

    File IO Functions link

    The following functions give you the ability to interact with the file system.

    IMPORTANT: File access functions are sandoxed and assume that the dragonruby binary lives alongside the game you are building. Do not expect these functions to return correct values if you are attempting to run the dragonruby binary from a shared location. It's recommended that the directory structure contained in the zip is not altered and games are built using that starter template.

    list_files link

    This function takes in one parameter. The parameter is the directory path and assumes the the game directory is the root. The method returns an Array of String representing all files within the directory. Use stat_file to determine whether a specific path is a file or a directory.

    stat_file link

    This function takes in one parameter. The parameter is the file path and assumes the the game directory is the root. The method returns nil if the file doesn't exist otherwise it returns a Hash with the following information: 

    # {
#   path: String,
#   file_size: Int,
#   mod_time: Int,
#   create_time: Int,
#   access_time: Int,
#   readonly: Boolean,
#   file_type: Symbol (:regular, :directory, :symlink, :other),
# }

def tick args
  if args.inputs.mouse.click
    args.gtk.write_file "last-mouse-click.txt", "Mouse was clicked at #{args.state.tick_count}."
  end

  file_info = args.gtk.stat_file "last-mouse-click.txt"

  if file_info
    args.outputs.labels << {
      x: 30,
      y: 30.from_top,
      text: file_info.to_s,
      size_enum: -3
    }
  else
    args.outputs.labels << {
      x: 30,
      y: 30.from_top,
      text: "file does not exist, click to create file",
      size_enum: -3
    }
  end
end

    read_file link

    Given a file path, a string will be returned representing the contents of the file. nil will be returned if the file does not exist. You can use stat_file to get additional information of a file.

    write_file link

    This function takes in two parameters. The first parameter is the file path and assumes the the game directory is the root. The second parameter is the string that will be written. The method **overwrites** whatever is currently in the file. Use append_file to append to the file as opposed to overwriting. 

    def tick args
  if args.inputs.mouse.click
    args.gtk.write_file "last-mouse-click.txt", "Mouse was clicked at #{args.state.tick_count}."
  end
end

    append_file link

    This function takes in two parameters. The first parameter is the file path and assumes the the game directory is the root. The second parameter is the string that will be written. The method appends to whatever is currently in the file (a new file is created if one does not alread exist). Use write_file to overwrite the file's contents as opposed to appending. 

    def tick args
  if args.inputs.mouse.click
    args.gtk.write_file "last-mouse-click.txt", "Mouse was clicked at #{args.state.tick_count}."
  end
end

    delete_file link

    This function takes in a single parameters. The parameter is the file path that should be deleted. This function will raise an exception if the path requesting to be deleted does not exist.

    Notes:

    Here is a list of reasons an exception could be raised:

    - If the path is not found. - If the path is still open (for reading or writing). - If the path is not a file or directory. - If the path is a circular symlink. - If you do not have permissions to delete the path. - If the directory attempting to be deleted is not empty. 

    def tick args
  if args.inputs.mouse.click
    args.gtk.write_file "last-mouse-click.txt", "Mouse was clicked at #{args.state.tick_count}."
  end
end

    delete_file_if_exist link

    Has the same behavior as delete_file except this function does not throw an exception.

    XML and JSON link

    The following functions help with parsing xml and json.

    parse_json link

    Given a json string, this function returns a hash representing the json data. 

    hash = args.gtk.parse_json '{ "name": "John Doe", "aliases": ["JD"] }'
# structure of hash: { "name"=>"John Doe", "aliases"=>["JD"] }

    parse_json_file link

    Same behavior as parse_json_file except a file path is read for the json string.

    parse_xml link

    Given xml data as a string, this function will return a hash that represents the xml data in the following recursive structure: 

    
type: :element,
name: "Person",
children: [...]

    parse_xml_file link

    Function has the same behavior as parse_xml except that the parameter must be a file path that contains xml contents.

    Network IO Functions link

    The following functions help with interacting with the network.

    http_get link

    Returns an object that represents an http response which will eventually have a value. This http_get method is invoked asynchronously. Check for completion before attempting to read results. 

    def tick args
  # perform an http get and print the response when available
  args.state.result ||= args.gtk.http_get "https://httpbin.org/html"

  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

    http_post link

    Returns an object that represents an http response which will eventually have a value. This http_post method is invoked asynchronously. Check for completion before attempting to read results. 

    def tick args
  # perform an http get and print the response when available

  args.state.form_fields ||= { "userId" => "1701999309" }
  args.state.result ||= args.gtk.http_post "http://httpbin.org/post",
                                           args.state.form_fields,
                                           ["Content-Type: application/x-www-form-urlencoded"]


  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

    http_post_body link

    Returns an object that represents an http response which will eventually have a value. This http_post_body method is invoked asynchronously. Check for completion before attempting to read results. 

    def tick args
  # perform an http get and print the response when available

  args.state.json ||= "{ "userId": "#{Time.now.to_i}"}"
  args.state.result ||= args.gtk.http_post_body "http://httpbin.org/post",
                                                args.state.json,
                                                ["Content-Type: application/json", "Content-Length: #{args.state.json.length}"]


  if args.state.result && args.state.result[:complete] && !args.state.printed
    if args.state.result[:http_response_code] == 200
      puts "The response was successful. The body is:"
      puts args.state.result[:response_data]
    else
      puts "The response failed. Status code:"
      puts args.state.result[:http_response_code]
    end
    # set a flag denoting that the response has been printed
    args.state.printed = true

    # show the console
    args.gtk.show_console
  end
end

    start_server! link

    Starts a in-game http server that can be process http requests. When your game is running in development mode. A dev server is started at http://localhost:9001

    You can start an in-game http server in production via: 

    def tick args
  # server explicitly enabled in production
  args.gtk.start_server! port: 9001, enable_in_prod: true
end

    Here's how you would responde to http requests: 

    def tick args
  # server explicitly enabled in production
  args.gtk.start_server! port: 9001, enable_in_prod: true

  # loop through pending requests and respond to them
  args.inputs.http_requests.each do |request|
    puts "#{request}"
    request.respond 200, "ok"
  end
end

    Developer Support Functions link

    The following functions help support the development process. It is not recommended to use this functions in "production" game logic.

    version link

    Returns a string representing the version of DragonRuby you are running.

    version_pro? link

    Returns true if the version of DragonRuby is NOT Standard Edition.

    reset link

    Resets DragonRuby's internal state as if it were just started. args.state.tick_count is set to 0 and args.state is cleared of any values. This function is helpful when you are developing your game and want to reset everything as if the game just booted up. 

    def tick args
end

# reset the game if this file is hotloaded/required
# (removes the need to press "r" when I file is updated)
$gtk.reset

    Resetting iVars (advanced)

    NOTE: args.gtk.reset does not reset global variables or instance of classes you have have constructed. If you want to also reset global variables or instances of classes when $gtk.reset is called. Define a reset method. Here's an example: 

    class Game
  def initialize
    puts "Game initialize called"
  end
end

def tick args
  $game ||= Game.new

  if args.state.tick_count == 0
    puts "tick_count is 0"
  end

  # if r is pressed on the keyboard, reset the game
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
  end
end

# custom reset function
def reset
  puts "Custom reset function was called."
  $game = nil
end

    seed and RNG (advanced)

    Optionally, $gtk.reset (args.gtk.reset) can take in a named parameter for RNG called seed:. Passing in seed: will reset RNG so that rand returns a repeatable set of random numbers. This seed value is initialized with the start time of your game ($gtk.started_at). Having this option is is helpful for replays and unit tests.

    Don't worry about this capability if you aren't using DragonRuby's unit testing, or replay capabilities.

    Here is the behavior of $gtk.reset when given a seed: 

    def tick args
  if args.state.tick_count == 0
    puts rand
    puts rand
    puts rand
    puts rand
  end
end

puts "Started at (RNG seed inital value)"
puts $gtk.started_at # Time as an integer that your game was started at

puts "Seed value that will be used on reset"
puts $gtk.seed # current value that RNG was seeded with

# reset the game and use the last seed to reset RNG
$gtk.reset

# === OR ===
# sets the seed value to predefined value
# subsequent resets will use the new predefined value
# $gtk.reset seed: 100
# (or shorthand)
# $gtk.reset 100

# sets the seed back to its original value
# $gtk.reset seed: $gtk.started_at

    If you want to set RNG without resetting your game state, you can use $gtk.set_rng VALUE.

    reset_next_tick link

    Has the same behavior as reset except the reset occurs before tick is executed again. reset resets the environment immediately (while the tick method is inflight). It's recommended that reset should be called outside of the tick method (invoked when a file is saved/hotloaded), and reset_next_tick be used inside of the tick method so you don't accidentally blow away state the your game depends on to complete the current tick without exceptions. 

    def tick args
  # reset the game if "r" is pressed on the keyboard
  if args.inputs.keyboard.key_down.r
    args.gtk.reset_next_tick # use reset_next_tick instead of reset
  end
end

# reset the game if this file is hotloaded/required
# (removes the need to press "r" when I file is updated)
$gtk.reset

    reset_sprite link

    Sprites when loaded are cached. Given a string parameter, this method invalidates the cache record of a sprite so that updates on from the disk can be loaded.

    reset_sprites link

    Sprites when loaded are cached. This method invalidates the cache record of all sprites so that updates on from the disk can be loaded. This function is automatically called when args.gtk.reset ($gtk.reset) is invoked.

    calcspritebox link

    Given a path to a sprite, this method returns the width and height of a sprite as a tuple.

    NOTE: This method should be used for development purposes only and is expensive to call every frame. Do not use this method to set the size of sprite when rendering (hard code those values since you know what they are beforehand).

    current_framerate link

    Returns a float value representing the framerate of your game. This is an approximation/moving average of your framerate and should eventually settle to 60fps. 

    def tick args
  # render a label to the screen that shows the current framerate
  # formatted as a floating point number with two decimal places
  args.outputs.labels << { x: 30, y: 30.from_top, text: "#{args.gtk.current_framerate.to_sf}" }
end

    framerate_diagnostics_primitives link

    Returns a set of primitives that can be rendered to the screen which provide more detailed information about the speed of your simulation (framerate, draw call count, mouse position, etc). 

    def tick args
  args.outputs.primitives << args.gtk.framerate_diagnostics_primitives
end

    warn_array_primitives! link

    This function helps you audit your game of usages of array-based primitives. While array-based primitives are simple to create and use, they are slower to process than Hash or Class based primitives. 

    def tick args
  # enable array based primitives warnings
  args.gtk.warn_array_primitives!

  # array-based primitive elsewhere in code
  # an log message will be posted giving the location of the array
  # based primitive usage
  args.outputs.sprites << [100, 100, 200, 200, "sprites/square/blue.png"]

  # instead of using array based primitives, migrate to hashes as needed
  args.outputs.sprites << {
    x: 100,
    y: 100,
    w: 200,
    h: 200, path:
    "sprites/square/blue.png"
  }
end

    benchmark link

    You can use this function to compare the relative performance of blocks of code. 

    def tick args
  # press r to run benchmark
  if args.inputs.keyboard.key_down.r
    args.gtk.console.show
    args.gtk.benchmark iterations: 1000, # number of iterations
                       # label for experiment
                       using_numeric_map: -> () {
                         # experiment body
                         v = 100.map_with_index do |i|
                           i * 100
                         end
                       },
                       # label for experiment
                       using_numeric_times: -> () {
                         # experiment body
                         v = []
                         100.times do |i|
                           v << i * 100
                         end
                       }
  end
end

    notify! link

    Given a string, this function will present a message at the bottom of your game. This method is only invoked in dev mode and is useful for debugging.

    An optional parameter of duration (number value representing ticks) can also be passed in. The default value if 300 ticks (5 seconds). 

    def tick args
  if args.inputs.mouse.click
    args.gtk.notify! "Mouse was clicked!"
  end

  if args.inputs.keyboard.key_down.r
    # optional duration parameter
    args.gtk.notify! "R key was pressed!", 600 # present message for 10 seconds/600 frames
  end
end

    notify_extended! link

    Has similar behavior as notify! except you have additional options to show messages in a production environment. 

    def tick args
  if args.inputs.mouse.click
    args.gtk.notify_extended! message: "message",
                              duration: 300,
                              env: :prod
  end
end

    slowmo! link

    Given a numeric value representing the factor of 60fps. This function will bring your simulation loop down to slower rate. This method is intended to be used for debugging purposes. 

    def tick args
  # set your simulation speed to (15 fps): args.gtk.slowmo! 4
  # set your simulation speed to (1 fps): args.gtk.slowmo! 60
  # set your simulation speed to (30 fps):
  args.gtk.slowmo! 2
end

    Remove this line from your tick method will automatically set your simulation speed back to 60 fps.

    show_console link

    Shows the DragonRuby console. Useful when debugging/customizing an in-game dev workflow.

    hide_console link

    Shows the DragonRuby console. Useful when debugging/customizing an in-game dev workflow.

    enable_console link

    Enables the DragonRuby Console so that it can be presented by pressing the tilde key (the key next to the number 1 key).

    disable_console link

    Disables the DragonRuby Console so that it won't show up even if you press the tilde key or call args.gtk.show_console.

    start_recording link

    Resets the game to tick 0 and starts recording gameplay. Useful for visual regression tests/verification.

    stop_recording link

    Function takes in a destination file for the currently recording gameplay. This file can be used to replay a recording.

    cancel_recording link

    Function cancels a gameplay recording session and discards the replay.

    start_replay link

    Given a file that represents a recording, this method will run the recording against the current codebase.

    You can start a replay from the command line also: 

    # first argument: the game directory
# --replay switch is the file path relative to the game directory
# --speed switch is optional. a value of 4 will run the replay and game at 4x speed
# cli command example is in the context of Linux and Mac, for Windows the binary would be ./dragonruby.exe
./dragonruby ./mygame --replay ./replay.txt --speed 4

    stop_replay link

    Function stops a replay that is currently executing.

    get_base_dir link

    Returns the path to the location of the dragonruby binary. In production mode, this value will be the same as the value returned by get_game_dir. Function should only be used for debugging/development workflows.

    get_game_dir link

    Returns the location within sandbox storage that the game is running. When developing your game, this value will be your mygame directory. In production, it'll return a value that is OS specific (eg the Roaming directory on Windows or the Application Support directory on Mac).

    Invocations of ~(write|append)_file will write to this sandboxed directory.

    get_game_dir_url link

    Returns a url encoded string representing the sandbox location for game data.

    open_game_dir link

    Opens the game directory in the OS's file explorer. This should be used for debugging purposes only.

    write_file_root link

    Given a file path and contents, the contents will be written to a directory outside of the game directory. This method should be used for development purposes only. In production this method will write to the same sandboxed location as write_file.

    append_file_root link

    Has the same behavior as write_file_root except that it appends the contents as opposed to overwriting them.

    argv link

    Returns a string representing the command line arguments passed to the DragonRuby binary. This should be used for development/debugging purposes only.

    cli_arguments link

    Returns a Hash for command line arguments in the format of --switch value (two hyphens preceding the switch flag with the value seperated by a space). This should be used for development/debugging purposes only.

    download_stb_rb(_raw) link

    These two functions can help facilitate the integration of external code files. OSS contributors are encouraged to create libraries that all fit in one file (lowering the barrier to entry for adoption).

    Examples: 

    def tick args
end

# option 1:
# source code will be downloaded from the specified GitHub url, and saved locally with a
# predefined folder convension.
$gtk.download_stb_rb "https://github.com/xenobrain/ruby_vectormath/blob/main/vectormath_2d.rb"

# option 2:
# source code will be downloaded from the specified GitHub username, repository, and file.
# code will be saved locally with a predefined folder convension.
$gtk.download_stb_rb "xenobrain", "ruby_vectormath", "vectormath_2d.rb"

# option 3:
# source code will be downloaded from a direct/raw url and saved to a direct/raw local path.
$gtk.download_stb_rb_raw "https://raw.githubusercontent.com/xenobrain/ruby_vectormath/main/vectormath_2d.rb",
                         "lib/xenobrain/ruby_vectionmath/vectormath_2d.rb"

    reload_history link

    Returns a Hash representing the code files that have be loaded for your game along with timings for the events. This should be used for development/debugging purposes only.

    reload_history_pending link

    Returns a Hash for files that have been queued for reload, but haven't been processed yet. This should be used for development/debugging purposes only.

    reload_if_needed link

    Given a file name, this function will queue the file for reload if it's been modified. An optional second parameter can be passed in to signify if the file should be forced loaded regardless of modified time (true means to force load, false means to load only if the file has been modified). This function should be used for development/debugging purposes only.

    State (args.state) link

    Store your game state inside of this state. Properties with arbitrary nesting is allowed and a backing Entity will be created on your behalf. 

    def tick args
  args.state.player.x ||= 0
  args.state.player.y ||= 0
end

    entity_id link

    Entities automatically receive an entity_id of type Fixnum.

    entity_type link

    Entities can have an entity_type which is represented as a Symbol.

    created_at link

    Entities have created_at set to args.state.tick_count when they are created.

    created_at_elapsed link

    Returns the elapsed number of ticks since creation.

    global_created_at link

    Entities have global_created_at set to Kernel.global_tick_count when they are created.

    global_created_at_elapsed link

    Returns the elapsed number of global ticks since creation.

    as_hash link

    Entity cast to a Hash so you can update values as if you were updating a Hash.

    new_entity link

    Creates a new Entity with a type, and initial properties. An option block can be passed to change the newly created entity: 

    def tick args
  args.state.player ||= args.state.new_entity :player, x: 0, y: 0 do |e|
    e.max_hp = 100
    e.hp     = e.max_hp * rand
  end
end

    new_entity_strict link

    Creates a new Strict Entity. While Entities created via args.state.new_entity can have new properties added later on, Entities created using args.state.new_entity_strict must define all properties that are allowed during its initialization. Attempting to add new properties after initialization will result in an exception.

    args.state.tick_count link

    Returns the current tick of the game. args.state.tick_count is 0 when the game is first started or if the game is reset via $gtk.reset.

    Geometry (args.geometry) link

    The Geometry module contains methods for calculations that are frequently used in game development.

    The following functions of Geometry are mixed into Hash, Array, and DragonRuby's Entity class:

    You can invoke the functions above using either the mixin variant or the module variant. Example: 

    def tick args
  # define to rectangles
  rect_1 = { x: 0, y: 0, w: 100, h: 100 }
  rect_2 = { x: 50, y: 50, w: 100, h: 100 }

  # mixin variant
  # call geometry method function from instance of a Hash class
  puts rect_1.intersect_rect?(rect_2)

  # OR

  # module variants
  puts args.geometry.intersect_rect?(rect_1, rect_2)
  puts Geometry.intersect_rect?(rect_1, rect_2)
end

    intersect_rect? link

    Invocation variants:

    Given two rectangle primitives this function will return true or false depending on if the two rectangles intersect or not. An optional final parameter can be passed in representing the tolerence of overlap needed to be considered a true intersection. The default value of tolerance is 0.1 which keeps the function from returning true if only the edges of the rectangles overlap.

    :anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

    Here is an example where one rectangle is stationary, and another rectangle is controlled using directional input. The rectangles change color from blue to read if they intersect. 

    def tick args
  # define a rectangle in state and position it
  # at the center of the screen with a color of blue
  args.state.box_1 ||= {
    x: 640 - 20,
    y: 360 - 20,
    w: 40,
    h: 40,
    r: 0,
    g: 0,
    b: 255
  }

  # create another rectangle in state and position it
  # at the far left center
  args.state.box_2 ||= {
    x: 0,
    y: 360 - 20,
    w: 40,
    h: 40,
    r: 0,
    g: 0,
    b: 255
  }

  # take the directional input and use that to move the second rectangle around
  # increase or decrease the x value based on if left or right is held
  args.state.box_2.x += args.inputs.left_right * 5
  # increase or decrease the y value based on if up or down is held
  args.state.box_2.y += args.inputs.up_down * 5

  # change the colors of the rectangles based on whether they
  # intersect or not
  if args.state.box_1.intersect_rect? args.state.box_2
    args.state.box_1.r = 255
    args.state.box_1.g = 0
    args.state.box_1.b = 0

    args.state.box_2.r = 255
    args.state.box_2.g = 0
    args.state.box_2.b = 0
  else
    args.state.box_1.r = 0
    args.state.box_1.g = 0
    args.state.box_1.b = 255

    args.state.box_2.r = 0
    args.state.box_2.g = 0
    args.state.box_2.b = 255
  end

  # render the rectangles as border primitives on the screen
  args.outputs.borders << args.state.box_1
  args.outputs.borders << args.state.box_2
end

    inside_rect? link

    Invocation variants:

    Given two rectangle primitives this function will return true or false depending on if the first rectangle (or self) is inside of the second rectangle.

    Here is an example where one rectangle is stationary, and another rectangle is controlled using directional input. The rectangles change color from blue to read if the movable rectangle is entirely inside the stationary rectangle.

    :anchor_x, and anchor_y is taken into consideration if the objects respond to these methods. 

    def tick args
  # define a rectangle in state and position it
  # at the center of the screen with a color of blue
  args.state.box_1 ||= {
    x: 640 - 40,
    y: 360 - 40,
    w: 80,
    h: 80,
    r: 0,
    g: 0,
    b: 255
  }

  # create another rectangle in state and position it
  # at the far left center
  args.state.box_2 ||= {
    x: 0,
    y: 360 - 10,
    w: 20,
    h: 20,
    r: 0,
    g: 0,
    b: 255
  }

  # take the directional input and use that to move the second rectangle around
  # increase or decrease the x value based on if left or right is held
  args.state.box_2.x += args.inputs.left_right * 5
  # increase or decrease the y value based on if up or down is held
  args.state.box_2.y += args.inputs.up_down * 5

  # change the colors of the rectangles based on whether they
  # intersect or not
  if args.state.box_2.inside_rect? args.state.box_1
    args.state.box_1.r = 255
    args.state.box_1.g = 0
    args.state.box_1.b = 0

    args.state.box_2.r = 255
    args.state.box_2.g = 0
    args.state.box_2.b = 0
  else
    args.state.box_1.r = 0
    args.state.box_1.g = 0
    args.state.box_1.b = 255

    args.state.box_2.r = 0
    args.state.box_2.g = 0
    args.state.box_2.b = 255
  end

  # render the rectangles as border primitives on the screen
  args.outputs.borders << args.state.box_1
  args.outputs.borders << args.state.box_2
end

    scale_rect link

    Given a Rectangle this function returns a new rectangle with a scaled size. 

    def tick args
  # a rect at the center of the screen
  args.state.rect_1 ||= { x: 640 - 20, y: 360 - 20, w: 40, h: 40 }

  # render the rect
  args.outputs.borders << args.state.rect_1

  # the rect half the size with the x and y position unchanged
  args.outputs.borders << args.state.rect_1.scale_rect(0.5)

  # the rect double the size, repositioned in the center given anchor optional arguments
  args.outputs.borders << args.state.rect_1.scale_rect(2, 0.5, 0.5)
end

    scale_rect_extended link

    The behavior is similar to scale_rect except that you can independently control the scale of each axis. The parameters are all named: 

    def tick args
  baseline_rect = { x: 640 - 20, y: 360 - 20, w: 40, h: 40 }
  args.state.rect_1 ||= baseline_rect
  args.state.rect_2 ||= baseline_rect.scale_rect_extended(percentage_x: 2,
                                                          percentage_y: 0.5,
                                                          anchor_x: 0.5,
                                                          anchor_y: 1.0)
  args.outputs.borders << args.state.rect_1
  args.outputs.borders << args.state.rect_2
end

    anchor_rect link

    Returns a new rect that is anchored by an anchor_x and anchor_y value. The width and height of the rectangle is taken into consideration when determining the anchor position: 

    def tick args
  args.state.rect ||= {
    x: 640,
    y: 360,
    w: 100,
    h: 100
  }

  # rect's center: 640 + 50, 360 + 50
  args.outputs.borders << args.state.rect.anchor_rect(0, 0)

  # rect's center: 640, 360
  args.outputs.borders << args.state.rect.anchor_rect(0.5, 0.5)

  # rect's center: 640, 360
  args.outputs.borders << args.state.rect.anchor_rect(0.5, 0)
end

    angle_from link

    Invocation variants:

    Returns an angle in degrees from the end_point to the start_point (if you want the value in radians, you can call .to_radians on the value returned): 

    def tick args
  rect_1 ||= {
    x: 0,
    y: 0,
  }

  rect_2 ||= {
    x: 100,
    y: 100,
  }

  angle = rect_1.angle_from rect_2 # returns 225 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 30.from_top, text: "#{angle}, #{angle_radians}" }

  angle = args.geometry.angle_from rect_1, rect_2 # returns 225 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 60.from_top, text: "#{angle}, #{angle_radians}" }
end

    angle_to link

    Invocation variants:

    Returns an angle in degrees to the end_point from the start_point (if you want the value in radians, you can call .to_radians on the value returned): 

    def tick args
  rect_1 ||= {
    x: 0,
    y: 0,
  }

  rect_2 ||= {
    x: 100,
    y: 100,
  }

  angle = rect_1.angle_to rect_2 # returns 45 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 30.from_top, text: "#{angle}, #{angle_radians}" }

  angle = args.geometry.angle_to rect_1, rect_2 # returns 45 degrees
  angle_radians = angle.to_radians
  args.outputs.labels << { x: 30, y: 60.from_top, text: "#{angle}, #{angle_radians}" }
end

    distance link

    Returns the distance between two points; 

    def tick args
  rect_1 ||= {
    x: 0,
    y: 0,
  }

  rect_2 ||= {
    x: 100,
    y: 100,
  }

  distance = args.geometry.distance rect_1, rect_2
  args.outputs.labels << {
    x: 30,
    y: 30.from_top,
    text: "#{distance}"
  }

  args.outputs.lines << {
    x: rect_1.x,
    y: rect_1.y,
    x2: rect_2.x,
    y2: rect_2.y
  }
end

    point_inside_circle? link

    Invocation variants:

    Returns true if a point is inside of a circle defined as a center point and radius. 

    def tick args
  # define circle center
  args.state.circle_center ||= {
    x: 640,
    y: 360
  }

  # define circle radius
  args.state.circle_radius ||= 100

  # define point
  args.state.point_1 ||= {
    x: 100,
    y: 100
  }

  # allow point to be moved using keyboard
  args.state.point_1.x += args.inputs.left_right * 5
  args.state.point_1.y += args.inputs.up_down * 5

  # determine if point is inside of circle
  intersection = args.geometry.point_inside_circle? args.state.point_1,
                                                    args.state.circle_center,
                                                    args.state.circle_radius

  # render point as a square
  args.outputs.sprites << {
    x: args.state.point_1.x - 20,
    y: args.state.point_1.y - 20,
    w: 40,
    h: 40,
    path: "sprites/square/blue.png"
  }

  # if there is an intersection, render a red circle
  # otherwise render a blue circle
  if intersection
    args.outputs.sprites << {
      x: args.state.circle_center.x - args.state.circle_radius,
      y: args.state.circle_center.y - args.state.circle_radius,
      w: args.state.circle_radius * 2,
      h: args.state.circle_radius * 2,
      path: "sprites/circle/red.png",
      a: 128
    }
  else
    args.outputs.sprites << {
      x: args.state.circle_center.x - args.state.circle_radius,
      y: args.state.circle_center.y - args.state.circle_radius,
      w: args.state.circle_radius * 2,
      h: args.state.circle_radius * 2,
      path: "sprites/circle/blue.png",
      a: 128
    }
  end
end

    center_inside_rect link

    Invocation variants:

    Given a target rect and a reference rect, the target rect is centered inside the reference rect (a new rect is returned). 

    def tick args
  rect_1 = {
    x: 0,
    y: 0,
    w: 100,
    h: 100
  }

  rect_2 = {
    x: 640 - 100,
    y: 360 - 100,
    w: 200,
    h: 200
  }

  centered_rect = args.geometry.center_inside_rect rect_1, rect_2
  # OR
  # centered_rect = rect_1.center_inside_rect rect_2

  args.outputs.solids << rect_1.merge(r: 255)
  args.outputs.solids << rect_2.merge(b: 255)
  args.outputs.solids << centered_rect.merge(g: 255)
end

    ray_test link

    Given a point and a line, ray_test returns one of the following symbols based on the location of the point relative to the line: :left, :right, :on 

    def tick args
  # create a point based off of the mouse location
  point = {
    x: args.inputs.mouse.x,
    y: args.inputs.mouse.y
  }

  # draw a line from the bottom left to the top right
  line = {
    x: 0,
    y: 0,
    x2: 1280,
    y2: 720
  }

  # perform ray_test on point and line
  ray = args.geometry.ray_test point, line

  # output the results of ray test at mouse location
  args.outputs.labels << {
    x: point.x,
    y: point.y + 25,
    text: "#{ray}",
    alignment_enum: 1,
    vertical_alignment_enum: 1,
  }

  # render line
  args.outputs.lines << line

  # render point
  args.outputs.solids << {
    x: point.x - 5,
    y: point.y - 5,
    w: 10,
    h: 10
  }
end

    line_rise_run link

    Given a line, this function returns a Hash with x and y keys representing a normalized representation of the rise and run of the line. 

    def tick args
  # draw a line from the bottom left to the top right
  line = {
    x: 0,
    y: 0,
    x2: 1280,
    y2: 720
  }

  # get rise and run of line
  rise_run = args.geometry.line_rise_run line

  # output the rise and run of line
  args.outputs.labels << {
    x: 640,
    y: 360,
    text: "#{rise_run}",
    alignment_enum: 1,
    vertical_alignment_enum: 1,
  }

  # render the line
  args.outputs.lines << line
end

    rotate_point link

    Given a point and an angle in degrees, a new point is returned that is rotated around the origin by the degrees amount. An optional third argument can be provided to rotate the angle around a point other than the origin. 

    def tick args
  args.state.rotate_amount ||= 0
  args.state.rotate_amount  += 1

  if args.state.rotate_amount >= 360
    args.state.rotate_amount = 0
  end

  point_1 = {
    x: 100,
    y: 100
  }

  # rotate point around 0, 0
  rotated_point_1 = args.geometry.rotate_point point_1,
                                               args.state.rotate_amount

  args.outputs.solids << {
    x: rotated_point_1.x - 5,
    y: rotated_point_1.y - 5,
    w: 10,
    h: 10
  }

  point_2 = {
    x: 640 + 100,
    y: 360 + 100
  }

  # rotate point around center screen
  rotated_point_2 = args.geometry.rotate_point point_2,
                                               args.state.rotate_amount,
                                               x: 640, y: 360

  args.outputs.solids << {
    x: rotated_point_2.x - 5,
    y: rotated_point_2.y - 5,
    w: 10,
    h: 10
  }
end

    find_intersect_rect link

    Given a rect and a collection of rects, find_intersect_rect returns the first rect that intersects with the the first parameter.

    :anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

    If you find yourself doing this: 

    collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

    Consider using find_intersect_rect instead (it's more descriptive and faster): 

    collision = args.geometry.find_intersect_rect args.state.player, args.state.terrain

    find_all_intersect_rect link

    Given a rect and a collection of rects, find_all_intersect_rect returns all rects that intersects with the the first parameter.

    :anchor_x, and anchor_y is taken into consideration if the objects respond to these methods.

    If you find yourself doing this: 

    collisions = args.state.terrain.find_all { |t| t.intersect_rect? args.state.player }

    Consider using find_all_intersect_rect instead (it's more descriptive and faster): 

    collisions = args.geometry.find_all_intersect_rect args.state.player, args.state.terrain

    find_intersect_rect_quad_tree link

    This is a faster collision algorithm for determining if a rectangle intersects any rectangle in an array. In order to use find_intersect_rect_quad_tree, you must first generate a quad tree data structure using create_quad_tree. Use this function if find_intersect_rect isn't fast enough. 

    def tick args
  # create a player
  args.state.player ||= {
    x: 640 - 10,
    y: 360 - 10,
    w: 20,
    h: 20
  }

  # allow control of player movement using arrow keys
  args.state.player.x += args.inputs.left_right * 5
  args.state.player.y += args.inputs.up_down * 5

  # generate 40 random rectangles
  args.state.boxes ||= 40.map do
    {
      x: 1180 * rand + 50,
      y: 620 * rand + 50,
      w: 100,
      h: 100
    }
  end

  # generate a quad tree based off of rectangles.
  # the quad tree should only be generated once for
  # a given array of rectangles. if the rectangles
  # change, then the quad tree must be regenerated
  args.state.quad_tree ||= args.geometry.quad_tree_create args.state.boxes

  # use quad tree and find_intersect_rect_quad_tree to determine collision with player
  collision = args.geometry.find_intersect_rect_quad_tree args.state.player,
                                                          args.state.quad_tree

  # if there is a collision render a red box
  if collision
    args.outputs.solids << collision.merge(r: 255)
  end

  # render player as green
  args.outputs.solids << args.state.player.merge(g: 255)

  # render boxes as borders
  args.outputs.borders << args.state.boxes
end

    find_all_intersect_rect_quad_tree link

    This is a faster collision algorithm for determining if a rectangle intersects other rectangles in an array. In order to use find_all_intersect_rect_quad_tree, you must first generate a quad tree data structure using create_quad_tree. Use this function if find_all_intersect_rect isn't fast enough. 

    def tick args
  # create a player
  args.state.player ||= {
    x: 640 - 10,
    y: 360 - 10,
    w: 20,
    h: 20
  }

  # allow control of player movement using arrow keys
  args.state.player.x += args.inputs.left_right * 5
  args.state.player.y += args.inputs.up_down * 5

  # generate 40 random rectangles
  args.state.boxes ||= 40.map do
    {
      x: 1180 * rand + 50,
      y: 620 * rand + 50,
      w: 100,
      h: 100
    }
  end

  # generate a quad tree based off of rectangles.
  # the quad tree should only be generated once for
  # a given array of rectangles. if the rectangles
  # change, then the quad tree must be regenerated
  args.state.quad_tree ||= args.geometry.quad_tree_create args.state.boxes

  # use quad tree and find_intersect_rect_quad_tree to determine collision with player
  collisions = args.geometry.find_all_intersect_rect_quad_tree args.state.player,
                                                              args.state.quad_tree

  # if there is a collision render a red box
  args.outputs.solids << collisions.map { |c| c.merge(r: 255) }

  # render player as green
  args.outputs.solids << args.state.player.merge(g: 255)

  # render boxes as borders
  args.outputs.borders << args.state.boxes
end

    create_quad_tree link

    Generates a quad tree from an array of rectangles. See find_intersect_rect_quad_tree for usage.

    Audio (args.audio) link

    Hash that contains audio sources that are playing.

    Sounds that don't specify looping: true will be removed automatically from the hash after the playback ends. Looping sounds or sounds that should stop early must be removed manually.

    When you assign a hash to an audio output, a :length key will be added to the hash on the following tick. This will tell you the duration of the audio file in seconds (float).

    volume link

    You can globally control the volume for all audio using args.audio.volume. Example: 

    def tick args
  if args.inputs.down
    args.audio.volume -= 0.01
  elsif args.inputs.up
    args.audio.volume += 0.01
  end
end

    One-Time Sounds link

    Here's how to play audio one-time (does not loop). 

    def tick args
  # play a one-time non-looping sound every second
  if (args.state.tick_count % 60) == 0
    args.audio[:coin] = { input: "sounds/coin.wav" }
    # OR
    args.outputs.sounds << "sounds/coin.wav"
  end
end

    Looping Audio link

    Here's how to play audio that loops (eg background music), and how to stop the sound. 

    def tick args
  if args.state.tick_count == 0
    args.audio[:bg_music] = { input: "sounds/bg-music.ogg", looping: true }
  end

  # stop sound if space key is pressed
  if args.inputs.keyboard.key_down.space
    args.audio[:bg_music] = nil
    # OR
    args.audio.delete :bg_music
  end
end

    Setting Additional Audio Properties link

    Here are additional properties that can be set. 

    def tick args
  # The values below (except for input of course) are the default values that apply if you don't
  # specify the value in the hash.
  args.audio[:my_audio] ||= {
    input: 'sound/boom.wav',  # file path relative to mygame directory
    gain:    1.0,             # Volume (float value 0.0 to 1.0)
    pitch:   1.0,             # Pitch of the sound (1.0 = original pitch)
    paused:  false,           # Set to true to pause the sound at the current playback position
    looping: true,            # Set to true to loop the sound/music until you stop it
    foobar:  :baz,            # additional keys/values can be safely added to help with context/game logic (ie metadata)
    x: 0.0, y: 0.0, z: 0.0    # Relative position to the listener, x, y, z from -1.0 to 1.0
  }
end

    IMPORTANT: Please take note that gain and pitch must be given float values (eg gain: 1.0, not gain: 1 or game: 0).

    Advanced Audio Manipulation (Crossfade) link

    Take a look at the Audio Mixer sample app for a non-trival example of how to use these properties. The sample app is located within the DragonRuby zip file at ./samples/07_advanced_audio/01_audio_mixer.

    Here's an example of crossfading two bg music tracks. 

    def tick args
  # start bg-1.ogg at the start
  if args.state.tick_count == 0
    args.audio[:bg_music] = { input: "sounds/bg-1.ogg", looping: true, gain: 0.0 }
  end

  # if space is pressed cross fade to new bg music
  if args.inputs.keyboard.key_down.space
    # get the current bg music and create a new audio entry that represents the crossfade
    current_bg_music = args.audio[:bg_music]

    # cross fade audio entry
    args.audio[:bg_music_fade] = {
      input:    current_bg_music[:input],
      looping:  true,
      gain:     current_bg_music[:gain],
      pitch:    current_bg_music[:pitch],
      paused:   false,
      playtime: current_bg_music[:playtime]
    }

    # replace the current playing background music (toggling between bg-1.ogg and bg-2.ogg)
    # set the gain/volume to 0.0 (this will be increased to 1.0 accross ticks)
    new_background_music = { looping: true, gain: 0.0 }

    # determine track to play (swap between bg-1 and bg-2)
    new_background_music[:input] = if current_bg_music.input == "sounds/bg-1.ogg"
                                     "sounds/bg-2.ogg"
                                   else
                                     "sounds/bg-2.ogg"
                                   end

    # bg music audio entry
    args.audio[:bg_music] = new_background_music
  end

  # process cross fade (happens every tick)
  # increase the volume of bg_music every tick until it's at 100%
  if args.audio[:bg_music] && args.audio[:bg_music].gain < 1.0
    # increase the gain 1% every tick until we are at 100%
    args.audio[:bg_music].gain += 0.01
    # clamp value to 1.0 max value
    args.audio[:bg_music].gain = 1.0 if args.audio[:bg_music].gain > 1.0
  end

  # decrease the volume of cross fade bg music until it's 0.0, then delete it
  if args.audio[:bg_music_fade] && args.audio[:bg_music_fade].gain > 0.0
    # decrease by 1% every frame
    args.audio[:bg_music_fade].gain -= 0.01
    # delete audio when it's at 0%
    if args.audio[:bg_music_fade].gain <= 0.0
      args.audio[:bg_music_fade] = nil
    end
  end
end

    Audio encoding trouble shooting link

    If audio doesn't seem to be working, try re-encoding it via ffmpeg: 

    # re-encode ogg
ffmpeg -i ./mygame/sounds/SOUND.ogg -ac 2 -b:a 160k -ar 44100 -acodec libvorbis ./mygame/sounds/SOUND-converted.ogg

# convert wav to ogg
ffmpeg -i ./mygame/sounds/SOUND.wav -ac 2 -b:a 160k -ar 44100 -acodec libvorbis ./mygame/sounds/SOUND-converted.ogg

    Audio synthesis link

    Instead of a path to an audio file you can specify an array [channels, sample_rate, sound_source] for input to procedurally generate sound. You do this by providing an array of float values between -1.0 and 1.0 that describe the waveform you want to play.

    Sound source link

    A sound source can be one of two things:

    When you specify 2 for channels, then the generated sample array will be played back in an interleaved manner. The first element is the first sample for the left channel, the second element is the first sample for the right channel, the third element is the second sample for the left channel etc.

    Example: link

    def tick args
  sample_rate = 48000

  generate_sine_wave = lambda do
    frequency = 440.0 # A5
    samples_per_period = (sample_rate / frequency).ceil
    one_period = samples_per_period.map_with_index { |i|
      Math.sin((2 * Math::PI) * (i / samples_per_period))
    }
    one_period * frequency # Generate 1 second worth of sound
  end

  args.audio[:my_audio] ||= {
    input: [1, sample_rate, generate_sine_wave]
  }
end

    Easing (args.easing) link

    A set of functions that allow you to determine the current progression of an easing function.

    ease link

    This function will give you a float value between 0 and 1 that represents a percentage. You need to give the funcation a start_tick, current_tick, duration, and easing definitions.

    This YouTube video is a fantastic introduction to easing functions: https://www.youtube.com/watch?v=mr5xkf6zSzk

    Examples link

    This example shows how to fade in a label at frame 60 over two seconds (120 ticks). The :identity definition implies a linear fade: f(x) -> x. 

    def tick args
  fade_in_at   = 60
  current_tick = args.state.tick_count
  duration     = 120
  percentage   = args.easing.ease fade_in_at,
                                  current_tick,
                                  duration,
                                  :identity
  alpha = 255 * percentage
  args.outputs.labels << { x: 640,
                           y: 320, text: "#{percentage.to_sf}",
                           alignment_enum: 1,
                           a: alpha }
end

    This example will move a box at a linear speed from 0 to 1280. 

    def tick args
  start_time = 10
  duration = 60
  current_progress = args.easing.ease start_time,
                                      args.state.tick_count,
                                      duration,
                                      :identity
  args.outputs.solids << { x: 1280 * current_progress, y: 360, w: 10, h: 10 }
end

    Easing Definitions link

    There are a number of easing definitions availble to you:

    :identity

    The easing definition for :identity is f(x) = x. For example, if start_tick is 0, current_tick is 50, and duration is 100, then args.easing.ease 0, 50, 100, :identity will return 0.5 (since tick 50 is half way between 0 and 100).

    :flip

    The easing definition for :flip is f(x) = 1 - x. For example, if start_tick is 0, current_tick is 10, and duration is 100, then args.easing.ease 0, 10, 100, :flip will return 0.9 (since tick 10 means 100% - 10%).

    :quad, :cube, :quart, :quint

    These are the power easing definitions. :quad is f(x) = x * x (x squared), :cube is f(x) = x * x * x (x cubed), etc.

    The power easing definitions represent Smooth Start easing (the percentage changes slow at first and speeds up at the end).

    Example

    Here is an example of Smooth Start (the percentage changes slow at first and speeds up at the end). 

    def tick args
  start_tick   = 60
  current_tick = args.state.tick_count
  duration     = 120
  percentage   = args.easing.ease start_tick,
                                  current_tick,
                                  duration,
                                  :quad
  start_x      = 100
  end_x        = 1180
  distance_x   = end_x - start_x
  final_x      = start_x + (distance_x * percentage)

  start_y      = 100
  end_y        = 620
  distance_y   = end_y - start_y
  final_y      = start_y + (distance_y * percentage)

  args.outputs.labels << { x: final_x,
                           y: final_y,
                           text: "#{percentage.to_sf}",
                           alignment_enum: 1 }
end

    Combining Easing Definitions

    The base easing definitions can be combined to create common easing functions.

    Example

    Here is an example of Smooth Stop (the percentage changes fast at first and slows down at the end). 

    def tick args
  start_tick   = 60
  current_tick = args.state.tick_count
  duration     = 120

  # :flip, :quad, :flip is Smooth Stop
  percentage   = args.easing.ease start_tick,
                                  current_tick,
                                  duration,
                                  :flip, :quad, :flip
  start_x      = 100
  end_x        = 1180
  distance_x   = end_x - start_x
  final_x      = start_x + (distance_x * percentage)

  start_y      = 100
  end_y        = 620
  distance_y   = end_y - start_y
  final_y      = start_y + (distance_y * percentage)

  args.outputs.labels << { x: final_x,
                           y: final_y,
                           text: "#{percentage.to_sf}",
                           alignment_enum: 1 }
end

    Custom Easing Functions

    You can define your own easing functions by passing in a lambda as a definition or extending the Easing module.

    Example - Using Lambdas

    This easing function goes from 0 to 1 for the first half of the ease, then 1 to 0 for the second half of the ease. 

    def tick args
  fade_in_at    = 60
  current_tick  = args.state.tick_count
  duration      = 600
  easing_lambda = lambda do |percentage, start_tick, duration|
                    fx = percentage
                    if fx < 0.5
                      fx = percentage * 2
                    else
                      fx = 1 - (percentage - 0.5) * 2
                    end
                    fx
                  end

  percentage    = args.easing.ease fade_in_at,
                                   current_tick,
                                   duration,
                                   easing_lambda

  alpha = 255 * percentage
  args.outputs.labels << { x: 640,
                           y: 320,
                           a: alpha,
                           text: "#{percentage.to_sf}",
                           alignment_enum: 1 }
end
    Example - Extending Easing Definitions

    If you don't want to create a lambda, you can register an easing definition like so: 

    # 1. Extend the Easing module
module Easing
  def self.saw_tooth x
    if x < 0.5
      x * 2
    else
      1 - (x - 0.5) * 2
    end
  end
end

def tick args
  fade_in_at    = 60
  current_tick  = args.state.tick_count
  duration      = 600

  # 2. Reference easing definition by name
  percentage    = args.easing.ease fade_in_at,
                                   current_tick,
                                   duration,
                                   :saw_tooth

  alpha = 255 * percentage
  args.outputs.labels << { x: 640,
                           y: 320,
                           a: alpha,
                           text: "#{percentage.to_sf}",
                           alignment_enum: 1 }

end

    Pixel Arrays (args.pixel_arrays) link

    A PixelArray object with a width, height and an Array of pixels which are hexadecimal color values in ABGR format.

    You can create a pixel array like this: 

    w = 200
h = 100
args.pixel_array(:my_pixel_array).w = w
args.pixel_array(:my_pixel_array).h = h

    You'll also need to fill the pixels with values, if they are nil, the array will render with the checkerboard texture. You can use #00000000 to fill with transparent pixels if desired. 

    args.pixel_array(:my_pixel_array).pixels.fill #FF00FF00, 0, w * h

    Note: To convert from rgb hex (like skyblue #87CEEB) to abgr hex, you split it in pairs pair (eg 87 CE EB) and reverse the order (eg EB CE 87) add join them again: #EBCE87. Then add the alpha component in front ie: FF for full opacity: #FFEBCE87.

    You can draw it by using the symbol for :path 

    args.outputs.sprites << { x: 500, y: 300, w: 200, h: 100, path: :my_pixel_array) }

    If you want access a specific x, y position, you can do it like this for a bottom-left coordinate system: 

    x = 150
y = 33
args.pixel_array(:my_pixel_array).pixels[(height - y) * width + x] = 0xFFFFFFFF

    Related Sample Apps link

    CVars (args.cvars) link

    Hash contains metadata pulled from the files under the ./metadata directory. To get the keys that are available type $args.cvars.keys in the Console. Here is an example of how to retrieve the game version number: 

    def tick args
  args.outputs.labels << {
    x: 640,
    y: 360,
    text: args.cvars["game_metadata.version"].value.to_s
  }
end

    Each CVar has the following properties value, name, description, type, locked.

    Layout (args.layout) link

    Layout provides apis for placing primitives on a virtual grid that's within the "safe area" accross all platforms. This virtual grid is useful for rendering static controls (buttons, menu items, configuration screens, etc).

    For reference implementations, take a look at the following sample apps:

    The following example creates two menu items and updates a label with the button that was clicked: 

    def tick args
  # render debug_primitives of args.layout for help with placement
  # args.outputs.primitives << args.layout.debug_primitives

  # capture the location for a label centered at the top
  args.state.label_rect ||= args.layout.rect(row: 0, col: 10, w: 4, h: 1)
  # state variable to hold the current click status
  args.state.label_message ||= "click a menu item"

  # capture the location of two menu items positioned in the center
  # with a cell width of 4 and cell height of 2
  args.state.menu_item_1_rect ||= args.layout.rect(row: 1, col: 10, w: 4, h: 2)
  args.state.menu_item_2_rect ||= args.layout.rect(row: 3, col: 10, w: 4, h: 2)

  # render the label at the center of the label_rect
  args.outputs.labels << args.state.label_rect.center.merge(text: args.state.label_message,
                                                            anchor_x: 0.5,
                                                            anchor_y: 0.5)

  # render menu items
  args.outputs.sprites << args.state.menu_item_1_rect.merge(path: :solid,
                                                            r: 100,
                                                            g: 100,
                                                            b: 200)
  args.outputs.labels << args.state.menu_item_1_rect.center.merge(text: "item 1",
                                                                  r: 255,
                                                                  g: 255,
                                                                  b: 255,
                                                                  anchor_x: 0.5,
                                                                  anchor_y: 0.5)

  args.outputs.sprites << args.state.menu_item_2_rect.merge(path: :solid,
                                                            r: 100,
                                                            g: 100,
                                                            b: 200)
  args.outputs.labels << args.state.menu_item_2_rect.center.merge(text: "item 2",
                                                                  r: 255,
                                                                  g: 255,
                                                                  b: 255,
                                                                  anchor_x: 0.5,
                                                                  anchor_y: 0.5)

  # if click occurs, then determine which menu item was clicked
  if args.inputs.mouse.click
    if args.inputs.mouse.intersect_rect?(args.state.menu_item_1_rect)
      args.state.label_message = "menu item 1 clicked"
    elsif args.inputs.mouse.intersect_rect?(args.state.menu_item_2_rect)
      args.state.label_message = "menu item 2 clicked"
    else
      args.state.label_message = "click a menu item"
    end
  end
end

    rect link

    Given a row:, col:, w:, h:, returns a Hash with properties x, y, w, h, and center (which contains a Hash with x, y). The virtual grid is 12 rows by 24 columns (or 24 columns by 12 rows in portrait mode).

    debug_primitives link

    Function returns an array of primities that can be rendered to the screen to help you place items within the grid.

    Example: 

    def tick args
  args.outputs.primitives << args.layout.debug_primitives
end

    Array link

    The Array class has been extend to provide methods that will help in common game development tasks. Array is one of the most powerful classes in Ruby and a very fundamental component of Game Toolkit.

    map_2d link

    Assuming the array is an array of arrays, Given a block, each 2D array index invoked against the block. A 2D array is a common way to store data/layout for a stage. 

    repl do
  stage = [
    [:enemy, :empty, :player],
    [:empty, :empty,  :empty],
    [:enemy, :empty,  :enemy],
  ]

  occupied_tiles = stage.map_2d do |row, col, tile|
    if tile == :empty
      nil
    else
      [row, col, tile]
    end
  end.reject_nil

  puts "Stage:"
  puts stage

  puts "Occupied Tiles"
  puts occupied_tiles
end

    include_any? link

    Given a collection of items, the function will return true if any of self's items exists in the collection of items passed in:

    any_intersect_rect? link

    Assuming the array contains objects that respond to left, right, top, bottom, this method returns true if any of the elements within the array intersect the object being passed in. You are given an optional parameter called tolerance which informs how close to the other rectangles the elements need to be for it to be considered intersecting.

    The default tolerance is set to 0.1, which means that the primitives are not considered intersecting unless they are overlapping by more than 0.1. 

    repl do
  # Here is a player class that has position and implement
  # the ~attr_rect~ contract.
  class Player
    attr_rect
    attr_accessor :x, :y, :w, :h

    def initialize x, y, w, h
      @x = x
      @y = y
      @w = w
      @h = h
    end

    def serialize
      { x: @x, y: @y, w: @w, h: @h }
    end

    def inspect
      "#{serialize}"
    end

    def to_s
      "#{serialize}"
    end
  end

  # Here is a definition of two walls.
  walls = [
     [10, 10, 10, 10],
     { x: 20, y: 20, w: 10, h: 10 },
   ]

  # Display the walls.
  puts "Walls."
  puts walls
  puts ""

  # Check any_intersect_rect? on player
  player = Player.new 30, 20, 10, 10
  puts "Is Player #{player} touching wall?"
  puts (walls.any_intersect_rect? player)
  # => false
  # The value is false because of the default tolerance is 0.1.
  # The overlap of the player rect and any of the wall rects is
  # less than 0.1 (for those that intersect).
  puts ""

  player = Player.new 9, 10, 10, 10
  puts "Is Player #{player} touching wall?"
  puts (walls.any_intersect_rect? player)
  # => true
  puts ""
end

    map link

    The function given a block returns a new Enumerable of values.

    Example of using Array#map in conjunction with args.state and args.outputs.sprites to render sprites to the screen. 

    def tick args
  # define the colors of the rainbow in ~args.state~
  # as an ~Array~ of ~Hash~es with :order and :name.
  # :order will be used to determine render location
  #  and :name will be used to determine sprite path.
  args.state.rainbow_colors ||= [
    { order: 0, name: :red    },
    { order: 1, name: :orange },
    { order: 2, name: :yellow },
    { order: 3, name: :green  },
    { order: 4, name: :blue   },
    { order: 5, name: :indigo },
    { order: 6, name: :violet },
  ]

  # render sprites diagonally to the screen
  # with a width and height of 50.
  args.outputs
      .sprites << args.state
                      .rainbow_colors
                      .map do |color| # <-- ~Array#map~ usage
                        [
                          color[:order] * 50,
                          color[:order] * 50,
                          50,
                          50,
                          "sprites/square-#{color[:name]}.png"
                        ]
                      end
end

    each link

    The function, given a block, invokes the block for each item in the Array. Array#each is synonymous to foreach constructs in other languages.

    Example of using Array#each in conjunction with args.state and args.outputs.sprites to render sprites to the screen: 

    def tick args
  # define the colors of the rainbow in ~args.state~
  # as an ~Array~ of ~Hash~es with :order and :name.
  # :order will be used to determine render location
  #  and :name will be used to determine sprite path.
  args.state.rainbow_colors ||= [
    { order: 0, name: :red    },
    { order: 1, name: :orange },
    { order: 2, name: :yellow },
    { order: 3, name: :green  },
    { order: 4, name: :blue   },
    { order: 5, name: :indigo },
    { order: 6, name: :violet },
  ]

  # render sprites diagonally to the screen
  # with a width and height of 50.
  args.state
      .rainbow_colors
      .map do |color| # <-- ~Array#each~ usage
        args.outputs.sprites << [
          color[:order] * 50,
          color[:order] * 50,
          50,
          50,
          "sprites/square-#{color[:name]}.png"
        ]
      end
end

    reject_nil link

    Returns an Enumerable rejecting items that are nil, this is an alias for Array#compact: 

    repl do
  a = [1, nil, 4, false, :a]
  puts a.reject_nil
  # => [1, 4, false, :a]
  puts a.compact
  # => [1, 4, false, :a]
end

    reject_false link

    Returns an `Enumerable` rejecting items that are `nil` or `false`. 

    repl do
  a = [1, nil, 4, false, :a]
  puts a.reject_false
  # => [1, 4, :a]
end

    product link

    Returns all combinations of values between two arrays.

    Here are some examples of using product. Paste the following code at the bottom of main.rb and save the file to see the results: 

    repl do
  a = [0, 1]
  puts a.product
  # => [[0, 0], [0, 1], [1, 0], [1, 1]]
end

    repl do
  a = [ 0,  1]
  b = [:a, :b]
  puts a.product b
  # => [[0, :a], [0, :b], [1, :a], [1, :b]]
end

    Numeric link

    The Numeric class has been extend to provide methods that will help in common game development tasks.

    frame_index link

    This function is helpful for determining the index of frame-by-frame sprite animation. The numeric value self represents the moment the animation started.

    frame_index takes three additional parameters:

    frame_index will return nil if the time for the animation is out of bounds of the parameter specification.

    Example using variables: 

    def tick args
  start_looping_at = 0
  number_of_sprites = 6
  number_of_frames_to_show_each_sprite = 4
  does_sprite_loop = true

  sprite_index =
    start_looping_at.frame_index number_of_sprites,
                                 number_of_frames_to_show_each_sprite,
                                 does_sprite_loop

  sprite_index ||= 0

  args.outputs.sprites << [
    640 - 50,
    360 - 50,
    100,
    100,
    "sprites/dragon-#{sprite_index}.png"
  ]
end

    Example using named parameters. The named parameters version allows you to also specify a repeat_index which is useful if your animation has starting frames that shouldn't be considered when looped: 

    def tick args
  start_looping_at = 0

  sprite_index =
    start_looping_at.frame_index count: 6,
                                 hold_for: 4,
                                 repeat: true,
                                 repeat_index: 0,
                                 tick_count_override: args.state.tick_count

  sprite_index ||= 0

  args.outputs.sprites << [
    640 - 50,
    360 - 50,
    100,
    100,
    "sprites/dragon-#{sprite_index}.png"
  ]
end

    The named parameter variant of frame_index is also available on Numeric: 

    def tick args
  sprite_index =
    Numeric.frame_index start_at: 0,
                        count: 6,
                        hold_for: 4,
                        repeat: true,
                        repeat_index: 0,
                        tick_count_override: args.state.tick_count

  sprite_index ||= 0

  args.outputs.sprites << [
    640 - 50,
    360 - 50,
    100,
    100,
    "sprites/dragon-#{sprite_index}.png"
  ]
end

    elapsed_time link

    For a given number, the elapsed frames since that number is returned. `Kernel.tick_count` is used to determine how many frames have elapsed. An optional numeric argument can be passed in which will be used instead of `Kernel.tick_count`.

    Here is an example of how elapsed_time can be used. 

    def tick args
  args.state.last_click_at ||= 0

  # record when a mouse click occurs
  if args.inputs.mouse.click
    args.state.last_click_at = args.state.tick_count
  end

  # Use Numeric#elapsed_time to determine how long it's been
  if args.state.last_click_at.elapsed_time > 120
    args.outputs.labels << [10, 710, "It has been over 2 seconds since the mouse was clicked."]
  end
end

    And here is an example where the override parameter is passed in: 

    def tick args
  args.state.last_click_at ||= 0

  # create a state variable that tracks time at half the speed of args.state.tick_count
  args.state.simulation_tick = args.state.tick_count.idiv 2

  # record when a mouse click occurs
  if args.inputs.mouse.click
    args.state.last_click_at = args.state.simulation_tick
  end

  # Use Numeric#elapsed_time to determine how long it's been
  if (args.state.last_click_at.elapsed_time args.state.simulation_tick) > 120
    args.outputs.labels << [10, 710, "It has been over 4 seconds since the mouse was clicked."]
  end
end

    elapsed? link

    Returns true if Numeric#elapsed_time is greater than the number. An optional parameter can be passed into elapsed? which is added to the number before evaluating whether elapsed? is true.

    Example usage (no optional parameter): 

    def tick args
  args.state.box_queue ||= []

  if args.state.box_queue.empty?
    args.state.box_queue << { name: :red,
                              destroy_at: args.state.tick_count + 60 }
    args.state.box_queue << { name: :green,
                              destroy_at: args.state.tick_count + 60 }
    args.state.box_queue << { name: :blue,
                              destroy_at: args.state.tick_count + 120 }
  end

  boxes_to_destroy = args.state
                         .box_queue
                         .find_all { |b| b[:destroy_at].elapsed? }

  if !boxes_to_destroy.empty?
    puts "boxes to destroy count: #{boxes_to_destroy.length}"
  end

  boxes_to_destroy.each { |b| puts "box #{b} was elapsed? on #{args.state.tick_count}." }

  args.state.box_queue -= boxes_to_destroy
end

    Example usage (with optional parameter): 

    def tick args
  args.state.box_queue ||= []

  if args.state.box_queue.empty?
    args.state.box_queue << { name: :red,
                              create_at: args.state.tick_count + 120,
                              lifespan: 60 }
    args.state.box_queue << { name: :green,
                              create_at: args.state.tick_count + 120,
                              lifespan: 60 }
    args.state.box_queue << { name: :blue,
                              create_at: args.state.tick_count + 120,
                              lifespan: 120 }
  end

  # lifespan is passed in as a parameter to ~elapsed?~
  boxes_to_destroy = args.state
                         .box_queue
                         .find_all { |b| b[:create_at].elapsed? b[:lifespan] }

  if !boxes_to_destroy.empty?
    puts "boxes to destroy count: #{boxes_to_destroy.length}"
  end

  boxes_to_destroy.each { |b| puts "box #{b} was elapsed? on #{args.state.tick_count}." }

  args.state.box_queue -= boxes_to_destroy
end

    new? link

    Returns true if Numeric#elapsed_time == 0. Essentially communicating that number is equal to the current frame.

    Example usage: 

    def tick args
  args.state.box_queue ||= []

  if args.state.box_queue.empty?
    args.state.box_queue << { name: :red,
                              create_at: args.state.tick_count + 60 }
  end

  boxes_to_spawn_this_frame = args.state
                                  .box_queue
                                  .find_all { |b| b[:create_at].new? }

  boxes_to_spawn_this_frame.each { |b| puts "box #{b} was new? on #{args.state.tick_count}." }

  args.state.box_queue -= boxes_to_spawn_this_frame
end

    Kernel link

    Kernel in the DragonRuby Runtime has patches for how standard out is handled and also contains a unit of time in games called a tick.

    tick_count link

    Returns the current tick of the game. This value is reset if you call $gtk.reset.

    global_tick_count link

    Returns the current tick of the application from the point it was started. This value is never reset.

    Grid (args.grid) link

    Returns the virtual grid for the game.

    name link

    Returns either :origin_bottom_left or :origin_center.

    bottom link

    Returns the y value that represents the bottom of the grid.

    top link

    Returns the y value that represents the top of the grid.

    left link

    Returns the x value that represents the left of the grid.

    right link

    Returns the x value that represents the right of the grid.

    rect link

    Returns a rectangle Primitive that represents the grid.

    origin_bottom_left! link

    Change the grids coordinate system to 0, 0 at the bottom left corner.

    origin_center! link

    Change the grids coordinate system to 0, 0 at the center of the screen.

    orientation link

    Returns either :portrait or :landscape. The orientation of your game is set within ./mygame/metadata/game_metadata.txt.

    w link

    Returns the grid's width (value is 1280 if orientation :landscape, and 720 if orientation is :portrait).

    h link

    Returns the grid's width (value is 720 if orientation :landscape, and 1280 if orientation is :portrait).

    Grid HD Properties link

    The following properties are available to Pro license holders. Setting hd=true and hd=true in ./mygame/metadata/game_metadata.txt will enable All Screen Mode.

    Please review the sample app located at ./samples/07_advanced_rendering_hd/03_allscreen_properties.

    When All Screen mode is enabled, you can render outside of the 1280x720 safe area. The 1280x720 logical canvas will be centered within the screen and scaled to one of the following closest/bess-fit resolutions.

    Regardless of the rendering resolution, your logical canvas will always be 1280x720 and all hd_* values will be at this same logical scale.

    hd_left link

    Returns the position of the left edge of the screen at the logical scale of 1280x720. For example, if the window's width is 1290x720, then hd_left will be -5.

    hd_right link

    Returns the position of the right edge of the screen at the logical scale of 1280x720. For example, if the window's width is 1290x720, then hd_right will be 1285.

    hd_bottom link

    Returns the position of the bottom edge of the screen at the logical scale of 1280x720. For example, if the window's width is 1280x730, then hd_bottom will be -5.

    hd_top link

    Returns the position of the top edge of the screen at the logical scale of 1280x720. For example, if the window's width is 1280x730, then hd_top will be 725.

    hd_offset_x link

    Returns the number of pixels that the 1280x720 canvas is offset from the left so that it's centered in the screen.

    hd_offset_y link

    Returns the number of pixels that the 1280x720 canvas is offset from the bottom so that it's centered in the screen.

    window_width link

    Returns the true width of the window. High DPI settings are not taken into consideration.

    window_height link

    Returns the true height of the window. High DPI settings are not taken into consideration.

    native_width link

    Returns the true width of the window. High DPI settings (macOS, iOS, Android) are taken into consideration.

    native_height link

    Returns the true height of the window. High DPI settings (macOS, iOS, Android) are taken into consideration.

    native_scale link

    Returns a decimal value representing the rendering scale of the game.

    native_scale_enum link

    Returns an integer value representing the rendering scale of the game.

    The enum value is taken into consideration when rendering a sprite through texture atlases.

    Given the following code: 

    def tick args
  args.outputs.sprites << { x: 0, y: 0, w: 100, h: 100, path: "sprites/player.png" }
end

    The sprite path of sprites/player.png will be replaced according to the following naming conventions (fallback to a lower resolution is automatically handled if a sprite with naming convention isn't found):

    Samples link

    Follows is a source code listing for all files that have been open sourced. This code can be found in the ./samples directory.

    Learn Ruby Optional link

    Beginner Ruby Primer - automation.rb link

    # ./samples/00_learn_ruby_optional/00_beginner_ruby_primer/app/automation.rb
# ==========================================================================
#  _    _ ________     __  _      _____  _____ _______ ______ _   _ _ _ _ _
# | |  | |  ____\ \   / / | |    |_   _|/ ____|__   __|  ____| \ | | | | | |
# | |__| | |__   \ \_/ /  | |      | | | (___    | |  | |__  |  \| | | | | |
# |  __  |  __|   \   /   | |      | |  \___ \   | |  |  __| | . ` | | | | |
# | |  | | |____   | |    | |____ _| |_ ____) |  | |  | |____| |\  |_|_|_|_|
# |_|  |_|______|  |_|    |______|_____|_____/   |_|  |______|_| \_(_|_|_|_)
#
#
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                \  |  /
#                                 \ | /
#                                   +
#
# If you are new to the programming language Ruby, then you may find the
# following code a bit overwhelming. Come back to this file when you have
# a better grasp of Ruby and Game Toolkit.
#
# What follows is an automations script # that can be run via terminal:
# ./samples/00_beginner_ruby_primer $ ../../dragonruby . --eval app/automation.rb
# ==========================================================================

$gtk.reset
$gtk.scheduled_callbacks.clear
$gtk.schedule_callback 10 do
  $gtk.console.set_command 'puts "Hello DragonRuby!"'
end

$gtk.schedule_callback 20 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 30 do
  $gtk.console.set_command 'outputs.solids << [910, 200, 100, 100, 255, 0, 0]'
end

$gtk.schedule_callback 40 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 50 do
  $gtk.console.set_command 'outputs.solids << [1010, 200, 100, 100, 0, 0, 255]'
end

$gtk.schedule_callback 60 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 70 do
  $gtk.console.set_command 'outputs.sprites << [1110, 200, 100, 100, "sprites/dragon_fly_0.png"]'
end

$gtk.schedule_callback 80 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 90 do
  $gtk.console.set_command "outputs.labels << [1210, 200, state.tick_count, 0, 255, 0]"
end

$gtk.schedule_callback 100 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 110 do
  $gtk.console.set_command "state.sprite_frame = state.tick_count.idiv(4).mod(6)"
end

$gtk.schedule_callback 120 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 130 do
  $gtk.console.set_command "outputs.labels << [1210, 170, state.sprite_frame, 0, 255, 0]"
end

$gtk.schedule_callback 140 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 150 do
  $gtk.console.set_command "state.sprite_path =  \"sprites/dragon_fly_\#{state.sprite_frame}.png\""
end

$gtk.schedule_callback 160 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 170 do
  $gtk.console.set_command "outputs.labels    << [910, 330, \"path: \#{state.sprite_path}\", 0, 255, 0]"
end

$gtk.schedule_callback 180 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 190 do
  $gtk.console.set_command "outputs.sprites   << [910, 330, 370, 370, state.sprite_path]"
end

$gtk.schedule_callback 200 do
  $gtk.console.eval_the_set_command
end

$gtk.schedule_callback 300 do
  $gtk.console.set_command ":wq"
end

$gtk.schedule_callback 400 do
  $gtk.console.eval_the_set_command
end

    Beginner Ruby Primer - main.rb link

    # ./samples/00_learn_ruby_optional/00_beginner_ruby_primer/app/main.rb
# ==========================================================================
#  _    _ ________     __  _      _____  _____ _______ ______ _   _ _ _ _ _
# | |  | |  ____\ \   / / | |    |_   _|/ ____|__   __|  ____| \ | | | | | |
# | |__| | |__   \ \_/ /  | |      | | | (___    | |  | |__  |  \| | | | | |
# |  __  |  __|   \   /   | |      | |  \___ \   | |  |  __| | . ` | | | | |
# | |  | | |____   | |    | |____ _| |_ ____) |  | |  | |____| |\  |_|_|_|_|
# |_|  |_|______|  |_|    |______|_____|_____/   |_|  |______|_| \_(_|_|_|_)
#
#
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                   |
#                                \  |  /
#                                 \ | /
#                                   +
#
# If you are new to the programming language Ruby, then you may find the
# following code a bit overwhelming. This sample is only designed to be
# run interactively (as opposed to being manipulated via source code).
#
# Start up this sample and follow along by visiting:
# https://s3.amazonaws.com/s3.dragonruby.org/dragonruby-gtk-primer.mp4
#
# It is STRONGLY recommended that you work through all the samples before
# looking at the code in this file.
# ==========================================================================

class TutorialOutputs
  attr_accessor :solids, :sprites, :labels, :lines, :borders

  def initialize
    @solids  = []
    @sprites = []
    @labels  = []
    @lines   = []
    @borders = []
  end

  def tick
    @solids  ||= []
    @sprites ||= []
    @labels  ||= []
    @lines   ||= []
    @borders ||= []
    @solids.each  { |p| $gtk.args.outputs.reserved << p.solid  }
    @sprites.each { |p| $gtk.args.outputs.reserved << p.sprite }
    @labels.each  { |p| $gtk.args.outputs.reserved << p.label  }
    @lines.each   { |p| $gtk.args.outputs.reserved << p.line   }
    @borders.each { |p| $gtk.args.outputs.reserved << p.border }
  end

  def clear
    @solids.clear
    @sprites.clear
    @labels.clear
    @borders.clear
  end
end

def defaults
  state.reset_button ||=
    state.new_entity(
      :button,
      label:  [1190, 68, "RESTART", -2, 0, 0, 0, 0].label,
      background: [1160, 38, 120, 50, 255, 255, 255].solid
    )
  $gtk.log_level = :off
end

def tick_reset_button
  return unless state.hello_dragonruby_confirmed
  $gtk.args.outputs.reserved << state.reset_button.background
  $gtk.args.outputs.reserved << state.reset_button.label
  if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.reset_button.background)
    restart_tutorial
  end
end

def seperator
  @seperator = "=" * 80
end

def tick_intro
  queue_message "Welcome to the DragonRuby GTK primer! Try typing the
code below and press ENTER:

    puts \"Hello DragonRuby!\"
"
end

def tick_hello_dragonruby
  return unless console_has? "Hello DragonRuby!", "puts "

  $gtk.args.state.hello_dragonruby_confirmed = true

  queue_message "Well HELLO to you too!

If you ever want to RESTART the tutorial, just click the \"RESTART\"
button in the bottom right-hand corner.

Let's continue shall we? Type the code below and press ENTER:

    outputs.solids << [910, 200, 100, 100, 255, 0, 0]
"

end

def tick_explain_solid
  return unless $tutorial_outputs.solids.any? {|s| s == [910, 200, 100, 100, 255, 0, 0]}

  queue_message "Sweet!

The code: outputs.solids << [910, 200, 100, 100, 255, 0, 0]
Does the following:
1. GET the place where SOLIDS go: outputs.solids
2. Request that a new SOLID be ADDED: <<
3. The DEFINITION of a SOLID is the ARRAY:
   [910, 200, 100, 100, 255, 0, 0]

      GET       ADD     X      Y    WIDTH  HEIGHT RED  GREEN  BLUE
       |         |      |      |      |      |     |     |     |
       |         |      |      |      |      |     |     |     |
outputs.solids  <<    [910,   200,   100,   100,  255,   0,    0]
                      |_________________________________________|
                                           |
                                           |
                                         ARRAY

Now let's create a blue SOLID. Type:

    outputs.solids << [1010, 200, 100, 100, 0, 0, 255]
"

  state.explain_solid_confirmed = true
end

def tick_explain_solid_blue
  return unless state.explain_solid_confirmed
  return unless $tutorial_outputs.solids.any? {|s| s == [1010, 200, 100, 100, 0, 0, 255]}
  state.explain_solid_blue_confirmed = true

  queue_message "And there is our blue SOLID!

The ARRAY is the MOST important thing in DragonRuby GTK.

Let's create a SPRITE using an ARRAY:

  outputs.sprites << [1110, 200, 100, 100, 'sprites/dragon_fly_0.png']
"
end

def tick_explain_tick_count
  return unless $tutorial_outputs.sprites.any? {|s| s == [1110, 200, 100, 100, 'sprites/dragon_fly_0.png']}
  return if $tutorial_outputs.labels.any? {|l| l == [1210, 200, state.tick_count, 255, 255, 255]}
  state.explain_tick_count_confirmed = true

  queue_message "Look at the cute little dragon!

We can create a LABEL with ARRAYS too. Let's create a LABEL showing
THE PASSAGE OF TIME, which is called TICK_COUNT.

  outputs.labels << [1210, 200, state.tick_count, 0, 255, 0]
"
end

def tick_explain_mod
  return unless $tutorial_outputs.labels.any? {|l| l == [1210, 200, state.tick_count, 0, 255, 0]}
  state.explain_mod_confirmed = true
  queue_message "
The code: outputs.labels << [1210, 200, state.tick_count, 0, 255, 0]
Does the following:
1. GET the place where labels go: outputs.labels
2. Request that a new label be ADDED: <<
3. The DEFINITION of a LABEL is the ARRAY:
   [1210, 200, state.tick_count, 0, 255, 0]

      GET       ADD     X      Y          TEXT         RED  GREEN  BLUE
       |         |      |      |            |           |     |     |
       |         |      |      |            |           |     |     |
outputs.labels  <<    [1210,  200,   state.tick_count,  0,   255,   0]
                      |______________________________________________|
                                              |
                                              |
                                            ARRAY

Now let's do some MATH, save the result to STATE, and create a LABEL:

    state.sprite_frame = state.tick_count.idiv(4).mod(6)
    outputs.labels << [1210, 170, state.sprite_frame, 0, 255, 0]

Type the lines above (pressing ENTER after each line).
"
end

def tick_explain_string_interpolation
  return unless state.explain_mod_confirmed
  return unless state.sprite_frame == state.tick_count.idiv(4).mod(6)
  return unless $tutorial_outputs.labels.any? {|l| l == [1210, 170, state.sprite_frame, 0, 255, 0]}

  queue_message "Here is what the mathematical computation you just typed does:

1. Create an item of STATE named SPRITE_FRAME: state.sprite_frame =
2. Set this SPRITE_FRAME to the PASSAGE OF TIME (tick_count),
   DIVIDED EVENLY (idiv) into 4,
   and then compute the REMAINDER (mod) of 6.

   STATE   SPRITE_FRAME    PASSAGE OF      HOW LONG   HOW MANY
     |          |             TIME         TO SHOW    IMAGES
     |          |              |           AN IMAGE   TO FLIP THROUGH
     |          |              |               |      |
state.sprite_frame =     state.tick_count.idiv(4).mod(6)
                                           |       |
                                           |       +- REMAINDER OF DIVIDE
                                    DIVIDE EVENLY
                                    (NO DECIMALS)

With the information above, we can animate a SPRITE
using STRING INTERPOLATION: \#{}
which creates a unique SPRITE_PATH:

  state.sprite_path =  \"sprites/dragon_fly_\#{state.sprite_frame}.png\"
  outputs.labels    << [910, 330, \"path: \#{state.sprite_path}\", 0, 255, 0]
  outputs.sprites   << [910, 330, 370, 370, state.sprite_path]

Type the lines above (pressing ENTER after each line).
"
end

def tick_reprint_on_error
  return unless console.last_command_errored
  puts $gtk.state.messages.last
  puts "\nWhoops! Try again."
  console.last_command_errored = false
end

def tick_evals
  state.evals ||= []
  if console.last_command && (console.last_command.start_with?("outputs.") || console.last_command.start_with?("state."))
    state.evals << console.last_command
    console.last_command = nil
  end

  state.evals.each do |l|
    Kernel.eval l
  end
rescue Exception => e
  state.evals = state.evals[0..-2]
end

$tutorial_outputs ||= TutorialOutputs.new

def tick args
  $gtk.log_level = :off
  defaults
  console.show
  $tutorial_outputs.clear
  $tutorial_outputs.solids  << [900, 37, 480, 700,   0,   0,   0, 255]
  $tutorial_outputs.borders << [900, 37, 380, 683, 255, 255, 255]
  tick_evals
  $tutorial_outputs.tick
  tick_intro
  tick_hello_dragonruby
  tick_reset_button
  tick_explain_solid
  tick_explain_solid_blue
  tick_reprint_on_error
  tick_explain_tick_count
  tick_explain_mod
  tick_explain_string_interpolation
end

def console
  $gtk.console
end

def queue_message message
  $gtk.args.state.messages ||= []
  return if $gtk.args.state.messages.include? message
  $gtk.args.state.messages << message
  last_three = [$gtk.console.log[-3], $gtk.console.log[-2], $gtk.console.log[-1]].reject_nil
  $gtk.console.log.clear
  puts seperator
  $gtk.console.log += last_three
  puts seperator
  puts message
  puts seperator
end

def console_has? message, not_message = nil
  console.log
         .map(&:upcase)
         .reject { |s| not_message && s.include?(not_message.upcase) }
         .any?   { |s| s.include?("#{message.upcase}") }
end

def restart_tutorial
  $tutorial_outputs.clear
  $gtk.console.log.clear
  $gtk.reset
  puts "Starting the tutorial over!"
end

def state
  $gtk.args.state
end

def inputs
  $gtk.args.inputs
end

def outputs
  $tutorial_outputs
end

    Intermediate Ruby Primer - printing.txt link

    # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/01_printing.txt
# ====================================================================================
# Commenting Code
# ====================================================================================
#
# Prefixing text with a pound sign (#) is how you comment code in Ruby. Example:
#
# I am commented code. And so are the lines above.
#
# I you want more than a quick primer on Ruby, check out https://poignant.guide/. It's
# an entertaining read. Otherwise, go to the next txt file.
#
# Follow along by visiting:
# https://s3.amazonaws.com/s3.dragonruby.org/dragonruby-gtk-intermediate.mp4

# ====================================================================================
#  Printing to the Console:
# ====================================================================================
#
# Every time you save repl.rb file, DragonRuby runs the code within it. Copy this text
# to repl.rb and save to see Hello World printed to the console.

repl do
  puts '* RUBY PRIMER: Printing to the console using the ~puts~ function.'
  puts '===='
  puts '======'
  puts '================================'
  puts 'Hello World'
  puts '================================'
  puts '======'
  puts '===='
end

    Intermediate Ruby Primer - strings.txt link

    # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/02_strings.txt
# ====================================================================================
#  Strings
# ====================================================================================
#
# Here is how you work with strings in Ruby. Take the text
# in this file and paste it into repl.rb and save:

repl do
  puts '* RUBY PRIMER: strings'
  message = "Hello World"
  puts "The value of message is: " + message
  puts "Any value can be interpolated within a string using \#{}."
  puts "Interpolated message: #{message}."
  puts 'This #{message} is not interpolated because the string uses single quotes.'
end

    Intermediate Ruby Primer - numbers.txt link

    # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/03_numbers.txt
# ====================================================================================
#  Numerics
# ====================================================================================
#
# Here is how you work with numbers in Ruby. Take the text
# in this file and paste it into repl.rb and save:

repl do
  puts '* RUBY PRIMER: Fixnum and Floats'
  a = 10
  puts "The value of a is: #{a}"
  puts "a + 1 is: #{a + 1}"
  puts "a / 3 is: #{a / 3}"
  puts ''

  b = 10.12
  puts "The value of b is: #{b}"
  puts "b + 1 is: #{b + 1}"
  puts "b as an integer is: #{b.to_i}"
  puts ''
end

    Intermediate Ruby Primer - booleans.txt link

    # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/04_booleans.txt
# ====================================================================================
#  Booleans
# ====================================================================================
#
# Here is how you work with numbers in Ruby. Take the text
# in this file and paste it into repl.rb and save:

repl do
  puts '* RUBY PRIMER: TrueClass, FalseClass, NilClass (truthy / falsey values)'
  puts "Anything that *isn't* false or nil is true."

  c = 30
  puts "The value of c is #{c}."

  if c
    puts "This if statement ran because c is truthy."
  end

  d = false
  puts "The value if d is #{d}. The type for d is #{d.class}."

  if !d
    puts "This if statement ran because d is falsey, using the not operator (!)."
  end

  e = nil
  puts "Nil is also considered falsey. The value of e is: #{e} (a blank string when printed). Which is of type #{e.class}."

  if !e
    puts "This if statement ran because e is nil and the if statement applied the NOT operator. !e yields a type of #{(!e).class}."
  end
end

    Intermediate Ruby Primer - conditionals.txt link

    # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/05_conditionals.txt
# ====================================================================================
#  Conditionals
# ====================================================================================
#
# Here is how you create conditionals in Ruby. Take the text
# in this file and paste it into repl.rb and save:

repl do
  puts "* RUBY PRIMER: Conditionals"
end

# ====================================================================================
#  if
# ====================================================================================

repl do
  puts "** INFO: if statement"
  i_am_one = 1
  if i_am_one
    puts "This was printed because i_am_one is truthy."
  end
end

# ====================================================================================
#  if/else
# ====================================================================================

repl do
  puts "** INFO: if/else statement"
  i_am_false = false
  if i_am_false
    puts "This will NOT get printed because i_am_false is false."
  else
    puts "This was printed because i_am_false is false."
  end
end


# ====================================================================================
#  if/elsif/else
# ====================================================================================

repl do
  puts "** INFO: if/elsif/else statement"
  i_am_false = false
  i_am_true  = true
  if i_am_false
    puts "This will NOT get printed because i_am_false is false."
  elsif i_am_true
    puts "This was printed because i_am_true is true."
  else
    puts "This will NOT get printed i_am_true was true."
  end
end

# ====================================================================================
#  case
# ====================================================================================

repl do
  puts "** INFO case statement"
  i_am_one = 1 # change this value to see different results

  case i_am_one
  when 10
    puts "the value of i_am_one is 10"
  when 9
    puts "the value of i_am_one is 9"
  when 5
    puts "the value of i_am_one is 5"
  when 1
    puts "the value of i_am_one is 1"
  else
    puts "Value wasn't cased."
  end
end

# ====================================================================================
#  comparison operators
# ====================================================================================

repl do
  puts "** INFO: Different types of comparisons"
  if 4 == 4
    puts "4 equals 4 (==)"
  end

  if 4 != 3
    puts "4 does not equal 3 (!=)"
  end

  if 3 < 4
    puts "3 is less than 4 (<)"
  end

  if 4 > 3
    puts "4 is greater than 3 (>)"
  end
end

# ====================================================================================
#  and/or conditionals
# ====================================================================================

repl do
  puts "** INFO: AND, OR operator (&&, ||)"
  if (4 > 3) || (3 < 4) || false
    puts "print this if 4 is greater than 3 OR 3 is less than 4 OR false is true (||)"
  end

  if (4 > 3) && (3 < 4)
    puts "print this if 4 is greater than 3 AND 3 is less than 4 (&&)"
  end
end

    Intermediate Ruby Primer - looping.txt link

    # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/06_looping.txt
# ====================================================================================
#  Looping
# ====================================================================================
#
# Looping looks a whole lot different than other languages.
# But it's pretty awesome when you get used to it.

repl do
  puts "* RUBY PRIMER: Loops"
end

# ====================================================================================
#  times
# ====================================================================================

repl do
  puts "** INFO: ~Numeric#times~ (for loop)"
  3.times do |i|
    puts i
  end
end

# ====================================================================================
#  foreach
# ====================================================================================

repl do
  puts "** INFO: ~Array#each~ (for each loop)"
  array = ["a", "b", "c", "d"]
  array.each do |char|
    puts char
  end

  puts "** INFO: ~Array#each_with_index~ (for each loop)"
  array = ["a", "b", "c", "d"]
  array.each do |char, i|
    puts "index #{i}: #{char}"
  end
end

# ====================================================================================
#  ranges
# ====================================================================================

repl do
  puts "** INFO: range block exclusive (three dots)"
  (0...3).each do |i|
    puts i
  end

  puts "** INFO: range block inclusive (two dots)"
  (0..3).each do |i|
    puts i
  end
end

    Intermediate Ruby Primer - functions.txt link

    # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/07_functions.txt
# ====================================================================================
# Functions
# ====================================================================================

# The last statement of a function is implictly returned. Parenthesis for functions
# are optional as long as the statement can be envaluated disambiguously.

repl do
  puts "* RUBY PRIMER: Functions"
end

# ====================================================================================
# Functions single parameter
# ====================================================================================

repl do
  puts "* INFO: Function with one parameter"

  # function definition
  def add_one_to n
    n + 1
  end

  # Parenthesis are optional in Ruby as long as the
  # parsing is disambiguous. Here are a couple of variations.
  # Generally speaking, don't put parenthesis is you don't have to.

  # Conventional Usage of Parenthesis.
  puts add_one_to(3)

  # DragonRuby's recommended use of parenthesis (inner function has parenthesis).
  puts (add_one_to 3)

  # Full parens.
  puts(add_one_to(3))

  # Outer function has parenthesis
  puts(add_one_to 3)
end

# ====================================================================================
# Functions with default parameter values
# ====================================================================================

repl do
  puts "* INFO: Function with default value"
  def function_with_default_value v = 10
    v * 10
  end

  puts "Passing the argument three yields: #{function_with_default_value 3}"
  puts "Passing no argument yields: #{function_with_default_value}"
end

# ====================================================================================
# Nil default parameter value and ||= operator.
# ====================================================================================

repl do
  puts "* INFO: Using the OR EQUAL operator (||=)"
  def function_with_nil_default_with_local a = nil
    result   = a
    result ||= "DEFAULT_VALUE_OF_A_IS_NIL_OR_FALSE"
    "value is #{result}."
  end

  puts "Passing 'hi' as the argument yields: #{function_with_nil_default_with_local 'hi'}"
  puts "Passing nil: #{function_with_nil_default_with_local}"
end

    Intermediate Ruby Primer - arrays.txt link

    # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/08_arrays.txt
# ====================================================================================
# Arrays
# ====================================================================================

# Arrays are incredibly powerful in Ruby. Learn to use them well.

repl do
  puts "* RUBY PRIMER: ARRAYS"
end

# ====================================================================================
# Enumerable ranges and .to_a
# ====================================================================================

repl do
  puts "** INFO: Create an array with the numbers 1 to 10."
  one_to_ten = (1..10).to_a
  puts one_to_ten
end

# ====================================================================================
# Finding elements
# ====================================================================================

repl do
  puts "** INFO: Finding elements in an array using ~Array#find_all~."
  puts "Create a new array that only contains even numbers from the previous array."

  one_to_ten = (1..10).to_a
  evens = one_to_ten.find_all do |number|
    number % 2 == 0
  end

  puts evens
end

# ====================================================================================
# Rejecting elements
# ====================================================================================

repl do
  puts "** INFO: Removing elements in an array using ~Array#reject~."
  puts "Create a new array that rejects odd numbers."

  one_to_ten = (1..10).to_a
  also_even = one_to_ten.reject do |number|
    number % 2 != 0
  end

  puts also_even
end

# ====================================================================================
# Array transform using the map function.
# ====================================================================================

repl do
  puts "** INFO: Creating new derived values from an array using ~Array#map~."
  puts "Create an array that doubles every number."

  one_to_ten = (1..10).to_a
  doubled = one_to_ten.map do |number|
    number * 2
  end

  puts doubled
end

# ====================================================================================
# Combining array functions.
# ====================================================================================

repl do
  puts "** INFO: Combining ~Array#find_all~ along with ~Array#map~."
  puts "Create an array that selects only odd numbers and then multiply those by 10."

  one_to_ten = (1..10).to_a
  odd_doubled = one_to_ten.find_all do |number|
    number % 2 != 0
  end.map do |odd_number|
    odd_number * 10
  end

  puts odd_doubled
end

# ====================================================================================
# Product function.
# ====================================================================================

repl do
  puts "** INFO: Create all combinations of array values using ~Array#product~."
  puts "All two-item pairs of numbers 1 to 10."
  one_to_ten = (1..10).to_a
  all_combinations = one_to_ten.product(one_to_ten)
  puts all_combinations
end

# ====================================================================================
# Uniq and sort function.
# ====================================================================================

repl do
  puts "** INFO: Providing uniq values using ~Array#uniq~ and ~Array#sort~."
  puts "All uniq combinations of numbers regardless of order."
  puts "For example: [1, 2] is the same as [2, 1]."
  one_to_ten = (1..10).to_a
  uniq_combinations =
    one_to_ten.product(one_to_ten)
              .map do |unsorted_number|
                unsorted_number.sort
              end.uniq
  puts uniq_combinations
end

# ====================================================================================
# Example of an advanced array transform.
# ====================================================================================

repl do
  puts "** INFO: Advanced chaining. Combining ~Array's ~map~, ~find_all~, ~sort~, and ~sort_by~."
  puts "All unique Pythagorean Triples between 1 and 100 sorted by area of the triangle."

  one_to_hundred = (1..100).to_a

  triples =
    one_to_hundred.product(one_to_hundred).map do |width, height|
                [width, height, Math.sqrt(width ** 2 + height ** 2)]
              end.find_all do |_, _, hypotenuse|
                hypotenuse.to_i == hypotenuse
              end.map do |triangle|
                triangle.map(&:to_i)
              end.uniq do |triangle|
                triangle.sort
              end.map do |width, height, hypotenuse|
                [width, height, hypotenuse, (width * height) / 2]
              end.sort_by do |_, _, _, area|
                area
              end

  triples.each do |width, height, hypotenuse, _|
    puts "(#{width}, #{height}, #{hypotenuse})"
  end
end

# ====================================================================================
# Example of an sorting.
# ====================================================================================

repl do
  puts "** INFO: Implementing a custom sort function that operates on the ~Hash~ datatype."

  things_to_sort = [
    { type: :background, order: 1 },
    { type: :foreground, order: 1 },
    { type: :foreground, order: 2 }
  ]
  puts "*** Original array."
  puts things_to_sort

  puts "*** Simple sort using key."
  # For a simple sort, you can use sort_by
  results = things_to_sort.sort_by do |hash|
    hash[:order]
  end

  puts results

  puts "*** Custom sort."
  puts "**** Sorting process."
  # for a more complicated sort, you can provide a block that returns
  # -1, 0, 1 for a left and right operand
  results = things_to_sort.sort do |l, r|
    sort_result = 0
    puts "here is l: #{l}"
    puts "here is r: #{r || "nil"}"
    # if either value is nil/false return 0
    if !l || !r
      sort_result = 0
    # if the type of "left" is background and the
    # type of "right" is foreground, then return
    # -1 (which means "left" is less than "right"
    elsif l[:type] == :background && r[:type] == :foreground
      sort_result = -1
    # if the type of "left" is foreground and the
    # type of "right" is background, then return
    #  1 (which means "left" is greater than "right"
    elsif l[:type] == :foreground && r[:type] == :background
      sort_result = 1
    # if "left" and "right"'s type are the same, then
    # use the order as the tie breaker
    elsif l[:order] < r[:order]
      sort_result = -1
    elsif l[:order] > r[:order]
      sort_result = 1
    # returning 0 means both values are equal
    else
      sort_result = 0
    end
    sort_result
  end.to_a

  puts "**** Sort result."
  puts results
end

# ====================================================================================
# Api documention for Array that is worth commiting to memory because arrays are so
# awesome in Ruby: https://docs.ruby-lang.org/en/2.0.0/Array.html
# ====================================================================================

    Intermediate Ruby Primer - main.rb link

    # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/main.rb
def tick args
  args.outputs.labels << [640, 380, "Open repl.rb in the text editor of your choice and follow the document.", 0, 1]
end

    Intermediate Ruby Primer - repl.rb link

    # ./samples/00_learn_ruby_optional/00_intermediate_ruby_primer/app/repl.rb
# Copy and paste the code inside of the txt files here.

    Rendering Basics link

    Labels - main.rb link

    # ./samples/01_rendering_basics/01_labels/app/main.rb
=begin

APIs listing that haven't been encountered in a previous sample apps:

- args.outputs.labels: An array. Values in this array generate labels the screen.

=end

# Labels are used to represent text elements in DragonRuby

# An example of creating a label is:
# args.outputs.labels << [320, 640, "Example", 3, 1, 255, 0, 0, 200, manaspace.ttf]

# The code above does the following:
# 1. GET the place where labels go: args.outputs.labels
# 2. Request a new LABEL be ADDED: <<
# 3. The DEFINITION of a LABEL is the ARRAY:
#     [320, 640, "Example", 3,     1,   255,   0,    0,    200,  manaspace.ttf]
#     [ X ,  Y,    TEXT,   SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
# 4. It's recommended to use hashes so that you're not reliant on positional values:
#    { x: 320, y: 640, text: "Example", size_enum: 3, alignment_enum: 1, r: 255, g: 0, b: 0, a: 200, font: "manaspace.ttf" }


# The tick method is called by DragonRuby every frame
# args contains all the information regarding the game.
def tick args
  # render the current frame to the screen centered vertically and horizontally at 640, 620
  args.outputs.labels << { x: 640, y: 620, anchor_x: 0.5, anchor_y: 0.5, text: "frame: #{args.state.tick_count}" }

  # Here are some examples of simple labels, with the minimum number of parameters
  # Note that the default values for the other parameters are 0, except for Alpha which is 255 and Font Style which is the default font
  args.outputs.labels << { x: 5,          y: 720 - 5, text: "This is a label located at the top left." }
  args.outputs.labels << { x: 5,          y:      30, text: "This is a label located at the bottom left." }
  args.outputs.labels << { x: 1280 - 420, y: 720 - 5, text: "This is a label located at the top right." }
  args.outputs.labels << { x: 1280 - 440, y: 30,      text: "This is a label located at the bottom right." }

  # Demonstration of the Size Parameter
  args.outputs.labels << { x: 175 + 150, y: 610 - 50, text: "Smaller label.",  size_enum: -2 } # size_enum of -2 is equivalent to using size_px: 18
  args.outputs.labels << { x: 175 + 150, y: 580 - 50, text: "Small label.",    size_enum: -1 } # size_enum of -1 is equivalent to using size_px: 20
  args.outputs.labels << { x: 175 + 150, y: 550 - 50, text: "Medium label.",   size_enum:  0 } # size_enum of  0 is equivalent to using size_px: 22
  args.outputs.labels << { x: 175 + 150, y: 520 - 50, text: "Large label.",    size_enum:  1 } # size_enum of  0 is equivalent to using size_px: 24
  args.outputs.labels << { x: 175 + 150, y: 490 - 50, text: "Larger label.",   size_enum:  2 } # size_enum of  0 is equivalent to using size_px: 26

  # Demonstration of the Align Parameter
  args.outputs.lines  << { x: 175 + 150, y: 0, h: 720 }

  args.outputs.labels << { x: 175 + 150, y: 345 - 50, text: "Left aligned.",   alignment_enum: 0 } # alignment_enum: 0 is equivalent to anchor_x: 0
  args.outputs.labels << { x: 175 + 150, y: 325 - 50, text: "Center aligned.", alignment_enum: 1 } # alignment_enum: 1 is equivalent to anchor_x: 0.5
  args.outputs.labels << { x: 175 + 150, y: 305 - 50, text: "Right aligned.",  alignment_enum: 2 } # alignment_enum: 2 is equivalent to anchor_x: 1

  # Demonstration of the RGBA parameters
  args.outputs.labels << { x: 600  + 150, y: 590 - 50, text: "Red Label.",   r: 255, g:   0, b:   0 }
  args.outputs.labels << { x: 600  + 150, y: 570 - 50, text: "Green Label.", r:   0, g: 255, b:   0 }
  args.outputs.labels << { x: 600  + 150, y: 550 - 50, text: "Blue Label.",  r:   0, g:   0, b: 255 }
  args.outputs.labels << { x: 600  + 150, y: 530 - 50, text: "Faded Label.", r:   0, g:   0, b:   0, a: 128 }

  # Demonstration of the Font parameter
  # In order to use a font of your choice, add its ttf file to the project folder, where the app folder is
  # Again, it's recommended to use hashes so that you're not reliant on positional values.
  args.outputs.labels << [690 + 150,               # x
                          330 - 20,                # y
                          "Custom font (Array)",   # text
                          0,                       # size_enum
                          1,                       # alignment_enum
                          125,                     # r
                          0,                       # g
                          200,                     # b
                          255,                     # a
                          "manaspc.ttf" ]          # font

  args.outputs.labels << { x: 690 + 150,
                           y: 330 - 50,
                           text: "Custom font (Hash)",
                           size_enum: 0,                 # equivalent to size_px:  22
                           alignment_enum: 1,            # equivalent to anchor_x: 0.5
                           vertical_alignment_enum: 2,   # equivalent to anchor_y: 1
                           r: 125,
                           g: 0,
                           b: 200,
                           a: 255,
                           font: "manaspc.ttf" }

  # Primitives can hold anything, and can be given a label in the following forms
  args.outputs.primitives << { x: 690 + 150,
                               y: 330 - 80,
                               text: "Custom font (.primitives Hash)",
                               size_enum: 0,
                               alignment_enum: 1,
                               r: 125,
                               g: 0,
                               b: 200,
                               a: 255,
                               font: "manaspc.ttf" }
end

    Labels Text Wrapping - main.rb link

    # ./samples/01_rendering_basics/01_labels_text_wrapping/app/main.rb
def tick args
  # create a really long string
  args.state.really_long_string =  "Lorem ipsum dolor sit amet, consectetur adipiscing elit. In vulputate viverra metus et vehicula. Aenean quis accumsan dolor. Nulla tempus, ex et lacinia elementum, nisi felis ullamcorper sapien, sed sagittis sem justo eu lectus. Etiam ut vehicula lorem, nec placerat ligula. Duis varius ultrices magna non sagittis. Aliquam et sem vel risus viverra hendrerit. Maecenas dapibus congue lorem, a blandit mauris feugiat sit amet."
  args.state.really_long_string += "\n"
  args.state.really_long_string += "Sed quis metus lacinia mi dapibus fermentum nec id nunc. Donec tincidunt ante a sem bibendum, eget ultricies ex mollis. Quisque venenatis erat quis pretium bibendum. Pellentesque vel laoreet nibh. Cras gravida nisi nec elit pulvinar, in feugiat leo blandit. Quisque sodales quam sed congue consequat. Vivamus placerat risus vitae ex feugiat viverra. In lectus arcu, pellentesque vel ipsum ac, dictum finibus enim. Quisque consequat leo in urna dignissim, eu tristique ipsum accumsan. In eros sem, iaculis ac rhoncus eu, laoreet vitae ipsum. In sodales, ante eu tempus vehicula, mi nulla luctus turpis, eu egestas leo sapien et mi."

  # length of characters on line
  max_character_length = 80

  # line height
  line_height = 25

  long_string = args.state.really_long_string

  # API: args.string.wrapped_lines string, max_character_length
  long_strings_split = args.string.wrapped_lines long_string, max_character_length

  # render a label for each line and offset by the line_height
  args.outputs.labels << long_strings_split.map_with_index do |s, i|
    {
      x: 60,
      y: 60.from_top - (i * line_height),
      text: s
    }
  end
end

    Lines - main.rb link

    # ./samples/01_rendering_basics/02_lines/app/main.rb
=begin

APIs listing that haven't been encountered in a previous sample apps:

- args.outputs.lines: An array. Values in this array generate lines on
  the screen.
- args.state.tick_count: This property contains an integer value that
  represents the current frame. GTK renders at 60 FPS. A value of 0
  for args.state.tick_count represents the initial load of the game.

=end

# The parameters required for lines are:
# 1. The initial point (x, y)
# 2. The end point (x2, y2)
# 3. The rgba values for the color and transparency (r, g, b, a)

# An example of creating a line would be:
# args.outputs.lines << [100, 100, 300, 300, 255, 0, 255, 255]

# This would create a line from (100, 100) to (300, 300)
# The RGB code (255, 0, 255) would determine its color, a purple
# It would have an Alpha value of 255, making it completely opaque

def tick args
  tick_instructions args, "Sample app shows how to create lines."

  args.outputs.labels << [480, 620, "Lines (x, y, x2, y2, r, g, b, a)"]

  # Some simple lines
  args.outputs.lines  << [380, 450, 675, 450]
  args.outputs.lines  << [380, 410, 875, 410]

  # These examples utilize args.state.tick_count to change the length of the lines over time
  # args.state.tick_count is the ticks that have occurred in the game
  # This is accomplished by making either the starting or ending point based on the args.state.tick_count
  args.outputs.lines  << [380, 370, 875, 370, args.state.tick_count % 255, 0, 0, 255]
  args.outputs.lines  << [380, 330 - args.state.tick_count % 25, 875, 330, 0, 0, 0, 255]
  args.outputs.lines  << [380 + args.state.tick_count % 400, 290, 875, 290, 0, 0, 0, 255]
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Solids Borders - main.rb link

    # ./samples/01_rendering_basics/03_solids_borders/app/main.rb
=begin

APIs listing that haven't been encountered in a previous sample apps:

- args.outputs.solids: An array. Values in this array generate
  solid/filled rectangles on the screen.

=end

# Rects are outputted in DragonRuby as rectangles
# If filled in, they are solids
# If hollow, they are borders

# Solids are added to args.outputs.solids
# Borders are added to args.outputs.borders

# The parameters required for rects are:
# 1. The upper right corner (x, y)
# 2. The width (w)
# 3. The height (h)
# 4. The rgba values for the color and transparency (r, g, b, a)

# Here is an example of a rect definition:
# [100, 100, 400, 500, 0, 255, 0, 180]

# The example would create a rect from (100, 100)
# Extending 400 pixels across the x axis
# and 500 pixels across the y axis
# The rect would be green (0, 255, 0)
# and mostly opaque with some transparency (180)

# Whether the rect would be filled or not depends on if
# it is added to args.outputs.solids or args.outputs.borders


def tick args
  tick_instructions args, "Sample app shows how to create solid squares."
  args.outputs.labels << [460, 600, "Solids (x, y, w, h, r, g, b, a)"]
  args.outputs.solids << [470, 520, 50, 50]
  args.outputs.solids << [530, 520, 50, 50, 0, 0, 0]
  args.outputs.solids << [590, 520, 50, 50, 255, 0, 0]
  args.outputs.solids << [650, 520, 50, 50, 255, 0, 0, 128]
  args.outputs.solids << [710, 520, 50, 50, 0, 0, 0, 128 + args.state.tick_count % 128]


  args.outputs.labels <<  [460, 400, "Borders (x, y, w, h, r, g, b, a)"]
  args.outputs.borders << [470, 320, 50, 50]
  args.outputs.borders << [530, 320, 50, 50, 0, 0, 0]
  args.outputs.borders << [590, 320, 50, 50, 255, 0, 0]
  args.outputs.borders << [650, 320, 50, 50, 255, 0, 0, 128]
  args.outputs.borders << [710, 320, 50, 50, 0, 0, 0, 128 + args.state.tick_count % 128]
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Sprites - main.rb link

    # ./samples/01_rendering_basics/04_sprites/app/main.rb
=begin

APIs listing that haven't been encountered in a previous sample apps:

- args.outputs.sprites: An array. Values in this array generate
  sprites on the screen. The location of the sprite is assumed to
  be under the mygame/ directory (the exception being dragonruby.png).

=end


# For all other display outputs, Sprites are your solution
# Sprites import images and display them with a certain rectangular area
# The image can be of any usual format and should be located within the folder,
# similar to additional fonts.

# Sprites have the following parameters
# Rectangular area (x, y, width, height)
# The image (path)
# Rotation (angle)
# Alpha (a)

def tick args
  tick_instructions args, "Sample app shows how to render a sprite. Set its alpha, and rotate it."
  args.outputs.labels <<  [460, 600, "Sprites (x, y, w, h, path, angle, a)"]
  args.outputs.sprites << [460, 470, 128, 101, 'dragonruby.png']
  args.outputs.sprites << [610, 470, 128, 101, 'dragonruby.png', args.state.tick_count % 360]
  args.outputs.sprites << [760, 470, 128, 101, 'dragonruby.png', 0, args.state.tick_count % 255]
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Sounds - main.rb link

    # ./samples/01_rendering_basics/05_sounds/app/main.rb
=begin

 APIs Listing that haven't been encountered in previous sample apps:

 - sample: Chooses random element from array.
   In this sample app, the target note is set by taking a sample from the collection
   of available notes.

 Reminders:

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.
=end

# This sample app allows users to test their musical skills by matching the piano sound that plays in each
# level to the correct note.

# Runs all the methods necessary for the game to function properly.
def tick args
  args.outputs.labels << [640, 360, "Click anywhere to play a random sound.", 0, 1]
  args.state.notes ||= [:C3, :D3, :E3, :F3, :G3, :A3, :B3, :C4]

  if args.inputs.mouse.click
    # Play a sound by adding a string to args.outputs.sounds
    args.outputs.sounds << "sounds/#{args.state.notes.sample}.wav" # sound of target note is output
  end
end

    Input Basics link

    Keyboard - main.rb link

    # ./samples/02_input_basics/01_keyboard/app/main.rb
=begin

APIs listing that haven't been encountered in a previous sample apps:

- args.inputs.keyboard.key_up.KEY: The value of the properties will be set
  to the frame  that the key_up event occurred (the frame correlates
  to args.state.tick_count). Otherwise the value will be nil. For a
  full listing of keys, take a look at mygame/documentation/06-keyboard.md.
- args.state.PROPERTY: The state property on args is a dynamic
  structure. You can define ANY property here with ANY type of
  arbitrary nesting. Properties defined on args.state will be retained
  across frames. If you attempt access a property that doesn't exist
  on args.state, it will simply return nil (no exception will be thrown).

=end

# Along with outputs, inputs are also an essential part of video game development
# DragonRuby can take input from keyboards, mouse, and controllers.
# This sample app will cover keyboard input.

# args.inputs.keyboard.key_up.a will check to see if the a key has been pressed
# This will work with the other keys as well


def tick args
  tick_instructions args, "Sample app shows how keyboard events are registered and accessed.", 360
  args.outputs.labels << { x: 460, y: row_to_px(args, 0), text: "Current game time: #{args.state.tick_count}", size_enum: -1 }
  args.outputs.labels << { x: 460, y: row_to_px(args, 2), text: "Keyboard input: args.inputs.keyboard.key_up.h", size_enum: -1 }
  args.outputs.labels << { x: 460, y: row_to_px(args, 3), text: "Press \"h\" on the keyboard.", size_enum: -1 }

  # Input on a specifc key can be found through args.inputs.keyboard.key_up followed by the key
  if args.inputs.keyboard.key_up.h
    args.state.h_pressed_at = args.state.tick_count
  end

  # This code simplifies to if args.state.h_pressed_at has not been initialized, set it to false
  args.state.h_pressed_at ||= false

  if args.state.h_pressed_at
    args.outputs.labels << { x: 460, y: row_to_px(args, 4), text: "\"h\" was pressed at time: #{args.state.h_pressed_at}", size_enum: -1 }
  else
    args.outputs.labels << { x: 460, y: row_to_px(args, 4), text: "\"h\" has never been pressed.", size_enum: -1 }
  end

  tick_help_text args
end

def row_to_px args, row_number, y_offset = 20
  # This takes a row_number and converts it to pixels DragonRuby understands.
  # Row 0 starts 5 units below the top of the grid
  # Each row afterward is 20 units lower
  args.grid.top - 5 - (y_offset * row_number)
end

# Don't worry about understanding the code within this method just yet.
# This method shows you the help text within the game.
def tick_help_text args
  return unless args.state.h_pressed_at

  args.state.key_value_history      ||= {}
  args.state.key_down_value_history ||= {}
  args.state.key_held_value_history ||= {}
  args.state.key_up_value_history   ||= {}

  if (args.inputs.keyboard.key_down.truthy_keys.length > 0 ||
      args.inputs.keyboard.key_held.truthy_keys.length > 0 ||
      args.inputs.keyboard.key_up.truthy_keys.length > 0)
    args.state.help_available = true
    args.state.no_activity_debounce = nil
  else
    args.state.no_activity_debounce ||= 5.seconds
    args.state.no_activity_debounce -= 1
    if args.state.no_activity_debounce <= 0
      args.state.help_available = false
      args.state.key_value_history        = {}
      args.state.key_down_value_history   = {}
      args.state.key_held_value_history   = {}
      args.state.key_up_value_history     = {}
    end
  end

  args.outputs.labels << { x: 10, y: row_to_px(args, 6), text: "This is the api for the keys you've pressed:", size_enum: -1, r: 180 }

  if !args.state.help_available
    args.outputs.labels << [10, row_to_px(args, 7),  "Press a key and I'll show code to access the key and what value will be returned if you used the code."]
    return
  end

  args.outputs.labels << { x: 10 , y: row_to_px(args, 7), text: "args.inputs.keyboard",          size_enum: -2 }
  args.outputs.labels << { x: 330, y: row_to_px(args, 7), text: "args.inputs.keyboard.key_down", size_enum: -2 }
  args.outputs.labels << { x: 650, y: row_to_px(args, 7), text: "args.inputs.keyboard.key_held", size_enum: -2 }
  args.outputs.labels << { x: 990, y: row_to_px(args, 7), text: "args.inputs.keyboard.key_up",   size_enum: -2 }

  fill_history args, :key_value_history,      :down_or_held, nil
  fill_history args, :key_down_value_history, :down,        :key_down
  fill_history args, :key_held_value_history, :held,        :key_held
  fill_history args, :key_up_value_history,   :up,          :key_up

  render_help_labels args, :key_value_history,      :down_or_held, nil,      10
  render_help_labels args, :key_down_value_history, :down,        :key_down, 330
  render_help_labels args, :key_held_value_history, :held,        :key_held, 650
  render_help_labels args, :key_up_value_history,   :up,          :key_up,   990
end

def fill_history args, history_key, state_key, keyboard_method
  fill_single_history args, history_key, state_key, keyboard_method, :raw_key
  fill_single_history args, history_key, state_key, keyboard_method, :char
  args.inputs.keyboard.keys[state_key].each do |key_name|
    fill_single_history args, history_key, state_key, keyboard_method, key_name
  end
end

def fill_single_history args, history_key, state_key, keyboard_method, key_name
  current_value = args.inputs.keyboard.send(key_name)
  if keyboard_method
    current_value = args.inputs.keyboard.send(keyboard_method).send(key_name)
  end
  args.state.as_hash[history_key][key_name] ||= []
  args.state.as_hash[history_key][key_name] << current_value
  args.state.as_hash[history_key][key_name] = args.state.as_hash[history_key][key_name].reverse.uniq.take(3).reverse
end

def render_help_labels args, history_key, state_key, keyboard_method, x
  idx = 8
  args.outputs.labels << args.state
                           .as_hash[history_key]
                           .keys
                           .reverse
                           .map
                           .with_index do |k, i|
    v = args.state.as_hash[history_key][k]
    current_value = args.inputs.keyboard.send(k)
    if keyboard_method
      current_value = args.inputs.keyboard.send(keyboard_method).send(k)
    end
    idx += 2
    [
      { x: x, y: row_to_px(args, idx + 0, 16), text: "    .#{k} is #{current_value || "nil"}", size_enum: -2 },
      { x: x, y: row_to_px(args, idx + 1, 16), text: "       was #{v}", size_enum: -2 }
    ]
  end
end


def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << { x: 0,   y: y - 50, w: 1280, h: 60 }.solid!
  args.outputs.debug << { x: 640, y: y,      text: text,
                          size_enum: 1, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  args.outputs.debug << { x: 640, y: y - 25, text: "(click to dismiss instructions)",
                          size_enum: -2, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
end

    Moving A Sprite - main.rb link

    # ./samples/02_input_basics/01_moving_a_sprite/app/main.rb
def tick args
  # create a player and set default values
  # for the player's x, y, w (width), and h (height)
  args.state.player.x ||= 100
  args.state.player.y ||= 100
  args.state.player.w ||=  50
  args.state.player.h ||=  50

  # render the player to the screen
  args.outputs.sprites << { x: args.state.player.x,
                            y: args.state.player.y,
                            w: args.state.player.w,
                            h: args.state.player.h,
                            path: 'sprites/square/green.png' }

  # move the player around using the keyboard
  if args.inputs.up
    args.state.player.y += 10
  elsif args.inputs.down
    args.state.player.y -= 10
  end

  if args.inputs.left
    args.state.player.x -= 10
  elsif args.inputs.right
    args.state.player.x += 10
  end
end

$gtk.reset

    Mouse - main.rb link

    # ./samples/02_input_basics/02_mouse/app/main.rb
=begin

APIs that haven't been encountered in a previous sample apps:

- args.inputs.mouse.click: This property will be set if the mouse was clicked.
- args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.
- args.inputs.mouse.click.point.created_at: The frame the mouse click occurred in.
- args.inputs.mouse.click.point.created_at_elapsed: How many frames have passed
  since the click event.

Reminder:

- args.state.PROPERTY: The state property on args is a dynamic
  structure. You can define ANY property here with ANY type of
  arbitrary nesting. Properties defined on args.state will be retained
  across frames. If you attempt access a property that doesn't exist
  on args.state, it will simply return nil (no exception will be thrown).

=end

# This code demonstrates DragonRuby mouse input

# To see if the a mouse click occurred
# Use args.inputs.mouse.click
# Which returns a boolean

# To see where a mouse click occurred
# Use args.inputs.mouse.click.point.x AND
# args.inputs.mouse.click.point.y

# To see which frame the click occurred
# Use args.inputs.mouse.click.created_at

# To see how many frames its been since the click occurred
# Use args.inputs.mouse.click.created_at_elapsed

# Saving the click in args.state can be quite useful

def tick args
  tick_instructions args, "Sample app shows how mouse events are registered and how to measure elapsed time."
  x = 460

  args.outputs.labels << small_label(args, x, 11, "Mouse input: args.inputs.mouse")

  if args.inputs.mouse.click
    args.state.last_mouse_click = args.inputs.mouse.click
  end

  if args.state.last_mouse_click
    click = args.state.last_mouse_click
    args.outputs.labels << small_label(args, x, 12, "Mouse click happened at: #{click.created_at}")
    args.outputs.labels << small_label(args, x, 13, "Mouse clicked #{click.created_at_elapsed} ticks ago")
    args.outputs.labels << small_label(args, x, 14, "Mouse click location: #{click.point.x}, #{click.point.y}")
  else
    args.outputs.labels << small_label(args, x, 12, "Mouse click has not occurred yet.")
    args.outputs.labels << small_label(args, x, 13, "Please click mouse.")
  end
end

def small_label args, x, row, message
  # This method effectively combines the row_to_px
  # It changes the given row value to a DragonRuby pixel value
  # and adds the customization parameters
  { x: x, y: row_to_px(args, row), text: message, alignment_enum: -2 }
end

def row_to_px args, row_number
  args.grid.top.shift_down(5).shift_down(20 * row_number)
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << { x: 0,   y: y - 50, w: 1280, h: 60 }.solid!
  args.outputs.debug << { x: 640, y: y, text: text, size_enum: 1, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  args.outputs.debug << { x: 640, y: y - 25, text: "(click to dismiss instructions)", size_enum: -2, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
end

    Mouse Point To Rect - main.rb link

    # ./samples/02_input_basics/03_mouse_point_to_rect/app/main.rb
=begin

APIs that haven't been encountered in a previous sample apps:

- args.outputus.borders: An array. Values in this array will be rendered as
  unfilled rectangles on the screen.
- ARRAY#inside_rect?: An array with at least two values is considered a point. An array
  with at least four values is considered a rect. The inside_rect? function returns true
  or false depending on if the point is inside the rect.

  ```
  # Point:  x: 100, y: 100
  # Rect:   x: 0, y: 0, w: 500, h: 500
  # Result: true

  [100, 100].inside_rect? [0, 0, 500, 500]
  ```

  ```
  # Point:  x: 100, y: 100
  # Rect:   x: 300, y: 300, w: 100, h: 100
  # Result: false

  [100, 100].inside_rect? [300, 300, 100, 100]
  ```

- args.inputs.mouse.click.point.created_at: The frame the mouse click occurred in.
- args.inputs.mouse.click.point.created_at_elapsed: How many frames have passed
  since the click event.

=end

# To determine whether a point is in a rect
# Use point.inside_rect? rect

# This is useful to determine if a click occurred in a rect

def tick args
  tick_instructions args, "Sample app shows how to determing if a click happened inside a rectangle."

  x = 460

  args.outputs.labels << small_label(args, x, 15, "Click inside the blue box maybe ---->")

  box = { x: 785, y: 370, w: 50, h: 50, r: 0, g: 0, b: 170 }
  args.outputs.borders << box

  # Saves the most recent click into args.state
  # Unlike the other components of args,
  # args.state does not reset every tick.
  if args.inputs.mouse.click
    args.state.last_mouse_click = args.inputs.mouse.click
  end

  if args.state.last_mouse_click
    if args.state.last_mouse_click.point.inside_rect? box
      args.outputs.labels << small_label(args, x, 16, "Mouse click happened *inside* the box.")
    else
      args.outputs.labels << small_label(args, x, 16, "Mouse click happened *outside* the box.")
    end
  else
    args.outputs.labels << small_label(args, x, 16, "Mouse click has not occurred yet.")
  end
end

def small_label args, x, row, message
  { x: x, y: row_to_px(args, row), text: message, size_enum: -2 }
end

def row_to_px args, row_number
  args.grid.top.shift_down(5).shift_down(20 * row_number)
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << { x: 0,   y: y - 50, w: 1280, h: 60 }.solid!
  args.outputs.debug << { x: 640, y: y, text: text, size_enum: 1, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  args.outputs.debug << { x: 640, y: y - 25, text: "(click to dismiss instructions)", size_enum: -2, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
end

    Mouse Drag And Drop - main.rb link

    # ./samples/02_input_basics/04_mouse_drag_and_drop/app/main.rb
def tick args
  # create 10 random squares on the screen
  if !args.state.squares
    # the squares will be contained in lookup/Hash so that we can access via their id
    args.state.squares = {}
    10.times_with_index do |id|
      # for each square, store it in the hash with
      # the id (we're just using the index 0-9 as the index)
      args.state.squares[id] = {
        id: id,
        x: 100 + (rand * 1080),
        y: 100 + (520 * rand),
        w: 100,
        h: 100,
        path: "sprites/square/blue.png"
      }
    end
  end

  # two key variables are set here
  # - square_reference: this represents the square that is currently being dragged
  # - square_under_mouse: this represents the square that the mouse is currently being hovered over
  if args.state.currently_dragging_square_id
    # if the currently_dragging_square_id is set, then set the "square_under_mouse" to
    # the same square as square_reference
    square_reference = args.state.squares[args.state.currently_dragging_square_id]
    square_under_mouse = square_reference
  else
    # if currently_dragging_square_id isn't set, then see if there is a square that
    # the mouse is currently hovering over (the square reference will be nil since
    # we haven't selected a drag target yet)
    square_under_mouse = args.geometry.find_intersect_rect args.inputs.mouse, args.state.squares.values
    square_reference = nil
  end


  # if a click occurs, and there is a square under the mouse
  if args.inputs.mouse.click && square_under_mouse
    # capture the id of the square that the mouse is hovering over
    args.state.currently_dragging_square_id = square_under_mouse.id

    # also capture where in the square the mouse was clicked so that
    # the movement of the square will smoothly transition with the mouse's
    # location
    args.state.mouse_point_inside_square = {
      x: args.inputs.mouse.x - square_under_mouse.x,
      y: args.inputs.mouse.y - square_under_mouse.y,
    }
  elsif args.inputs.mouse.held && args.state.currently_dragging_square_id
    # if the mouse is currently being held and the currently_dragging_square_id was set,
    # then update the x and y location of the referenced square (taking into consideration the
    # relative position of the mouse when the square was clicked)
    square_reference.x = args.inputs.mouse.x - args.state.mouse_point_inside_square.x
    square_reference.y = args.inputs.mouse.y - args.state.mouse_point_inside_square.y
  elsif args.inputs.mouse.up
    # if the mouse is released, then clear out the currently_dragging_square_id
    args.state.currently_dragging_square_id = nil
  end

  # render all the squares on the screen
  args.outputs.sprites << args.state.squares.values

  # if there was a square under the mouse, add an "overlay"
  if square_under_mouse
    args.outputs.sprites << square_under_mouse.merge(path: "sprites/square/red.png")
  end
end

    Mouse Rect To Rect - main.rb link

    # ./samples/02_input_basics/04_mouse_rect_to_rect/app/main.rb
=begin

APIs that haven't been encountered in a previous sample apps:

- args.outputs.borders: An array. Values in this array will be rendered as
  unfilled rectangles on the screen.
- ARRAY#intersect_rect?: An array with at least four values is
  considered a rect. The intersect_rect? function returns true
  or false depending on if the two rectangles intersect.

  ```
  # Rect One: x: 100, y: 100, w: 100, h: 100
  # Rect Two: x: 0, y: 0, w: 500, h: 500
  # Result:   true

  [100, 100, 100, 100].intersect_rect? [0, 0, 500, 500]
  ```

  ```
  # Rect One: x: 100, y: 100, w: 10, h: 10
  # Rect Two: x: 500, y: 500, w: 10, h: 10
  # Result:   false

  [100, 100, 10, 10].intersect_rect? [500, 500, 10, 10]
  ```

=end

# Similarly, whether rects intersect can be found through
# rect1.intersect_rect? rect2

def tick args
  tick_instructions args, "Sample app shows how to determine if two rectangles intersect."
  x = 460

  args.outputs.labels << small_label(args, x, 3, "Click anywhere on the screen")
  # red_box = [460, 250, 355, 90, 170, 0, 0]
  # args.outputs.borders << red_box

  # args.state.box_collision_one and args.state.box_collision_two
  # Are given values of a solid when they should be rendered
  # They are stored in game so that they do not get reset every tick
  if args.inputs.mouse.click
    if !args.state.box_collision_one
      args.state.box_collision_one = { x: args.inputs.mouse.click.point.x - 25,
                                       y: args.inputs.mouse.click.point.y - 25,
                                       w: 125, h: 125,
                                       r: 180, g: 0, b: 0, a: 180 }
    elsif !args.state.box_collision_two
      args.state.box_collision_two = { x: args.inputs.mouse.click.point.x - 25,
                                       y: args.inputs.mouse.click.point.y - 25,
                                       w: 125, h: 125,
                                       r: 0, g: 0, b: 180, a: 180 }
    else
      args.state.box_collision_one = nil
      args.state.box_collision_two = nil
    end
  end

  if args.state.box_collision_one
    args.outputs.solids << args.state.box_collision_one
  end

  if args.state.box_collision_two
    args.outputs.solids << args.state.box_collision_two
  end

  if args.state.box_collision_one && args.state.box_collision_two
    if args.state.box_collision_one.intersect_rect? args.state.box_collision_two
      args.outputs.labels << small_label(args, x, 4, 'The boxes intersect.')
    else
      args.outputs.labels << small_label(args, x, 4, 'The boxes do not intersect.')
    end
  else
    args.outputs.labels << small_label(args, x, 4, '--')
  end
end

def small_label args, x, row, message
  { x: x, y: row_to_px(args, row), text: message, size_enum: -2 }
end

def row_to_px args, row_number
  args.grid.top - 5 - (20 * row_number)
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Controller - main.rb link

    # ./samples/02_input_basics/05_controller/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - args.current_controller.key_held.KEY: Will check to see if a specific key
   is being held down on the controller.
   If there is more than one controller being used, they can be differentiated by
   using names like controller_one and controller_two.

   For a full listing of buttons, take a look at mygame/documentation/08-controllers.md.

 Reminder:

 - args.state.PROPERTY: The state property on args is a dynamic
   structure. You can define ANY property here with ANY type of
   arbitrary nesting. Properties defined on args.state will be retained
   across frames. If you attempt to access a property that doesn't exist
   on args.state, it will simply return nil (no exception will be thrown).

   In this sample app, args.state.BUTTONS is an array that stores the buttons of the controller.
   The parameters of a button are:
   1. the position (x, y)
   2. the input key held on the controller
   3. the text or name of the button

=end

# This sample app provides a visual demonstration of a standard controller, including
# the placement and function of all buttons.

class ControllerDemo
  attr_accessor :inputs, :state, :outputs

  # Calls the methods necessary for the app to run successfully.
  def tick
    process_inputs
    render
  end

  # Starts with an empty collection of buttons.
  # Adds buttons that are on the controller to the collection.
  def process_inputs
    state.target  ||= :controller_one
    state.buttons = []

    if inputs.keyboard.key_down.tab
      if state.target == :controller_one
        state.target = :controller_two
      elsif state.target == :controller_two
        state.target = :controller_three
      elsif state.target == :controller_three
        state.target = :controller_four
      elsif state.target == :controller_four
        state.target = :controller_one
      end
    end

    state.buttons << { x: 100,  y: 500, active: current_controller.key_held.l1, text: "L1"}
    state.buttons << { x: 100,  y: 600, active: current_controller.key_held.l2, text: "L2"}
    state.buttons << { x: 1100, y: 500, active: current_controller.key_held.r1, text: "R1"}
    state.buttons << { x: 1100, y: 600, active: current_controller.key_held.r2, text: "R2"}
    state.buttons << { x: 540,  y: 450, active: current_controller.key_held.select, text: "Select"}
    state.buttons << { x: 660,  y: 450, active: current_controller.key_held.start, text: "Start"}
    state.buttons << { x: 200,  y: 300, active: current_controller.key_held.left, text: "Left"}
    state.buttons << { x: 300,  y: 400, active: current_controller.key_held.up, text: "Up"}
    state.buttons << { x: 400,  y: 300, active: current_controller.key_held.right, text: "Right"}
    state.buttons << { x: 300,  y: 200, active: current_controller.key_held.down, text: "Down"}
    state.buttons << { x: 800,  y: 300, active: current_controller.key_held.x, text: "X"}
    state.buttons << { x: 900,  y: 400, active: current_controller.key_held.y, text: "Y"}
    state.buttons << { x: 1000, y: 300, active: current_controller.key_held.a, text: "A"}
    state.buttons << { x: 900,  y: 200, active: current_controller.key_held.b, text: "B"}
    state.buttons << { x: 450 + current_controller.left_analog_x_perc * 100,
                       y: 100 + current_controller.left_analog_y_perc * 100,
                       active: current_controller.key_held.l3,
                       text: "L3" }
    state.buttons << { x: 750 + current_controller.right_analog_x_perc * 100,
                       y: 100 + current_controller.right_analog_y_perc * 100,
                       active: current_controller.key_held.r3,
                       text: "R3" }
  end

  # Gives each button a square shape.
  # If the button is being pressed or held (which means it is considered active),
  # the square is filled in. Otherwise, the button simply has a border.
  def render
    state.buttons.each do |b|
      rect = { x: b.x, y: b.y, w: 75, h: 75 }

      if b.active # if button is pressed
        outputs.solids << rect # rect is output as solid (filled in)
      else
        outputs.borders << rect # otherwise, output as border
      end

      # Outputs the text of each button using labels.
      outputs.labels << { x: b.x, y: b.y + 95, text: b.text } # add 95 to place label above button
    end

    outputs.labels << { x:  10, y: 60, text: "Left Analog x: #{current_controller.left_analog_x_raw} (#{current_controller.left_analog_x_perc * 100}%)" }
    outputs.labels << { x:  10, y: 30, text: "Left Analog y: #{current_controller.left_analog_y_raw} (#{current_controller.left_analog_y_perc * 100}%)" }
    outputs.labels << { x: 1270, y: 60, text: "Right Analog x: #{current_controller.right_analog_x_raw} (#{current_controller.right_analog_x_perc * 100}%)", alignment_enum: 2 }
    outputs.labels << { x: 1270, y: 30, text: "Right Analog y: #{current_controller.right_analog_y_raw} (#{current_controller.right_analog_y_perc * 100}%)" , alignment_enum: 2 }

    outputs.labels << { x: 640, y: 60, text: "Target: #{state.target} (press tab to go to next controller)", alignment_enum: 1 }
    outputs.labels << { x: 640, y: 30, text: "Connected: #{current_controller.connected}", alignment_enum: 1 }
  end

  def current_controller
    if state.target == :controller_one
      return inputs.controller_one
    elsif state.target == :controller_two
      return inputs.controller_two
    elsif state.target == :controller_three
      return inputs.controller_three
    elsif state.target == :controller_four
      return inputs.controller_four
    end
  end
end

$controller_demo = ControllerDemo.new

def tick args
  tick_instructions args, "Sample app shows how controller input is handled. You'll need to connect a USB controller."
  $controller_demo.inputs = args.inputs
  $controller_demo.state = args.state
  $controller_demo.outputs = args.outputs
  $controller_demo.tick
end

# Resets the app.
def r
  $gtk.reset
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Touch - main.rb link

    # ./samples/02_input_basics/06_touch/app/main.rb
def tick args
  args.outputs.background_color = [ 0, 0, 0 ]
  args.outputs.primitives << [640, 700, "Touch your screen.", 5, 1, 255, 255, 255].label

  # If you don't want to get fancy, you can just look for finger_one
  #  (and _two, if you like), which are assigned in the order new touches hit
  #  the screen. If not nil, they are touching right now, and are just
  #  references to specific items in the args.input.touch hash.
  # If finger_one lifts off, it will become nil, but finger_two, if it was
  #  touching, remains until it also lifts off. When all fingers lift off, the
  #  the next new touch will be finger_one again, but until then, new touches
  #  don't fill in earlier slots.
  if !args.inputs.finger_one.nil?
    args.outputs.primitives << { x: 640, y: 650, text: "Finger #1 is touching at (#{args.inputs.finger_one.x}, #{args.inputs.finger_one.y}).",
                                 size_enum: 5, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  end
  if !args.inputs.finger_two.nil?
    args.outputs.primitives << { x: 640, y: 600, text: "Finger #2 is touching at (#{args.inputs.finger_two.x}, #{args.inputs.finger_two.y}).",
                                 size_enum: 5, alignment_enum: 1, r: 255, g: 255, b: 255 }.label!
  end

  # Here's the more flexible interface: this will report as many simultaneous
  #  touches as the system can handle, but it's a little more effort to track
  #  them. Each item in the args.input.touch hash has a unique key (an
  #  incrementing integer) that exists until the finger lifts off. You can
  #  tell which order the touches happened globally by the key value, or
  #  by the touch[id].touch_order field, which resets to zero each time all
  #  touches have lifted.

  args.state.colors ||= [
    0xFF0000, 0x00FF00, 0x1010FF, 0xFFFF00, 0xFF00FF, 0x00FFFF, 0xFFFFFF
  ]

  size = 100
  args.inputs.touch.each { |k,v|
    color = args.state.colors[v.touch_order % 7]
    r = (color & 0xFF0000) >> 16
    g = (color & 0x00FF00) >> 8
    b = (color & 0x0000FF)
    args.outputs.primitives << { x: v.x - (size / 2), y: v.y + (size / 2), w: size, h: size, r: r, g: g, b: b, a: 255 }.solid!
    args.outputs.primitives << { x: v.x, y: v.y + size, text: k.to_s, alignment_enum: 1 }.label!
  }
end

    Managing Scenes - main.rb link

    # ./samples/02_input_basics/07_managing_scenes/app/main.rb
def tick args
  # initialize the scene to scene 1
  args.state.current_scene ||= :title_scene
  # capture the current scene to verify it didn't change through
  # the duration of tick
  current_scene = args.state.current_scene

  # tick whichever scene is current
  case current_scene
  when :title_scene
    tick_title_scene args
  when :game_scene
    tick_game_scene args
  when :game_over_scene
    tick_game_over_scene args
  end

  # make sure that the current_scene flag wasn't set mid tick
  if args.state.current_scene != current_scene
    raise "Scene was changed incorrectly. Set args.state.next_scene to change scenes."
  end

  # if next scene was set/requested, then transition the current scene to the next scene
  if args.state.next_scene
    args.state.current_scene = args.state.next_scene
    args.state.next_scene = nil
  end
end

def tick_title_scene args
  args.outputs.labels << { x: 640,
                           y: 360,
                           text: "Title Scene (click to go to game)",
                           alignment_enum: 1 }

  if args.inputs.mouse.click
    args.state.next_scene = :game_scene
  end
end

def tick_game_scene args
  args.outputs.labels << { x: 640,
                           y: 360,
                           text: "Game Scene (click to go to game over)",
                           alignment_enum: 1 }

  if args.inputs.mouse.click
    args.state.next_scene = :game_over_scene
  end
end

def tick_game_over_scene args
  args.outputs.labels << { x: 640,
                           y: 360,
                           text: "Game Over Scene (click to go to title)",
                           alignment_enum: 1 }

  if args.inputs.mouse.click
    args.state.next_scene = :title_scene
  end
end

    Rendering Sprites link

    Animation Using Separate Pngs - main.rb link

    # ./samples/03_rendering_sprites/01_animation_using_separate_pngs/app/main.rb
=begin

 Reminders:

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

   In this sample app, we're using string interpolation to iterate through images in the
   sprites folder using their image path names.

 - args.outputs.sprites: An array. Values in this array generate sprites on the screen.
   The parameters are [X, Y, WIDTH, HEIGHT, IMAGE PATH]
   For more information about sprites, go to mygame/documentation/05-sprites.md.

 - args.outputs.labels: An array. Values in the array generate labels on the screen.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.inputs.keyboard.key_down.KEY: Determines if a key is in the down state, or pressed.
   Stores the frame that key was pressed on.
   For more information about the keyboard, go to mygame/documentation/06-keyboard.md.

=end

# This sample app demonstrates how sprite animations work.
# There are two sprites that animate forever and one sprite
# that *only* animates when you press the "f" key on the keyboard.

# This is the entry point to your game. The `tick` method
# executes at 60 frames per second. There are two methods
# in this tick "entry point": `looping_animation`, and the
# second method is `one_time_animation`.
def tick args
  # uncomment the line below to see animation play out in slow motion
  # args.gtk.slowmo! 6
  looping_animation args
  one_time_animation args
end

# This function shows how to animate a sprite that loops forever.
def looping_animation args
  # Here we define a few local variables that will be sent
  # into the magic function that gives us the correct sprite image
  # over time. There are four things we need in order to figure
  # out which sprite to show.

  # 1. When to start the animation.
  start_looping_at = 0

  # 2. The number of pngs that represent the full animation.
  number_of_sprites = 6

  # 3. How long to show each png.
  number_of_frames_to_show_each_sprite = 4

  # 4. Whether the animation should loop once, or forever.
  does_sprite_loop = true

  # With the variables defined above, we can get a number
  # which represents the sprite to show by calling the `frame_index` function.
  # In this case the number will be between 0, and 5 (you can see the sprites
  # in the ./sprites directory).
  sprite_index = start_looping_at.frame_index number_of_sprites,
                                              number_of_frames_to_show_each_sprite,
                                              does_sprite_loop

  # Now that we have `sprite_index, we can present the correct file.
  args.outputs.sprites << { x: 100, y: 100, w: 100, h: 100, path: "sprites/dragon_fly_#{sprite_index}.png" }

  # Try changing the numbers below to see how the animation changes:
  args.outputs.sprites << { x: 100, y: 200, w: 100, h: 100, path: "sprites/dragon_fly_#{0.frame_index 6, 4, true}.png" }
end

# This function shows how to animate a sprite that executes
# only once when the "f" key is pressed.
def one_time_animation args
  # This is just a label the shows instructions within the game.
  args.outputs.labels <<  { x: 220, y: 350, text: "(press f to animate)" }

  # If "f" is pressed on the keyboard...
  if args.inputs.keyboard.key_down.f
    # Print the frame that "f" was pressed on.
    puts "Hello from main.rb! The \"f\" key was in the down state on frame: #{args.state.tick_count}"

    # And MOST IMPORTANTLY set the point it time to start the animation,
    # equal to "now" which is represented as args.state.tick_count.

    # Also IMPORTANT, you'll notice that the value of when to start looping
    # is stored in `args.state`. This construct's values are retained across
    # executions of the `tick` method.
    args.state.start_looping_at = args.state.tick_count
  end

  # These are the same local variables that were defined
  # for the `looping_animation` function.
  number_of_sprites = 6
  number_of_frames_to_show_each_sprite = 4

  # Except this sprite does not loop again. If the animation time has passed,
  # then the frame_index function returns nil.
  does_sprite_loop = false

  if args.state.start_looping_at
    sprite_index = args.state
                       .start_looping_at
                       .frame_index number_of_sprites,
                                    number_of_frames_to_show_each_sprite,
                                    does_sprite_loop
  end

  # This line sets the frame index to zero, if
  # the animation duration has passed (frame_index returned nil).

  # Remeber: we are not looping forever here.
  sprite_index ||= 0

  # Present the sprite.
  args.outputs.sprites << { x: 100, y: 300, w: 100, h: 100, path: "sprites/dragon_fly_#{sprite_index}.png" }

  tick_instructions args, "Sample app shows how to use Numeric#frame_index and string interpolation to animate a sprite over time."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Animation Using Sprite Sheet - main.rb link

    # ./samples/03_rendering_sprites/02_animation_using_sprite_sheet/app/main.rb
def tick args
  args.state.player.x ||= 100
  args.state.player.y ||= 100
  args.state.player.w ||= 64
  args.state.player.h ||= 64
  args.state.player.direction ||= 1

  args.state.player.is_moving = false

  # get the keyboard input and set player properties
  if args.inputs.keyboard.right
    args.state.player.x += 3
    args.state.player.direction = 1
    args.state.player.started_running_at ||= args.state.tick_count
  elsif args.inputs.keyboard.left
    args.state.player.x -= 3
    args.state.player.direction = -1
    args.state.player.started_running_at ||= args.state.tick_count
  end

  if args.inputs.keyboard.up
    args.state.player.y += 1
    args.state.player.started_running_at ||= args.state.tick_count
  elsif args.inputs.keyboard.down
    args.state.player.y -= 1
    args.state.player.started_running_at ||= args.state.tick_count
  end

  # if no arrow keys are being pressed, set the player as not moving
  if !args.inputs.keyboard.directional_vector
    args.state.player.started_running_at = nil
  end

  # wrap player around the stage
  if args.state.player.x > 1280
    args.state.player.x = -64
    args.state.player.started_running_at ||= args.state.tick_count
  elsif args.state.player.x < -64
    args.state.player.x = 1280
    args.state.player.started_running_at ||= args.state.tick_count
  end

  if args.state.player.y > 720
    args.state.player.y = -64
    args.state.player.started_running_at ||= args.state.tick_count
  elsif args.state.player.y < -64
    args.state.player.y = 720
    args.state.player.started_running_at ||= args.state.tick_count
  end

  # render player as standing or running
  if args.state.player.started_running_at
    args.outputs.sprites << running_sprite(args)
  else
    args.outputs.sprites << standing_sprite(args)
  end
  args.outputs.labels << [30, 700, "Use arrow keys to move around."]
end

def standing_sprite args
  {
    x: args.state.player.x,
    y: args.state.player.y,
    w: args.state.player.w,
    h: args.state.player.h,
    path: "sprites/horizontal-stand.png",
    flip_horizontally: args.state.player.direction > 0
  }
end

def running_sprite args
  if !args.state.player.started_running_at
    tile_index = 0
  else
    how_many_frames_in_sprite_sheet = 6
    how_many_ticks_to_hold_each_frame = 3
    should_the_index_repeat = true
    tile_index = args.state
                     .player
                     .started_running_at
                     .frame_index(how_many_frames_in_sprite_sheet,
                                  how_many_ticks_to_hold_each_frame,
                                  should_the_index_repeat)
  end

  {
    x: args.state.player.x,
    y: args.state.player.y,
    w: args.state.player.w,
    h: args.state.player.h,
    path: 'sprites/horizontal-run.png',
    tile_x: 0 + (tile_index * args.state.player.w),
    tile_y: 0,
    tile_w: args.state.player.w,
    tile_h: args.state.player.h,
    flip_horizontally: args.state.player.direction > 0,
  }
end

    Animation States - main.rb link

    # ./samples/03_rendering_sprites/03_animation_states/app/main.rb
class Game
  attr_gtk

  def defaults
    state.show_debug_layer  = true if state.tick_count == 0
    player.tile_size        = 64
    player.speed            = 3
    player.slash_frames     = 15
    player.x              ||= 50
    player.y              ||= 400
    player.dir_x          ||=  1
    player.dir_y          ||= -1
    player.is_moving      ||= false
    state.watch_list      ||= {}
    state.enemies         ||= []
  end

  def add_enemy
    state.enemies << {
      x: 1200 * rand,
      y: 600 * rand,
      w: 64,
      h: 64,
      anchor_x: 0.5,
      anchor_y: 0.5,
      path: 'sprites/enemy.png'
    }
  end

  def sprite_horizontal_run
    tile_index = 0.frame_index(6, 3, true)
    tile_index = 0 if !player.is_moving

    {
      x: player.x,
      y: player.y,
      w: player.tile_size,
      h: player.tile_size,
      anchor_x: 0.5,
      anchor_y: 0.5,
      path: 'sprites/horizontal-run.png',
      tile_x: 0 + (tile_index * player.tile_size),
      tile_y: 0,
      tile_w: player.tile_size,
      tile_h: player.tile_size,
      flip_horizontally: player.dir_x > 0,
      # a: 40
    }
  end

  def sprite_horizontal_stand
    {
      x: player.x,
      y: player.y,
      w: player.tile_size,
      h: player.tile_size,
      anchor_x: 0.5,
      anchor_y: 0.5,
      path: 'sprites/horizontal-stand.png',
      flip_horizontally: player.dir_x > 0,
      # a: 40
    }
  end

  def sprite_horizontal_slash
    tile_index   = player.slash_at.frame_index(5, player.slash_frames.idiv(5), false) || 0

    {
      x: player.x + player.dir_x.sign * 9.25,
      y: player.y + 9.25,
      w: 165,
      h: 165,
      anchor_x: 0.5,
      anchor_y: 0.5,
      path: 'sprites/horizontal-slash.png',
      tile_x: 0 + (tile_index * 128),
      tile_y: 0,
      tile_w: 128,
      tile_h: 128,
      flip_horizontally: player.dir_x > 0
    }
  end

  def render_player
    if player.slash_at
      outputs.sprites << sprite_horizontal_slash
    elsif player.is_moving
      outputs.sprites << sprite_horizontal_run
    else
      outputs.sprites << sprite_horizontal_stand
    end
  end

  def render_enemies
    outputs.borders << state.enemies
  end

  def render_debug_layer
    return if !state.show_debug_layer
    outputs.labels << state.watch_list.map.with_index do |(k, v), i|
       [30, 710 - i * 28, "#{k}: #{v || "(nil)"}"]
    end

    outputs.borders << player.slash_collision_rect
  end

  def slash_initiate?
    # buffalo usb controller has a button and b button swapped lol
    inputs.controller_one.key_down.a || inputs.keyboard.key_down.j
  end

  def input
    # player movement
    if slash_complete? && (vector = inputs.directional_vector)
      player.x += vector.x * player.speed
      player.y += vector.y * player.speed
    end
    player.slash_at = slash_initiate? if slash_initiate?
  end

  def calc_movement
    # movement
    if vector = inputs.directional_vector
      state.debug_label = vector
      player.dir_x = vector.x if vector.x != 0
      player.dir_y = vector.y if vector.y != 0
      player.is_moving = true
    else
      state.debug_label = vector
      player.is_moving = false
    end
  end

  def calc_slash
    player.slash_collision_rect = {
      x: player.x + player.dir_x.sign * 52,
      y: player.y,
      w: 40,
      h: 20,
      anchor_x: 0.5,
      anchor_y: 0.5,
      path: "sprites/debug-slash.png"
    }

    # recalc sword's slash state
    player.slash_at = nil if slash_complete?

    # determine collision if the sword is at it's point of damaging
    return unless slash_can_damage?

    state.enemies.reject! { |e| e.intersect_rect? player.slash_collision_rect }
  end

  def slash_complete?
    !player.slash_at || player.slash_at.elapsed?(player.slash_frames)
  end

  def slash_can_damage?
    # damage occurs half way into the slash animation
    return false if slash_complete?
    return false if (player.slash_at + player.slash_frames.idiv(2)) != state.tick_count
    return true
  end

  def calc
    # generate an enemy if there aren't any on the screen
    add_enemy if state.enemies.length == 0
    calc_movement
    calc_slash
  end

  # source is at http://github.com/amirrajan/dragonruby-link-to-the-past
  def tick
    defaults
    render_enemies
    render_player
    outputs.labels << [30, 30, "Gamepad: D-Pad to move. B button to attack."]
    outputs.labels << [30, 52, "Keyboard: WASD/Arrow keys to move. J to attack."]
    render_debug_layer
    input
    calc
  end

  def player
    state.player
  end
end

$game = Game.new

def tick args
  $game.args = args
  $game.tick
end

$gtk.reset

    Animation States Advanced - main.rb link

    # ./samples/03_rendering_sprites/03_animation_states_advanced/app/main.rb
class Game
  attr_gtk

  def request_action name, at: nil
    at ||= state.tick_count
    state.player.requested_action = name
    state.player.requested_action_at = at
  end

  def defaults
    state.player.x                  ||= 64
    state.player.y                  ||= 0
    state.player.dx                 ||= 0
    state.player.dy                 ||= 0
    state.player.action             ||= :standing
    state.player.action_at          ||= 0
    state.player.next_action_queue  ||= {}
    state.player.facing             ||= 1
    state.player.jump_at            ||= 0
    state.player.jump_count         ||= 0
    state.player.max_speed          ||= 1.0
    state.sabre.x                   ||= state.player.x
    state.sabre.y                   ||= state.player.y
    state.actions_lookup            ||= new_actions_lookup
  end

  def render
    outputs.background_color = [32, 32, 32]
    outputs[:scene].transient!
    outputs[:scene].w = 128
    outputs[:scene].h = 128
    outputs[:scene].borders << { x: 0, y: 0, w: 128, h: 128, r: 255, g: 255, b: 255 }
    render_player
    render_sabre
    args.outputs.sprites << { x: 320, y: 0, w: 640, h: 640, path: :scene }
    args.outputs.labels << { x: 10, y: 100, text: "Controls:", r: 255, g: 255, b: 255, size_enum: -1 }
    args.outputs.labels << { x: 10, y: 80, text: "Move:   left/right", r: 255, g: 255, b: 255, size_enum: -1 }
    args.outputs.labels << { x: 10, y: 60, text: "Jump:   space | up | right click", r: 255, g: 255, b: 255, size_enum: -1 }
    args.outputs.labels << { x: 10, y: 40, text: "Attack: f     | j  | left click", r: 255, g: 255, b: 255, size_enum: -1 }
  end

  def render_sabre
    return if !state.sabre.is_active
    sabre_index = 0.frame_index count:    4,
                                hold_for: 2,
                                repeat:   true
    offset =  0
    offset = -8 if state.player.facing == -1
    outputs[:scene].sprites << { x: state.sabre.x + offset,
                        y: state.sabre.y, w: 16, h: 16, path: "sprites/sabre-throw/#{sabre_index}.png" }
  end

  def new_actions_lookup
    r = {
      slash_0: {
        frame_count: 6,
        interrupt_count: 4,
        path: "sprites/kenobi/slash-0/:index.png"
      },
      slash_1: {
        frame_count: 6,
        interrupt_count: 4,
        path: "sprites/kenobi/slash-1/:index.png"
      },
      throw_0: {
        frame_count: 8,
        throw_frame: 2,
        catch_frame: 6,
        path: "sprites/kenobi/slash-2/:index.png"
      },
      throw_1: {
        frame_count: 9,
        throw_frame: 2,
        catch_frame: 7,
        path: "sprites/kenobi/slash-3/:index.png"
      },
      throw_2: {
        frame_count: 9,
        throw_frame: 2,
        catch_frame: 7,
        path: "sprites/kenobi/slash-4/:index.png"
      },
      slash_5: {
        frame_count: 11,
        path: "sprites/kenobi/slash-5/:index.png"
      },
      slash_6: {
        frame_count: 8,
        interrupt_count: 6,
        path: "sprites/kenobi/slash-6/:index.png"
      }
    }

    r.each.with_index do |(k, v), i|
      v.name               ||= k
      v.index              ||= i

      v.hold_for           ||= 5
      v.duration           ||= v.frame_count * v.hold_for
      v.last_index         ||= v.frame_count - 1

      v.interrupt_count    ||= v.frame_count
      v.interrupt_duration ||= v.interrupt_count * v.hold_for

      v.repeat             ||= false
      v.next_action        ||= r[r.keys[i + 1]]
    end

    r
  end

  def render_player
    flip_horizontally = if state.player.facing == -1
                          true
                        else
                          false
                        end

    player_sprite = { x: state.player.x + 1 - 8,
                      y: state.player.y,
                      w: 16,
                      h: 16,
                      flip_horizontally: flip_horizontally }

    if state.player.action == :standing
      if state.player.y != 0
        if state.player.jump_count <= 1
          outputs[:scene].sprites << { **player_sprite, path: "sprites/kenobi/jumping.png" }
        else
          index = state.player.jump_at.frame_index count: 8, hold_for: 5, repeat: false
          index ||= 7
          outputs[:scene].sprites << { **player_sprite, path: "sprites/kenobi/second-jump/#{index}.png" }
        end
      elsif state.player.dx != 0
        index = state.player.action_at.frame_index count: 4, hold_for: 5, repeat: true
        outputs[:scene].sprites << { **player_sprite, path: "sprites/kenobi/run/#{index}.png" }
      else
        outputs[:scene].sprites << { **player_sprite, path: 'sprites/kenobi/standing.png'}
      end
    else
      v = state.actions_lookup[state.player.action]
      slash_frame_index = state.player.action_at.frame_index count:    v.frame_count,
                                                             hold_for: v.hold_for,
                                                             repeat:   v.repeat
      slash_frame_index ||= v.last_index
      slash_path          = v.path.sub ":index", slash_frame_index.to_s
      outputs[:scene].sprites << { **player_sprite, path: slash_path }
    end
  end

  def calc_input
    if state.player.next_action_queue.length > 2
      raise "Code in calc assums that key length of state.player.next_action_queue will never be greater than 2."
    end

    if inputs.controller_one.key_down.a ||
       inputs.mouse.button_left  ||
       inputs.keyboard.key_down.j ||
       inputs.keyboard.key_down.f
      request_action :attack
    end

    should_update_facing = false
    if state.player.action == :standing
      should_update_facing = true
    else
      key_0 = state.player.next_action_queue.keys[0]
      key_1 = state.player.next_action_queue.keys[1]
      if state.tick_count == key_0
        should_update_facing = true
      elsif state.tick_count == key_1
        should_update_facing = true
      elsif key_0 && key_1 && state.tick_count.between?(key_0, key_1)
        should_update_facing = true
      end
    end

    if should_update_facing && inputs.left_right.sign != state.player.facing.sign
      state.player.dx = 0

      if inputs.left
        state.player.facing = -1
      elsif inputs.right
        state.player.facing = 1
      end

      state.player.dx += 0.1 * inputs.left_right
    end

    if state.player.action == :standing
      state.player.dx += 0.1 * inputs.left_right
      if state.player.dx.abs > state.player.max_speed
        state.player.dx = state.player.max_speed * state.player.dx.sign
      end
    end

    was_jump_requested = inputs.keyboard.key_down.up ||
                         inputs.keyboard.key_down.w  ||
                         inputs.mouse.button_right  ||
                         inputs.controller_one.key_down.up ||
                         inputs.controller_one.key_down.b ||
                         inputs.keyboard.key_down.space

    can_jump = state.player.jump_at.elapsed_time > 20
    if state.player.jump_count <= 1
      can_jump = state.player.jump_at.elapsed_time > 10
    end

    if was_jump_requested && can_jump
      if state.player.action == :slash_6
        state.player.action = :standing
      end
      state.player.dy = 1
      state.player.jump_count += 1
      state.player.jump_at     = state.tick_count
    end
  end

  def calc
    calc_input
    calc_requested_action
    calc_next_action
    calc_sabre
    calc_player_movement

    if state.player.y <= 0 && state.player.dy < 0
      state.player.y = 0
      state.player.dy = 0
      state.player.jump_at = 0
      state.player.jump_count = 0
    end
  end

  def calc_player_movement
    state.player.x += state.player.dx
    state.player.y += state.player.dy
    state.player.dy -= 0.05
    if state.player.y <= 0
      state.player.y = 0
      state.player.dy = 0
      state.player.jump_at = 0
      state.player.jump_count = 0
    end

    if state.player.dx.abs < 0.09
      state.player.dx = 0
    end

    state.player.x = 8  if state.player.x < 8
    state.player.x = 120 if state.player.x > 120
  end

  def calc_requested_action
    return if !state.player.requested_action
    return if state.player.requested_action_at > state.tick_count

    player_action = state.player.action
    player_action_at = state.player.action_at

    # first attack
    if state.player.requested_action == :attack
      if player_action == :standing
        state.player.next_action_queue.clear
        state.player.next_action_queue[state.tick_count] = :slash_0
        state.player.next_action_queue[state.tick_count + state.actions_lookup.slash_0.duration] = :standing
      else
        current_action = state.actions_lookup[state.player.action]
        state.player.next_action_queue.clear
        queue_at = player_action_at + current_action.interrupt_duration
        queue_at = state.tick_count if queue_at < state.tick_count
        next_action = current_action.next_action
        next_action ||= { name: :standing,
                          duration: 4 }
        if next_action
        state.player.next_action_queue[queue_at] = next_action.name
        state.player.next_action_queue[player_action_at +
                                       current_action.interrupt_duration +
                                       next_action.duration] = :standing
        end
      end
    end

    state.player.requested_action = nil
    state.player.requested_action_at = nil
  end

  def calc_sabre
    can_throw_sabre = true
    sabre_throws = [:throw_0, :throw_1, :throw_2]
    if !sabre_throws.include? state.player.action
      state.sabre.facing = nil
      state.sabre.is_active = false
      return
    end

    current_action = state.actions_lookup[state.player.action]
    throw_at = state.player.action_at + (current_action.throw_frame) * 5
    catch_at = state.player.action_at + (current_action.catch_frame) * 5
    if !state.tick_count.between? throw_at, catch_at
      state.sabre.facing = nil
      state.sabre.is_active = false
      return
    end

    state.sabre.facing ||= state.player.facing

    state.sabre.is_active = true

    spline = [
      [  0, 0.25, 0.75, 1.0],
      [1.0, 0.75, 0.25,   0]
    ]

    throw_duration = catch_at - throw_at

    current_progress = args.easing.ease_spline throw_at,
                                               state.tick_count,
                                               throw_duration,
                                               spline

    farthest_sabre_x = 32
    state.sabre.y = state.player.y
    state.sabre.x = state.player.x + farthest_sabre_x * current_progress * state.sabre.facing
  end

  def calc_next_action
    return if !state.player.next_action_queue[state.tick_count]

    state.player.previous_action = state.player.action
    state.player.previous_action_at = state.player.action_at
    state.player.previous_action_ended_at = state.tick_count
    state.player.action = state.player.next_action_queue[state.tick_count]
    state.player.action_at = state.tick_count

    is_air_born = state.player.y != 0

    if state.player.action == :slash_0
      state.player.dy = 0 if state.player.dy > 0
      if is_air_born
        state.player.dy  = 0.5
      else
        state.player.dx += 0.25 * state.player.facing
      end
    elsif state.player.action == :slash_1
      state.player.dy = 0 if state.player.dy > 0
      if is_air_born
        state.player.dy  = 0.5
      else
        state.player.dx += 0.25 * state.player.facing
      end
    elsif state.player.action == :throw_0
      if is_air_born
        state.player.dy  = 1.0
      end

      state.player.dx += 0.5 * state.player.facing
    elsif state.player.action == :throw_1
      if is_air_born
        state.player.dy  = 1.0
      end

      state.player.dx += 0.5 * state.player.facing
    elsif state.player.action == :throw_2
      if is_air_born
        state.player.dy  = 1.0
      end

      state.player.dx += 0.5 * state.player.facing
    elsif state.player.action == :slash_5
      state.player.dy = 0 if state.player.dy < 0
      if is_air_born
        state.player.dy += 1.0
      else
        state.player.dy += 1.0
      end

      state.player.dx += 1.0 * state.player.facing
    elsif state.player.action == :slash_6
      state.player.dy = 0 if state.player.dy > 0
      if is_air_born
        state.player.dy  = -0.5
      end

      state.player.dx += 0.5 * state.player.facing
    end
  end

  def tick
    defaults
    calc
    render
  end
end

$game = Game.new

def tick args
  $game.args = args
  $game.tick
end

$gtk.reset

    Animation States Advanced - Metadata - ios_metadata.txt link

    # ./samples/03_rendering_sprites/03_animation_states_advanced/metadata/ios_metadata.txt
teamid=L7H57V9CRD
appid=com.scratchworkdevelopment.1bitanimate
appname=1-Bit Animate
version=1.0
devcert=iPhone Developer: Amirali Rajan (P2B6225J87)
prodcert=

    Animation States Intermediate - main.rb link

    # ./samples/03_rendering_sprites/03_animation_states_intermediate/app/main.rb
def tick args
  defaults args
  input args
  calc args
  render args
end

def defaults args
  # uncomment the line below to slow the game down by a factor of 4 -> 15 fps (for debugging)
  # args.gtk.slowmo! 4

  args.state.player ||= {
    x: 144,                # render x of the player
    y: 32,                 # render y of the player
    w: 144 * 2,            # render width of the player
    h: 72 * 2,             # render height of the player
    dx: 0,                 # velocity x of the player
    action: :standing,     # current action/status of the player
    action_at: 0,          # frame that the action occurred
    previous_direction: 1, # direction the player was facing last frame
    direction: 1,          # direction the player is facing this frame
    launch_speed: 4,       # speed the player moves when they start running
    run_acceleration: 1,   # how much the player accelerates when running
    run_top_speed: 8,      # the top speed the player can run
    friction: 0.9,         # how much the player slows down when have stopped attempting to run
    anchor_x: 0.5,         # render anchor x of the player
    anchor_y: 0            # render anchor y of the player
  }
end

def input args
  # if the directional has been pressed on the input device
  if args.inputs.left_right != 0
    # determine if the player is currently running or not,
    # if they aren't, set their dx to their launch speed
    # otherwise, add the run acceleration to their dx
    if args.state.player.action != :running
      args.state.player.dx = args.state.player.launch_speed * args.inputs.left_right.sign
    else
      args.state.player.dx += args.inputs.left_right * args.state.player.run_acceleration
    end

    # capture the direction the player is facing and the previous direction
    args.state.player.previous_direction = args.state.player.direction
    args.state.player.direction = args.inputs.left_right.sign
  end
end

def calc args
  # clamp the player's dx to the top speed
  args.state.player.dx = args.state.player.dx.clamp(-args.state.player.run_top_speed, args.state.player.run_top_speed)

  # move the player by their dx
  args.state.player.x += args.state.player.dx

  # capture the player's hitbox
  player_hitbox = hitbox args.state.player

  # check boundary collisions and stop the player if they are colliding with the ednges of the screen
  if (player_hitbox.x - player_hitbox.w / 2) < 0
    args.state.player.x = player_hitbox.w / 2
    args.state.player.dx = 0
    # if the player is not standing, set them to standing and capture the frame
    if args.state.player.action != :standing
      args.state.player.action = :standing
      args.state.player.action_at = args.state.tick_count
    end
  elsif (player_hitbox.x + player_hitbox.w / 2) > 1280
    args.state.player.x = 1280 - player_hitbox.w / 2
    args.state.player.dx = 0

    # if the player is not standing, set them to standing and capture the frame
    if args.state.player.action != :standing
      args.state.player.action = :standing
      args.state.player.action_at = args.state.tick_count
    end
  end

  # if the player's dx is not 0, they are running. update their action and capture the frame if needed
  if args.state.player.dx.abs > 0
    if args.state.player.action != :running || args.state.player.direction != args.state.player.previous_direction
      args.state.player.action = :running
      args.state.player.action_at = args.state.tick_count
    end
  elsif args.inputs.left_right == 0
    # if the player's dx is 0 and they are not currently trying to run (left_right == 0), set them to standing and capture the frame
    if args.state.player.action != :standing
      args.state.player.action = :standing
      args.state.player.action_at = args.state.tick_count
    end
  end

  # if the player is not trying to run (left_right == 0), slow them down by the friction amount
  if args.inputs.left_right == 0
    args.state.player.dx *= args.state.player.friction

    # if the player's dx is less than 1, set it to 0
    if args.state.player.dx.abs < 1
      args.state.player.dx = 0
    end
  end
end

def render args
  # determine if the player should be flipped horizontally
  flip_horizontally = args.state.player.direction == -1
  # determine the path to the sprite to render, the idle sprite is used if action == :standing
  path = "sprites/link-idle.png"

  # if the player is running, determine the frame to render
  if args.state.player.action == :running
    # the sprite animation's first 3 frames represent the launch of the run, so we skip them on the animation loop
    # by setting the repeat_index to 3 (the 4th frame)
    frame_index = args.state.player.action_at.frame_index(count: 9, hold_for: 8, repeat: true, repeat_index: 3)
    path = "sprites/link-run-#{frame_index}.png"

    args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 230, text: "action:      #{args.state.player.action}" }
    args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 200, text: "action_at:   #{args.state.player.action_at}" }
    args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 170, text: "frame_index: #{frame_index}" }
  else
    args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 230, text: "action:      #{args.state.player.action}" }
    args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 200, text: "action_at:   #{args.state.player.action_at}" }
    args.outputs.labels << { x: args.state.player.x - 144, y: args.state.player.y + 170, text: "frame_index: n/a" }
  end


  # render the player's hitbox and sprite (the hitbox is used to determine boundary collision)
  args.outputs.borders << hitbox(args.state.player)
  args.outputs.borders << args.state.player

  # render the player's sprite
  args.outputs.sprites << args.state.player.merge(path: path, flip_horizontally: flip_horizontally)
end

def hitbox entity
  {
    x: entity.x,
    y: entity.y + 5,
    w: 64,
    h: 96,
    anchor_x: 0.5,
    anchor_y: 0
  }
end


$gtk.reset

    Color And Rotation - main.rb link

    # ./samples/03_rendering_sprites/04_color_and_rotation/app/main.rb
=begin
 APIs listing that haven't been encountered in previous sample apps:

 - merge: Returns a hash containing the contents of two original hashes.
   Merge does not allow duplicate keys, so the value of a repeated key
   will be overwritten.

   For example, if we had two hashes
   h1 = { "a" => 1, "b" => 2}
   h2 = { "b" => 3, "c" => 3}
   and we called the command
   h1.merge(h2)
   the result would the following hash
   { "a" => 1, "b" => 3, "c" => 3}.

 Reminders:

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.
   In this sample app, we're using a hash to create a sprite.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
   Before continuing with this sample app, it is HIGHLY recommended that you look
   at mygame/documentation/05-sprites.md.

 - args.inputs.keyboard.key_held.KEY: Determines if a key is being pressed.
   For more information about the keyboard, go to mygame/documentation/06-keyboard.md.

 - args.inputs.controller_one: Takes input from the controller based on what key is pressed.
   For more information about the controller, go to mygame/documentation/08-controllers.md.

 - num1.lesser(num2): Finds the lower value of the given options.

=end

# This sample app shows a car moving across the screen. It loops back around if it exceeds the dimensions of the screen,
# and also can be moved in different directions through keyboard input from the user.

# Calls the methods necessary for the game to run successfully.
def tick args
  default args
  render args.grid, args.outputs, args.state
  calc args.state
  process_inputs args
end

# Sets default values for the car sprite
# Initialization ||= only happens in the first frame
def default args
  args.state.sprite.width    = 19
  args.state.sprite.height   = 10
  args.state.sprite.scale    = 4
  args.state.max_speed       = 5
  args.state.x             ||= 100
  args.state.y             ||= 100
  args.state.speed         ||= 1
  args.state.angle         ||= 0
end

# Outputs sprite onto screen
def render grid, outputs, state
  outputs.solids  <<  [grid.rect, 70, 70, 70] # outputs gray background
  outputs.sprites <<  [destination_rect(state), # sets first four parameters of car sprite
  'sprites/86.png', # image path of car
  state.angle,
  opacity, # transparency
  saturation,
  source_rect(state), # sprite sub division/tile (tile x, y, w, h)
  false, false,  # don't flip sprites
  rotation_anchor]

  # also look at the create_sprite helper method
  #
  # For example:
  #
  # dest   = destination_rect(state)
  # source = source_rect(state),
  # outputs.sprites << create_sprite(
  #   'sprites/86.png',
  #   x: dest.x,
  #   y: dest.y,
  #   w: dest.w,
  #   h: dest.h,
  #   angle: state.angle,
  #   source_x: source.x,
  #   source_y: source.y,
  #   source_w: source.w,
  #   source_h: source.h,
  #   flip_h: false,
  #   flip_v: false,
  #   rotation_anchor_x: 0.7,
  #   rotation_anchor_y: 0.5
  # )
end

# Creates sprite by setting values inside of a hash
def create_sprite path, options = {}
  options = {

    # dest x, y, w, h
    x: 0,
    y: 0,
    w: 100,
    h: 100,

    # angle, rotation
    angle: 0,
    rotation_anchor_x: 0.5,
    rotation_anchor_y: 0.5,

    # color saturation (red, green, blue), transparency
    r: 255,
    g: 255,
    b: 255,
    a: 255,

    # source x, y, width, height
    source_x: 0,
    source_y: 0,
    source_w: -1,
    source_h: -1,

    # flip horiztonally, flip vertically
    flip_h: false,
    flip_v: false,

  }.merge options

  [
    options[:x], options[:y], options[:w], options[:h], # dest rect keys
    path,
    options[:angle], options[:a], options[:r], options[:g], options[:b], # angle, color, alpha
    options[:source_x], options[:source_y], options[:source_w], options[:source_h], # source rect keys
    options[:flip_h], options[:flip_v], # flip
    options[:rotation_anchor_x], options[:rotation_anchor_y], # rotation anchor
  ] # hash keys contain corresponding values
end

# Calls the calc_pos and calc_wrap methods.
def calc state
  calc_pos state
  calc_wrap state
end

# Changes sprite's position on screen
# Vectors have magnitude and direction, so the incremented x and y values give the car direction
def calc_pos state
  state.x     += state.angle.vector_x * state.speed # increments x by product of angle's x vector and speed
  state.y     += state.angle.vector_y * state.speed # increments y by product of angle's y vector and speed
  state.speed *= 1.1 # scales speed up
  state.speed  = state.speed.lesser(state.max_speed) # speed is either current speed or max speed, whichever has a lesser value (ensures that the car doesn't go too fast or exceed the max speed)
end

# The screen's dimensions are 1280x720. If the car goes out of scope,
# it loops back around on the screen.
def calc_wrap state

  # car returns to left side of screen if it disappears on right side of screen
  # sprite.width refers to tile's size, which is multipled by scale (4) to make it bigger
  state.x = -state.sprite.width * state.sprite.scale if state.x - 20 > 1280

  # car wraps around to right side of screen if it disappears on the left side
  state.x = 1280 if state.x + state.sprite.width * state.sprite.scale + 20 < 0

  # car wraps around to bottom of screen if it disappears at the top of the screen
  # if you subtract 520 pixels instead of 20 pixels, the car takes longer to reappear (try it!)
  state.y = 0    if state.y - 20 > 720 # if 20 pixels less than car's y position is greater than vertical scope

  # car wraps around to top of screen if it disappears at the bottom of the screen
  state.y = 720  if state.y + state.sprite.height * state.sprite.scale + 20 < 0
end

# Changes angle of sprite based on user input from keyboard or controller
def process_inputs args

  # NOTE: increasing the angle doesn't mean that the car will continue to go
  # in a specific direction. The angle is increasing, which means that if the
  # left key was kept in the "down" state, the change in the angle would cause
  # the car to go in a counter-clockwise direction and form a circle (360 degrees)
  if args.inputs.keyboard.key_held.left # if left key is pressed
    args.state.angle += 2 # car's angle is incremented by 2

  # The same applies to decreasing the angle. If the right key was kept in the
  # "down" state, the decreasing angle would cause the car to go in a clockwise
  # direction and form a circle (360 degrees)
  elsif args.inputs.keyboard.key_held.right # if right key is pressed
    args.state.angle -= 2 # car's angle is decremented by 2

  # Input from a controller can also change the angle of the car
  elsif args.inputs.controller_one.left_analog_x_perc != 0
    args.state.angle += 2 * args.inputs.controller_one.left_analog_x_perc * -1
  end
end

# A sprite's center of rotation can be altered
# Increasing either of these numbers would dramatically increase the
# car's drift when it turns!
def rotation_anchor
  [0.7, 0.5]
end

# Sets opacity value of sprite to 255 so that it is not transparent at all
# Change it to 0 and you won't be able to see the car sprite on the screen
def opacity
  255
end

# Sets the color of the sprite to white.
def saturation
  [255, 255, 255]
end

# Sets definition of destination_rect (used to define the car sprite)
def destination_rect state
  [state.x, state.y,
  state.sprite.width  * state.sprite.scale, # multiplies by 4 to set size
  state.sprite.height * state.sprite.scale]
end

# Portion of a sprite (a tile)
# Sub division of sprite is denoted as a rectangle directly related to original size of .png
# Tile is located at bottom left corner within a 19x10 pixel rectangle (based on sprite.width, sprite.height)
def source_rect state
  [0, 0, state.sprite.width, state.sprite.height]
end

    Physics And Collisions link

    Simple - main.rb link

    # ./samples/04_physics_and_collisions/01_simple/app/main.rb
=begin

 Reminders:
 - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.

 - args.outputs.solids: An array. The values generate a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]

=end

# This sample app shows collisions between two boxes.

# Runs methods needed for game to run properly.
def tick args
  tick_instructions args, "Sample app shows how to move a square over time and determine collision."
  defaults args
  render args
  calc args
end

# Sets default values.
def defaults args
  # These values represent the moving box.
  args.state.moving_box_speed   = 10
  args.state.moving_box_size    = 100
  args.state.moving_box_dx    ||=  1
  args.state.moving_box_dy    ||=  1
  args.state.moving_box       ||= [0, 0, args.state.moving_box_size, args.state.moving_box_size] # moving_box_size is set as the width and height

  # These values represent the center box.
  args.state.center_box ||= [540, 260, 200, 200, 180]
  args.state.center_box_collision ||= false # initially no collision
end

def render args
  # If the game state denotes that a collision has occured,
  # render a solid square, otherwise render a border instead.
  if args.state.center_box_collision
    args.outputs.solids << args.state.center_box
  else
    args.outputs.borders << args.state.center_box
  end

  # Then render the moving box.
  args.outputs.solids << args.state.moving_box
end

# Generally in a pipeline for a game engine, you have rendering,
# game simulation (calculation), and input processing.
# This fuction represents the game simulation.
def calc args
  position_moving_box args
  determine_collision_center_box args
end

# Changes the position of the moving box on the screen by multiplying the change in x (dx) and change in y (dy) by the speed,
# and adding it to the current position.
# dx and dy are positive if the box is moving right and up, respectively
# dx and dy are negative if the box is moving left and down, respectively
def position_moving_box args
  args.state.moving_box.x += args.state.moving_box_dx * args.state.moving_box_speed
  args.state.moving_box.y += args.state.moving_box_dy * args.state.moving_box_speed

  # 1280x720 are the virtual pixels you work with (essentially 720p).
  screen_width  = 1280
  screen_height = 720

  # Position of the box is denoted by the bottom left hand corner, in
  # that case, we have to subtract the width of the box so that it stays
  # in the scene (you can try deleting the subtraction to see how it
  # impacts the box's movement).
  if args.state.moving_box.x > screen_width - args.state.moving_box_size
    args.state.moving_box_dx = -1 # moves left
  elsif args.state.moving_box.x < 0
    args.state.moving_box_dx =  1 # moves right
  end

  # Here, we're making sure the moving box remains within the vertical scope of the screen
  if args.state.moving_box.y > screen_height - args.state.moving_box_size # if the box moves too high
    args.state.moving_box_dy = -1 # moves down
  elsif args.state.moving_box.y < 0 # if the box moves too low
    args.state.moving_box_dy =  1 # moves up
  end
end

def determine_collision_center_box args
  # Collision is handled by the engine. You simply have to call the
  # `intersect_rect?` function.
  if args.state.moving_box.intersect_rect? args.state.center_box # if the two boxes intersect
    args.state.center_box_collision = true # then a collision happened
  else
    args.state.center_box_collision = false # otherwise, no collision happened
  end
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Simple Aabb Collision - main.rb link

    # ./samples/04_physics_and_collisions/01_simple_aabb_collision/app/main.rb
def tick args
  # define terrain of 32x32 sized squares
  args.state.terrain ||= [
    { x: 640,          y: 360,          w: 32, h: 32, path: 'sprites/square/blue.png' },
    { x: 640,          y: 360 - 32,     w: 32, h: 32, path: 'sprites/square/blue.png' },
    { x: 640,          y: 360 - 32 * 2, w: 32, h: 32, path: 'sprites/square/blue.png' },
    { x: 640 + 32,     y: 360 - 32 * 2, w: 32, h: 32, path: 'sprites/square/blue.png' },
    { x: 640 + 32 * 2, y: 360 - 32 * 2, w: 32, h: 32, path: 'sprites/square/blue.png' },
  ]

  # define player
  args.state.player ||= {
    x: 600,
    y: 360,
    w: 32,
    h: 32,
    dx: 0,
    dy: 0,
    path: 'sprites/square/red.png'
  }

  # render terrain and player
  args.outputs.sprites << args.state.terrain
  args.outputs.sprites << args.state.player

  # set dx and dy based on inputs
  args.state.player.dx = args.inputs.left_right * 2
  args.state.player.dy = args.inputs.up_down * 2

  # check for collisions on the x and y axis independently

  # increment the player's position by dx
  args.state.player.x += args.state.player.dx

  # check for collision on the x axis first
  collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

  # if there is a collision, move the player to the edge of the collision
  # based on the direction of the player's movement and set the player's
  # dx to 0
  if collision
    if args.state.player.dx > 0
      args.state.player.x = collision.x - args.state.player.w
    elsif args.state.player.dx < 0
      args.state.player.x = collision.x + collision.w
    end
    args.state.player.dx = 0
  end

  # increment the player's position by dy
  args.state.player.y += args.state.player.dy

  # check for collision on the y axis next
  collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

  # if there is a collision, move the player to the edge of the collision
  # based on the direction of the player's movement and set the player's
  # dy to 0
  if collision
    if args.state.player.dy > 0
      args.state.player.y = collision.y - args.state.player.h
    elsif args.state.player.dy < 0
      args.state.player.y = collision.y + collision.h
    end
    args.state.player.dy = 0
  end
end

    Simple Aabb Collision With Map Editor - main.rb link

    # ./samples/04_physics_and_collisions/01_simple_aabb_collision_with_map_editor/app/main.rb
# the sample app is an expansion of ./01_simple_aabb_collision
# but includes an in game map editor that saves map data to disk
def tick args
  # if it's the first tick, read the terrain data from disk
  # and create the player
  if args.state.tick_count == 0
    args.state.terrain = read_terrain_data args

    args.state.player = {
      x: 320,
      y: 320,
      w: 32,
      h: 32,
      dx: 0,
      dy: 0,
      path: 'sprites/square/red.png'
    }
  end

  # tick the game (where input and aabb collision is processed)
  tick_game args

  # tick the map editor
  tick_map_editor args
end

def tick_game args
  # render terrain and player
  args.outputs.sprites << args.state.terrain
  args.outputs.sprites << args.state.player

  # set dx and dy based on inputs
  args.state.player.dx = args.inputs.left_right * 2
  args.state.player.dy = args.inputs.up_down * 2

  # check for collisions on the x and y axis independently

  # increment the player's position by dx
  args.state.player.x += args.state.player.dx

  # check for collision on the x axis first
  collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

  # if there is a collision, move the player to the edge of the collision
  # based on the direction of the player's movement and set the player's
  # dx to 0
  if collision
    if args.state.player.dx > 0
      args.state.player.x = collision.x - args.state.player.w
    elsif args.state.player.dx < 0
      args.state.player.x = collision.x + collision.w
    end
    args.state.player.dx = 0
  end

  # increment the player's position by dy
  args.state.player.y += args.state.player.dy

  # check for collision on the y axis next
  collision = args.state.terrain.find { |t| t.intersect_rect? args.state.player }

  # if there is a collision, move the player to the edge of the collision
  # based on the direction of the player's movement and set the player's
  # dy to 0
  if collision
    if args.state.player.dy > 0
      args.state.player.y = collision.y - args.state.player.h
    elsif args.state.player.dy < 0
      args.state.player.y = collision.y + collision.h
    end
    args.state.player.dy = 0
  end
end

def tick_map_editor args
  # determine the location of the mouse, but
  # aligned to the grid
  grid_aligned_mouse_rect = {
    x: args.inputs.mouse.x.idiv(32) * 32,
    y: args.inputs.mouse.y.idiv(32) * 32,
    w: 32,
    h: 32
  }

  # determine if there's a tile at the grid aligned mouse location
  existing_terrain = args.state.terrain.find { |t| t.intersect_rect? grid_aligned_mouse_rect }

  # if there is, then render a red square to denote that
  # the tile will be deleted
  if existing_terrain
    args.outputs.sprites << {
      x: args.inputs.mouse.x.idiv(32) * 32,
      y: args.inputs.mouse.y.idiv(32) * 32,
      w: 32,
      h: 32,
      path: "sprites/square/red.png",
      a: 128
    }
  else
    # otherwise, render a blue square to denote that
    # a tile will be added
    args.outputs.sprites << {
      x: args.inputs.mouse.x.idiv(32) * 32,
      y: args.inputs.mouse.y.idiv(32) * 32,
      w: 32,
      h: 32,
      path: "sprites/square/blue.png",
      a: 128
    }
  end

  # if the mouse is clicked, then add or remove a tile
  if args.inputs.mouse.click
    if existing_terrain
      args.state.terrain.delete existing_terrain
    else
      args.state.terrain << { **grid_aligned_mouse_rect, path: "sprites/square/blue.png" }
    end

    # once the terrain state has been updated
    # save the terrain data to disk
    write_terrain_data args
  end
end

def read_terrain_data args
  # create the terrain data file if it doesn't exist
  contents = args.gtk.read_file "data/terrain.txt"
  if !contents
    args.gtk.write_file "data/terrain.txt", ""
  end

  # read the terrain data from disk which is a csv
  args.gtk.read_file('data/terrain.txt').split("\n").map do |line|
    x, y, w, h = line.split(',').map(&:to_i)
    { x: x, y: y, w: w, h: h, path: 'sprites/square/blue.png' }
  end
end

def write_terrain_data args
  terrain_csv = args.state.terrain.map { |t| "#{t.x},#{t.y},#{t.w},#{t.h}" }.join "\n"
  args.gtk.write_file 'data/terrain.txt', terrain_csv
end

    Simple Aabb Collision With Map Editor - Data - terrain.txt link

    # ./samples/04_physics_and_collisions/01_simple_aabb_collision_with_map_editor/data/terrain.txt

    Moving Objects - main.rb link

    # ./samples/04_physics_and_collisions/02_moving_objects/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.

   For example, if we have a "numbers" hash that stores numbers in English as the
   key and numbers in Spanish as the value, we'd have a hash that looks like this...
   numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
   and on it goes.

   Now if we wanted to find the corresponding value of the "one" key, we could say
   puts numbers["one"]
   which would print "uno" to the console.

 - num1.greater(num2): Returns the greater value.
   For example, if we have the command
   puts 4.greater(3)
   the number 4 would be printed to the console since it has a greater value than 3.
   Similar to lesser, which returns the lesser value.

 - num1.lesser(num2): Finds the lower value of the given options.
   For example, in the statement
   a = 4.lesser(3)
   3 has a lower value than 4, which means that the value of a would be set to 3,
   but if the statement had been
   a = 4.lesser(5)
   4 has a lower value than 5, which means that the value of a would be set to 4.

 - reject: Removes elements from a collection if they meet certain requirements.
   For example, you can derive an array of odd numbers from an original array of
   numbers 1 through 10 by rejecting all elements that are even (or divisible by 2).

 - find_all: Finds all values that satisfy specific requirements.
   For example, you can find all elements of a collection that are divisible by 2
   or find all objects that have intersected with another object.

 - abs: Returns the absolute value.
   For example, the command
   (-30).abs
   would return 30 as a result.

 - map: Ruby method used to transform data; used in arrays, hashes, and collections.
   Can be used to perform an action on every element of a collection, such as multiplying
   each element by 2 or declaring every element as a new entity.

 Reminders:

 - args.inputs.keyboard.KEY: Determines if a key has been pressed.
   For more information about the keyboard, take a look at mygame/documentation/06-keyboard.md.

 - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.

 - args.outputs.solids: An array. The values generate a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

=end

# Calls methods needed for game to run properly
def tick args
  tick_instructions args, "Use LEFT and RIGHT arrow keys to move and SPACE to jump."
  defaults args
  render args
  calc args
  input args
end

# sets default values and creates empty collections
# initialization only happens in the first frame
def defaults args
  fiddle args
  args.state.enemy.hammers ||= []
  args.state.enemy.hammer_queue ||= []
  args.state.tick_count = args.state.tick_count
  args.state.bridge_top = 128
  args.state.player.x  ||= 0                        # initializes player's properties
  args.state.player.y  ||= args.state.bridge_top
  args.state.player.w  ||= 64
  args.state.player.h  ||= 64
  args.state.player.dy ||= 0
  args.state.player.dx ||= 0
  args.state.enemy.x   ||= 800                      # initializes enemy's properties
  args.state.enemy.y   ||= 0
  args.state.enemy.w   ||= 128
  args.state.enemy.h   ||= 128
  args.state.enemy.dy  ||= 0
  args.state.enemy.dx  ||= 0
  args.state.game_over_at ||= 0
end

# sets enemy, player, hammer values
def fiddle args
  args.state.gravity                     = -0.3
  args.state.enemy_jump_power            = 10       # sets enemy values
  args.state.enemy_jump_interval         = 60
  args.state.hammer_throw_interval       = 40       # sets hammer values
  args.state.hammer_launch_power_default = 5
  args.state.hammer_launch_power_near    = 2
  args.state.hammer_launch_power_far     = 7
  args.state.hammer_upward_launch_power  = 15
  args.state.max_hammers_per_volley      = 10
  args.state.gap_between_hammers         = 10
  args.state.player_jump_power           = 10       # sets player values
  args.state.player_jump_power_duration  = 10
  args.state.player_max_run_speed        = 10
  args.state.player_speed_slowdown_rate  = 0.9
  args.state.player_acceleration         = 1
  args.state.hammer_size                 = 32
end

# outputs objects onto the screen
def render args
  args.outputs.solids << 20.map_with_index do |i| # uses 20 squares to form bridge
    # sets x by multiplying 64 to index to find pixel value (places all squares side by side)
    # subtracts 64 from bridge_top because position is denoted by bottom left corner
    [i * 64, args.state.bridge_top - 64, 64, 64]
  end

  args.outputs.solids << [args.state.x, args.state.y, args.state.w, args.state.h, 255, 0, 0]
  args.outputs.solids << [args.state.player.x, args.state.player.y, args.state.player.w, args.state.player.h, 255, 0, 0] # outputs player onto screen (red box)
  args.outputs.solids << [args.state.enemy.x, args.state.enemy.y, args.state.enemy.w, args.state.enemy.h, 0, 255, 0] # outputs enemy onto screen (green box)
  args.outputs.solids << args.state.enemy.hammers # outputs enemy's hammers onto screen
end

# Performs calculations to move objects on the screen
def calc args

  # Since velocity is the change in position, the change in x increases by dx. Same with y and dy.
  args.state.player.x  += args.state.player.dx
  args.state.player.y  += args.state.player.dy

  # Since acceleration is the change in velocity, the change in y (dy) increases every frame
  args.state.player.dy += args.state.gravity

  # player's y position is either current y position or y position of top of
  # bridge, whichever has a greater value
  # ensures that the player never goes below the bridge
  args.state.player.y  = args.state.player.y.greater(args.state.bridge_top)

  # player's x position is either the current x position or 0, whichever has a greater value
  # ensures that the player doesn't go too far left (out of the screen's scope)
  args.state.player.x  = args.state.player.x.greater(0)

  # player is not falling if it is located on the top of the bridge
  args.state.player.falling = false if args.state.player.y == args.state.bridge_top
  args.state.player.rect = [args.state.player.x, args.state.player.y, args.state.player.h, args.state.player.w] # sets definition for player

  args.state.enemy.x += args.state.enemy.dx # velocity; change in x increases by dx
  args.state.enemy.y += args.state.enemy.dy # same with y and dy

  # ensures that the enemy never goes below the bridge
  args.state.enemy.y  = args.state.enemy.y.greater(args.state.bridge_top)

  # ensures that the enemy never goes too far left (outside the screen's scope)
  args.state.enemy.x  = args.state.enemy.x.greater(0)

  # objects that go up must come down because of gravity
  args.state.enemy.dy += args.state.gravity

  args.state.enemy.y  = args.state.enemy.y.greater(args.state.bridge_top)

  #sets definition of enemy
  args.state.enemy.rect = [args.state.enemy.x, args.state.enemy.y, args.state.enemy.h, args.state.enemy.w]

  if args.state.enemy.y == args.state.bridge_top # if enemy is located on the top of the bridge
    args.state.enemy.dy = 0 # there is no change in y
  end

  # if 60 frames have passed and the enemy is not moving vertically
  if args.state.tick_count.mod_zero?(args.state.enemy_jump_interval) && args.state.enemy.dy == 0
    args.state.enemy.dy = args.state.enemy_jump_power # the enemy jumps up
  end

  # if 40 frames have passed or 5 frames have passed since the game ended
  if args.state.tick_count.mod_zero?(args.state.hammer_throw_interval) || args.state.game_over_at.elapsed_time == 5
    # rand will return a number greater than or equal to 0 and less than given variable's value (since max is excluded)
    # that is why we're adding 1, to include the max possibility
    volley_dx   = (rand(args.state.hammer_launch_power_default) + 1) * -1 # horizontal movement (follow order of operations)

    # if the horizontal distance between the player and enemy is less than 128 pixels
    if (args.state.player.x - args.state.enemy.x).abs < 128
      # the change in x won't be that great since the enemy and player are closer to each other
      volley_dx = (rand(args.state.hammer_launch_power_near) + 1) * -1
    end

    # if the horizontal distance between the player and enemy is greater than 300 pixels
    if (args.state.player.x - args.state.enemy.x).abs > 300
      # change in x will be more drastic since player and enemy are so far apart
      volley_dx = (rand(args.state.hammer_launch_power_far) + 1) * -1 # more drastic change
    end

    (rand(args.state.max_hammers_per_volley) + 1).map_with_index do |i|
      args.state.enemy.hammer_queue << { # stores hammer values in a hash
        x: args.state.enemy.x,
        w: args.state.hammer_size,
        h: args.state.hammer_size,
        dx: volley_dx, # change in horizontal position
        # multiplication operator takes precedence over addition operator
        throw_at: args.state.tick_count + i * args.state.gap_between_hammers
      }
    end
  end

  # add elements from hammer_queue collection to the hammers collection by
  # finding all hammers that were thrown before the current frame (have already been thrown)
  args.state.enemy.hammers += args.state.enemy.hammer_queue.find_all do |h|
    h[:throw_at] < args.state.tick_count
  end

  args.state.enemy.hammers.each do |h| # sets values for all hammers in collection
    h[:y]  ||= args.state.enemy.y + 130
    h[:dy] ||= args.state.hammer_upward_launch_power
    h[:dy]  += args.state.gravity # acceleration is change in gravity
    h[:x]   += h[:dx] # incremented by change in position
    h[:y]   += h[:dy]
    h[:rect] = [h[:x], h[:y], h[:w], h[:h]] # sets definition of hammer's rect
  end

  # reject hammers that have been thrown before current frame (have already been thrown)
  args.state.enemy.hammer_queue = args.state.enemy.hammer_queue.reject do |h|
    h[:throw_at] < args.state.tick_count
  end

  # any hammers with a y position less than 0 are rejected from the hammers collection
  # since they have gone too far down (outside the scope's screen)
  args.state.enemy.hammers = args.state.enemy.hammers.reject { |h| h[:y] < 0 }

  # if there are any hammers that intersect with (or hit) the player,
  # the reset_player method is called (so the game can start over)
  if args.state.enemy.hammers.any? { |h| h[:rect].intersect_rect?(args.state.player.rect) }
    reset_player args
  end

  # if the enemy's rect intersects with (or hits) the player,
  # the reset_player method is called (so the game can start over)
  if args.state.enemy.rect.intersect_rect? args.state.player.rect
    reset_player args
  end
end

# Resets the player by changing its properties back to the values they had at initialization
def reset_player args
  args.state.player.x = 0
  args.state.player.y = args.state.bridge_top
  args.state.player.dy = 0
  args.state.player.dx = 0
  args.state.enemy.hammers.clear # empties hammer collection
  args.state.enemy.hammer_queue.clear # empties hammer_queue
  args.state.game_over_at = args.state.tick_count # game_over_at set to current frame (or passage of time)
end

# Processes input from the user to move the player
def input args
  if args.inputs.keyboard.space # if the user presses the space bar
    args.state.player.jumped_at ||= args.state.tick_count # jumped_at is set to current frame

    # if the time that has passed since the jump is less than the player's jump duration and
    # the player is not falling
    if args.state.player.jumped_at.elapsed_time < args.state.player_jump_power_duration && !args.state.player.falling
      args.state.player.dy = args.state.player_jump_power # change in y is set to power of player's jump
    end
  end

  # if the space bar is in the "up" state (or not being pressed down)
  if args.inputs.keyboard.key_up.space
    args.state.player.jumped_at = nil # jumped_at is empty
    args.state.player.falling = true # the player is falling
  end

  if args.inputs.keyboard.left # if left key is pressed
    args.state.player.dx -= args.state.player_acceleration # dx decreases by acceleration (player goes left)
    # dx is either set to current dx or the negative max run speed (which would be -10),
    # whichever has a greater value
    args.state.player.dx = args.state.player.dx.greater(-args.state.player_max_run_speed)
  elsif args.inputs.keyboard.right # if right key is pressed
    args.state.player.dx += args.state.player_acceleration # dx increases by acceleration (player goes right)
    # dx is either set to current dx or max run speed (which would be 10),
    # whichever has a lesser value
    args.state.player.dx = args.state.player.dx.lesser(args.state.player_max_run_speed)
  else
    args.state.player.dx *= args.state.player_speed_slowdown_rate # dx is scaled down
  end
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.space ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Entities - main.rb link

    # ./samples/04_physics_and_collisions/03_entities/app/main.rb
=begin

 Reminders:

 - map: Ruby method used to transform data; used in arrays, hashes, and collections.
   Can be used to perform an action on every element of a collection, such as multiplying
   each element by 2 or declaring every element as a new entity.

 - reject: Removes elements from a collection if they meet certain requirements.
   For example, you can derive an array of odd numbers from an original array of
   numbers 1 through 10 by rejecting all elements that are even (or divisible by 2).

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   In this sample app, new_entity is used to define the properties of enemies and bullets.
   (Remember, you can use state to define ANY property and it will be retained across frames.)

 - args.outputs.labels: An array. The values generate a label on the screen.
   The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]

 - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.

 - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.

=end

# This sample app shows enemies that contain an id value and the time they were created.
# These enemies can be removed by shooting at them with bullets.

# Calls all methods necessary for the game to function properly.
def tick args
  tick_instructions args, "Sample app shows how to use args.state.new_entity along with collisions. CLICK to shoot a bullet."
  defaults args
  render args
  calc args
  process_inputs args
end

# Sets default values
# Enemies and bullets start off as empty collections
def defaults args
  args.state.enemies ||= []
  args.state.bullets ||= []
end

# Provides each enemy in enemies collection with rectangular border,
# as well as a label showing id and when they were created
def render args
  # When you're calling a method that takes no arguments, you can use this & syntax on map.
  # Numbers are being added to x and y in order to keep the text within the enemy's borders.
  args.outputs.borders << args.state.enemies.map(&:rect)
  args.outputs.labels  << args.state.enemies.flat_map do |enemy|
    [
      [enemy.x + 4, enemy.y + 29, "id: #{enemy.entity_id}", -3, 0],
      [enemy.x + 4, enemy.y + 17, "created_at: #{enemy.created_at}", -3, 0] # frame enemy was created
    ]
  end

  # Outputs bullets in bullets collection as rectangular solids
  args.outputs.solids << args.state.bullets.map(&:rect)
end

# Calls all methods necessary for performing calculations
def calc args
  add_new_enemies_if_needed args
  move_bullets args
  calculate_collisions args
  remove_bullets_of_screen args
end

# Adds enemies to the enemies collection and sets their values
def add_new_enemies_if_needed args
  return if args.state.enemies.length >= 10 # if 10 or more enemies, enemies are not added
  return unless args.state.bullets.length == 0 # if user has not yet shot bullet, no enemies are added

  args.state.enemies += (10 - args.state.enemies.length).map do # adds enemies so there are 10 total
    args.state.new_entity(:enemy) do |e| # each enemy is declared as a new entity
      e.x = 640 + 500 * rand # each enemy is given random position on screen
      e.y = 600 * rand + 50
      e.rect = [e.x, e.y, 130, 30] # sets definition for enemy's rect
    end
  end
end

# Moves bullets across screen
# Sets definition of the bullets
def move_bullets args
  args.state.bullets.each do |bullet| # perform action on each bullet in collection
    bullet.x += bullet.speed # increment x by speed (bullets fly horizontally across screen)

    # By randomizing the value that increments bullet.y, the bullet does not fly straight up and out
    # of the scope of the screen. Try removing what follows bullet.speed, or changing 0.25 to 1.25 to
    # see what happens to the bullet's movement.
    bullet.y += bullet.speed.*(0.25).randomize(:ratio, :sign)
    bullet.rect = [bullet.x, bullet.y, bullet.size, bullet.size] # sets definition of bullet's rect
  end
end

# Determines if a bullet hits an enemy
def calculate_collisions args
  args.state.bullets.each do |bullet| # perform action on every bullet and enemy in collections
    args.state.enemies.each do |enemy|
      # if bullet has not exploded yet and the bullet hits an enemy
      if !bullet.exploded && bullet.rect.intersect_rect?(enemy.rect)
        bullet.exploded = true # bullet explodes
        enemy.dead = true # enemy is killed
      end
    end
  end

  # All exploded bullets are rejected or removed from the bullets collection
  # and any dead enemy is rejected from the enemies collection.
  args.state.bullets = args.state.bullets.reject(&:exploded)
  args.state.enemies = args.state.enemies.reject(&:dead)
end

# Bullets are rejected from bullets collection once their position exceeds the width of screen
def remove_bullets_of_screen args
  args.state.bullets = args.state.bullets.reject { |bullet| bullet.x > 1280 } # screen width is 1280
end

# Calls fire_bullet method
def process_inputs args
  fire_bullet args
end

# Once mouse is clicked by the user to fire a bullet, a new bullet is added to bullets collection
def fire_bullet args
  return unless args.inputs.mouse.click # return unless mouse is clicked
  args.state.bullets << args.state.new_entity(:bullet) do |bullet| # new bullet is declared a new entity
    bullet.y = args.inputs.mouse.click.point.y # set to the y value of where the mouse was clicked
    bullet.x = 0 # starts on the left side of the screen
    bullet.size = 10
    bullet.speed = 10 * rand + 2 # speed of a bullet is randomized
    bullet.rect = [bullet.x, bullet.y, bullet.size, bullet.size] # definition is set
  end
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.space ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Box Collision - main.rb link

    # ./samples/04_physics_and_collisions/04_box_collision/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - first: Returns the first element of the array.
   For example, if we have an array
   numbers = [1, 2, 3, 4, 5]
   and we call first by saying
   numbers.first
   the number 1 will be returned because it is the first element of the numbers array.

 - num1.idiv(num2): Divides two numbers and returns an integer.
   For example,
   16.idiv(3) = 5, because 16 / 3 is 5.33333 returned as an integer.
   16.idiv(4) = 4, because 16 / 4 is 4 and already has no decimal.

 Reminders:

 - find_all: Finds all values that satisfy specific requirements.

 - ARRAY#intersect_rect?: An array with at least four values is
   considered a rect. The intersect_rect? function returns true
   or false depending on if the two rectangles intersect.

 - reject: Removes elements from a collection if they meet certain requirements.

=end

# This sample app allows users to create tiles and place them anywhere on the screen as obstacles.
# The player can then move and maneuver around them.

class PoorManPlatformerPhysics
  attr_accessor :grid, :inputs, :state, :outputs

  # Calls all methods necessary for the app to run successfully.
  def tick
    defaults
    render
    calc
    process_inputs
  end

  # Sets default values for variables.
  # The ||= sign means that the variable will only be set to the value following the = sign if the value has
  # not already been set before. Intialization happens only in the first frame.
  def defaults
    state.tile_size               = 64
    state.gravity                 = -0.2
    state.previous_tile_size    ||= state.tile_size
    state.x                     ||= 0
    state.y                     ||= 800
    state.dy                    ||= 0
    state.dx                    ||= 0
    state.world                 ||= []
    state.world_lookup          ||= {}
    state.world_collision_rects ||= []
  end

  # Outputs solids and borders of different colors for the world and collision_rects collections.
  def render

    # Sets a black background on the screen (Comment this line out and the background will become white.)
    # Also note that black is the default color for when no color is assigned.
    outputs.solids << grid.rect

    # The position, size, and color (white) are set for borders given to the world collection.
    # Try changing the color by assigning different numbers (between 0 and 255) to the last three parameters.
    outputs.borders << state.world.map do |x, y|
      [x * state.tile_size,
       y * state.tile_size,
       state.tile_size,
       state.tile_size, 255, 255, 255]
    end

    # The top, bottom, and sides of the borders for collision_rects are different colors.
    outputs.borders << state.world_collision_rects.map do |e|
      [
        [e[:top],                             0, 170,   0], # top is a shade of green
        [e[:bottom],                          0, 100, 170], # bottom is a shade of greenish-blue
        [e[:left_right],                    170,   0,   0], # left and right are a shade of red
      ]
    end

    # Sets the position, size, and color (a shade of green) of the borders of only the player's
    # box and outputs it. If you change the 180 to 0, the player's box will be black and you
    # won't be able to see it (because it will match the black background).
    outputs.borders << [state.x,
                        state.y,
                        state.tile_size,
                        state.tile_size,  0, 180, 0]
  end

  # Calls methods needed to perform calculations.
  def calc
    calc_world_lookup
    calc_player
  end

  # Performs calculations on world_lookup and sets values.
  def calc_world_lookup

    # If the tile size isn't equal to the previous tile size,
    # the previous tile size is set to the tile size,
    # and world_lookup hash is set to empty.
    if state.tile_size != state.previous_tile_size
      state.previous_tile_size = state.tile_size
      state.world_lookup = {} # empty hash
    end

    # return if the world_lookup hash has keys (or, in other words, is not empty)
    # return unless the world collection has values inside of it (or is not empty)
    return if state.world_lookup.keys.length > 0
    return unless state.world.length > 0

    # Starts with an empty hash for world_lookup.
    # Searches through the world and finds the coordinates that exist.
    state.world_lookup = {}
    state.world.each { |x, y| state.world_lookup[[x, y]] = true }

    # Assigns world_collision_rects for every sprite drawn.
    state.world_collision_rects =
      state.world_lookup
          .keys
          .map do |coord_x, coord_y|
            s = state.tile_size
            # multiply by tile size so the grid coordinates; sets pixel value
            # don't forget that position is denoted by bottom left corner
            # set x = coord_x or y = coord_y and see what happens!
            x = s * coord_x
            y = s * coord_y
            {
              # The values added to x, y, and s position the world_collision_rects so they all appear
              # stacked (on top of world rects) but don't directly overlap.
              # Remove these added values and mess around with the rect placement!
              args:       [coord_x, coord_y],
              left_right: [x,     y + 4, s,     s - 6], # hash keys and values
              top:        [x + 4, y + 6, s - 8, s - 6],
              bottom:     [x + 1, y - 1, s - 2, s - 8],
            }
          end
  end

  # Performs calculations to change the x and y values of the player's box.
  def calc_player

    # Since acceleration is the change in velocity, the change in y (dy) increases every frame.
    # What goes up must come down because of gravity.
    state.dy += state.gravity

    # Calls the calc_box_collision and calc_edge_collision methods.
    calc_box_collision
    calc_edge_collision

    # Since velocity is the change in position, the change in y increases by dy. Same with x and dx.
    state.y += state.dy
    state.x += state.dx

    # Scales dx down.
    state.dx *= 0.8
  end

  # Calls methods needed to determine collisions between player and world_collision rects.
  def calc_box_collision
    return unless state.world_lookup.keys.length > 0 # return unless hash has atleast 1 key
    collision_floor!
    collision_left!
    collision_right!
    collision_ceiling!
  end

  # Finds collisions between the bottom of the player's rect and the top of a world_collision_rect.
  def collision_floor!
    return unless state.dy <= 0 # return unless player is going down or is as far down as possible
    player_rect = [state.x, state.y - 0.1, state.tile_size, state.tile_size] # definition of player

    # Goes through world_collision_rects to find all intersections between the bottom of player's rect and
    # the top of a world_collision_rect (hence the "-0.1" above)
    floor_collisions = state.world_collision_rects
                           .find_all { |r| r[:top].intersect_rect?(player_rect, collision_tollerance) }
                           .first

    return unless floor_collisions # return unless collision occurred
    state.y = floor_collisions[:top].top # player's y is set to the y of the top of the collided rect
    state.dy = 0 # if a collision occurred, the player's rect isn't moving because its path is blocked
  end

  # Finds collisions between the player's left side and the right side of a world_collision_rect.
  def collision_left!
    return unless state.dx < 0 # return unless player is moving left
    player_rect = [state.x - 0.1, state.y, state.tile_size, state.tile_size]

    # Goes through world_collision_rects to find all intersections beween the player's left side and the
    # right side of a world_collision_rect.
    left_side_collisions = state.world_collision_rects
                               .find_all { |r| r[:left_right].intersect_rect?(player_rect, collision_tollerance) }
                               .first

    return unless left_side_collisions # return unless collision occurred

    # player's x is set to the value of the x of the collided rect's right side
    state.x = left_side_collisions[:left_right].right
    state.dx = 0 # player isn't moving left because its path is blocked
  end

  # Finds collisions between the right side of the player and the left side of a world_collision_rect.
  def collision_right!
    return unless state.dx > 0 # return unless player is moving right
    player_rect = [state.x + 0.1, state.y, state.tile_size, state.tile_size]

    # Goes through world_collision_rects to find all intersections between the player's right side
    # and the left side of a world_collision_rect (hence the "+0.1" above)
    right_side_collisions = state.world_collision_rects
                                .find_all { |r| r[:left_right].intersect_rect?(player_rect, collision_tollerance) }
                                .first

    return unless right_side_collisions # return unless collision occurred

    # player's x is set to the value of the collided rect's left, minus the size of a rect
    # tile size is subtracted because player's position is denoted by bottom left corner
    state.x = right_side_collisions[:left_right].left - state.tile_size
    state.dx = 0 # player isn't moving right because its path is blocked
  end

  # Finds collisions between the top of the player's rect and the bottom of a world_collision_rect.
  def collision_ceiling!
    return unless state.dy > 0 # return unless player is moving up
    player_rect = [state.x, state.y + 0.1, state.tile_size, state.tile_size]

    # Goes through world_collision_rects to find intersections between the bottom of a
    # world_collision_rect and the top of the player's rect (hence the "+0.1" above)
    ceil_collisions = state.world_collision_rects
                          .find_all { |r| r[:bottom].intersect_rect?(player_rect, collision_tollerance) }
                          .first

    return unless ceil_collisions # return unless collision occurred

    # player's y is set to the bottom y of the rect it collided with, minus the size of a rect
    state.y = ceil_collisions[:bottom].y - state.tile_size
    state.dy = 0 # if a collision occurred, the player isn't moving up because its path is blocked
  end

  # Makes sure the player remains within the screen's dimensions.
  def calc_edge_collision

    #Ensures that the player doesn't fall below the map.
    if state.y < 0
      state.y = 0
      state.dy = 0

    #Ensures that the player doesn't go too high.
    # Position of player is denoted by bottom left hand corner, which is why we have to subtract the
    # size of the player's box (so it remains visible on the screen)
    elsif state.y > 720 - state.tile_size # if the player's y position exceeds the height of screen
      state.y = 720 - state.tile_size # the player will remain as high as possible while staying on screen
      state.dy = 0
    end

    # Ensures that the player remains in the horizontal range that it is supposed to.
    if state.x >= 1280 - state.tile_size && state.dx > 0 # if player moves too far right
      state.x = 1280 - state.tile_size # player will remain as right as possible while staying on screen
      state.dx = 0
    elsif state.x <= 0 && state.dx < 0 # if player moves too far left
      state.x = 0 # player will remain as left as possible while remaining on screen
      state.dx = 0
    end
  end

  # Processes input from the user on the keyboard.
  def process_inputs
    if inputs.mouse.down
      state.world_lookup = {}
      x, y = to_coord inputs.mouse.down.point  # gets x, y coordinates for the grid

      if state.world.any? { |loc| loc == [x, y] }  # checks if coordinates duplicate
        state.world = state.world.reject { |loc| loc == [x, y] }  # erases tile space
      else
        state.world << [x, y] # If no duplicates, adds to world collection
      end
    end

    # Sets dx to 0 if the player lets go of arrow keys.
    if inputs.keyboard.key_up.right
      state.dx = 0
    elsif inputs.keyboard.key_up.left
      state.dx = 0
    end

    # Sets dx to 3 in whatever direction the player chooses.
    if inputs.keyboard.key_held.right # if right key is pressed
      state.dx =  3
    elsif inputs.keyboard.key_held.left # if left key is pressed
      state.dx = -3
    end

    #Sets dy to 5 to make the player ~fly~ when they press the space bar
    if inputs.keyboard.key_held.space
      state.dy = 5
    end
  end

  def to_coord point

    # Integer divides (idiv) point.x to turn into grid
    # Then, you can just multiply each integer by state.tile_size later so the grid coordinates.
    [point.x.idiv(state.tile_size), point.y.idiv(state.tile_size)]
  end

  # Represents the tolerance for a collision between the player's rect and another rect.
  def collision_tollerance
    0.0
  end
end

$platformer_physics = PoorManPlatformerPhysics.new

def tick args
  $platformer_physics.grid    = args.grid
  $platformer_physics.inputs  = args.inputs
  $platformer_physics.state    = args.state
  $platformer_physics.outputs = args.outputs
  $platformer_physics.tick
  tick_instructions args, "Sample app shows platformer collisions. CLICK to place box. ARROW keys to move around. SPACE to jump."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Box Collision 2 - main.rb link

    # ./samples/04_physics_and_collisions/05_box_collision_2/app/main.rb
=begin
 APIs listing that haven't been encountered in previous sample apps:

 - times: Performs an action a specific number of times.
   For example, if we said
   5.times puts "Hello DragonRuby",
   then we'd see the words "Hello DragonRuby" printed on the console 5 times.

 - split: Divides a string into substrings based on a delimiter.
   For example, if we had a command
   "DragonRuby is awesome".split(" ")
   then the result would be
   ["DragonRuby", "is", "awesome"] because the words are separated by a space delimiter.

 - join: Opposite of split; converts each element of array to a string separated by delimiter.
   For example, if we had a command
   ["DragonRuby","is","awesome"].join(" ")
   then the result would be
   "DragonRuby is awesome".

 Reminders:

 - to_s: Returns a string representation of an object.
   For example, if we had
   500.to_s
   the string "500" would be returned.
   Similar to to_i, which returns an integer representation of an object.

 - elapsed_time: How many frames have passed since the click event.

 - args.outputs.labels: An array. Values in the array generate labels on the screen.
   The parameters are: [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - inputs.mouse.down: Determines whether or not the mouse is being pressed down.
   The position of the mouse when it is pressed down can be found using inputs.mouse.down.point.(x|y).

 - first: Returns the first element of the array.

 - num1.idiv(num2): Divides two numbers and returns an integer.

 - find_all: Finds all values that satisfy specific requirements.

 - ARRAY#intersect_rect?: Returns true or false depending on if two rectangles intersect.

 - reject: Removes elements from a collection if they meet certain requirements.

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

=end

MAP_FILE_PATH = 'app/map.txt' # the map.txt file in the app folder contains exported map

class MetroidvaniaStarter
  attr_accessor :grid, :inputs, :state, :outputs, :gtk

  # Calls methods needed to run the game properly.
  def tick
    defaults
    render
    calc
    process_inputs
  end

  # Sets all the default variables.
  # '||' states that initialization occurs only in the first frame.
  def defaults
    state.tile_size                = 64
    state.gravity                  = -0.2
    state.player_width             = 60
    state.player_height            = 64
    state.collision_tolerance      = 0.0
    state.previous_tile_size     ||= state.tile_size
    state.x                      ||= 0
    state.y                      ||= 800
    state.dy                     ||= 0
    state.dx                     ||= 0
    attempt_load_world_from_file
    state.world_lookup           ||= { }
    state.world_collision_rects  ||= []
    state.mode                   ||= :creating # alternates between :creating and :selecting for sprite selection
    state.select_menu            ||= [0, 720, 1280, 720]
    #=======================================IMPORTANT=======================================#
    # When adding sprites, please label them "image1.png", "image2.png", image3".png", etc.
    # Once you have done that, adjust "state.sprite_quantity" to how many sprites you have.
    #=======================================================================================#
    state.sprite_quantity        ||= 20 # IMPORTANT TO ALTER IF SPRITES ADDED IF YOU ADD MORE SPRITES
    state.sprite_coords          ||= []
    state.banner_coords          ||= [640, 680 + 720]
    state.sprite_selected        ||= 1
    state.map_saved_at           ||= 0

    # Sets all the cordinate values for the sprite selection screen into a grid
    # Displayed when 's' is pressed by player to access sprites
    if state.sprite_coords == [] # if sprite_coords is an empty array
      count = 1
      temp_x = 165 # sets a starting x and y position for display
      temp_y = 500 + 720
      state.sprite_quantity.times do # for the number of sprites you have
        state.sprite_coords += [[temp_x, temp_y, count]] # add element to sprite_coords array
        temp_x += 100 # increment temp_x
        count += 1 # increment count
        if temp_x > 1280 - (165 + 50) # if exceeding specific horizontal width on screen
          temp_x = 165 # a new row of sprites starts
          temp_y -= 75 # new row of sprites starts 75 units lower than the previous row
        end
      end
    end
  end

  # Places sprites
  def render

    # Sets the x, y, width, height, and image path for each sprite in the world collection.
    outputs.sprites << state.world.map do |x, y, sprite|
      [x * state.tile_size, # multiply by size so grid coordinates; pixel value of location
       y * state.tile_size,
       state.tile_size,
       state.tile_size,
       'sprites/image' + sprite.to_s + '.png'] # uses concatenation to create unique image path
    end

    # Outputs sprite for the player by setting x, y, width, height, and image path
    outputs.sprites << [state.x,
                        state.y,
                        state.player_width,
                        state.player_height,'sprites/player.png']

    # Outputs labels as primitives in top right of the screen
    outputs.primitives << [920, 700, 'Press \'s\' to access sprites.', 1, 0].label
    outputs.primitives << [920, 675, 'Click existing sprite to delete.', 1, 0].label

    outputs.primitives << [920, 640, '<- and -> to move.', 1, 0].label
    outputs.primitives << [920, 615, 'Press and hold space to jump.', 1, 0].label

    outputs.primitives << [920, 580, 'Press \'e\' to export current map.', 1, 0].label

    # if the map is saved and less than 120 frames have passed, the label is displayed
    if state.map_saved_at > 0 && state.map_saved_at.elapsed_time < 120
      outputs.primitives << [920, 555, 'Map has been exported!', 1, 0, 50, 100, 50].label
    end

    # If player hits 's', following appears
    if state.mode == :selecting
      # White background for sprite selection
      outputs.primitives << [state.select_menu, 255, 255, 255].solid

      # Select tile label at the top of the screen
      outputs.primitives << [state.banner_coords.x, state.banner_coords.y, "Select Sprite (sprites located in \"sprites\" folder)", 10, 1, 0, 0, 0, 255].label

      # Places sprites in locations calculated in the defaults function
      outputs.primitives << state.sprite_coords.map do |x, y, order|
        [x, y, 50, 50, 'sprites/image' + order.to_s + ".png"].sprite
      end
    end

    # Creates sprite following mouse to help indicate which sprite you have selected
    # 10 is subtracted from the mouse's x position so that the sprite is not covered by the mouse icon
    outputs.primitives << [inputs.mouse.position.x - 10, inputs.mouse.position.y,
                           10, 10, 'sprites/image' + state.sprite_selected.to_s + ".png"].sprite
  end

  # Calls methods that perform calculations
  def calc
    calc_in_game
    calc_sprite_selection
  end

  # Calls methods that perform calculations (if in creating mode)
  def calc_in_game
    return unless state.mode == :creating
    calc_world_lookup
    calc_player
  end

  def calc_world_lookup
    # If the tile size isn't equal to the previous tile size,
    # the previous tile size is set to the tile size,
    # and world_lookup hash is set to empty.
    if state.tile_size != state.previous_tile_size
      state.previous_tile_size = state.tile_size
      state.world_lookup = {}
    end

    # return if world_lookup is not empty or if world is empty
    return if state.world_lookup.keys.length > 0
    return unless state.world.length > 0

    # Searches through the world and finds the coordinates that exist
    state.world_lookup = {}
    state.world.each { |x, y| state.world_lookup[[x, y]] = true }

    # Assigns collision rects for every sprite drawn
    state.world_collision_rects =
      state.world_lookup
           .keys
           .map do |coord_x, coord_y|
             s = state.tile_size
             # Multiplying by s (the size of a tile) ensures that the rect is
             # placed exactly where you want it to be placed (causes grid to coordinate)
             # How many pixels horizontally across and vertically up and down
             x = s * coord_x
             y = s * coord_y
             {
               args:       [coord_x, coord_y],
               left_right: [x,     y + 4, s,     s - 6], # hash keys and values
               top:        [x + 4, y + 6, s - 8, s - 6],
               bottom:     [x + 1, y - 1, s - 2, s - 8],
             }
           end
  end

  # Calculates movement of player and calls methods that perform collision calculations
  def calc_player
    state.dy += state.gravity  # what goes up must come down because of gravity
    calc_box_collision
    calc_edge_collision
    state.y  += state.dy       # Since velocity is the change in position, the change in y increases by dy
    state.x  += state.dx       # Ditto line above but dx and x
    state.dx *= 0.8            # Scales dx down
  end

  # Calls methods that determine whether the player collides with any world_collision_rects.
  def calc_box_collision
    return unless state.world_lookup.keys.length > 0 # return unless hash has atleast 1 key
    collision_floor
    collision_left
    collision_right
    collision_ceiling
  end

  # Finds collisions between the bottom of the player's rect and the top of a world_collision_rect.
  def collision_floor
    return unless state.dy <= 0 # return unless player is going down or is as far down as possible
    player_rect = [state.x, next_y, state.tile_size, state.tile_size] # definition of player

    # Runs through all the sprites on the field and finds all intersections between player's
    # bottom and the top of a rect.
    floor_collisions = state.world_collision_rects
                         .find_all { |r| r[:top].intersect_rect?(player_rect, state.collision_tolerance) }
                         .first

    return unless floor_collisions # performs following changes if a collision has occurred
    state.y = floor_collisions[:top].top # y of player is set to the y of the colliding rect's top
    state.dy = 0 # no change in y because the player's path is blocked
  end

  # Finds collisions between the player's left side and the right side of a world_collision_rect.
  def collision_left
    return unless state.dx < 0 # return unless player is moving left
    player_rect = [next_x, state.y, state.tile_size, state.tile_size]

    # Runs through all the sprites on the field and finds all intersections between the player's left side
    # and the right side of a rect.
    left_side_collisions = state.world_collision_rects
                             .find_all { |r| r[:left_right].intersect_rect?(player_rect, state.collision_tolerance) }
                             .first

    return unless left_side_collisions # return unless collision occurred
    state.x = left_side_collisions[:left_right].right # sets player's x to the x of the colliding rect's right side
    state.dx = 0 # no change in x because the player's path is blocked
  end

  # Finds collisions between the right side of the player and the left side of a world_collision_rect.
  def collision_right
    return unless state.dx > 0 # return unless player is moving right
    player_rect = [next_x, state.y, state.tile_size, state.tile_size]

    # Runs through all the sprites on the field and finds all intersections between the  player's
    # right side and the left side of a rect.
    right_side_collisions = state.world_collision_rects
                              .find_all { |r| r[:left_right].intersect_rect?(player_rect, state.collision_tolerance) }
                              .first

    return unless right_side_collisions # return unless collision occurred
    state.x = right_side_collisions[:left_right].left - state.tile_size # player's x is set to the x of colliding rect's left side (minus tile size since x is the player's bottom left corner)
    state.dx = 0 # no change in x because the player's path is blocked
  end

  # Finds collisions between the top of the player's rect and the bottom of a world_collision_rect.
  def collision_ceiling
    return unless state.dy > 0 # return unless player is moving up
    player_rect = [state.x, next_y, state.player_width, state.player_height]

    # Runs through all the sprites on the field and finds all intersections between the player's top
    # and the bottom of a rect.
    ceil_collisions = state.world_collision_rects
                        .find_all { |r| r[:bottom].intersect_rect?(player_rect, state.collision_tolerance) }
                        .first

    return unless ceil_collisions # return unless collision occurred
    state.y = ceil_collisions[:bottom].y - state.tile_size # player's y is set to the y of the colliding rect's bottom (minus tile size)
    state.dy = 0 # no change in y because the player's path is blocked
  end

  # Makes sure the player remains within the screen's dimensions.
  def calc_edge_collision
    # Ensures that player doesn't fall below the map
    if next_y < 0 && state.dy < 0 # if player is moving down and is about to fall (next_y) below the map's scope
      state.y = 0 # 0 is the lowest the player can be while staying on the screen
      state.dy = 0
    # Ensures player doesn't go insanely high
    elsif next_y > 720 - state.tile_size && state.dy > 0 # if player is moving up, about to exceed map's scope
      state.y = 720 - state.tile_size # if we don't subtract tile_size, we won't be able to see the player on the screen
      state.dy = 0
    end

    # Ensures that player remains in the horizontal range its supposed to
    if state.x >= 1280 - state.tile_size && state.dx > 0 # if the player is moving too far right
      state.x = 1280 - state.tile_size # farthest right the player can be while remaining in the screen's scope
      state.dx = 0
    elsif state.x <= 0 && state.dx < 0 # if the player is moving too far left
      state.x = 0 # farthest left the player can be while remaining in the screen's scope
      state.dx = 0
    end
  end

  def calc_sprite_selection
    # Does the transition to bring down the select sprite screen
    if state.mode == :selecting && state.select_menu.y != 0
      state.select_menu.y = 0  # sets y position of select menu (shown when 's' is pressed)
      state.banner_coords.y = 680 # sets y position of Select Sprite banner
      state.sprite_coords = state.sprite_coords.map do |x, y, w, h|
        [x, y - 720, w, h] # sets definition of sprites (change '-' to '+' and the sprites can't be seen)
      end
    end

    # Does the transition to leave the select sprite screen
    if state.mode == :creating  && state.select_menu.y != 720
      state.select_menu.y = 720 # sets y position of select menu (menu is retreated back up)
      state.banner_coords.y = 1000 # sets y position of Select Sprite banner
      state.sprite_coords = state.sprite_coords.map do |x, y, w, h|
        [x, y + 720, w, h] # sets definition of all elements in collection
      end
    end
  end

  def process_inputs
    # If the state.mode is back and if the menu has retreated back up
    # call methods that process user inputs
    if state.mode == :creating
      process_inputs_player_movement
      process_inputs_place_tile
    end

    # For each sprite_coordinate added, check what sprite was selected
    if state.mode == :selecting
      state.sprite_coords.map do |x, y, order| # goes through all sprites in collection
        # checks that a specific sprite was pressed based on x, y position
        if inputs.mouse.down && # the && (and) sign means ALL statements must be true for the evaluation to be true
           inputs.mouse.down.point.x >= x      && # x is greater than or equal to sprite's x and
           inputs.mouse.down.point.x <= x + 50 && # x is less than or equal to 50 pixels to the right
           inputs.mouse.down.point.y >= y      && # y is greater than or equal to sprite's y
           inputs.mouse.down.point.y <= y + 50 # y is less than or equal to 50 pixels up
          state.sprite_selected = order # sprite is chosen
        end
      end
    end

    inputs_export_stage
    process_inputs_show_available_sprites
  end

  # Moves the player based on the keys they press on their keyboard
  def process_inputs_player_movement
    # Sets dx to 0 if the player lets go of arrow keys (player won't move left or right)
    if inputs.keyboard.key_up.right
      state.dx = 0
    elsif inputs.keyboard.key_up.left
      state.dx = 0
    end

    # Sets dx to 3 in whatever direction the player chooses when they hold down (or press) the left or right keys
    if inputs.keyboard.key_held.right
      state.dx =  3
    elsif inputs.keyboard.key_held.left
      state.dx = -3
    end

    # Sets dy to 5 to make the player ~fly~ when they press the space bar on their keyboard
    if inputs.keyboard.key_held.space
      state.dy = 5
    end
  end

  # Adds tile in the place the user holds down the mouse
  def process_inputs_place_tile
    if inputs.mouse.down # if mouse is pressed
      state.world_lookup = {}
      x, y = to_coord inputs.mouse.down.point # gets x, y coordinates for the grid

      # Checks if any coordinates duplicate (already exist in world)
      if state.world.any? { |existing_x, existing_y, n| existing_x == x && existing_y == y }
        #erases existing tile space by rejecting them from world
        state.world = state.world.reject do |existing_x, existing_y, n|
          existing_x == x && existing_y == y
        end
      else
        state.world << [x, y, state.sprite_selected] # If no duplicates, add the sprite
      end
    end
  end

  # Stores/exports world collection's info (coordinates, sprite number) into a file
  def inputs_export_stage
    if inputs.keyboard.key_down.e # if "e" is pressed
      export_string = state.world.map do |x, y, sprite_number| # stores world info in a string
        "#{x},#{y},#{sprite_number}"                           # using string interpolation
      end
      gtk.write_file(MAP_FILE_PATH, export_string.join("\n")) # writes string into a file
      state.map_saved_at = state.tick_count # frame number (passage of time) when the map was saved
    end
  end

  def process_inputs_show_available_sprites
    # Based on keyboard input, the entity (:creating and :selecting) switch
    if inputs.keyboard.key_held.s && state.mode == :creating # if "s" is pressed and currently creating
      state.mode = :selecting # will change to selecting
      inputs.keyboard.clear # VERY IMPORTANT! If not present, it'll flicker between on and off
    elsif inputs.keyboard.key_held.s && state.mode == :selecting # if "s" is pressed and currently selecting
      state.mode = :creating # will change to creating
      inputs.keyboard.clear # VERY IMPORTANT! If not present, it'll flicker between on and off
    end
  end

  # Loads the world collection by reading from the map.txt file in the app folder
  def attempt_load_world_from_file
    return if state.world # return if the world collection is already populated
    state.world ||= [] # initialized as an empty collection
    exported_world = gtk.read_file(MAP_FILE_PATH) # reads the file using the path mentioned at top of code
    return unless exported_world # return unless the file read was successful
    state.world = exported_world.each_line.map do |l| # perform action on each line of exported_world
        l.split(',').map(&:to_i) # calls split using ',' as a delimiter, and invokes .map on the collection,
                                 # calling to_i (converts to integers) on each element
    end
  end

  # Adds the change in y to y to determine the next y position of the player.
  def next_y
    state.y + state.dy
  end

  # Determines next x position of player
  def next_x
    if state.dx < 0 # if the player moves left
      return state.x - (state.tile_size - state.player_width) # subtracts since the change in x is negative (player is moving left)
    else
      return state.x + (state.tile_size - state.player_width) # adds since the change in x is positive (player is moving right)
    end
  end

  def to_coord point
    # Integer divides (idiv) point.x to turn into grid
    # Then, you can just multiply each integer by state.tile_size
    # later and huzzah. Grid coordinates
    [point.x.idiv(state.tile_size), point.y.idiv(state.tile_size)]
  end
end

$metroidvania_starter = MetroidvaniaStarter.new

def tick args
    $metroidvania_starter.grid    = args.grid
    $metroidvania_starter.inputs  = args.inputs
    $metroidvania_starter.state   = args.state
    $metroidvania_starter.outputs = args.outputs
    $metroidvania_starter.gtk     = args.gtk
    $metroidvania_starter.tick
end

    Box Collision 3 - main.rb link

    # ./samples/04_physics_and_collisions/06_box_collision_3/app/main.rb
class Game
  attr_gtk

  def tick
    defaults
    render
    input_edit_map
    input_player
    calc_player
  end

  def defaults
    state.gravity           = -0.4
    state.drag              = 0.15
    state.tile_size         = 32
    state.player.size       = 16
    state.player.jump_power = 12

    state.tiles                 ||= []
    state.player.y              ||= 800
    state.player.x              ||= 100
    state.player.dy             ||= 0
    state.player.dx             ||= 0
    state.player.jumped_down_at ||= 0
    state.player.jumped_at      ||= 0

    calc_player_rect if !state.player.rect
  end

  def render
    outputs.labels << [10, 10.from_top, "tile: click to add a tile, hold X key and click to delete a tile."]
    outputs.labels << [10, 35.from_top, "move: use left and right to move, space to jump, down and space to jump down."]
    outputs.labels << [10, 55.from_top, "      You can jump through or jump down through tiles with a height of 1."]
    outputs.background_color = [80, 80, 80]
    outputs.sprites << tiles.map(&:sprite)
    outputs.sprites << (player.rect.merge path: 'sprites/square/green.png')

    mouse_overlay = {
      x: (inputs.mouse.x.ifloor state.tile_size),
      y: (inputs.mouse.y.ifloor state.tile_size),
      w: state.tile_size,
      h: state.tile_size,
      a: 100
    }

    mouse_overlay = mouse_overlay.merge r: 255 if state.delete_mode

    if state.mouse_held
      outputs.primitives << mouse_overlay.border!
    else
      outputs.primitives << mouse_overlay.solid!
    end
  end

  def input_edit_map
    state.mouse_held = true  if inputs.mouse.down
    state.mouse_held = false if inputs.mouse.up

    if inputs.keyboard.x
      state.delete_mode = true
    elsif inputs.keyboard.key_up.x
      state.delete_mode = false
    end

    return unless state.mouse_held

    ordinal = { x: (inputs.mouse.x.idiv state.tile_size),
                y: (inputs.mouse.y.idiv state.tile_size) }

    found = find_tile ordinal
    if !found && !state.delete_mode
      tiles << (state.new_entity :tile, ordinal)
      recompute_tiles
    elsif found && state.delete_mode
      tiles.delete found
      recompute_tiles
    end
  end

  def input_player
    player.dx += inputs.left_right

    if inputs.keyboard.key_down.space && inputs.keyboard.down
      player.dy             = player.jump_power * -1
      player.jumped_at      = 0
      player.jumped_down_at = state.tick_count
    elsif inputs.keyboard.key_down.space
      player.dy             = player.jump_power
      player.jumped_at      = state.tick_count
      player.jumped_down_at = 0
    end
  end

  def calc_player
    calc_player_rect
    calc_below
    calc_left
    calc_right
    calc_above
    calc_player_dy
    calc_player_dx
    reset_player if player_off_stage?
  end

  def calc_player_rect
    player.rect      = current_player_rect
    player.next_rect = player.rect.merge x: player.x + player.dx,
                                         y: player.y + player.dy
    player.prev_rect = player.rect.merge x: player.x - player.dx,
                                         y: player.y - player.dy
  end

  def calc_below
    return unless player.dy <= 0
    tiles_below = find_tiles { |t| t.rect.top <= player.prev_rect.y }
    collision = find_colliding_tile tiles_below, (player.rect.merge y: player.next_rect.y)
    return unless collision
    if collision.neighbors.b == :none && player.jumped_down_at.elapsed_time < 10
      player.dy = -1
    else
      player.y  = collision.rect.y + state.tile_size
      player.dy = 0
    end
  end

  def calc_left
    return unless player.dx < 0
    tiles_left = find_tiles { |t| t.rect.right <= player.prev_rect.left }
    collision = find_colliding_tile tiles_left, (player.rect.merge x: player.next_rect.x)
    return unless collision
    player.x  = collision.rect.right
    player.dx = 0
  end

  def calc_right
    return unless player.dx > 0
    tiles_right = find_tiles { |t| t.rect.left >= player.prev_rect.right }
    collision = find_colliding_tile tiles_right, (player.rect.merge x: player.next_rect.x)
    return unless collision
    player.x  = collision.rect.left - player.rect.w
    player.dx = 0
  end

  def calc_above
    return unless player.dy > 0
    tiles_above = find_tiles { |t| t.rect.y >= player.prev_rect.y }
    collision = find_colliding_tile tiles_above, (player.rect.merge y: player.next_rect.y)
    return unless collision
    return if collision.neighbors.t == :none
    player.dy = 0
    player.y  = collision.rect.bottom - player.rect.h
  end

  def calc_player_dx
    player.dx  = player.dx.clamp(-5,  5)
    player.dx *= 0.9
    player.x  += player.dx
  end

  def calc_player_dy
    player.y  += player.dy
    player.dy += state.gravity
    player.dy += player.dy * state.drag ** 2 * -1
  end

  def reset_player
    player.x  = 100
    player.y  = 720
    player.dy = 0
  end

  def recompute_tiles
    tiles.each do |t|
      t.w = state.tile_size
      t.h = state.tile_size
      t.neighbors = tile_neighbors t, tiles

      t.rect = [t.x * state.tile_size,
                t.y * state.tile_size,
                state.tile_size,
                state.tile_size].rect.to_hash

      sprite_sub_path = t.neighbors.mask.map { |m| flip_bit m }.join("")

      t.sprite = {
        x: t.x * state.tile_size,
        y: t.y * state.tile_size,
        w: state.tile_size,
        h: state.tile_size,
        path: "sprites/tile/wall-#{sprite_sub_path}.png"
      }
    end
  end

  def flip_bit bit
    return 0 if bit == 1
    return 1
  end

  def player
    state.player
  end

  def player_off_stage?
    player.rect.top < grid.bottom ||
    player.rect.right < grid.left ||
    player.rect.left > grid.right
  end

  def current_player_rect
    { x: player.x, y: player.y, w: player.size, h: player.size }
  end

  def tiles
    state.tiles
  end

  def find_tile ordinal
    tiles.find { |t| t.x == ordinal.x && t.y == ordinal.y }
  end

  def find_tiles &block
    tiles.find_all(&block)
  end

  def find_colliding_tile tiles, target
    tiles.find { |t| t.rect.intersect_rect? target }
  end

  def tile_neighbors tile, other_points
    t = find_tile x: tile.x + 0, y: tile.y + 1
    r = find_tile x: tile.x + 1, y: tile.y + 0
    b = find_tile x: tile.x + 0, y: tile.y - 1
    l = find_tile x: tile.x - 1, y: tile.y + 0

    tile_t, tile_r, tile_b, tile_l = 0

    tile_t = 1 if t
    tile_r = 1 if r
    tile_b = 1 if b
    tile_l = 1 if l

    state.new_entity :neighbors, mask: [tile_t, tile_r, tile_b, tile_l],
                                 t:    t ? :some : :none,
                                 b:    b ? :some : :none,
                                 l:    l ? :some : :none,
                                 r:    r ? :some : :none
  end
end

def tick args
  $game ||= Game.new
  $game.args = args
  $game.tick
end

    Jump Physics - main.rb link

    # ./samples/04_physics_and_collisions/07_jump_physics/app/main.rb
=begin

 Reminders:

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   For example, if we want to create a new button, we would declare it as a new entity and
   then define its properties. (Remember, you can use state to define ANY property and it will
   be retained across frames.)

 - args.outputs.solids: An array. The values generate a solid.
   The parameters for a solid are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - num1.greater(num2): Returns the greater value.

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.

 - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.

=end

# This sample app is a game that requires the user to jump from one platform to the next.
# As the player successfully clears platforms, they become smaller and move faster.

class VerticalPlatformer
  attr_gtk

  # declares vertical platformer as new entity
  def s
    state.vertical_platformer ||= state.new_entity(:vertical_platformer)
    state.vertical_platformer
  end

  # creates a new platform using a hash
  def new_platform hash
    s.new_entity_strict(:platform, hash) # platform key
  end

  # calls methods needed for game to run properly
  def tick
    defaults
    render
    calc
    input
  end

  def init_game
    s.platforms ||= [ # initializes platforms collection with two platforms using hashes
      new_platform(x: 0, y: 0, w: 700, h: 32, dx: 1, speed: 0, rect: nil),
      new_platform(x: 0, y: 300, w: 700, h: 32, dx: 1, speed: 0, rect: nil), # 300 pixels higher
    ]

    s.tick_count  = args.state.tick_count
    s.gravity     = -0.3 # what goes up must come down because of gravity
    s.player.platforms_cleared ||= 0 # counts how many platforms the player has successfully cleared
    s.player.x  ||= 0           # sets player values
    s.player.y  ||= 100
    s.player.w  ||= 64
    s.player.h  ||= 64
    s.player.dy ||= 0           # change in position
    s.player.dx ||= 0
    s.player_jump_power           = 15
    s.player_jump_power_duration  = 10
    s.player_max_run_speed        = 5
    s.player_speed_slowdown_rate  = 0.9
    s.player_acceleration         = 1
    s.camera ||= { y: -100 } # shows view on screen (as the player moves upward, the camera does too)
  end

  # Sets default values
  def defaults
    init_game
  end

  # Outputs objects onto the screen
  def render
    outputs.solids << s.platforms.map do |p| # outputs platforms onto screen
      [p.x + 300, p.y - s.camera[:y], p.w, p.h] # add 300 to place platform in horizontal center
      # don't forget, position of platform is denoted by bottom left hand corner
    end

    # outputs player using hash
    outputs.solids << {
      x: s.player.x + 300, # player positioned on top of platform
      y: s.player.y - s.camera[:y],
      w: s.player.w,
      h: s.player.h,
      r: 100,              # color saturation
      g: 100,
      b: 200
    }
  end

  # Performs calculations
  def calc
    s.platforms.each do |p| # for each platform in the collection
      p.rect = [p.x, p.y, p.w, p.h] # set the definition
    end

    # sets player point by adding half the player's width to the player's x
    s.player.point = [s.player.x + s.player.w.half, s.player.y] # change + to - and see what happens!

    # search the platforms collection to find if the player's point is inside the rect of a platform
    collision = s.platforms.find { |p| s.player.point.inside_rect? p.rect }

    # if collision occurred and player is moving down (or not moving vertically at all)
    if collision && s.player.dy <= 0
      s.player.y = collision.rect.y + collision.rect.h - 2 # player positioned on top of platform
      s.player.dy = 0 if s.player.dy < 0 # player stops moving vertically
      if !s.player.platform
        s.player.dx = 0 # no horizontal movement
      end
      # changes horizontal position of player by multiplying collision change in x (dx) by speed and adding it to current x
      s.player.x += collision.dx * collision.speed
      s.player.platform = collision # player is on the platform that it collided with (or landed on)
      if s.player.falling # if player is falling
        s.player.dx = 0  # no horizontal movement
      end
      s.player.falling = false
      s.player.jumped_at = nil
    else
      s.player.platform = nil # player is not on a platform
      s.player.y  += s.player.dy # velocity is the change in position
      s.player.dy += s.gravity # acceleration is the change in velocity; what goes up must come down
    end

    s.platforms.each do |p| # for each platform in the collection
      p.x += p.dx * p.speed # x is incremented by product of dx and speed (causes platform to move horizontally)
      # changes platform's x so it moves left and right across the screen (between -300 and 300 pixels)
      if p.x < -300 # if platform goes too far left
        p.dx *= -1 # dx is scaled down
        p.x = -300 # as far left as possible within scope
      elsif p.x > (1000 - p.w) # if platform's x is greater than 300
        p.dx *= -1
        p.x = (1000 - p.w) # set to 300 (as far right as possible within scope)
      end
    end

    delta = (s.player.y - s.camera[:y] - 100) # used to position camera view

    if delta > -200
      s.camera[:y] += delta * 0.01 # allows player to see view as they move upwards
      s.player.x  += s.player.dx # velocity is change in position; change in x increases by dx

      # searches platform collection to find platforms located more than 300 pixels above the player
      has_platforms = s.platforms.find { |p| p.y > (s.player.y + 300) }
      if !has_platforms # if there are no platforms 300 pixels above the player
        width = 700 - (700 * (0.1 * s.player.platforms_cleared)) # the next platform is smaller than previous
        s.player.platforms_cleared += 1 # player successfully cleared another platform
        last_platform = s.platforms[-1] # platform just cleared becomes last platform
        # another platform is created 300 pixels above the last platform, and this
        # new platform has a smaller width and moves faster than all previous platforms
        s.platforms << new_platform(x: (700 - width) * rand, # random x position
                                    y: last_platform.y + 300,
                                    w: width,
                                    h: 32,
                                    dx: 1.randomize(:sign), # random change in x
                                    speed: 2 * s.player.platforms_cleared,
                                    rect: nil)
      end
    else
      # game over
      s.as_hash.clear # otherwise clear the hash (no new platform is necessary)
      init_game
    end
  end

  # Takes input from the user to move the player
  def input
    if inputs.keyboard.space # if the space bar is pressed
      s.player.jumped_at ||= s.tick_count # set to current frame

      # if the time that has passed since the jump is less than the duration of a jump (10 frames)
      # and the player is not falling
      if s.player.jumped_at.elapsed_time < s.player_jump_power_duration && !s.player.falling
        s.player.dy = s.player_jump_power # player jumps up
      end
    end

    if inputs.keyboard.key_up.space # if space bar is in "up" state
      s.player.falling = true # player is falling
    end

    if inputs.keyboard.left # if left key is pressed
      s.player.dx -= s.player_acceleration # player's position changes, decremented by acceleration
      s.player.dx = s.player.dx.greater(-s.player_max_run_speed) # dx is either current dx or -5, whichever is greater
    elsif inputs.keyboard.right # if right key is pressed
      s.player.dx += s.player_acceleration # player's position changes, incremented by acceleration
      s.player.dx  = s.player.dx.lesser(s.player_max_run_speed) # dx is either current dx or 5, whichever is lesser
    else
      s.player.dx *= s.player_speed_slowdown_rate # scales dx down
    end
  end
end

$game = VerticalPlatformer.new

def tick args
  $game.args = args
  $game.tick
end

    Bouncing On Collision - ball.rb link

    # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/ball.rb
GRAVITY = -0.08

class Ball
    attr_accessor :velocity, :center, :radius, :collision_enabled

    def initialize args
        #Start the ball in the top center
        #@x = args.grid.w / 2
        #@y = args.grid.h - 20

        @velocity = {x: 0, y: 0}
        #@width =  20
        #@height = @width
        @radius = 20.0 / 2.0
        @center = {x: (args.grid.w / 2), y: (args.grid.h)}

        #@left_wall = (args.state.board_width + args.grid.w / 8)
        #@right_wall = @left_wall + args.state.board_width
        @left_wall = 0
        @right_wall = $args.grid.right

        @max_velocity = 7
        @collision_enabled = true
    end

    #Move the ball according to its velocity
    def update args
      @center.x += @velocity.x
      @center.y += @velocity.y
      @velocity.y += GRAVITY

      alpha = 0.2
      if @center.y-@radius <= 0
        @velocity.y  = (@velocity.y.abs*0.7).abs
        @velocity.x  = (@velocity.x.abs*0.9).abs * ((@velocity.x < 0) ? -1 : 1)

        if @velocity.y.abs() < alpha
          @velocity.y=0
        end
        if @velocity.x.abs() < alpha
          @velocity.x=0
        end
      end

      if @center.x > args.grid.right+@radius*2
        @center.x = 0-@radius
      elsif @center.x< 0-@radius*2
        @center.x = args.grid.right + @radius
      end
    end

    def wallBounds args
        #if @x < @left_wall || @x + @width > @right_wall
            #@velocity.x *= -1.1
            #if @velocity.x > @max_velocity
                #@velocity.x = @max_velocity
            #elsif @velocity.x < @max_velocity * -1
                #@velocity.x = @max_velocity * -1
            #end
        #end
        #if @y < 0 || @y + @height > args.grid.h
            #@velocity.y *= -1.1
            #if @velocity.y > @max_velocity
                #@velocity.y = @max_velocity
            #elsif @velocity.y < @max_velocity * -1
                #@velocity.y = @max_velocity * -1
            #end
        #end
    end

    #render the ball to the screen
    def draw args
        #args.outputs.solids << [@x, @y, @width, @height, 255, 255, 0];
        args.outputs.sprites << [
          @center.x-@radius,
          @center.y-@radius,
          @radius*2,
          @radius*2,
          "sprites/circle-white.png",
          0,
          255,
          255,    #r
          0,    #g
          255   #b
        ]
    end
  end

    Bouncing On Collision - block.rb link

    # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/block.rb
DEGREES_TO_RADIANS = Math::PI / 180

class Block
  def initialize(x, y, block_size, rotation)
    @x = x
    @y = y
    @block_size = block_size
    @rotation = rotation

    #The repel velocity?
    @velocity = {x: 2, y: 0}

    horizontal_offset = (3 * block_size) * Math.cos(rotation * DEGREES_TO_RADIANS)
    vertical_offset = block_size * Math.sin(rotation * DEGREES_TO_RADIANS)

    if rotation >= 0
      theta = 90 - rotation
      #The line doesn't visually line up exactly with the edge of the sprite, so artificially move it a bit
      modifier = 5
      x_offset = modifier * Math.cos(theta * DEGREES_TO_RADIANS)
      y_offset = modifier * Math.sin(theta * DEGREES_TO_RADIANS)
      @x1 = @x - x_offset
      @y1 = @y + y_offset
      @x2 = @x1 + horizontal_offset
      @y2 = @y1 + (vertical_offset * 3)

      @imaginary_line = [ @x1, @y1, @x2, @y2 ]
    else
      theta = 90 + rotation
      x_offset = @block_size * Math.cos(theta * DEGREES_TO_RADIANS)
      y_offset = @block_size * Math.sin(theta * DEGREES_TO_RADIANS)
      @x1 = @x + x_offset
      @y1 = @y + y_offset + 19
      @x2 = @x1 + horizontal_offset
      @y2 = @y1 + (vertical_offset * 3)

      @imaginary_line = [ @x1, @y1, @x2, @y2 ]
    end

  end

  def draw args
    args.outputs.sprites << [
      @x,
      @y,
      @block_size*3,
      @block_size,
      "sprites/square-green.png",
      @rotation
    ]

    args.outputs.lines << @imaginary_line
    args.outputs.solids << @debug_shape
  end

  def multiply_matricies
  end

  def calc args
    if collision? args
        collide args
    end
  end

  #Determine if the ball and block are touching
  def collision? args
    #The minimum area enclosed by the center of the ball and the 2 corners of the block
    #If the area ever drops below this value, we know there is a collision
    min_area = ((@block_size * 3) * args.state.ball.radius) / 2

    #https://www.mathopenref.com/coordtrianglearea.html
    ax = @x1
    ay = @y1
    bx = @x2
    by = @y2
    cx = args.state.ball.center.x
    cy = args.state.ball.center.y

    current_area = (ax*(by-cy)+bx*(cy-ay)+cx*(ay-by))/2

    collision = false
    if @rotation >= 0
      if (current_area < min_area &&
        current_area > 0 &&
        args.state.ball.center.y > @y1 &&
        args.state.ball.center.x < @x2)

        collision = true
      end
    else
      if (current_area < min_area &&
        current_area > 0 &&
        args.state.ball.center.y > @y2 &&
        args.state.ball.center.x > @x1)

      collision = true
      end
    end

    return collision
  end

  def collide args
    #Slope of the block
    slope = (@y2 - @y1) / (@x2 - @x1)

    #Create a unit vector and tilt it (@rotation) number of degrees
    x = -Math.cos(@rotation * DEGREES_TO_RADIANS)
    y = Math.sin(@rotation * DEGREES_TO_RADIANS)

    #Find the vector that is perpendicular to the slope
    perpVect = { x: x, y: y }
    mag  = (perpVect.x**2 + perpVect.y**2)**0.5                                 # find the magniude of the perpVect
    perpVect = {x: perpVect.x/(mag), y: perpVect.y/(mag)}                       # divide the perpVect by the magniude to make it a unit vector

    previousPosition = {                                                        # calculate an ESTIMATE of the previousPosition of the ball
      x:args.state.ball.center.x-args.state.ball.velocity.x,
      y:args.state.ball.center.y-args.state.ball.velocity.y
    }

    velocityMag = (args.state.ball.velocity.x**2 + args.state.ball.velocity.y**2)**0.5 # the current velocity magnitude of the ball
    theta_ball = Math.atan2(args.state.ball.velocity.y, args.state.ball.velocity.x)         #the angle of the ball's velocity
    theta_repel = (180 * DEGREES_TO_RADIANS) - theta_ball + (@rotation * DEGREES_TO_RADIANS)

    fbx = velocityMag * Math.cos(theta_ball)                                    #the x component of the ball's velocity
    fby = velocityMag * Math.sin(theta_ball)                                    #the y component of the ball's velocity

    frx = velocityMag * Math.cos(theta_repel)                                       #the x component of the repel's velocity | magnitude is set to twice of fbx
    fry = velocityMag * Math.sin(theta_repel)                                       #the y component of the repel's velocity | magnitude is set to twice of fby

    args.state.display_value = velocityMag
    fsumx = fbx+frx                                                             #sum of x forces
    fsumy = fby+fry                                                             #sum of y forces
    fr = velocityMag                                                            #fr is the resulting magnitude
    thetaNew = Math.atan2(fsumy, fsumx)                                         #thetaNew is the resulting angle

    xnew = fr*Math.cos(thetaNew)                                                #resulting x velocity
    ynew = fr*Math.sin(thetaNew)                                                #resulting y velocity

    dampener = 0.3
    ynew *= dampener * 0.5

    #If the bounce is very low, that means the ball is rolling and we don't want to dampenen the X velocity
    if ynew > -0.1
      xnew *= dampener
    end

    #Add the sine component of gravity back in (X component)
    gravity_x = 4 * Math.sin(@rotation * DEGREES_TO_RADIANS)
    xnew += gravity_x

    args.state.ball.velocity.x = -xnew
    args.state.ball.velocity.y = -ynew

    #Set the position of the ball to the previous position so it doesn't warp throught the block
    args.state.ball.center.x = previousPosition.x
    args.state.ball.center.y = previousPosition.y
  end
end

    Bouncing On Collision - cannon.rb link

    # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/cannon.rb
class Cannon
  def initialize args
    @pointA = {x: args.grid.right/2,y: args.grid.top}
    @pointB = {x: args.inputs.mouse.x, y: args.inputs.mouse.y}
  end
  def update args
    activeBall = args.state.ball
    @pointB = {x: args.inputs.mouse.x, y: args.inputs.mouse.y}

    if args.inputs.mouse.click
      alpha = 0.01
      activeBall.velocity.y = (@pointB.y - @pointA.y) * alpha
      activeBall.velocity.x = (@pointB.x - @pointA.x) * alpha
      activeBall.center = {x: (args.grid.w / 2), y: (args.grid.h)}
    end
  end
  def render args
    args.outputs.lines << [@pointA.x, @pointA.y, @pointB.x, @pointB.y]
  end
end

    Bouncing On Collision - main.rb link

    # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/main.rb
INFINITY= 10**10

require 'app/vector2d.rb'
require 'app/peg.rb'
require 'app/block.rb'
require 'app/ball.rb'
require 'app/cannon.rb'


#Method to init default values
def defaults args
  args.state.pegs ||= []
  args.state.blocks ||= []
  args.state.cannon ||= Cannon.new args
  args.state.ball ||= Ball.new args
  args.state.horizontal_offset ||= 0
  init_pegs args
  init_blocks args

  args.state.display_value ||= "test"
end

begin :default_methods
  def init_pegs args
    num_horizontal_pegs = 14
    num_rows = 5

    return unless args.state.pegs.count < num_rows * num_horizontal_pegs

    block_size = 32
    block_spacing = 50
    total_width = num_horizontal_pegs * (block_size + block_spacing)
    starting_offset = (args.grid.w - total_width) / 2 + block_size

    for i in (0...num_rows)
      for j in (0...num_horizontal_pegs)
        row_offset = 0
        if i % 2 == 0
          row_offset = 20
        else
          row_offset = -20
        end
        args.state.pegs.append(Peg.new(j * (block_size+block_spacing) + starting_offset + row_offset, (args.grid.h - block_size * 2) - (i * block_size * 2)-90, block_size))
      end
    end

  end

  def init_blocks args
    return unless args.state.blocks.count < 10

    #Sprites are rotated in degrees, but the Ruby math functions work on radians
    radians_to_degrees = Math::PI / 180

    block_size = 25
    #Rotation angle (in degrees) of the blocks
    rotation = 30
    vertical_offset = block_size * Math.sin(rotation * radians_to_degrees)
    horizontal_offset = (3 * block_size) * Math.cos(rotation * radians_to_degrees)
    center = args.grid.w / 2

    for i in (0...5)
      #Create a ramp of blocks. Not going to be perfect because of the float to integer conversion and anisotropic to isotropic coversion
      args.state.blocks.append(Block.new((center + 100 + (i * horizontal_offset)).to_i, 100 + (vertical_offset * i) + (i * block_size), block_size, rotation))
      args.state.blocks.append(Block.new((center - 100 - (i * horizontal_offset)).to_i, 100 + (vertical_offset * i) + (i * block_size), block_size, -rotation))
    end
  end
end

#Render loop
def render args
  args.outputs.borders << args.state.game_area
  render_pegs args
  render_blocks args
  args.state.cannon.render args
  args.state.ball.draw args
end

begin :render_methods
  #Draw the pegs in a grid pattern
  def render_pegs args
    args.state.pegs.each do |peg|
      peg.draw args
    end
  end

  def render_blocks args
    args.state.blocks.each do |block|
      block.draw args
    end
  end

end

#Calls all methods necessary for performing calculations
def calc args
  args.state.pegs.each do |peg|
    peg.calc args
  end

  args.state.blocks.each do |block|
    block.calc args
  end

  args.state.ball.update args
  args.state.cannon.update args
end

begin :calc_methods

end

def tick args
  defaults args
  render args
  calc args
end

    Bouncing On Collision - peg.rb link

    # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/peg.rb
class Peg
  def initialize(x, y, block_size)
    @x = x                    # x cordinate of the LEFT side of the peg
    @y = y                    # y cordinate of the RIGHT side of the peg
    @block_size = block_size  # diameter of the peg

    @radius = @block_size/2.0 # radius of the peg
    @center = {               # cordinatees of the CENTER of the peg
      x: @x+@block_size/2.0,
      y: @y+@block_size/2.0
    }

    @r = 255 # color of the peg
    @g = 0
    @b = 0

    @velocity = {x: 2, y: 0}
  end

  def draw args
    args.outputs.sprites << [ # draw the peg according to the @x, @y, @radius, and the RGB
      @x,
      @y,
      @radius*2.0,
      @radius*2.0,
      "sprites/circle-white.png",
      0,
      255,
      @r,    #r
      @g,    #g
      @b   #b
    ]
  end


  def calc args
    if collisionWithBounce? args # if the is a collision with the bouncing ball
      collide args
      @r = 0
      @b = 0
      @g = 255
    else
    end
  end


  # do two circles (the ball and this peg) intersect
  def collisionWithBounce? args
    squareDistance = (  # the squared distance between the ball's center and this peg's center
      (args.state.ball.center.x - @center.x) ** 2.0 +
      (args.state.ball.center.y - @center.y) ** 2.0
    )
    radiusSum = (  # the sum of the radius squared of the this peg and the ball
      (args.state.ball.radius + @radius) ** 2.0
    )
    # if the squareDistance is less or equal to radiusSum, then there is a radial intersection between the ball and this peg
    return (squareDistance <= radiusSum)
  end

  # ! The following links explain the getRepelMagnitude function !
  # https://raw.githubusercontent.com/DragonRuby/dragonruby-game-toolkit-physics/master/docs/docImages/LinearCollider_4.png
  # https://raw.githubusercontent.com/DragonRuby/dragonruby-game-toolkit-physics/master/docs/docImages/LinearCollider_5.png
  # https://github.com/DragonRuby/dragonruby-game-toolkit-physics/blob/master/docs/LinearCollider.md
  def getRepelMagnitude (args, fbx, fby, vrx, vry, ballMag)
    a = fbx ; b = vrx ; c = fby
    d = vry ; e = ballMag
    if b**2 + d**2 == 0
      #unexpected
    end

    x1 = (-a*b+-c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 + d**2 - a**2 * d**2)**0.5)/(b**2 + d**2)
    x2 = -((a*b + c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 * d**2 - a**2 * d**2)**0.5)/(b**2 + d**2))

    err = 0.00001
    o = ((fbx + x1*vrx)**2 + (fby + x1*vry)**2 ) ** 0.5
    p = ((fbx + x2*vrx)**2 + (fby + x2*vry)**2 ) ** 0.5
    r = 0

    if (ballMag >= o-err and ballMag <= o+err)
      r = x1
    elsif (ballMag >= p-err and ballMag <= p+err)
      r = x2
    else
      #unexpected
    end

    if (args.state.ball.center.x > @center.x)
      return x2*-1
    end

    return x2

    #return r
  end

  #this sets the new velocity of the ball once it has collided with this peg
  def collide args
    normalOfRCCollision = [                                                     #this is the normal of the collision in COMPONENT FORM
      {x: @center.x, y: @center.y},                                             #see https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.mathscard.co.uk%2Fonline%2Fcircle-coordinate-geometry%2F&psig=AOvVaw2GcD-e2-nJR_IUKpw3hO98&ust=1605731315521000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCMjBo7e1iu0CFQAAAAAdAAAAABAD
      {x: args.state.ball.center.x, y: args.state.ball.center.y},
    ]

    normalSlope = (                                                             #normalSlope is the slope of normalOfRCCollision
      (normalOfRCCollision[1].y - normalOfRCCollision[0].y) /
      (normalOfRCCollision[1].x - normalOfRCCollision[0].x)
    )
    slope = normalSlope**-1.0 * -1                                              # slope is the slope of the tangent
    # args.state.display_value = slope
    pointA = {                                                                  # pointA and pointB are using the var slope to tangent in COMPONENT FORM
      x: args.state.ball.center.x-1,
      y: -(slope-args.state.ball.center.y)
    }
    pointB = {
      x: args.state.ball.center.x+1,
      y: slope+args.state.ball.center.y
    }

    perpVect = {x: pointB.x - pointA.x, y:pointB.y - pointA.y}                  # perpVect is to be VECTOR of the perpendicular tangent
    mag  = (perpVect.x**2 + perpVect.y**2)**0.5                                 # find the magniude of the perpVect
    perpVect = {x: perpVect.x/(mag), y: perpVect.y/(mag)}                       # divide the perpVect by the magniude to make it a unit vector
    perpVect = {x: -perpVect.y, y: perpVect.x}                                  # swap the x and y and multiply by -1 to make the vector perpendicular
    args.state.display_value = perpVect
    if perpVect.y > 0                                                           #ensure perpVect points upward
      perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
    end

    previousPosition = {                                                        # calculate an ESTIMATE of the previousPosition of the ball
      x:args.state.ball.center.x-args.state.ball.velocity.x,
      y:args.state.ball.center.y-args.state.ball.velocity.y
    }

    yInterc = pointA.y + -slope*pointA.x
    if slope == INFINITY                                                        # the perpVect presently either points in the correct dirrection or it is 180 degrees off we need to correct this
      if previousPosition.x < pointA.x
        perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
        yInterc = -INFINITY
      end
    elsif previousPosition.y < slope*previousPosition.x + yInterc               # check if ball is bellow or above the collider to determine if perpVect is - or +
      perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
    end

    velocityMag =                                                               # the current velocity magnitude of the ball
      (args.state.ball.velocity.x**2 + args.state.ball.velocity.y**2)**0.5
    theta_ball=
      Math.atan2(args.state.ball.velocity.y,args.state.ball.velocity.x)         #the angle of the ball's velocity
    theta_repel=
      Math.atan2(args.state.ball.center.y,args.state.ball.center.x)             #the angle of the repelling force(perpVect)

    fbx = velocityMag * Math.cos(theta_ball)                                    #the x component of the ball's velocity
    fby = velocityMag * Math.sin(theta_ball)                                    #the y component of the ball's velocity
    repelMag = getRepelMagnitude(                                               # the magniude of the collision vector
      args,
      fbx,
      fby,
      perpVect.x,
      perpVect.y,
      (args.state.ball.velocity.x**2 + args.state.ball.velocity.y**2)**0.5
    )
    frx = repelMag* Math.cos(theta_repel)                                       #the x component of the repel's velocity | magnitude is set to twice of fbx
    fry = repelMag* Math.sin(theta_repel)                                       #the y component of the repel's velocity | magnitude is set to twice of fby

    fsumx = fbx+frx                            # sum of x forces
    fsumy = fby+fry                            # sum of y forces
    fr = velocityMag                           # fr is the resulting magnitude
    thetaNew = Math.atan2(fsumy, fsumx)        # thetaNew is the resulting angle
    xnew = fr*Math.cos(thetaNew)               # resulting x velocity
    ynew = fr*Math.sin(thetaNew)               # resulting y velocity
    if (args.state.ball.center.x >= @center.x) # this is necessary for the ball colliding on the right side of the peg
      xnew=xnew.abs
    end

    args.state.ball.velocity.x = xnew                                           # set the x-velocity to the new velocity
    if args.state.ball.center.y > @center.y                                     # if the ball is above the middle of the peg we need to temporarily ignore some of the gravity
      args.state.ball.velocity.y = ynew + GRAVITY * 0.01
    else
      args.state.ball.velocity.y = ynew - GRAVITY * 0.01                        # if the ball is bellow the middle of the peg we need to temporarily increase the power of the gravity
    end

    args.state.ball.center.x+= args.state.ball.velocity.x                       # update the position of the ball so it never looks like the ball is intersecting the circle
    args.state.ball.center.y+= args.state.ball.velocity.y
  end
end

    Bouncing On Collision - vector2d.rb link

    # ./samples/04_physics_and_collisions/08_bouncing_on_collision/app/vector2d.rb
class Vector2d
    attr_accessor :x, :y

    def initialize x=0, y=0
      @x=x
      @y=y
    end

    #returns a vector multiplied by scalar x
    #x [float] scalar
    def mult x
      r = Vector2d.new(0,0)
      r.x=@x*x
      r.y=@y*x
      r
    end

    # vect [Vector2d] vector to copy
    def copy vect
      Vector2d.new(@x, @y)
    end

    #returns a new vector equivalent to this+vect
    #vect [Vector2d] vector to add to self
    def add vect
      Vector2d.new(@x+vect.x,@y+vect.y)
    end

    #returns a new vector equivalent to this-vect
    #vect [Vector2d] vector to subtract to self
    def sub vect
      Vector2d.new(@x-vect.c, @y-vect.y)
    end

    #return the magnitude of the vector
    def mag
      ((@x**2)+(@y**2))**0.5
    end

    #returns a new normalize version of the vector
    def normalize
      Vector2d.new(@x/mag, @y/mag)
    end

    #TODO delet?
    def distABS vect
      (((vect.x-@x)**2+(vect.y-@y)**2)**0.5).abs()
    end
  end

    Arbitrary Collision - ball.rb link

    # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/ball.rb

class Ball
    attr_accessor :velocity, :child, :parent, :number, :leastChain
    attr_reader :x, :y, :hypotenuse, :width, :height

    def initialize args, number, leastChain, parent, child
        #Start the ball in the top center
        @number = number
        @leastChain = leastChain
        @x = args.grid.w / 2
        @y = args.grid.h - 20

        @velocity = Vector2d.new(2, -2)
        @width =  10
        @height = 10

        @left_wall = (args.state.board_width + args.grid.w / 8)
        @right_wall = @left_wall + args.state.board_width

        @max_velocity = MAX_VELOCITY

        @child = child
        @parent = parent

        @past = [{x: @x, y: @y}]
        @next = nil
    end

    def reassignLeastChain (lc=nil)
      if (lc == nil)
        lc = @number
      end
      @leastChain = lc
      if (parent != nil)
        @parent.reassignLeastChain(lc)
      end

    end

    def makeLeader args
      if isLeader
        return
      end
      @parent.reassignLeastChain
      args.state.ballParents.push(self)
      @parent = nil

    end

    def isLeader
      return (parent == nil)
    end

    def receiveNext (p)
      #trace!
      if parent != nil
        @x = p[:x]
        @y = p[:y]
        @velocity = p[:velocity]
        #puts @x.to_s + "|" + @y.to_s + "|"[email protected]_s
        @past.append(p)
        if (@past.length >= BALL_DISTANCE)
          if (@child != nil)
            @child.receiveNext(@past[0])
            @past.shift
          end
        end
      end
    end

    #Move the ball according to its velocity
    def update args

        if isLeader
          wallBounds args
          @x += @velocity.x
          @y += @velocity.y
          @past.append({x: @x, y: @y, velocity: @velocity})
          #puts @past

          if (@past.length >= BALL_DISTANCE)
            if (@child != nil)
              @child.receiveNext(@past[0])
              @past.shift
            end
          end

        else
          puts "unexpected"
          raise "unexpected"
        end
    end

    def wallBounds args
        b= false
        if @x < @left_wall
          @velocity.x = @velocity.x.abs() * 1
          b=true
        elsif @x + @width > @right_wall
          @velocity.x = @velocity.x.abs() * -1
          b=true
        end
        if @y < 0
          @velocity.y = @velocity.y.abs() * 1
          b=true
        elsif @y + @height > args.grid.h
          @velocity.y = @velocity.y.abs() * -1
          b=true
        end
        mag = (@velocity.x**2.0 + @velocity.y**2.0)**0.5
        if (b == true && mag < MAX_VELOCITY)
          @velocity.x*=1.1;
          @velocity.y*=1.1;
        end

    end

    #render the ball to the screen
    def draw args

        #update args
        #args.outputs.solids << [@x, @y, @width, @height, 255, 255, 0];
        #args.outputs.sprits << {
          #x: @x,
          #y: @y,
          #w: @width,
          #h: @height,
          #path: "sprites/ball10.png"
        #}
        #args.outputs.sprites <<[@x, @y, @width, @height, "sprites/ball10.png"]
        args.outputs.sprites << {x: @x, y: @y, w: @width, h: @height, path:"sprites/ball10.png" }
    end

    def getDraw args
      #wallBounds args
      #update args
      #args.outputs.labels << [@x, @y, @number.to_s + "|" + @leastChain.to_s]
      return [@x, @y, @width, @height, "sprites/ball10.png"]
    end

    def getPoints args
      points = [
        {x:@x+@width/2, y: @y},
        {x:@x+@width, y:@y+@height/2},
        {x:@x+@width/2,y:@y+@height},
        {x:@x,y:@y+@height/2}
      ]
      #psize = 5.0
      #for p in points
        #args.outputs.solids << [p.x-psize/2.0, p.y-psize/2.0, psize, psize, 0, 0, 0];
      #end
      return points
    end

    def serialize
      {x: @x, y:@y}
    end

    def inspect
      serialize.to_s
    end

    def to_s
      serialize.to_s
    end
  end

    Arbitrary Collision - blocks.rb link

    # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/blocks.rb
MAX_COUNT=100

def universalUpdateOne args, shape
  didHit = false
  hitters = []
  #puts shape.to_s
  toCollide = nil
  for b in args.state.balls
    if [b.x, b.y, b.width, b.height].intersect_rect?(shape.bold)
      didSquare = false
      for s in shape.squareColliders
        if (s.collision?(args, b))
          didSquare = true
          didHit = true
          #s.collide(args, b)
          toCollide = s
          #hitter = b
          hitters.append(b)
        end #end if
      end #end for
      if (didSquare == false)
        for c in shape.colliders
          #puts args.state.ball.velocity
          if c.collision?(args, b.getPoints(args),b)
            #c.collide args, b
            toCollide = c
            didHit = true
            hitters.append(b)
          end #end if
        end #end for
      end #end if
    end#end if
  end#end for
  if (didHit)
    shape.count=0
    hitters = hitters.uniq
    for hitter in hitters
      hitter.makeLeader args
      #toCollide.collide(args, hitter)
      if shape.home == "squares"
        args.state.squares.delete(shape)
      elsif shape.home == "tshapes"
        args.state.tshapes.delete(shape)
      else shape.home == "lines"
        args.state.lines.delete(shape)
      end
    end

    #puts "HIT!" + hitter.number
  end
end

def universalUpdate args, shape
  #puts shape.home
  if (shape.count <= 1)
    universalUpdateOne args, shape
    return
  end

  didHit = false
  hitter = nil
  for b in args.state.ballParents
    if [b.x, b.y, b.width, b.height].intersect_rect?(shape.bold)
      didSquare = false
      for s in shape.squareColliders
        if (s.collision?(args, b))
          didSquare = true
          didHit = true
          s.collide(args, b)
          hitter = b
        end
      end
      if (didSquare == false)
        for c in shape.colliders
          #puts args.state.ball.velocity
          if c.collision?(args, b.getPoints(args),b)
            c.collide args, b
            didHit = true
            hitter = b
          end
        end
      end
    end
  end
  if (didHit)
    shape.count=shape.count-1
    shape.damageCount.append([(hitter.leastChain+1 - hitter.number)-1, args.state.tick_count])

  end
  i=0
  while i < shape.damageCount.length
    if shape.damageCount[i][0] <= 0
      shape.damageCount.delete_at(i)
      i-=1
    elsif shape.damageCount[i][1].elapsed_time > BALL_DISTANCE and shape.damageCount[i][0] > 1
      shape.count-=1
      shape.damageCount[i][0]-=1
      shape.damageCount[i][1] = args.state.tick_count
    end
    i+=1
  end
end


class Square
   attr_accessor :count, :x, :y, :home, :bold, :squareColliders, :colliders, :damageCount
   def initialize(args, x, y, block_size, orientation, block_offset)
        @x = x * block_size
        @y = y * block_size
        @block_size = block_size
        @block_offset = block_offset
        @orientation = orientation
        @damageCount = []
        @home = 'squares'


        Kernel.srand()
        @r = rand(255)
        @g = rand(255)
        @b = rand(255)

        @count = rand(MAX_COUNT)+1

        x_offset = (args.state.board_width + args.grid.w / 8) + @block_offset / 2
        @x_adjusted = @x + x_offset
        @y_adjusted = @y
        @size_adjusted = @block_size * 2 - @block_offset

        hypotenuse=args.state.ball_hypotenuse
        @bold = [(@x_adjusted-hypotenuse/2)-1, (@y_adjusted-hypotenuse/2)-1, @size_adjusted + hypotenuse + 2, @size_adjusted + hypotenuse + 2]

        @points = [
          {x:@x_adjusted, y:@y_adjusted},
          {x:@x_adjusted+@size_adjusted, y:@y_adjusted},
          {x:@x_adjusted+@size_adjusted, y:@y_adjusted+@size_adjusted},
          {x:@x_adjusted, y:@y_adjusted+@size_adjusted}
        ]
        @squareColliders = [
          SquareCollider.new(@points[0].x,@points[0].y,{x:-1,y:-1}),
          SquareCollider.new(@points[1].x-COLLISIONWIDTH,@points[1].y,{x:1,y:-1}),
          SquareCollider.new(@points[2].x-COLLISIONWIDTH,@points[2].y-COLLISIONWIDTH,{x:1,y:1}),
          SquareCollider.new(@points[3].x,@points[3].y-COLLISIONWIDTH,{x:-1,y:1}),
        ]
        @colliders = [
          LinearCollider.new(@points[0],@points[1], :neg),
          LinearCollider.new(@points[1],@points[2], :neg),
          LinearCollider.new(@points[2],@points[3], :pos),
          LinearCollider.new(@points[0],@points[3], :pos)
        ]
   end

   def draw(args)
    #Offset the coordinates to the edge of the game area
    x_offset = (args.state.board_width + args.grid.w / 8) + @block_offset / 2
    #args.outputs.solids << [@x + x_offset, @y, @block_size * 2 - @block_offset, @block_size * 2 - @block_offset, @r, @g, @b]
    args.outputs.solids <<{x: (@x + x_offset), y: (@y), w: (@block_size * 2 - @block_offset), h: (@block_size * 2 - @block_offset), r: @r , g: @g , b: @b }
    #args.outputs.solids << @bold.append([255,0,0])
    args.outputs.labels << [@x + x_offset + (@block_size * 2 - @block_offset)/2, (@y) + (@block_size * 2 - @block_offset)/2, @count.to_s]

   end

   def update args
     universalUpdate args, self
   end
end

class TShape
    attr_accessor :count, :x, :y, :home, :bold, :squareColliders, :colliders, :damageCount
    def initialize(args, x, y, block_size, orientation, block_offset)
        @x = x * block_size
        @y = y * block_size
        @block_size = block_size
        @block_offset = block_offset
        @orientation = orientation
        @damageCount = []
        @home = "tshapes"

        Kernel.srand()
        @r = rand(255)
        @g = rand(255)
        @b = rand(255)

        @count = rand(MAX_COUNT)+1


        @shapePoints = getShapePoints(args)
        minX={x:INFINITY, y:0}
        minY={x:0, y:INFINITY}
        maxX={x:-INFINITY, y:0}
        maxY={x:0, y:-INFINITY}
        for p in @shapePoints
          if p.x < minX.x
            minX = p
          end
          if p.x > maxX.x
            maxX = p
          end
          if p.y < minY.y
            minY = p
          end
          if p.y > maxY.y
            maxY = p
          end
        end


        hypotenuse=args.state.ball_hypotenuse

        @bold = [(minX.x-hypotenuse/2)-1, (minY.y-hypotenuse/2)-1, -((minX.x-hypotenuse/2)-1)+(maxX.x + hypotenuse + 2), -((minY.y-hypotenuse/2)-1)+(maxY.y + hypotenuse + 2)]
    end
    def getShapePoints(args)
      points=[]
      x_offset = (args.state.board_width + args.grid.w / 8) + (@block_offset / 2)

      if @orientation == :right
          #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
          #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2, @block_size, @r, @g, @b]
          points = [
            {x:@x + x_offset, y:@y},
            {x:(@x + x_offset)+(@block_size - @block_offset), y:@y},
            {x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size},
            {x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size},
            {x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size+@block_size},
            {x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size+@block_size},
            {x:(@x + x_offset)+(@block_size - @block_offset), y:@y+ @block_size * 3 - @block_offset},
            {x:@x + x_offset , y:@y+ @block_size * 3 - @block_offset}
          ]
          @squareColliders = [
            SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
            SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
            SquareCollider.new(points[2].x,points[2].y-COLLISIONWIDTH,{x:1,y:-1}),
            SquareCollider.new(points[3].x-COLLISIONWIDTH,points[3].y,{x:1,y:-1}),
            SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[5].x,points[5].y,{x:1,y:1}),
            SquareCollider.new(points[6].x-COLLISIONWIDTH,points[6].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[7].x,points[7].y-COLLISIONWIDTH,{x:-1,y:1}),
          ]
          @colliders = [
            LinearCollider.new(points[0],points[1], :neg),
            LinearCollider.new(points[1],points[2], :neg),
            LinearCollider.new(points[2],points[3], :neg),
            LinearCollider.new(points[3],points[4], :neg),
            LinearCollider.new(points[4],points[5], :pos),
            LinearCollider.new(points[5],points[6], :neg),
            LinearCollider.new(points[6],points[7], :pos),
            LinearCollider.new(points[0],points[7], :pos)
          ]
      elsif @orientation == :up
          #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
          #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size, @block_size * 2, @r, @g, @b]
          points = [
            {x:@x + x_offset, y:@y},
            {x:(@x + x_offset)+(@block_size * 3 - @block_offset), y:@y},
            {x:(@x + x_offset)+(@block_size * 3 - @block_offset), y:@y+(@block_size - @block_offset)},
            {x:@x + x_offset + @block_size + @block_size, y:@y+(@block_size - @block_offset)},
            {x:@x + x_offset + @block_size + @block_size, y:@y+@block_size*2},
            {x:@x + x_offset + @block_size, y:@y+@block_size*2},
            {x:@x + x_offset + @block_size, y:@y+(@block_size - @block_offset)},
            {x:@x + x_offset, y:@y+(@block_size - @block_offset)}
          ]
          @squareColliders = [
            SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
            SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
            SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[3].x,points[3].y,{x:1,y:1}),
            SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[5].x,points[5].y-COLLISIONWIDTH,{x:-1,y:1}),
            SquareCollider.new(points[6].x-COLLISIONWIDTH,points[6].y,{x:-1,y:1}),
            SquareCollider.new(points[7].x,points[7].y-COLLISIONWIDTH,{x:-1,y:1}),
          ]
          @colliders = [
            LinearCollider.new(points[0],points[1], :neg),
            LinearCollider.new(points[1],points[2], :neg),
            LinearCollider.new(points[2],points[3], :pos),
            LinearCollider.new(points[3],points[4], :neg),
            LinearCollider.new(points[4],points[5], :pos),
            LinearCollider.new(points[5],points[6], :neg),
            LinearCollider.new(points[6],points[7], :pos),
            LinearCollider.new(points[0],points[7], :pos)
          ]
      elsif @orientation == :left
          #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
          #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2 - @block_offset, @block_size - @block_offset, @r, @g, @b]
          xh = @x + x_offset
          #points = [
            #{x:@x + x_offset, y:@y},
            #{x:(@x + x_offset)+(@block_size - @block_offset), y:@y},
            #{x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size},
            #{x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size},
            #{x:(@x + x_offset)+ @block_size * 2,y:@y + @block_size+@block_size},
            #{x:(@x + x_offset)+(@block_size - @block_offset),y:@y + @block_size+@block_size},
            #{x:(@x + x_offset)+(@block_size - @block_offset), y:@y+ @block_size * 3 - @block_offset},
            #{x:@x + x_offset , y:@y+ @block_size * 3 - @block_offset}
          #]
          points = [
            {x:@x + x_offset + @block_size, y:@y},
            {x:@x + x_offset + @block_size + (@block_size - @block_offset), y:@y},
            {x:@x + x_offset + @block_size + (@block_size - @block_offset),y:@y+@block_size*3- @block_offset},
            {x:@x + x_offset + @block_size, y:@y+@block_size*3- @block_offset},
            {x:@x + x_offset+@block_size, y:@y+@block_size*2- @block_offset},
            {x:@x + x_offset, y:@y+@block_size*2- @block_offset},
            {x:@x + x_offset, y:@y+@block_size},
            {x:@x + x_offset+@block_size, y:@y+@block_size}
          ]
          @squareColliders = [
            SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
            SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
            SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[3].x,points[3].y-COLLISIONWIDTH,{x:-1,y:1}),
            SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y,{x:-1,y:1}),
            SquareCollider.new(points[5].x,points[5].y-COLLISIONWIDTH,{x:-1,y:1}),
            SquareCollider.new(points[6].x,points[6].y,{x:-1,y:-1}),
            SquareCollider.new(points[7].x-COLLISIONWIDTH,points[7].y-COLLISIONWIDTH,{x:-1,y:-1}),
          ]
          @colliders = [
            LinearCollider.new(points[0],points[1], :neg),
            LinearCollider.new(points[1],points[2], :neg),
            LinearCollider.new(points[2],points[3], :pos),
            LinearCollider.new(points[3],points[4], :neg),
            LinearCollider.new(points[4],points[5], :pos),
            LinearCollider.new(points[5],points[6], :neg),
            LinearCollider.new(points[6],points[7], :neg),
            LinearCollider.new(points[0],points[7], :pos)
          ]
      elsif @orientation == :down
          #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
          #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 2 - @block_offset, @r, @g, @b]

          points = [
            {x:@x + x_offset, y:@y+(@block_size*2)-@block_offset},
            {x:@x + x_offset+ @block_size*3-@block_offset, y:@y+(@block_size*2)-@block_offset},
            {x:@x + x_offset+ @block_size*3-@block_offset, y:@y+(@block_size)},
            {x:@x + x_offset+ @block_size*2-@block_offset, y:@y+(@block_size)},
            {x:@x + x_offset+ @block_size*2-@block_offset, y:@y},#
            {x:@x + x_offset+ @block_size, y:@y},#
            {x:@x + x_offset + @block_size, y:@y+(@block_size)},
            {x:@x + x_offset, y:@y+(@block_size)}
          ]
          @squareColliders = [
            SquareCollider.new(points[0].x,points[0].y-COLLISIONWIDTH,{x:-1,y:1}),
            SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y-COLLISIONWIDTH,{x:1,y:1}),
            SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y,{x:1,y:-1}),
            SquareCollider.new(points[3].x,points[3].y-COLLISIONWIDTH,{x:1,y:-1}),
            SquareCollider.new(points[4].x-COLLISIONWIDTH,points[4].y,{x:1,y:-1}),
            SquareCollider.new(points[5].x,points[5].y,{x:-1,y:-1}),
            SquareCollider.new(points[6].x-COLLISIONWIDTH,points[6].y-COLLISIONWIDTH,{x:-1,y:-1}),
            SquareCollider.new(points[7].x,points[7].y,{x:-1,y:-1}),
          ]
          @colliders = [
            LinearCollider.new(points[0],points[1], :pos),
            LinearCollider.new(points[1],points[2], :pos),
            LinearCollider.new(points[2],points[3], :neg),
            LinearCollider.new(points[3],points[4], :pos),
            LinearCollider.new(points[4],points[5], :neg),
            LinearCollider.new(points[5],points[6], :pos),
            LinearCollider.new(points[6],points[7], :neg),
            LinearCollider.new(points[0],points[7], :neg)
          ]
      end
      return points
    end

    def draw(args)
        #Offset the coordinates to the edge of the game area
        x_offset = (args.state.board_width + args.grid.w / 8) + (@block_offset / 2)

        if @orientation == :right
            #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset), y: @y, w: @block_size - @block_offset, h: (@block_size * 3 - @block_offset), r: @r , g: @g, b: @b}
            #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2, @block_size, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset), y: (@y + @block_size), w: (@block_size * 2), h: (@block_size), r: @r , g: @g, b: @b }
        elsif @orientation == :up
            #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset), y: (@y), w: (@block_size * 3 - @block_offset), h: (@block_size - @block_offset), r: @r , g: @g, b: @b}
            #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size, @block_size * 2, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset + @block_size), y: (@y), w: (@block_size), h: (@block_size * 2), r: @r , g: @g, b: @b}
        elsif @orientation == :left
            #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset + @block_size), y: (@y), w: (@block_size - @block_offset), h: (@block_size * 3 - @block_offset), r: @r , g: @g, b: @b}
            #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 2 - @block_offset, @block_size - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset), y: (@y + @block_size), w: (@block_size * 2 - @block_offset), h: (@block_size - @block_offset), r: @r , g: @g, b: @b}
        elsif @orientation == :down
            #args.outputs.solids << [@x + x_offset, @y + @block_size, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset), y: (@y + @block_size), w: (@block_size * 3 - @block_offset), h: (@block_size - @block_offset), r: @r , g: @g, b: @b}
            #args.outputs.solids << [@x + x_offset + @block_size, @y, @block_size - @block_offset, @block_size * 2 - @block_offset, @r, @g, @b]
            args.outputs.solids << {x: (@x + x_offset + @block_size), y: (@y), w: (@block_size - @block_offset), h: ( @block_size * 2 - @block_offset), r: @r , g: @g, b: @b}
        end

        #psize = 5.0
        #for p in @shapePoints
          #args.outputs.solids << [p.x-psize/2, p.y-psize/2, psize, psize, 0, 0, 0]
        #end
        args.outputs.labels << [@x + x_offset + (@block_size * 2 - @block_offset)/2, (@y) + (@block_size * 2 - @block_offset)/2, @count.to_s]

    end

    def updateOne_old args
      didHit = false
      hitter = nil
      toCollide = nil
      for b in args.state.balls
        if [b.x, b.y, b.width, b.height].intersect_rect?(@bold)
          didSquare = false
          for s in @squareColliders
            if (s.collision?(args, b))
              didSquare = true
              didHit = true
              #s.collide(args, b)
              toCollide = s
              hitter = b
              break
            end
          end
          if (didSquare == false)
            for c in @colliders
              #puts args.state.ball.velocity
              if c.collision?(args, b.getPoints(args),b)
                #c.collide args, b
                toCollide = c
                didHit = true
                hitter = b
                break
              end
            end
          end
        end
        if didHit
          break
        end
      end
      if (didHit)
        @count=0
        hitter.makeLeader args
        #toCollide.collide(args, hitter)
        args.state.tshapes.delete(self)
        #puts "HIT!" + hitter.number
      end
    end

    def update_old args
      if (@count == 1)
        updateOne args
        return
      end
      didHit = false
      hitter = nil
      for b in args.state.ballParents
        if [b.x, b.y, b.width, b.height].intersect_rect?(@bold)
          didSquare = false
          for s in @squareColliders
            if (s.collision?(args, b))
              didSquare = true
              didHit=true
              s.collide(args, b)
              hitter = b
            end
          end
          if (didSquare == false)
            for c in @colliders
              #puts args.state.ball.velocity
              if c.collision?(args, b.getPoints(args), b)
                c.collide args, b
                didHit=true
                hitter = b
              end
            end
          end
        end
      end
      if (didHit)
        @count=@count-1
        @damageCount.append([(hitter.leastChain+1 - hitter.number)-1, args.state.tick_count])

        if (@count == 0)
          args.state.tshapes.delete(self)
          return
        end
      end
      i=0

      while i < @damageCount.length
        if @damageCount[i][0] <= 0
          @damageCount.delete_at(i)
          i-=1
        elsif @damageCount[i][1].elapsed_time > BALL_DISTANCE
          @count-=1
          @damageCount[i][0]-=1
        end
        if (@count == 0)
          args.state.tshapes.delete(self)
          return
        end
        i+=1
      end
    end #end update

    def update args
      universalUpdate args, self
    end

end

class Line
    attr_accessor :count, :x, :y, :home, :bold, :squareColliders, :colliders, :damageCount
    def initialize(args, x, y, block_size, orientation, block_offset)
        @x = x * block_size
        @y = y * block_size
        @block_size = block_size
        @block_offset = block_offset
        @orientation = orientation
        @damageCount = []
        @home = "lines"

        Kernel.srand()
        @r = rand(255)
        @g = rand(255)
        @b = rand(255)

        @count = rand(MAX_COUNT)+1

        @shapePoints = getShapePoints(args)
        minX={x:INFINITY, y:0}
        minY={x:0, y:INFINITY}
        maxX={x:-INFINITY, y:0}
        maxY={x:0, y:-INFINITY}
        for p in @shapePoints
          if p.x < minX.x
            minX = p
          end
          if p.x > maxX.x
            maxX = p
          end
          if p.y < minY.y
            minY = p
          end
          if p.y > maxY.y
            maxY = p
          end
        end


        hypotenuse=args.state.ball_hypotenuse

        @bold = [(minX.x-hypotenuse/2)-1, (minY.y-hypotenuse/2)-1, -((minX.x-hypotenuse/2)-1)+(maxX.x + hypotenuse + 2), -((minY.y-hypotenuse/2)-1)+(maxY.y + hypotenuse + 2)]
    end

    def getShapePoints(args)
      points=[]
      x_offset = (args.state.board_width + args.grid.w / 8) + (@block_offset / 2)

      if @orientation == :right
        #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
        xa =@x + x_offset
        ya =@y
        wa =@block_size * 3 - @block_offset
        ha =(@block_size - @block_offset)
      elsif @orientation == :up
        #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
        xa =@x + x_offset
        ya =@y
        wa =@block_size - @block_offset
        ha =@block_size * 3 - @block_offset

      elsif @orientation == :left
        #args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
        xa =@x + x_offset
        ya =@y
        wa =@block_size * 3 - @block_offset
        ha =@block_size - @block_offset
      elsif @orientation == :down
        #args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
        xa =@x + x_offset
        ya =@y
        wa =@block_size - @block_offset
        ha =@block_size * 3 - @block_offset
      end
      points = [
        {x: xa, y:ya},
        {x: xa + wa,y:ya},
        {x: xa + wa,y:ya+ha},
        {x: xa, y:ya+ha},
      ]
      @squareColliders = [
        SquareCollider.new(points[0].x,points[0].y,{x:-1,y:-1}),
        SquareCollider.new(points[1].x-COLLISIONWIDTH,points[1].y,{x:1,y:-1}),
        SquareCollider.new(points[2].x-COLLISIONWIDTH,points[2].y-COLLISIONWIDTH,{x:1,y:1}),
        SquareCollider.new(points[3].x,points[3].y-COLLISIONWIDTH,{x:-1,y:1}),
      ]
      @colliders = [
        LinearCollider.new(points[0],points[1], :neg),
        LinearCollider.new(points[1],points[2], :neg),
        LinearCollider.new(points[2],points[3], :pos),
        LinearCollider.new(points[0],points[3], :pos),
      ]
      return points
    end

    def update args
      universalUpdate args, self
    end

    def draw(args)
        x_offset = (args.state.board_width + args.grid.w / 8) + @block_offset / 2

        if @orientation == :right
            args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
        elsif @orientation == :up
            args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
        elsif @orientation == :left
            args.outputs.solids << [@x + x_offset, @y, @block_size * 3 - @block_offset, @block_size - @block_offset, @r, @g, @b]
        elsif @orientation == :down
            args.outputs.solids << [@x + x_offset, @y, @block_size - @block_offset, @block_size * 3 - @block_offset, @r, @g, @b]
        end

        args.outputs.labels << [@x + x_offset + (@block_size * 2 - @block_offset)/2, (@y) + (@block_size * 2 - @block_offset)/2, @count.to_s]

    end
end

    Arbitrary Collision - linear_collider.rb link

    # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/linear_collider.rb

COLLISIONWIDTH=8

class LinearCollider
  attr_reader :pointA, :pointB
  def initialize (pointA, pointB, mode,collisionWidth=COLLISIONWIDTH)
    @pointA = pointA
    @pointB = pointB
    @mode = mode
    @collisionWidth = collisionWidth

    if (@pointA.x > @pointB.x)
      @pointA, @pointB = @pointB, @pointA
    end

    @linearCollider_collision_once = false
  end

  def collisionSlope args
    if (@[email protected] == 0)
      return INFINITY
    end
    return (@pointB.y - @pointA.y) / (@pointB.x - @pointA.x)
  end


  def collision? (args, points, ball=nil)

    slope = collisionSlope args
    result = false

    # calculate a vector with a magnitude of (1/2)collisionWidth and a direction perpendicular to the collision line
    vect=nil;mag=nil;vect=nil;
    if @mode == :both
      vect = {x: @pointB.x - @pointA.x, y:@pointB.y - @pointA.y}
      mag  = (vect.x**2 + vect.y**2)**0.5
      vect = {y: -1*(vect.x/(mag))*@collisionWidth*0.5, x: (vect.y/(mag))*@collisionWidth*0.5}
    else
      vect = {x: @pointB.x - @pointA.x, y:@pointB.y - @pointA.y}
      mag  = (vect.x**2 + vect.y**2)**0.5
      vect = {y: -1*(vect.x/(mag))*@collisionWidth, x: (vect.y/(mag))*@collisionWidth}
    end

    rpointA=nil;rpointB=nil;rpointC=nil;rpointD=nil;
    if @mode == :pos
      rpointA = {x:@pointA.x + vect.x, y:@pointA.y + vect.y}
      rpointB = {x:@pointB.x + vect.x, y:@pointB.y + vect.y}
      rpointC = {x:@pointB.x, y:@pointB.y}
      rpointD = {x:@pointA.x, y:@pointA.y}
    elsif @mode == :neg
      rpointA = {x:@pointA.x, y:@pointA.y}
      rpointB = {x:@pointB.x, y:@pointB.y}
      rpointC = {x:@pointB.x - vect.x, y:@pointB.y - vect.y}
      rpointD = {x:@pointA.x - vect.x, y:@pointA.y - vect.y}
    elsif @mode == :both
      rpointA = {x:@pointA.x + vect.x, y:@pointA.y + vect.y}
      rpointB = {x:@pointB.x + vect.x, y:@pointB.y + vect.y}
      rpointC = {x:@pointB.x - vect.x, y:@pointB.y - vect.y}
      rpointD = {x:@pointA.x - vect.x, y:@pointA.y - vect.y}
    end
    #four point rectangle



    if ball != nil
      xs = [rpointA.x,rpointB.x,rpointC.x,rpointD.x]
      ys = [rpointA.y,rpointB.y,rpointC.y,rpointD.y]
      correct = 1
      rect1 = [ball.x, ball.y, ball.width, ball.height]
      #$r1 = rect1
      rect2 = [xs.min-correct,ys.min-correct,(xs.max-xs.min)+correct*2,(ys.max-ys.min)+correct*2]
      #$r2 = rect2
      if rect1.intersect_rect?(rect2) == false
        return false
      end
    end


    #area of a triangle
    triArea = -> (a,b,c) { ((a.x * (b.y - c.y) + b.x * (c.y - a.y) + c.x * (a.y - b.y))/2.0).abs }

    #if at least on point is in the rectangle then collision? is true - otherwise false
    for point in points
      #Check whether a given point lies inside a rectangle or not:
      #if the sum of the area of traingls, PAB, PBC, PCD, PAD equal the area of the rec, then an intersection has occured
      areaRec =  triArea.call(rpointA, rpointB, rpointC)+triArea.call(rpointA, rpointC, rpointD)
      areaSum = [
        triArea.call(point, rpointA, rpointB),triArea.call(point, rpointB, rpointC),
        triArea.call(point, rpointC, rpointD),triArea.call(point, rpointA, rpointD)
      ].inject(0){|sum,x| sum + x }
      e = 0.0001 #allow for minor error
      if areaRec>= areaSum-e and areaRec<= areaSum+e
        result = true
        #return true
        break
      end
    end

    #args.outputs.lines << [@pointA.x, @pointA.y, @pointB.x, @pointB.y,     000, 000, 000]
    #args.outputs.lines << [rpointA.x, rpointA.y, rpointB.x, rpointB.y,     255, 000, 000]
    #args.outputs.lines << [rpointC.x, rpointC.y, rpointD.x, rpointD.y,     000, 000, 255]


    #puts (rpointA.x.to_s + " " +  rpointA.y.to_s + " " + rpointB.x.to_s + " "+ rpointB.y.to_s)
    return result
  end #end collision?

  def getRepelMagnitude (fbx, fby, vrx, vry, ballMag)
    a = fbx ; b = vrx ; c = fby
    d = vry ; e = ballMag
    if b**2 + d**2 == 0
      #unexpected
    end
    x1 = (-a*b+-c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 + d**2 - a**2 * d**2)**0.5)/(b**2 + d**2)
    x2 = -((a*b + c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 * d**2 - a**2 * d**2)**0.5)/(b**2 + d**2))
    err = 0.00001
    o = ((fbx + x1*vrx)**2 + (fby + x1*vry)**2 ) ** 0.5
    p = ((fbx + x2*vrx)**2 + (fby + x2*vry)**2 ) ** 0.5
    r = 0
    if (ballMag >= o-err and ballMag <= o+err)
      r = x1
    elsif (ballMag >= p-err and ballMag <= p+err)
      r = x2
    else
      #unexpected
    end
    return r
  end

  def collide args, ball
    slope = collisionSlope args

    # perpVect: normal vector perpendicular to collision
    perpVect = {x: @pointB.x - @pointA.x, y:@pointB.y - @pointA.y}
    mag  = (perpVect.x**2 + perpVect.y**2)**0.5
    perpVect = {x: perpVect.x/(mag), y: perpVect.y/(mag)}
    perpVect = {x: -perpVect.y, y: perpVect.x}
    if perpVect.y > 0 #ensure perpVect points upward
      perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
    end
    previousPosition = {
      x:ball.x-ball.velocity.x,
      y:ball.y-ball.velocity.y
    }
    yInterc = @pointA.y + -slope*@pointA.x
    if slope == INFINITY
      if previousPosition.x < @pointA.x
        perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
        yInterc = -INFINITY
      end
    elsif previousPosition.y < slope*previousPosition.x + yInterc #check if ball is bellow or above the collider to determine if perpVect is - or +
      perpVect = {x: perpVect.x*-1, y: perpVect.y*-1}
    end

    velocityMag = (ball.velocity.x**2 + ball.velocity.y**2)**0.5
    theta_ball=Math.atan2(ball.velocity.y,ball.velocity.x) #the angle of the ball's velocity
    theta_repel=Math.atan2(perpVect.y,perpVect.x) #the angle of the repelling force(perpVect)

    fbx = velocityMag * Math.cos(theta_ball) #the x component of the ball's velocity
    fby = velocityMag * Math.sin(theta_ball) #the y component of the ball's velocity

    #the magnitude of the repelling force
    repelMag = getRepelMagnitude(fbx, fby, perpVect.x, perpVect.y, (ball.velocity.x**2 + ball.velocity.y**2)**0.5)
    frx = repelMag* Math.cos(theta_repel) #the x component of the repel's velocity | magnitude is set to twice of fbx
    fry = repelMag* Math.sin(theta_repel) #the y component of the repel's velocity | magnitude is set to twice of fby

    fsumx = fbx+frx #sum of x forces
    fsumy = fby+fry #sum of y forces
    fr = velocityMag#fr is the resulting magnitude
    thetaNew = Math.atan2(fsumy, fsumx)  #thetaNew is the resulting angle
    xnew = fr*Math.cos(thetaNew)#resulting x velocity
    ynew = fr*Math.sin(thetaNew)#resulting y velocity
    if (velocityMag < MAX_VELOCITY)
      ball.velocity =  Vector2d.new(xnew*1.1, ynew*1.1)
    else
      ball.velocity =  Vector2d.new(xnew, ynew)
    end

  end
end

    Arbitrary Collision - main.rb link

    # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/main.rb
INFINITY= 10**10
MAX_VELOCITY = 8.0
BALL_COUNT = 90
BALL_DISTANCE = 20
require 'app/vector2d.rb'
require 'app/blocks.rb'
require 'app/ball.rb'
require 'app/rectangle.rb'
require 'app/linear_collider.rb'
require 'app/square_collider.rb'



#Method to init default values
def defaults args
  args.state.board_width ||= args.grid.w / 4
  args.state.board_height ||= args.grid.h
  args.state.game_area ||= [(args.state.board_width + args.grid.w / 8), 0, args.state.board_width, args.grid.h]
  args.state.balls ||= []
  args.state.num_balls ||= 0
  args.state.ball_created_at ||= args.state.tick_count
  args.state.ball_hypotenuse = (10**2 + 10**2)**0.5
  args.state.ballParents ||= []

  init_blocks args
  init_balls args
end

begin :default_methods
  def init_blocks args
    block_size = args.state.board_width / 8
    #Space inbetween each block
    block_offset = 4

    args.state.squares ||=[
      Square.new(args, 2, 0, block_size, :right, block_offset),
      Square.new(args, 5, 0, block_size, :right, block_offset),
      Square.new(args, 6, 7, block_size, :right, block_offset)
    ]


    #Possible orientations are :right, :left, :up, :down


    args.state.tshapes ||= [
      TShape.new(args, 0, 6, block_size, :left, block_offset),
      TShape.new(args, 3, 3, block_size, :down, block_offset),
      TShape.new(args, 0, 3, block_size, :right, block_offset),
      TShape.new(args, 0, 11, block_size, :up, block_offset)
    ]

    args.state.lines ||= [
      Line.new(args,3, 8, block_size, :down, block_offset),
      Line.new(args, 7, 3, block_size, :up, block_offset),
      Line.new(args, 3, 7, block_size, :right, block_offset)
    ]

    #exit()
  end

  def init_balls args
    return unless args.state.num_balls < BALL_COUNT


    #only create a new ball every 10 ticks
    return unless args.state.ball_created_at.elapsed_time > 10

    if (args.state.num_balls == 0)
      args.state.balls.append(Ball.new(args,args.state.num_balls,BALL_COUNT-1, nil, nil))
      args.state.ballParents = [args.state.balls[0]]
    else
      args.state.balls.append(Ball.new(args,args.state.num_balls,BALL_COUNT-1, args.state.balls.last, nil) )
      args.state.balls[-2].child = args.state.balls[-1]
    end
    args.state.ball_created_at = args.state.tick_count
    args.state.num_balls += 1
  end
end

#Render loop
def render args
  bgClr = {r:10, g:10, b:200}
  bgClr = {r:255-30, g:255-30, b:255-30}

  args.outputs.solids << [0, 0, $args.grid.right, $args.grid.top, bgClr[:r], bgClr[:g], bgClr[:b]];
  args.outputs.borders << args.state.game_area

  render_instructions args
  render_shapes args

  render_balls args

  #args.state.rectangle.draw args

  args.outputs.sprites << [$args.grid.right-(args.state.board_width + args.grid.w / 8), 0, $args.grid.right, $args.grid.top, "sprites/square-white-2.png", 0, 255, bgClr[:r], bgClr[:g], bgClr[:b]]
  args.outputs.sprites << [0, 0, (args.state.board_width + args.grid.w / 8), $args.grid.top, "sprites/square-white-2.png", 0, 255, bgClr[:r], bgClr[:g], bgClr[:b]]

end

begin :render_methods
  def render_instructions args
    #gtk.current_framerate
    args.outputs.labels << [20, $args.grid.top-20, "FPS: " + $gtk.current_framerate.to_s]
    if (args.state.balls != nil && args.state.balls[0] != nil)
        bx =  args.state.balls[0].velocity.x
        by =  args.state.balls[0].velocity.y
        bmg = (bx**2.0 + by**2.0)**0.5
        args.outputs.labels << [20, $args.grid.top-20-20, "V: " + bmg.to_s ]
    end


  end

  def render_shapes args
    for s in args.state.squares
      s.draw args
    end

    for l in args.state.lines
      l.draw args
    end

    for t in args.state.tshapes
      t.draw args
    end


  end

  def render_balls args
    #args.state.balls.each do |ball|
      #ball.draw args
    #end

    args.outputs.sprites << args.state.balls.map do |ball|
      ball.getDraw args
    end
  end
end

#Calls all methods necessary for performing calculations
def calc args
  for b in args.state.ballParents
    b.update args
  end

  for s in args.state.squares
    s.update args
  end

  for l in args.state.lines
    l.update args
  end

  for t in args.state.tshapes
    t.update args
  end



end

begin :calc_methods

end

def tick args
  defaults args
  render args
  calc args
end

    Arbitrary Collision - paddle.rb link

    # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/paddle.rb
class Paddle
  attr_accessor :enabled

  def initialize ()
    @x=WIDTH/2
    @y=100
    @width=100
    @height=20
    @speed=10

    @xyCollision  = LinearCollider.new({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
    @xyCollision2 = LinearCollider.new({x: @x,y: @y}, {x: @x+@width, y: @y}, :pos)
    @xyCollision3 = LinearCollider.new({x: @x,y: @y}, {x: @x, y: @y+@height+5})
    @xyCollision4 = LinearCollider.new({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5}, :pos)

    @enabled = true
  end

  def update args
    @xyCollision.resetPoints({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
    @xyCollision2.resetPoints({x: @x,y: @y}, {x: @x+@width, y: @y})
    @xyCollision3.resetPoints({x: @x,y: @y}, {x: @x, y: @y+@height+5})
    @xyCollision4.resetPoints({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5})

    @xyCollision.update  args
    @xyCollision2.update args
    @xyCollision3.update args
    @xyCollision4.update args

    args.inputs.keyboard.key_held.left  ||= false
    args.inputs.keyboard.key_held.right  ||= false

    if not (args.inputs.keyboard.key_held.left == args.inputs.keyboard.key_held.right)
      if args.inputs.keyboard.key_held.left && @enabled
        @x-=@speed
      elsif args.inputs.keyboard.key_held.right && @enabled
        @x+=@speed
      end
    end

    xmin =WIDTH/4
    xmax = 3*(WIDTH/4)
    @x = (@x+@width > xmax) ? xmax-@width : (@x<xmin) ? xmin : @x;
  end

  def render args
    args.outputs.solids << [@x,@y,@width,@height,255,0,0];
  end

  def rect
    [@x, @y, @width, @height]
  end
end

    Arbitrary Collision - rectangle.rb link

    # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/rectangle.rb
class Rectangle
  def initialize args

    @image = "sprites/roundSquare_white.png"
    @width  = 160.0
    @height = 80.0
    @x=$args.grid.right/2.0 - @width/2.0
    @y=$args.grid.top/2.0 - @height/2.0

    @xtmp = @width  * (1.0/10.0)
    @ytmp = @height * (1.0/10.0)

    #ball0 = args.state.balls[0]
    #hypotenuse = (args.state.balls[0].width**2 + args.state.balls[0].height**2)**0.5
    hypotenuse=args.state.ball_hypotenuse
    @boldXY = {x:(@x-hypotenuse/2)-1, y:(@y-hypotenuse/2)-1}
    @boldWidth = @width + hypotenuse + 2
    @boldHeight = @height + hypotenuse + 2
    @bold = [(@x-hypotenuse/2)-1,(@y-hypotenuse/2)-1,@width + hypotenuse + 2,@height + hypotenuse + 2]


    @points = [
      {x:@x,        y:@y+@ytmp},
      {x:@x+@xtmp,        y:@y},
      {x:@x+@width-@xtmp, y:@y},
      {x:@x+@width, y:@y+@ytmp},
      {x:@x+@width, y:@y+@height-@ytmp},#
      {x:@x+@width-@xtmp, y:@y+@height},
      {x:@x+@xtmp,        y:@y+@height},
      {x:@x,        y:@y+@height-@ytmp}
    ]

    @colliders = []
    #i = 0
    #while i < @points.length-1
      #@colliders.append(LinearCollider.new(@points[i],@points[i+1],:pos))
      #i+=1
    #end
    @colliders.append(LinearCollider.new(@points[0],@points[1], :neg))
    @colliders.append(LinearCollider.new(@points[1],@points[2], :neg))
    @colliders.append(LinearCollider.new(@points[2],@points[3], :neg))
    @colliders.append(LinearCollider.new(@points[3],@points[4], :neg))
    @colliders.append(LinearCollider.new(@points[4],@points[5], :pos))
    @colliders.append(LinearCollider.new(@points[5],@points[6], :pos))
    @colliders.append(LinearCollider.new(@points[6],@points[7], :pos))
    @colliders.append(LinearCollider.new(@points[0],@points[7], :pos))

  end

  def update args

    for b in args.state.balls
      if [b.x, b.y, b.width, b.height].intersect_rect?(@bold)
        for c in @colliders
          if c.collision?(args, b.getPoints(args),b)
            c.collide args, b
          end
        end
      end
    end
  end

  def draw args
    args.outputs.sprites << [
      @x,                                       # X
      @y,                                       # Y
      @width,                                   # W
      @height,                                  # H
      @image,                                   # PATH
      0,                                        # ANGLE
      255,                                      # ALPHA
      219,                                      # RED_SATURATION
      112,                                      # GREEN_SATURATION
      147                                       # BLUE_SATURATION
    ]
    #args.outputs.sprites << [@x, @y, @width, @height, "sprites/roundSquare_small_black.png"]
  end

  def serialize
  	{x: @x, y:@y}
  end

  def inspect
  	serialize.to_s
  end

  def to_s
  	serialize.to_s
  end
end

    Arbitrary Collision - square_collider.rb link

    # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/square_collider.rb

class SquareCollider
  def initialize x,y,direction,size=COLLISIONWIDTH
    @x = x
    @y = y
    @size = size
    @direction = direction

  end
  def collision? args, ball
    #args.outputs.solids <<  [@x, @y, @size, @size,     000, 255, 255]


    return [@x,@y,@size,@size].intersect_rect?([ball.x,ball.y,ball.width,ball.height])
  end

  def collide args, ball
    vmag = (ball.velocity.x**2.0 +ball.velocity.y**2.0)**0.5
    a = ((2.0**0.5)*vmag)/2.0
    if vmag < MAX_VELOCITY
      ball.velocity.x = (a) * @direction.x * 1.1
      ball.velocity.y = (a) * @direction.y * 1.1
    else
      ball.velocity.x = (a) * @direction.x
      ball.velocity.y = (a) * @direction.y
    end

  end
end

    Arbitrary Collision - vector2d.rb link

    # ./samples/04_physics_and_collisions/09_arbitrary_collision/app/vector2d.rb
class Vector2d
    attr_accessor :x, :y

    def initialize x=0, y=0
      @x=x
      @y=y
    end

    #returns a vector multiplied by scalar x
    #x [float] scalar
    def mult x
      r = Vector2d.new(0,0)
      r.x=@x*x
      r.y=@y*x
      r
    end

    # vect [Vector2d] vector to copy
    def copy vect
      Vector2d.new(@x, @y)
    end

    #returns a new vector equivalent to this+vect
    #vect [Vector2d] vector to add to self
    def add vect
      Vector2d.new(@x+vect.x,@y+vect.y)
    end

    #returns a new vector equivalent to this-vect
    #vect [Vector2d] vector to subtract to self
    def sub vect
      Vector2d.new(@x-vect.c, @y-vect.y)
    end

    #return the magnitude of the vector
    def mag
      ((@x**2)+(@y**2))**0.5
    end

    #returns a new normalize version of the vector
    def normalize
      Vector2d.new(@x/mag, @y/mag)
    end

    #TODO delet?
    def distABS vect
      (((vect.x-@x)**2+(vect.y-@y)**2)**0.5).abs()
    end
  end

    Collision With Object Removal - ball.rb link

    # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/ball.rb
class Ball
  #TODO limit accessors?
  attr_accessor :xy, :width, :height, :velocity


  #@xy [Vector2d] x,y position
  #@velocity [Vector2d] velocity of ball
  def initialize
    @xy = Vector2d.new(WIDTH/2,500)
    @velocity = Vector2d.new(4,-4)
    @width =  20
    @height = 20
  end

  #move the ball according to its velocity
  def update args
    @[email protected]
    @[email protected]
  end

  #render the ball to the screen
  def render args
    args.outputs.solids << [@xy.x,@xy.y,@width,@height,255,0,255];
    #args.outputs.labels << [20,HEIGHT-50,"velocity: " [email protected]_s+","[email protected]_s + "   magnitude:" + @velocity.mag.to_s]
  end

  def rect
    [@xy.x,@xy.y,@width,@height]
  end

end

    Collision With Object Removal - linear_collider.rb link

    # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/linear_collider.rb
#The LinearCollider (theoretically) produces collisions upon a line segment defined point.y two x,y cordinates

class LinearCollider

  #start [Array of length 2] start of the line segment as a x,y cordinate
  #last [Array of length 2] end of the line segment as a x,y cordinate

  #inorder for the LinearCollider to be functional the line segment must be said to have a thickness
  #(as it is unlikly that a colliding object will land exactly on the linesegment)

  #extension defines if the line's thickness extends negatively or positively
  #extension :pos     extends positively
  #extension :neg     extends negatively

  #thickness [float] how thick the line should be (should always be atleast as large as the magnitude of the colliding object)
  def initialize (pointA, pointB, extension=:neg, thickness=10)
    @pointA = pointA
    @pointB = pointB
    @thickness = thickness
    @extension = extension

    @pointAExtended={
      x: @pointA.x + @thickness*(@extension == :neg ? -1 : 1),
      y: @pointA.y + @thickness*(@extension == :neg ? -1 : 1)
    }
    @pointBExtended={
      x: @pointB.x + @thickness*(@extension == :neg ? -1 : 1),
      y: @pointB.y + @thickness*(@extension == :neg ? -1 : 1)
    }

  end

  def resetPoints(pointA,pointB)
    @pointA = pointA
    @pointB = pointB

    @pointAExtended={
      x:@pointA.x + @thickness*(@extension == :neg ? -1 : 1),
      y:@pointA.y + @thickness*(@extension == :neg ? -1 : 1)
    }
    @pointBExtended={
      x:@pointB.x + @thickness*(@extension == :neg ? -1 : 1),
      y:@pointB.y + @thickness*(@extension == :neg ? -1 : 1)
    }
  end

  #TODO: Ugly function
  def slope (pointA, pointB)
    return (pointB.x==pointA.x) ? INFINITY : (pointB.y+-pointA.y)/(pointB.x+-pointA.x)
  end

  #TODO: Ugly function
  def intercept(pointA, pointB)
    if (slope(pointA, pointB) == INFINITY)
      -INFINITY
    elsif slope(pointA, pointB) == -1*INFINITY
      INFINITY
    else
      pointA.y+-1.0*(slope(pointA, pointB)*pointA.x)
    end
  end

  def calcY(pointA, pointB, x)
    return slope(pointA, pointB)*x + intercept(pointA, pointB)
  end

  #test if a collision has occurred
  def isCollision? (point)
    #INFINITY slop breaks down when trying to determin collision, ergo it requires a special test
    if slope(@pointA, @pointB) ==  INFINITY &&
      point.x >= [@pointA.x,@pointB.x].min+(@extension == :pos ? -@thickness : 0) &&
      point.x <= [@pointA.x,@pointB.x].max+(@extension == :neg ?  @thickness : 0) &&
      point.y >= [@pointA.y,@pointB.y].min && point.y <= [@pointA.y,@pointB.y].max
        return true
    end

    isNegInLine   = @extension == :neg &&
                    point.y <= slope(@pointA, @pointB)*point.x+intercept(@pointA,@pointB) &&
                    point.y >= point.x*slope(@pointAExtended, @pointBExtended)+intercept(@pointAExtended,@pointBExtended)
    isPosInLine   = @extension == :pos &&
                    point.y >= slope(@pointA, @pointB)*point.x+intercept(@pointA,@pointB) &&
                    point.y <= point.x*slope(@pointAExtended, @pointBExtended)+intercept(@pointAExtended,@pointBExtended)
    isInBoxBounds = point.x >= [@pointA.x,@pointB.x].min &&
                    point.x <= [@pointA.x,@pointB.x].max &&
                    point.y >= [@pointA.y,@pointB.y].min+(@extension == :neg ? -@thickness : 0) &&
                    point.y <= [@pointA.y,@pointB.y].max+(@extension == :pos ? @thickness : 0)

    return isInBoxBounds && (isNegInLine || isPosInLine)

  end

  def getRepelMagnitude (fbx, fby, vrx, vry, args)
    a = fbx ; b = vrx ; c = fby
    d = vry ; e = args.state.ball.velocity.mag

    if b**2 + d**2 == 0
      puts "magnitude error"
    end

    x1 = (-a*b+-c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 + d**2 - a**2 * d**2)**0.5)/(b**2 + d**2)
    x2 = -((a*b + c*d + (e**2 * b**2 - b**2 * c**2 + 2*a*b*c*d + e**2 * d**2 - a**2 * d**2)**0.5)/(b**2 + d**2))
    return ((a+x1*b)**2 + (c+x1*d)**2 == e**2) ? x1 : x2
  end

  def update args
    #each of the four points on the square ball - NOTE simple to extend to a circle
    points= [ {x: args.state.ball.xy.x,                          y: args.state.ball.xy.y},
              {x: args.state.ball.xy.x+args.state.ball.width,    y: args.state.ball.xy.y},
              {x: args.state.ball.xy.x,                          y: args.state.ball.xy.y+args.state.ball.height},
              {x: args.state.ball.xy.x+args.state.ball.width,    y: args.state.ball.xy.y + args.state.ball.height}
            ]

    #for each point p in points
    for point in points
      #isCollision.md has more information on this section
      #TODO: section can certainly be simplifyed
      if isCollision?(point)
        u = Vector2d.new(1.0,((slope(@pointA, @pointB)==0) ? INFINITY : -1/slope(@pointA, @pointB))*1.0).normalize #normal perpendicular (to line segment) vector

        #the vector with the repeling force can be u or -u depending of where the ball was coming from in relation to the line segment
        previousBallPosition=Vector2d.new(point.x-args.state.ball.velocity.x,point.y-args.state.ball.velocity.y)
        choiceA = (u.mult(1))
        choiceB =  (u.mult(-1))
        vectorRepel = nil

        if (slope(@pointA, @pointB))!=INFINITY && u.y < 0
          choiceA, choiceB = choiceB, choiceA
        end
        vectorRepel = (previousBallPosition.y > calcY(@pointA, @pointB, previousBallPosition.x)) ? choiceA : choiceB

        #vectorRepel = (previousBallPosition.y > slope(@pointA, @pointB)*previousBallPosition.x+intercept(@pointA,@pointB)) ? choiceA : choiceB)
        if (slope(@pointA, @pointB) == INFINITY) #slope INFINITY breaks down in the above test, ergo it requires a custom test
          vectorRepel = (previousBallPosition.x > @pointA.x) ? (u.mult(1)) : (u.mult(-1))
        end
        #puts ("     " + $t[0].to_s + "," + $t[1].to_s + "    " + $t[2].to_s + "," + $t[3].to_s + "     " + "   " + u.x.to_s + "," + u.y.to_s)
        #vectorRepel now has the repeling force

        mag = args.state.ball.velocity.mag
        theta_ball=Math.atan2(args.state.ball.velocity.y,args.state.ball.velocity.x) #the angle of the ball's velocity
        theta_repel=Math.atan2(vectorRepel.y,vectorRepel.x) #the angle of the repeling force
        #puts ("theta:" + theta_ball.to_s + " " + theta_repel.to_s) #theta okay

        fbx = mag * Math.cos(theta_ball) #the x component of the ball's velocity
        fby = mag * Math.sin(theta_ball) #the y component of the ball's velocity

        repelMag = getRepelMagnitude(fbx, fby, vectorRepel.x, vectorRepel.y, args)

        frx = repelMag* Math.cos(theta_repel) #the x component of the repel's velocity | magnitude is set to twice of fbx
        fry = repelMag* Math.sin(theta_repel) #the y component of the repel's velocity | magnitude is set to twice of fby

        fsumx = fbx+frx #sum of x forces
        fsumy = fby+fry #sum of y forces
        fr = mag#fr is the resulting magnitude
        thetaNew = Math.atan2(fsumy, fsumx)  #thetaNew is the resulting angle
        xnew = fr*Math.cos(thetaNew) #resulting x velocity
        ynew = fr*Math.sin(thetaNew) #resulting y velocity

        args.state.ball.velocity = Vector2d.new(xnew,ynew)
        #args.state.ball.xy.add(args.state.ball.velocity)
        break #no need to check the other points ?
      else
      end
    end
  end #end update

end

    Collision With Object Removal - main.rb link

    # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/main.rb
# coding: utf-8
INFINITY= 10**10
WIDTH=1280
HEIGHT=720

require 'app/vector2d.rb'
require 'app/paddle.rb'
require 'app/ball.rb'
require 'app/linear_collider.rb'

#Method to init default values
def defaults args
  args.state.game_board ||= [(args.grid.w / 2 - args.grid.w / 4), 0, (args.grid.w / 2), args.grid.h]
  args.state.bricks ||= []
  args.state.num_bricks ||= 0
  args.state.game_over_at ||= 0
  args.state.paddle ||= Paddle.new
  args.state.ball   ||= Ball.new
  args.state.westWall  ||= LinearCollider.new({x: args.grid.w/4,      y: 0},          {x: args.grid.w/4,      y: args.grid.h}, :pos)
  args.state.eastWall  ||= LinearCollider.new({x: 3*args.grid.w*0.25, y: 0},          {x: 3*args.grid.w*0.25, y: args.grid.h})
  args.state.southWall ||= LinearCollider.new({x: 0,                  y: 0},          {x: args.grid.w,        y: 0})
  args.state.northWall ||= LinearCollider.new({x: 0,                  y:args.grid.h}, {x: args.grid.w,        y: args.grid.h}, :pos)

  #args.state.testWall ||= LinearCollider.new({x:0 , y:0},{x:args.grid.w, y:args.grid.h})
end

#Render loop
def render args
  render_instructions args
  render_board args
  render_bricks args
end

begin :render_methods
  #Method to display the instructions of the game
  def render_instructions args
    args.outputs.labels << [225, args.grid.h - 30, "← and → to move the paddle left and right",  0, 1]
  end

  def render_board args
    args.outputs.borders << args.state.game_board
  end

  def render_bricks args
    args.outputs.solids << args.state.bricks.map(&:rect)
  end
end

#Calls all methods necessary for performing calculations
def calc args
  add_new_bricks args
  reset_game args
  calc_collision args
  win_game args

  args.state.westWall.update args
  args.state.eastWall.update args
  args.state.southWall.update args
  args.state.northWall.update args
  args.state.paddle.update args
  args.state.ball.update args

  #args.state.testWall.update args

  args.state.paddle.render args
  args.state.ball.render args
end

begin :calc_methods
  def add_new_bricks args
    return if args.state.num_bricks > 40

    #Width of the game board is 640px
    brick_width = (args.grid.w / 2) / 10
    brick_height = brick_width / 2

    (4).map_with_index do |y|
      #Make a box that is 10 bricks wide and 4 bricks tall
      args.state.bricks += (10).map_with_index do |x|
        args.state.new_entity(:brick) do |b|
          b.x = x * brick_width + (args.grid.w / 2 - args.grid.w / 4)
          b.y = args.grid.h - ((y + 1) * brick_height)
          b.rect = [b.x + 1, b.y - 1, brick_width - 2, brick_height - 2, 235, 50 * y, 52]

          #Add linear colliders to the brick
          b.collider_bottom = LinearCollider.new([(b.x-2), (b.y-5)], [(b.x+brick_width+1), (b.y-5)], :pos, brick_height)
          b.collider_right = LinearCollider.new([(b.x+brick_width+1), (b.y-5)], [(b.x+brick_width+1), (b.y+brick_height+1)], :pos)
          b.collider_left = LinearCollider.new([(b.x-2), (b.y-5)], [(b.x-2), (b.y+brick_height+1)], :neg)
          b.collider_top = LinearCollider.new([(b.x-2), (b.y+brick_height+1)], [(b.x+brick_width+1), (b.y+brick_height+1)], :neg)

          # @xyCollision  = LinearCollider.new({x: @x,y: @y+@height}, {x: @x+@width, y: @y+@height})
          # @xyCollision2 = LinearCollider.new({x: @x,y: @y}, {x: @x+@width, y: @y}, :pos)
          # @xyCollision3 = LinearCollider.new({x: @x,y: @y}, {x: @x, y: @y+@height})
          # @xyCollision4 = LinearCollider.new({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height}, :pos)

          b.broken = false

          args.state.num_bricks += 1
        end
      end
    end
  end

  def reset_game args
    if args.state.ball.xy.y < 20 && args.state.game_over_at.elapsed_time > 60
      #Freeze the ball
      args.state.ball.velocity.x = 0
      args.state.ball.velocity.y = 0
      #Freeze the paddle
      args.state.paddle.enabled = false

      args.state.game_over_at = args.state.tick_count
    end

    if args.state.game_over_at.elapsed_time < 60 && args.state.tick_count > 60 && args.state.bricks.count != 0
      #Display a "Game over" message
      args.outputs.labels << [100, 100, "GAME OVER", 10]
    end

    #If 60 frames have passed since the game ended, restart the game
    if args.state.game_over_at != 0 && args.state.game_over_at.elapsed_time == 60
      # FIXME: only put value types in state
      args.state.ball = Ball.new

      # FIXME: only put value types in state
      args.state.paddle = Paddle.new

      args.state.bricks = []
      args.state.num_bricks = 0
    end
  end

  def calc_collision args
    #Remove the brick if it is hit with the ball
    ball = args.state.ball
    ball_rect = [ball.xy.x, ball.xy.y, 20, 20]

    #Loop through each brick to see if the ball is colliding with it
    args.state.bricks.each do |b|
      if b.rect.intersect_rect?(ball_rect)
        #Run the linear collider for the brick if there is a collision
        b[:collider_bottom].update args
        b[:collider_right].update args
        b[:collider_left].update args
        b[:collider_top].update args

        b.broken = true
      end
    end

    args.state.bricks = args.state.bricks.reject(&:broken)
  end

  def win_game args
    if args.state.bricks.count == 0 && args.state.game_over_at.elapsed_time > 60
      #Freeze the ball
      args.state.ball.velocity.x = 0
      args.state.ball.velocity.y = 0
      #Freeze the paddle
      args.state.paddle.enabled = false

      args.state.game_over_at = args.state.tick_count
    end

    if args.state.game_over_at.elapsed_time < 60 && args.state.tick_count > 60 && args.state.bricks.count == 0
      #Display a "Game over" message
      args.outputs.labels << [100, 100, "CONGRATULATIONS!", 10]
    end
  end

end

def tick args
  defaults args
  render args
  calc args

  #args.outputs.lines << [0, 0, args.grid.w, args.grid.h]

  #$tc+=1
  #if $tc == 5
    #$train << [args.state.ball.xy.x, args.state.ball.xy.y]
    #$tc = 0
  #end
  #for t in $train

    #args.outputs.solids << [t[0],t[1],5,5,255,0,0];
  #end
end

    Collision With Object Removal - paddle.rb link

    # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/paddle.rb
class Paddle
  attr_accessor :enabled

  def initialize ()
    @x=WIDTH/2
    @y=100
    @width=100
    @height=20
    @speed=10

    @xyCollision  = LinearCollider.new({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
    @xyCollision2 = LinearCollider.new({x: @x,y: @y}, {x: @x+@width, y: @y}, :pos)
    @xyCollision3 = LinearCollider.new({x: @x,y: @y}, {x: @x, y: @y+@height+5})
    @xyCollision4 = LinearCollider.new({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5}, :pos)

    @enabled = true
  end

  def update args
    @xyCollision.resetPoints({x: @x,y: @y+@height+5}, {x: @x+@width, y: @y+@height+5})
    @xyCollision2.resetPoints({x: @x,y: @y}, {x: @x+@width, y: @y})
    @xyCollision3.resetPoints({x: @x,y: @y}, {x: @x, y: @y+@height+5})
    @xyCollision4.resetPoints({x: @x+@width,y: @y}, {x: @x+@width, y: @y+@height+5})

    @xyCollision.update  args
    @xyCollision2.update args
    @xyCollision3.update args
    @xyCollision4.update args

    args.inputs.keyboard.key_held.left  ||= false
    args.inputs.keyboard.key_held.right  ||= false

    if not (args.inputs.keyboard.key_held.left == args.inputs.keyboard.key_held.right)
      if args.inputs.keyboard.key_held.left && @enabled
        @x-=@speed
      elsif args.inputs.keyboard.key_held.right && @enabled
        @x+=@speed
      end
    end

    xmin =WIDTH/4
    xmax = 3*(WIDTH/4)
    @x = (@x+@width > xmax) ? xmax-@width : (@x<xmin) ? xmin : @x;
  end

  def render args
    args.outputs.solids << [@x,@y,@width,@height,255,0,0];
  end

  def rect
    [@x, @y, @width, @height]
  end
end

    Collision With Object Removal - tests.rb link

    # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/tests.rb
# For advanced users:
# You can put some quick verification tests here, any method
# that starts with the `test_` will be run when you save this file.

# Here is an example test and game

# To run the test: ./dragonruby mygame --eval app/tests.rb --no-tick

class MySuperHappyFunGame
  attr_gtk

  def tick
    outputs.solids << [100, 100, 300, 300]
  end
end

def test_universe args, assert
  game = MySuperHappyFunGame.new
  game.args = args
  game.tick
  assert.true!  args.outputs.solids.length == 1, "failure: a solid was not added after tick"
  assert.false! 1 == 2, "failure: some how, 1 equals 2, the world is ending"
  puts "test_universe completed successfully"
end

puts "running tests"
$gtk.reset 100
$gtk.log_level = :off
$gtk.tests.start

    Collision With Object Removal - vector2d.rb link

    # ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/vector2d.rb

class Vector2d
  attr_accessor :x, :y

  def initialize x=0, y=0
    @x=x
    @y=y
  end

  #returns a vector multiplied by scalar x
  #x [float] scalar
  def mult x
    r = Vector2d.new(0,0)
    r.x=@x*x
    r.y=@y*x
    r
  end

  # vect [Vector2d] vector to copy
  def copy vect
    Vector2d.new(@x, @y)
  end

  #returns a new vector equivalent to this+vect
  #vect [Vector2d] vector to add to self
  def add vect
    Vector2d.new(@x+vect.x,@y+vect.y)
  end

  #returns a new vector equivalent to this-vect
  #vect [Vector2d] vector to subtract to self
  def sub vect
    Vector2d.new(@x-vect.c, @y-vect.y)
  end

  #return the magnitude of the vector
  def mag
    ((@x**2)+(@y**2))**0.5
  end

  #returns a new normalize version of the vector
  def normalize
    Vector2d.new(@x/mag, @y/mag)
  end

  #TODO delet?
  def distABS vect
    (((vect.x-@x)**2+(vect.y-@y)**2)**0.5).abs()
  end
end

    Bouncing Ball With Gravity - main.rb link

    # ./samples/04_physics_and_collisions/11_bouncing_ball_with_gravity/app/main.rb
include MatrixFunctions

class BouncingBall
  attr_gtk

  def tick
    defaults
    render
    input
    calc

    reset_ball if args.inputs.keyboard.key_down.r

    args.state.debug = !args.state.debug if inputs.keyboard.key_down.g
    debug if args.state.debug
  end

  def defaults
    args.state.rest ||= false
    args.state.debug ||= false

    state.walls ||= [
      { x: 50.from_left, y: 50.from_bottom, x2: 50.from_left, y2: 50.from_top },
      { x: 50.from_left, y: 50.from_bottom, x2: 50.from_right, y2: 50.from_bottom },
      { x: 50.from_left, y: 50.from_top, x2: 50.from_right, y2: 50.from_top },
      { x: 50.from_right, y: 50.from_bottom, x2: 50.from_right, y2: 50.from_top },
    ]

    state.ball ||= { x: 250, y: 250, w: 50, h: 50, path: 'circle-white.png' }
    state.ball_old_x ||= state.ball[:x]
    state.ball_old_y ||= state.ball[:y]
    state.ball_vector ||= vec2(0, 0)

    state.stick_length = 200
    state.stick_angle ||= 0
    state.stick_power ||= 0

    # Prevent consecutive bounces on the same normal vector
    # Solves issue where ball gets stuck on a wall
    state.prevent_collision ||= {}

    state.physics.gravity = 0.4
    state.physics.restitution = 0.80
    state.physics.friction = 0.70
  end

  def render
    outputs.lines << state.walls
    outputs.sprites << state.ball
    render_stick
    render_point_one
  end

  def render_stick
    stick_vec_x = Math.cos(state.stick_angle.to_radians)
    stick_vec_y = Math.sin(state.stick_angle.to_radians)
    ball_center_x = state.ball[:x] + (state.ball[:w] / 2)
    ball_center_y = state.ball[:y] + (state.ball[:h] / 2)
    # Draws the line starting 15% of stick_length away from the ball
    outputs.lines << {
      x: ball_center_x + (stick_vec_x * state.stick_length * -0.15),
      y: ball_center_y + (stick_vec_y * state.stick_length * -0.15),
      w: stick_vec_x * state.stick_length * -1,
      h: stick_vec_y * state.stick_length * -1,
    }
  end

  def render_point_one
    return unless state.point_one

    outputs.lines << { x: state.point_one.x, y: state.point_one.y,
                       x2: inputs.mouse.x, y2: inputs.mouse.y,
                       r: 255 }
  end

  def input
    input_stick
    input_lines
    state.point_one = nil if inputs.keyboard.key_down.escape
  end

  def input_stick
    if inputs.keyboard.key_up.space
      hit_ball
      state.stick_power = 0
    end

    if inputs.keyboard.key_held.space
      state.stick_power += 1 unless state.stick_power >= 50
      outputs.labels << [100, 100, state.stick_power]
    end

    state.stick_angle += inputs.keyboard.left_right
  end

  def input_lines
    return unless inputs.mouse.click

    if state.point_one
      x = snap(state.point_one.x)
      y = snap(state.point_one.y)
      x2 = snap(inputs.mouse.click.x)
      y2 = snap(inputs.mouse.click.y)
      state.walls << { x: x, y: y, x2: x2, y2: y2 }
      state.point_one = nil
    else
      state.point_one = inputs.mouse.click.point
    end
  end

  # FIX: does not snap negative numbers properly
  def snap value
    snap_number = 10
    min = value.to_i.idiv(snap_number) * snap_number
    max = min + snap_number
    result = (max - value).abs < (min - value).abs ? max : min
    puts "SNAP: #{ value } --> #{ result }" if state.debug
    result
  end

  def hit_ball
    vec_x = Math.cos(state.stick_angle.to_radians) * state.stick_power
    vec_y = Math.sin(state.stick_angle.to_radians) * state.stick_power
    state.ball_vector = vec2(vec_x, vec_y)
    state.rest = false
  end

  def entropy
    state.ball_vector[:x].abs + state.ball_vector[:y].abs
  end

  # Ball is resting if
  # entropy is low, ball is touching a line
  # the line is not steep and the ball is above the line
  def ball_is_resting?(walls, true_normal)
    entropy < 1.5 && !walls.empty? && true_normal[:y] > 0.96
  end

  def calc
    walls = []
    state.walls.each do |wall|
      if line_intersect_rect?(wall, state.ball)
        walls << wall unless state.prevent_collision.key?(wall)
      end
    end

    state.prevent_collision = {}
    walls.each { |w| state.prevent_collision[w] = true }

    normals = walls.map { |w| compute_proper_normal(w) }
    true_normal = normals.inject { |a, b| normalize(vector_add(a, b)) }

    unless state.rest
      state.ball_vector = collision(true_normal) unless walls.empty?
      state.ball_old_x = state.ball[:x]
      state.ball_old_y = state.ball[:y]
      state.ball[:x] += state.ball_vector[:x]
      state.ball[:y] += state.ball_vector[:y]
      state.ball_vector[:y] -= state.physics.gravity

      if ball_is_resting?(walls, true_normal)
        state.ball[:y] += 1
        state.rest = true
      end
    end
  end

  # Line segment intersects rect if it intersects
  # any of the lines that make up the rect
  # This doesn't cover the case where the line is completely within the rect
  def line_intersect_rect?(line, rect)
    rect_to_lines(rect).each do |rect_line|
      return true if segments_intersect?(line, rect_line)
    end

    false
  end

  # https://stackoverflow.com/questions/573084/
  def collision(normal_vector)
    dot_product = dot(state.ball_vector, normal_vector)
    normal_square = dot(normal_vector, normal_vector)
    perpendicular = vector_multiply(normal_vector, (dot_product / normal_square))
    parallel = vector_minus(state.ball_vector, perpendicular)
    perpendicular = vector_multiply(perpendicular, state.physics.restitution)
    parallel = vector_multiply(parallel, state.physics.friction)
    vector_minus(parallel, perpendicular)
  end

  # https://stackoverflow.com/questions/1243614/
  def compute_normals(line)
    h = line[:y2] - line[:y]
    w = line[:x2] - line[:x]
    a = normalize vec2(-h, w)
    b = normalize vec2(h, -w)
    [a, b]
  end

  # https://stackoverflow.com/questions/3838319/
  # Get the normal vector that points at the ball from the center of the line
  def compute_proper_normal(line)
    normals = compute_normals(line)
    ball_center_x = state.ball_old_x + (state.ball[:w] / 2)
    ball_center_y = state.ball_old_y + (state.ball[:h] / 2)
    v1 = vec2(line[:x2] - line[:x], line[:y2] - line[:y])
    v2 = vec2(line[:x2] - ball_center_x, line[:y2] - ball_center_y)
    cp = v1[:x] * v2[:y] - v1[:y] * v2[:x]
    cp < 0 ? normals[0] : normals[1]
  end

  def vector_multiply(vector, value)
    vec2(vector[:x] * value, vector[:y] * value)
  end

  def vector_minus(vec_a, vec_b)
    vec2(vec_a[:x] - vec_b[:x], vec_a[:y] - vec_b[:y])
  end

  def vector_add a, b
    vec2(a[:x] + b[:x], a[:y] + b[:y])
  end

  # The lines composing the boundaries of a rectangle
  def rect_to_lines(rect)
    x = rect[:x]
    y = rect[:y]
    x2 = rect[:x] + rect[:w]
    y2 = rect[:y] + rect[:h]
    [{ x: x, y: y, x2: x2, y2: y },
     { x: x, y: y, x2: x, y2: y2 },
     { x: x2, y: y, x2: x2, y2: y2 },
     { x: x, y: y2, x2: x2, y2: y2 }]
  end

  # This is different from args.geometry.line_intersect
  # This considers line segments instead of lines
  # http://jeffreythompson.org/collision-detection/line-line.php
  def segments_intersect?(line_one, line_two)
    x1 = line_one[:x]
    y1 = line_one[:y]
    x2 = line_one[:x2]
    y2 = line_one[:y2]

    x3 = line_two[:x]
    y3 = line_two[:y]
    x4 = line_two[:x2]
    y4 = line_two[:y2]

    uA = ((x4-x3)*(y1-y3) - (y4-y3)*(x1-x3)) / ((y4-y3)*(x2-x1) - (x4-x3)*(y2-y1))
    uB = ((x2-x1)*(y1-y3) - (y2-y1)*(x1-x3)) / ((y4-y3)*(x2-x1) - (x4-x3)*(y2-y1))

    uA >= 0 && uA <= 1 && uB >= 0 && uB <= 1
  end

  def reset_ball
    state.ball = nil
    state.ball_vector = nil
    state.rest = false
  end

  def debug
    outputs.labels << { x: 50.from_left, y: 50.from_top, text: "Entropy: #{entropy}"}
  end
end


def tick args
  $game ||= BouncingBall.new
  $game.args = args
  $game.tick
end

    Ramp Collision - main.rb link

    # ./samples/04_physics_and_collisions/12_ramp_collision/app/main.rb
# sample app shows how to do ramp collision
# based off of the writeup here:
# http://higherorderfun.com/blog/2012/05/20/the-guide-to-implementing-2d-platformers/

# NOTE: at the bottom of the file you'll find $gtk.reset_and_replay "replay.txt"
#       whenever you make changes to this file, a replay will automatically run so you can
#       see how your changes affected the game. Comment out the line at the bottom if you
#       don't want the replay to autmatically run.

# toolbar interaction is in a seperate file
require 'app/toolbar.rb'

def tick args
  tick_toolbar args
  tick_game args
end

def tick_game args
  game_defaults args
  game_input args
  game_calc args
  game_render args
end

def game_input args
  # if space is pressed or held (signifying a jump)
  if args.inputs.keyboard.space
    # change the player's dy to the jump power if the
    # player is not currently touching a ceiling
    if !args.state.player.on_ceiling
      args.state.player.dy = args.state.player.jump_power
      args.state.player.on_floor = false
      args.state.player.jumping = true
    end
  else
    # if the space key is released, then jumping is false
    # and the player will no longer be on the ceiling
    args.state.player.jumping = false
    args.state.player.on_ceiling = false
  end

  # set the player's dx value to the left/right input
  # NOTE: that the speed of the player's dx movement has
  #       a sensitive relation ship with collision detection.
  #       If you increase the speed of the player, you may
  #       need to tweak the collision code to compensate for
  #       the extra horizontal speed.
  args.state.player.dx = args.inputs.left_right * 2
end

def game_render args
  # for each terrain entry, render the line that represents the connection
  # from the tile's left_height to the tile's right_height
  args.outputs.primitives << args.state.terrain.map { |t| t.line }

  # determine if the player sprite needs to be flipped hoizontally
  flip_horizontally = args.state.player.facing == -1

  # render the player
  args.outputs.sprites << args.state.player.merge(flip_horizontally: flip_horizontally)

  args.outputs.labels << {
    x: 640,
    y: 100,
    alignment_enum: 1,
    text: "Left and Right to move player. Space to jump. Use the toolbar at the top to add more terrain."
  }

  args.outputs.labels << {
    x: 640,
    y: 60,
    alignment_enum: 1,
    text: "Click any existing terrain on the map to delete it."
  }
end

def game_calc args
  # set the direction the player is facing based on the
  # the dx value of the player
  if args.state.player.dx > 0
    args.state.player.facing = 1
  elsif args.state.player.dx < 0
    args.state.player.facing = -1
  end

  # preform the calcuation of ramp collision
  calc_collision args

  # reset the player if the go off screen
  calc_off_screen args
end

def game_defaults args
  # how much gravity is in the game
  args.state.gravity ||= 0.1

  # initialized the player to the center of the screen
  args.state.player ||= {
    x: 640,
    y: 360,
    w: 16,
    h: 16,
    dx: 0,
    dy: 0,
    jump_power: 3,
    path: 'sprites/square/blue.png',
    on_floor: false,
    on_ceiling: false,
    facing: 1
  }
end

def calc_collision args
  # increment the players x position by the dx value
  args.state.player.x += args.state.player.dx

  # if the player is not on the floor
  if !args.state.player.on_floor
    # then apply gravity
    args.state.player.dy -= args.state.gravity
    # clamp the max dy value to -12 to 12
    args.state.player.dy = args.state.player.dy.clamp(-12, 12)

    # update the player's y position by the dy value
    args.state.player.y += args.state.player.dy
  end

  # get all colisions between the player and the terrain
  collisions = args.state.geometry.find_all_intersect_rect args.state.player, args.state.terrain

  # if there are no collisions, then the player is not on the floor or ceiling
  # return from the method since there is nothing more to process
  if collisions.length == 0
    args.state.player.on_floor = false
    args.state.player.on_ceiling = false
    return
  end

  # set a local variable to the player since
  # we'll be accessing it a lot
  player = args.state.player

  # sort the collisions by the distance from the collision's center to the player's center
  sorted_collisions = collisions.sort_by do |collision|
    player_center = player.x + player.w / 2
    collision_center = collision.x + collision.w / 2
    (player_center - collision_center).abs
  end

  # define a one pixel wide rectangle that represents the center of the player
  # we'll use this value to determine the location of the player's feet on
  # a ramp
  player_center_rect = {
    x: player.x + player.w / 2 - 0.5,
    y: player.y,
    w: 1,
    h: player.h
  }

  # for each collision...
  sorted_collisions.each do |collision|
    # if the player doesn't intersect with the collision,
    # then set the player's on_floor and on_ceiling values to false
    # and continue to the next collision
    if !collision.intersect_rect? player_center_rect
      player.on_floor = false
      player.on_ceiling = false
      next
    end

    if player.dy < 0
      # if the player is falling
      # the percentage of the player's center relative to the collision
      # is a difference from the collision to the player (as opposed to the player to the collision)
      perc = (collision.x - player_center_rect.x) / player.w
      height_of_slope = collision.tile.left_height - collision.tile.right_height

      new_y = (collision.y + collision.tile.left_height + height_of_slope * perc)
      diff = new_y - player.y

      if diff < 0
        # if the current fall rate of the player is less than the difference
        # of the player's new y position and the player's current y position
        # then don't set the player's y position to the new y position
        # and wait for another application of gravity to bring the player a little
        # closer
        if player.dy.abs >= diff.abs
          # if the player's current fall speed can cover the distance to the
          # new y position, then set the player's y position to the new y position
          # and mark them as being on the floor so that gravity no longer get's processed
          player.y = new_y
          player.on_floor = true

          # given the player's speed, set the player's dy to a value that will
          # keep them from bouncing off the floor when the ramp is steep
          # NOTE: if you change the player's speed, then this value will need to be adjusted
          #       to keep the player from bouncing off the floor
          player.dy = -1
        end
      elsif diff > 0 && diff < 8
        # there's a small edge case where collision may be processed from
        # below the terrain (eg when the player is jumping up and hitting the
        # ramp from below). The moment when jump is released, the player's dy
        # value could result in the player tunneling through the terrain,
        # and get popped on to the top side.

        # testing to make sure the distance that will be displaced is less than
        # 8 pixels will keep this tunneling from happening
        player.y = new_y
        player.on_floor = true

        # given the player's speed, set the player's dy to a value that will
        # keep them from bouncing off the floor when the ramp is steep
        # NOTE: if you change the player's speed, then this value will need to be adjusted
        #       to keep the player from bouncing off the floor
        player.dy = -1
      end
    elsif player.dy > 0
      # if the player is jumping
      # the percentage of the player's center relative to the collision
      # is a difference is reversed from the player to the collision (as opposed to the player to the collision)
      perc = (player_center_rect.x - collision.x) / player.w

      # the height of the slope is also reversed when approaching the collision from the bottom
      height_of_slope = collision.tile.right_height - collision.tile.left_height

      new_y = collision.y + collision.tile.left_height + height_of_slope * perc

      # since this collision is being processed from below, the difference
      # between the current players position and the new y position is
      # based off of the player's top position (their head)
      player_top = player.y + player.h

      diff = new_y - player_top

      # we also need to calculate the difference between the player's bottom
      # and the new position. This will be used to determine if the player
      # can jump from the new_y position
      diff_bottom = new_y - player.y


      # if the player's current rising speed can cover the distance to the
      # new y position, then set the player's y position to the new y position
      # an mark them as being on the floor so that gravity no longer get's processed
      can_cover_distance_to_new_y = player.dy >= diff.abs && player.dy.sign == diff.sign

      # another scenario that needs to be covered is if the player's top is already passed
      # the new_y position (their rising speed made them partially clip through the collision)
      player_top_above_new_y = player_top > new_y

      # if either of the conditions above is true then we want to set the player's y position
      if can_cover_distance_to_new_y || player_top_above_new_y
        # only set the player's y position to the new y position if the player's
        # cannot escape the collision by jumping up from the new_y position
        if diff_bottom >= player.jump_power
          player.y = new_y.floor - player.h

          # after setting the new_y position, we need to determine if the player
          # if the player is touching the ceiling or not
          # touching the ceiling disables the ability for the player to jump/increase
          # their dy value any more than it already is
          if player.jumping
            # disable jumping if the player is currently moving upwards
            player.on_ceiling = true

            # NOTE: if you change the player's speed, then this value will need to be adjusted
            #       to keep the player from bouncing off the ceiling as they move right and left
            player.dy = 1
          else
            # if the player is not currently jumping, then set their dy to 0
            # so they can immediately start falling after the collision
            # this also means that they are no longer on the ceiling and can jump again
            player.dy = 0
            player.on_ceiling = false
          end
        end
      end
    end
  end
end

def calc_off_screen args
  below_screen = args.state.player.y + args.state.player.h < 0
  above_screen = args.state.player.y > 720 + args.state.player.h
  off_screen_left = args.state.player.x + args.state.player.w < 0
  off_screen_right = args.state.player.x > 1280

  # if the player is off the screen, then reset them to the top of the screen
  if below_screen || above_screen || off_screen_left || off_screen_right
    args.state.player.x = 640
    args.state.player.y = 720
    args.state.player.dy = 0
    args.state.player.on_floor = false
  end
end

$gtk.reset_and_replay "replay.txt", speed: 2

    Ramp Collision - toolbar.rb link

    # ./samples/04_physics_and_collisions/12_ramp_collision/app/toolbar.rb
def tick_toolbar args
  # ================================================
  # tollbar defaults
  # ================================================
  if !args.state.toolbar
    # these are the tiles you can select from
    tile_definitions = [
      { name: "16-12", left_height: 16, right_height: 12  },
      { name: "12-8",  left_height: 12, right_height: 8   },
      { name: "8-4",   left_height: 8,  right_height: 4   },
      { name: "4-0",   left_height: 4,  right_height: 0   },
      { name: "0-4",   left_height: 0,  right_height: 4   },
      { name: "4-8",   left_height: 4,  right_height: 8   },
      { name: "8-12",  left_height: 8,  right_height: 12  },
      { name: "12-16", left_height: 12, right_height: 16  },

      { name: "16-8",  left_height: 16, right_height: 8   },
      { name: "8-0",   left_height: 8,  right_height: 0   },
      { name: "0-8",   left_height: 0,  right_height: 8   },
      { name: "8-16",  left_height: 8,  right_height: 16  },

      { name: "0-0",   left_height: 0,  right_height: 0   },
      { name: "8-8",   left_height: 8,  right_height: 8   },
      { name: "16-16", left_height: 16, right_height: 16  },
    ]

    # toolbar data representation which will be used to render the toolbar.
    # the buttons array will be used to render the buttons
    # the toolbar_rect will be used to restrict the creation of tiles
    # within the toolbar area
    args.state.toolbar = {
      toolbar_rect: nil,
      buttons: []
    }

    # for each tile definition, create a button
    args.state.toolbar.buttons = tile_definitions.map_with_index do |spec, index|
      left_height  = spec.left_height
      right_height = spec.right_height
      button_size  = 48
      column_size  = 15
      column_padding = 2
      column = index % column_size
      column_padding = column * column_padding
      margin = 10
      row = index.idiv(column_size)
      row_padding = row * 2
      x = margin + column_padding + (column * button_size)
      y = (margin + button_size + row_padding + (row * button_size)).from_top

      # when a tile is added, the data of this button will be used
      # to construct the terrain

      # each tile has an x, y, w, h which represents the bounding box
      # of the button.
      # the button also contains the left_height and right_height which is
      # important when determining collision of the ramps
      {
        name: spec.name,
        left_height: left_height,
        right_height: right_height,
        button_rect: {
          x: x,
          y: y,
          w: 48,
          h: 48
        }
      }
    end

    # with the buttons populated, compute the bounding box of the entire
    # toolbar (again this will be used to restrict the creation of tiles)
    min_x = args.state.toolbar.buttons.map { |t| t.button_rect.x }.min
    min_y = args.state.toolbar.buttons.map { |t| t.button_rect.y }.min

    max_x = args.state.toolbar.buttons.map { |t| t.button_rect.x }.max
    max_y = args.state.toolbar.buttons.map { |t| t.button_rect.y }.max

    args.state.toolbar.rect = {
      x: min_x - 10,
      y: min_y - 10,
      w: max_x - min_x + 10 + 64,
      h: max_y - min_y + 10 + 64
    }
  end

  # set the selected tile to the last button in the toolbar
  args.state.selected_tile ||= args.state.toolbar.buttons.last

  # ================================================
  # starting terrain generation
  # ================================================
  if !args.state.terrain
    world = [
      { row: 14, col: 25, name: "0-8"   },
      { row: 14, col: 26, name: "8-16"  },
      { row: 15, col: 27, name: "0-8"   },
      { row: 15, col: 28, name: "8-16"  },
      { row: 16, col: 29, name: "0-8"   },
      { row: 16, col: 30, name: "8-16"  },
      { row: 17, col: 31, name: "0-8"   },
      { row: 17, col: 32, name: "8-16"  },
      { row: 18, col: 33, name: "0-8"   },
      { row: 18, col: 34, name: "8-16"  },
      { row: 18, col: 35, name: "16-12" },
      { row: 18, col: 36, name: "12-8"  },
      { row: 18, col: 37, name: "8-4"   },
      { row: 18, col: 38, name: "4-0"   },
      { row: 18, col: 39, name: "0-0"   },
      { row: 18, col: 40, name: "0-0"   },
      { row: 18, col: 41, name: "0-0"   },
      { row: 18, col: 42, name: "0-4"   },
      { row: 18, col: 43, name: "4-8"   },
      { row: 18, col: 44, name: "8-12"  },
      { row: 18, col: 45, name: "12-16" },
    ]

    args.state.terrain = world.map do |tile|
      template = tile_by_name(args, tile.name)
      next if !template
      grid_rect = grid_rect_for(tile.row, tile.col)
      new_terrain_definition(grid_rect, template)
    end
  end

  # ================================================
  # toolbar input and rendering
  # ================================================
  # store the mouse position alligned to the tile grid
  mouse_grid_aligned_rect = grid_aligned_rect args.inputs.mouse, 16

  # determine if the mouse intersects the toolbar
  mouse_intersects_toolbar = args.state.toolbar.rect.intersect_rect? args.inputs.mouse

  # determine if the mouse intersects a toolbar button
  toolbar_button = args.state.toolbar.buttons.find { |t| t.button_rect.intersect_rect? args.inputs.mouse }

  # determine if the mouse click occurred over a tile in the terrain
  terrain_tile = args.geometry.find_intersect_rect mouse_grid_aligned_rect, args.state.terrain


  # if a mouse click occurs....
  if args.inputs.mouse.click
    if toolbar_button
      # if a toolbar button was clicked, set the currently selected tile to the toolbar tile
      args.state.selected_tile = toolbar_button
    elsif terrain_tile
      # if a tile was clicked, delete it from the terrain
      args.state.terrain.delete terrain_tile
    elsif !args.state.toolbar.rect.intersect_rect? args.inputs.mouse
      # if the mouse was not clicked in the toolbar area
      # add a new terrain based off of the information in the selected tile
      args.state.terrain << new_terrain_definition(mouse_grid_aligned_rect, args.state.selected_tile)
    end
  end

  # render a light blue background for the toolbar button that is currently
  # being hovered over (if any)
  if toolbar_button
    args.outputs.primitives << toolbar_button.button_rect.merge(primitive_marker: :solid, a: 64, b: 255)
  end

  # put a blue background around the currently selected tile
  args.outputs.primitives << args.state.selected_tile.button_rect.merge(primitive_marker: :solid, b: 255, r: 128, a: 64)

  if !mouse_intersects_toolbar
    if terrain_tile
      # if the mouse is hoving over an existing terrain tile, render a red border around the
      # tile to signify that it will be deleted if the mouse is clicked
      args.outputs.borders << terrain_tile.merge(a: 255, r: 255)
    else
      # if the mouse is not hovering over an existing terrain tile, render the currently
      # selected tile at the mouse position
      grid_aligned_rect = grid_aligned_rect args.inputs.mouse, 16

      args.outputs.solids << {
        **grid_aligned_rect,
        a: 30,
        g: 128
      }

      args.outputs.lines << {
        x:  grid_aligned_rect.x,
        y:  grid_aligned_rect.y + args.state.selected_tile.left_height,
        x2: grid_aligned_rect.x + grid_aligned_rect.w,
        y2: grid_aligned_rect.y + args.state.selected_tile.right_height,
      }
    end
  end

  # render each toolbar button using two primitives, a border to denote
  # the click area of the button, and a line to denote the terrain that
  # will be created when the button is clicked
  args.outputs.primitives << args.state.toolbar.buttons.map do |toolbar_tile|
    primitives = []
    scale = toolbar_tile.button_rect.w / 16

    primitive_type = :border

    [
      {
        **toolbar_tile.button_rect,
        primitive_marker: primitive_type,
        a: 64,
        g: 128
      },
      {
        x:  toolbar_tile.button_rect.x,
        y:  toolbar_tile.button_rect.y + toolbar_tile.left_height * scale,
        x2: toolbar_tile.button_rect.x + toolbar_tile.button_rect.w,
        y2: toolbar_tile.button_rect.y + toolbar_tile.right_height * scale
      }
    ]
  end
end

# ================================================
# helper methods
#=================================================

# converts a row and column on the grid to
# a rect
def grid_rect_for row, col
  { x: col * 16, y: row * 16, w: 16, h: 16 }
end

# find a tile by name
def tile_by_name args, name
  args.state.toolbar.buttons.find { |b| b.name == name }
end

# data structure containing terrain information
# specifcially tile.left_height and tile.right_height
def new_terrain_definition grid_rect, tile
  grid_rect.merge(
    tile: tile,
    line: {
      x:  grid_rect.x,
      y:  grid_rect.y + tile.left_height,
      x2: grid_rect.x + grid_rect.w,
      y2: grid_rect.y + tile.right_height
    }
  )
end

# helper method that returns a grid aligned rect given
# an arbitrary rect and a grid size
def grid_aligned_rect point, size
  grid_aligned_x = point.x - (point.x % size)
  grid_aligned_y = point.y - (point.y % size)
  { x: grid_aligned_x.to_i, y: grid_aligned_y.to_i, w: size.to_i, h: size.to_i }
end

    Mouse link

    Mouse Click - main.rb link

    # ./samples/05_mouse/01_mouse_click/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - product: Returns an array of all combinations of elements from all arrays.

   For example, [1,2].product([1,2]) would return the following array...
   [[1,1], [1,2], [2,1], [2,2]]
   More than two arrays can be given to product and it will still work,
   such as [1,2].product([1,2],[3,4]). What would product return in this case?

   Answer:
   [[1,1,3],[1,1,4],[1,2,3],[1,2,4],[2,1,3],[2,1,4],[2,2,3],[2,2,4]]

 - num1.fdiv(num2): Returns the float division (will have a decimal) of the two given numbers.
   For example, 5.fdiv(2) = 2.5 and 5.fdiv(5) = 1.0

 - yield: Allows you to call a method with a code block and yield to that block.

 Reminders:

 - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - args.inputs.mouse.click: This property will be set if the mouse was clicked.

 - Ternary operator (?): Will evaluate a statement (just like an if statement)
   and perform an action if the result is true or another action if it is false.

 - reject: Removes elements from a collection if they meet certain requirements.

 - args.outputs.borders: An array. The values generate a border.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
   For more information about borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.

=end

# This sample app is a classic game of Tic Tac Toe.

class TicTacToe
  attr_accessor :_, :state, :outputs, :inputs, :grid, :gtk

  # Starts the game with player x's turn and creates an array (to_a) for space combinations.
  # Calls methods necessary for the game to run properly.
  def tick
    init_new_game
    render_board
    input_board
  end

  def init_new_game
    state.current_turn       ||= :x
    state.space_combinations ||= [-1, 0, 1].product([-1, 0, 1]).to_a

    state.spaces             ||= {}

    state.space_combinations.each do |x, y|
      state.spaces[x]    ||= {}
      state.spaces[x][y] ||= state.new_entity(:space)
    end
  end

  # Uses borders to create grid squares for the game's board. Also outputs the game pieces using labels.
  def render_board
    square_size = 80

    # Positions the game's board in the center of the screen.
    # Try removing what follows grid.w_half or grid.h_half and see how the position changes!
    board_left = grid.w_half - square_size * 1.5
    board_top  = grid.h_half - square_size * 1.5

    # At first glance, the add(1) looks pretty trivial. But if you remove it,
    # you'll see that the positioning of the board would be skewed without it!
    # Or if you put 2 in the parenthesis, the pieces will be placed in the wrong squares
    # due to the change in board placement.
    outputs.borders << all_spaces do |x, y, space| # outputs borders for all board spaces
      space.border ||= [
        board_left + x.add(1) * square_size, # space.border is initialized using this definition
        board_top  + y.add(1) * square_size,
        square_size,
        square_size
      ]
    end

    # Again, the calculations ensure that the piece is placed in the center of the grid square.
    # Remove the '- 20' and the piece will be placed at the top of the grid square instead of the center.
    outputs.labels << filled_spaces do |x, y, space| # put label in each filled space of board
          label board_left + x.add(1) * square_size + square_size.fdiv(2),
          board_top  + y.add(1) * square_size + square_size - 20,
          space.piece # text of label, either "x" or "o"
    end

    # Uses a label to output whether x or o won, or if a draw occurred.
    # If the game is ongoing, a label shows whose turn it currently is.
    outputs.labels << if state.x_won
                        label grid.w_half, grid.top - 80, "x won" # the '-80' positions the label 80 pixels lower than top
                      elsif state.o_won
                        label grid.w_half, grid.top - 80, "o won" # grid.w_half positions the label in the center horizontally
                      elsif state.draw
                        label grid.w_half, grid.top - 80, "a draw"
                      else # if no one won and the game is ongoing
                        label grid.w_half, grid.top - 80, "turn: #{state.current_turn}"
                      end
  end

  # Calls the methods responsible for handling user input and determining the winner.
  # Does nothing unless the mouse is clicked.
  def input_board
    return unless inputs.mouse.click
    input_place_piece
    input_restart_game
    determine_winner
  end

  # Handles user input for placing pieces on the board.
  def input_place_piece
    return if state.game_over

    # Checks to find the space that the mouse was clicked inside of, and makes sure the space does not already
    # have a piece in it.
    __, __, space = all_spaces.find do |__, __, space|
      inputs.mouse.click.point.inside_rect?(space.border) && !space.piece
    end

    # The piece that goes into the space belongs to the player whose turn it currently is.
    return unless space
    space.piece = state.current_turn

    # This ternary operator statement allows us to change the current player's turn.
    # If it is currently x's turn, it becomes o's turn. If it is not x's turn, it become's x's turn.
    state.current_turn = state.current_turn == :x ? :o : :x
  end

  # Resets the game.
  def input_restart_game
    return unless state.game_over
    gtk.reset
    init_new_game
  end

  # Checks if x or o won the game.
  # If neither player wins and all nine squares are filled, a draw happens.
  # Once a player is chosen as the winner or a draw happens, the game is over.
  def determine_winner
    state.x_won = won? :x # evaluates to either true or false (boolean values)
    state.o_won = won? :o
    state.draw = true if filled_spaces.length == 9 && !state.x_won && !state.o_won
    state.game_over = state.x_won || state.o_won || state.draw
  end

  # Determines if a player won by checking if there is a horizontal match or vertical match.
  # Horizontal_match and vertical_match have boolean values. If either is true, the game has been won.
  def won? piece
    # performs action on all space combinations
    won = [[-1, 0, 1]].product([-1, 0, 1]).map do |xs, y|

      # Checks if the 3 grid spaces with the same y value (or same row) and
      # x values that are next to each other have pieces that belong to the same player.
      # Remember, the value of piece is equal to the current turn (which is the player).
      horizontal_match = state.spaces[xs[0]][y].piece == piece &&
                         state.spaces[xs[1]][y].piece == piece &&
                         state.spaces[xs[2]][y].piece == piece

      # Checks if the 3 grid spaces with the same x value (or same column) and
      # y values that are next to each other have pieces that belong to the same player.
      # The && represents an "and" statement: if even one part of the statement is false,
      # the entire statement evaluates to false.
      vertical_match = state.spaces[y][xs[0]].piece == piece &&
                       state.spaces[y][xs[1]].piece == piece &&
                       state.spaces[y][xs[2]].piece == piece

      horizontal_match || vertical_match # if either is true, true is returned
    end

    # Sees if there is a diagonal match, starting from the bottom left and ending at the top right.
    # Is added to won regardless of whether the statement is true or false.
    won << (state.spaces[-1][-1].piece == piece && # bottom left
            state.spaces[ 0][ 0].piece == piece && # center
            state.spaces[ 1][ 1].piece == piece)   # top right

    # Sees if there is a diagonal match, starting at the bottom right and ending at the top left
    # and is added to won.
    won << (state.spaces[ 1][-1].piece == piece && # bottom right
            state.spaces[ 0][ 0].piece == piece && # center
            state.spaces[-1][ 1].piece == piece)   # top left

    # Any false statements (meaning false diagonal matches) are rejected from won
    won.reject_false.any?
  end

  # Defines filled spaces on the board by rejecting all spaces that do not have game pieces in them.
  # The ! before a statement means "not". For example, we are rejecting any space combinations that do
  # NOT have pieces in them.
  def filled_spaces
    state.space_combinations
      .reject { |x, y| !state.spaces[x][y].piece } # reject spaces with no pieces in them
      .map do |x, y|
        if block_given?
          yield x, y, state.spaces[x][y]
        else
          [x, y, state.spaces[x][y]] # sets definition of space
        end
    end
  end

  # Defines all spaces on the board.
  def all_spaces
    if !block_given?
      state.space_combinations.map do |x, y|
        [x, y, state.spaces[x][y]] # sets definition of space
      end
    else # if a block is given (block_given? is true)
      state.space_combinations.map do |x, y|
        yield x, y, state.spaces[x][y] # yield if a block is given
      end
    end
  end

  # Sets values for a label, such as the position, value, size, alignment, and color.
  def label x, y, value
    [x, y + 10, value, 20, 1, 0, 0, 0]
  end
end

$tic_tac_toe = TicTacToe.new

def tick args
  $tic_tac_toe._       = args
  $tic_tac_toe.state   = args.state
  $tic_tac_toe.outputs = args.outputs
  $tic_tac_toe.inputs  = args.inputs
  $tic_tac_toe.grid    = args.grid
  $tic_tac_toe.gtk     = args.gtk
  $tic_tac_toe.tick
  tick_instructions args, "Sample app shows how to work with mouse clicks."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Mouse Move - main.rb link

    # ./samples/05_mouse/02_mouse_move/app/main.rb
=begin

 Reminders:

 - num1.greater(num2): Returns the greater value.
   For example, if we have the command
   puts 4.greater(3)
   the number 4 would be printed to the console since it has a greater value than 3.
   Similar to lesser, which returns the lesser value.

 - find_all: Finds all elements of a collection that meet certain requirements.
   For example, in this sample app, we're using find_all to find all zombies that have intersected
   or hit the player's sprite since these zombies have been killed.

 - args.inputs.keyboard.key_down.KEY: Determines if a key is being held or pressed.
   Stores the frame the "down" event occurred.
   For more information about the keyboard, go to mygame/documentation/06-keyboard.md.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
   For more information about sprites, go to mygame/documentation/05-sprites.md.

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   When we want to create a new object, we can declare it as a new entity and then define
   its properties. (Remember, you can use state to define ANY property and it will
   be retained across frames.)

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - map: Ruby method used to transform data; used in arrays, hashes, and collections.
   Can be used to perform an action on every element of a collection, such as multiplying
   each element by 2 or declaring every element as a new entity.

 - sample: Chooses a random element from the array.

 - reject: Removes elements that meet certain requirements.
   In this sample app, we're removing/rejecting zombies that reach the center of the screen. We're also
   rejecting zombies that were killed more than 30 frames ago.

=end

# This sample app allows users to move around the screen in order to kill zombies. Zombies appear from every direction so the goal
# is to kill the zombies as fast as possible!

class ProtectThePuppiesFromTheZombies
  attr_accessor :grid, :inputs, :state, :outputs

  # Calls the methods necessary for the game to run properly.
  def tick
    defaults
    render
    calc
    input
  end

  # Sets default values for the zombies and for the player.
  # Initialization happens only in the first frame.
  def defaults
    state.flash_at               ||= 0
    state.zombie_min_spawn_rate  ||= 60
    state.zombie_spawn_countdown ||= random_spawn_countdown state.zombie_min_spawn_rate
    state.zombies                ||= []
    state.killed_zombies         ||= []

    # Declares player as a new entity and sets its properties.
    # The player begins the game in the center of the screen, not moving in any direction.
    state.player ||= state.new_entity(:player, { x: 640,
                                               y: 360,
                                               attack_angle: 0,
                                               dx: 0,
                                               dy: 0 })
  end

  # Outputs a gray background.
  # Calls the methods needed to output the player, zombies, etc onto the screen.
  def render
    outputs.solids << [grid.rect, 100, 100, 100]
    render_zombies
    render_killed_zombies
    render_player
    render_flash
  end

  # Outputs the zombies on the screen and sets values for the sprites, such as the position, width, height, and animation.
  def render_zombies
    outputs.sprites << state.zombies.map do |z| # performs action on all zombies in the collection
      z.sprite = [z.x, z.y, 4 * 3, 8 * 3, animation_sprite(z)].sprite # sets definition for sprite, calls animation_sprite method
      z.sprite
    end
  end

  # Outputs sprites of killed zombies, and displays a slash image to show that a zombie has been killed.
  def render_killed_zombies
    outputs.sprites << state.killed_zombies.map do |z| # performs action on all killed zombies in collection
      z.sprite = [z.x,
                  z.y,
                  4 * 3,
                  8 * 3,
                  animation_sprite(z, z.death_at), # calls animation_sprite method
                  0, # angle
                  255 * z.death_at.ease(30, :flip)].sprite # transparency of a zombie changes when they die
                  # change the value of 30 and see what happens when a zombie is killed

      # Sets values to output the slash over the zombie's sprite when a zombie is killed.
      # The slash is tilted 45 degrees from the angle of the player's attack.
      # Change the 3 inside scale_rect to 30 and the slash will be HUGE! Scale_rect positions
      # the slash over the killed zombie's sprite.
      [z.sprite, [z.sprite.rect, 'sprites/slash.png', 45 + state.player.attack_angle_on_click, z.sprite.a].scale_rect(3, 0.5, 0.5)]
    end
  end

  # Outputs the player sprite using the images in the sprites folder.
  def render_player
    state.player_sprite = [state.player.x,
                           state.player.y,
                          4 * 3,
                          8 * 3, "sprites/player-#{animation_index(state.player.created_at_elapsed)}.png"] # string interpolation
    outputs.sprites << state.player_sprite

    # Outputs a small red square that previews the angles that the player can attack in.
    # It can be moved in a perfect circle around the player to show possible movements.
    # Change the 60 in the parenthesis and see what happens to the movement of the red square.
    outputs.solids <<  [state.player.x + state.player.attack_angle.vector_x(60),
                        state.player.y + state.player.attack_angle.vector_y(60),
                        3, 3, 255, 0, 0]
  end

  # Renders flash as a solid. The screen turns white for 10 frames when a zombie is killed.
  def render_flash
    return if state.flash_at.elapsed_time > 10 # return if more than 10 frames have passed since flash.
    # Transparency gradually changes (or eases) during the 10 frames of flash.
    outputs.primitives << [grid.rect, 255, 255, 255, 255 * state.flash_at.ease(10, :flip)].solid
  end

  # Calls all methods necessary for performing calculations.
  def calc
    calc_spawn_zombie
    calc_move_zombies
    calc_player
    calc_kill_zombie
  end

  # Decreases the zombie spawn countdown by 1 if it has a value greater than 0.
  def calc_spawn_zombie
    if state.zombie_spawn_countdown > 0
      state.zombie_spawn_countdown -= 1
      return
    end

    # New zombies are created, positioned on the screen, and added to the zombies collection.
    state.zombies << state.new_entity(:zombie) do |z| # each zombie is declared a new entity
      if rand > 0.5
        z.x = grid.rect.w.randomize(:ratio) # random x position on screen (within grid scope)
        z.y = [-10, 730].sample # y position is set to either -10 or 730 (randomly chosen)
        # the possible values exceed the screen's scope so zombies appear to be coming from far away
      else
        z.x = [-10, 1290].sample # x position is set to either -10 or 1290 (randomly chosen)
        z.y = grid.rect.w.randomize(:ratio) # random y position on screen
      end
    end

    # Calls random_spawn_countdown method (determines how fast new zombies appear)
    state.zombie_spawn_countdown = random_spawn_countdown state.zombie_min_spawn_rate
    state.zombie_min_spawn_rate -= 1
    # set to either the current zombie_min_spawn_rate or 0, depending on which value is greater
    state.zombie_min_spawn_rate  = state.zombie_min_spawn_rate.greater(0)
  end

  # Moves all zombies towards the center of the screen.
  # All zombies that reach the center (640, 360) are rejected from the zombies collection and disappear.
  def calc_move_zombies
    state.zombies.each do |z| # for each zombie in the collection
      z.y = z.y.towards(360, 0.1) # move the zombie towards the center (640, 360) at a rate of 0.1
      z.x = z.x.towards(640, 0.1) # change 0.1 to 1.1 and see how much faster the zombies move to the center
    end
    state.zombies = state.zombies.reject { |z| z.y == 360 && z.x == 640 } # remove zombies that are in center
  end

  # Calculates the position and movement of the player on the screen.
  def calc_player
    state.player.x += state.player.dx # changes x based on dx (change in x)
    state.player.y += state.player.dy # changes y based on dy (change in y)

    state.player.dx *= 0.9 # scales dx down
    state.player.dy *= 0.9 # scales dy down

    # Compares player's x to 1280 to find lesser value, then compares result to 0 to find greater value.
    # This ensures that the player remains within the screen's scope.
    state.player.x = state.player.x.lesser(1280).greater(0)
    state.player.y = state.player.y.lesser(720).greater(0) # same with player's y
  end

  # Finds all zombies that intersect with the player's sprite. These zombies are removed from the zombies collection
  # and added to the killed_zombies collection since any zombie that intersects with the player is killed.
  def calc_kill_zombie

    # Find all zombies that intersect with the player. They are considered killed.
    killed_this_frame = state.zombies.find_all { |z| z.sprite && (z.sprite.intersect_rect? state.player_sprite) }
    state.zombies = state.zombies - killed_this_frame # remove newly killed zombies from zombies collection
    state.killed_zombies += killed_this_frame # add newly killed zombies to killed zombies

    if killed_this_frame.length > 0 # if atleast one zombie was killed in the frame
      state.flash_at = state.tick_count # flash_at set to the frame when the zombie was killed
    # Don't forget, the rendered flash lasts for 10 frames after the zombie is killed (look at render_flash method)
    end

    # Sets the tick_count (passage of time) as the value of the death_at variable for each killed zombie.
    # Death_at stores the frame a zombie was killed.
    killed_this_frame.each do |z|
      z.death_at = state.tick_count
    end

    # Zombies are rejected from the killed_zombies collection depending on when they were killed.
    # They are rejected if more than 30 frames have passed since their death.
    state.killed_zombies = state.killed_zombies.reject { |z| state.tick_count - z.death_at > 30 }
  end

  # Uses input from the user to move the player around the screen.
  def input

    # If the "a" key or left key is pressed, the x position of the player decreases.
    # Otherwise, if the "d" key or right key is pressed, the x position of the player increases.
    if inputs.keyboard.key_held.a || inputs.keyboard.key_held.left
      state.player.x -= 5
    elsif inputs.keyboard.key_held.d || inputs.keyboard.key_held.right
      state.player.x += 5
    end

    # If the "w" or up key is pressed, the y position of the player increases.
    # Otherwise, if the "s" or down key is pressed, the y position of the player decreases.
    if inputs.keyboard.key_held.w || inputs.keyboard.key_held.up
      state.player.y += 5
    elsif inputs.keyboard.key_held.s || inputs.keyboard.key_held.down
      state.player.y -= 5
    end

    # Sets the attack angle so the player can move and attack in the precise direction it wants to go.
    # If the mouse is moved, the attack angle is changed (based on the player's position and mouse position).
    # Attack angle also contributes to the position of red square.
    if inputs.mouse.moved
      state.player.attack_angle = inputs.mouse.position.angle_from [state.player.x, state.player.y]
    end

    if inputs.mouse.click && state.player.dx < 0.5 && state.player.dy < 0.5
      state.player.attack_angle_on_click = inputs.mouse.position.angle_from [state.player.x, state.player.y]
      state.player.attack_angle = state.player.attack_angle_on_click # player's attack angle is set
      state.player.dx = state.player.attack_angle.vector_x(25) # change in player's position
      state.player.dy = state.player.attack_angle.vector_y(25)
    end
  end

  # Sets the zombie spawn's countdown to a random number.
  # How fast zombies appear (change the 60 to 6 and too many zombies will appear at once!)
  def random_spawn_countdown minimum
    10.randomize(:ratio, :sign).to_i + 60
  end

  # Helps to iterate through the images in the sprites folder by setting the animation index.
  # 3 frames is how long to show an image, and 6 is how many images to flip through.
  def animation_index at
    at.idiv(3).mod(6)
  end

  # Animates the zombies by using the animation index to go through the images in the sprites folder.
  def animation_sprite zombie, at = nil
    at ||= zombie.created_at_elapsed # how long it is has been since a zombie was created
    index = animation_index at
    "sprites/zombie-#{index}.png" # string interpolation to iterate through images
  end
end

$protect_the_puppies_from_the_zombies = ProtectThePuppiesFromTheZombies.new

def tick args
  $protect_the_puppies_from_the_zombies.grid    = args.grid
  $protect_the_puppies_from_the_zombies.inputs  = args.inputs
  $protect_the_puppies_from_the_zombies.state    = args.state
  $protect_the_puppies_from_the_zombies.outputs = args.outputs
  $protect_the_puppies_from_the_zombies.tick
  tick_instructions args, "How to get the mouse position and translate it to an x, y position using .vector_x and .vector_y. CLICK to play."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Mouse Move Paint App - main.rb link

    # ./samples/05_mouse/03_mouse_move_paint_app/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Floor: Method that returns an integer number smaller than or equal to the original with no decimal.

   For example, if we have a variable, a = 13.7, and we called floor on it, it would look like this...
   puts a.floor()
   which would print out 13.
   (There is also a ceil method, which returns an integer number greater than or equal to the original
   with no decimal. If we had called ceil on the variable a, the result would have been 14.)

 Reminders:

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.

   For example, if we have a "numbers" hash that stores numbers in English as the
   key and numbers in Spanish as the value, we'd have a hash that looks like this...
   numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
   and on it goes.

   Now if we wanted to find the corresponding value of the "one" key, we could say
   puts numbers["one"]
   which would print "uno" to the console.

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   In this sample app, new_entity is used to create a new button that clears the grid.
   (Remember, you can use state to define ANY property and it will be retained across frames.)

 - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.

 - args.inputs.mouse.click.point.created_at: The frame the mouse click occurred in.

 - args.outputs.labels: An array. The values in the array generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.

=end

# This sample app shows an empty grid that the user can paint on.
# To paint, the user must keep their mouse presssed and drag it around the grid.
# The "clear" button allows users to clear the grid so they can start over.

class PaintApp
  attr_accessor :inputs, :state, :outputs, :grid, :args

  # Runs methods necessary for the game to function properly.
  def tick
    print_title
    add_grid
    check_click
    draw_buttons
  end

  # Prints the title onto the screen by using a label.
  # Also separates the title from the grid with a line as a horizontal separator.
  def print_title
    args.outputs.labels << [ 640, 700, 'Paint!', 0, 1 ]
    outputs.lines << horizontal_separator(660, 0, 1280)
  end

  # Sets the starting position, ending position, and color for the horizontal separator.
  # The starting and ending positions have the same y values.
  def horizontal_separator y, x, x2
    [x, y, x2, y, 150, 150, 150]
  end

  # Sets the starting position, ending position, and color for the vertical separator.
  # The starting and ending positions have the same x values.
  def vertical_separator x, y, y2
    [x, y, x, y2, 150, 150, 150]
  end

  # Outputs a border and a grid containing empty squares onto the screen.
  def add_grid

    # Sets the x, y, height, and width of the grid.
    # There are 31 horizontal lines and 31 vertical lines in the grid.
    # Feel free to count them yourself before continuing!
    x, y, h, w = 640 - 500/2, 640 - 500, 500, 500 # calculations done so the grid appears in screen's center
    lines_h = 31
    lines_v = 31

    # Sets values for the grid's border, grid lines, and filled squares.
    # The filled_squares variable is initially set to an empty array.
    state.grid_border ||= [ x, y, h, w ] # definition of grid's outer border
    state.grid_lines ||= draw_grid(x, y, h, w, lines_h, lines_v) # calls draw_grid method
    state.filled_squares ||= [] # there are no filled squares until the user fills them in

    # Outputs the grid lines, border, and filled squares onto the screen.
    outputs.lines.concat state.grid_lines
    outputs.borders << state.grid_border
    outputs.solids << state.filled_squares
  end

  # Draws the grid by adding in vertical and horizontal separators.
  def draw_grid x, y, h, w, lines_h, lines_v

    # The grid starts off empty.
    grid = []

    # Calculates the placement and adds horizontal lines or separators into the grid.
    curr_y = y # start at the bottom of the box
    dist_y = h / (lines_h + 1) # finds distance to place horizontal lines evenly throughout 500 height of grid
    lines_h.times do
      curr_y += dist_y # increment curr_y by the distance between the horizontal lines
      grid << horizontal_separator(curr_y, x, x + w - 1) # add a separator into the grid
    end

    # Calculates the placement and adds vertical lines or separators into the grid.
    curr_x = x # now start at the left of the box
    dist_x = w / (lines_v + 1) # finds distance to place vertical lines evenly throughout 500 width of grid
    lines_v.times do
      curr_x += dist_x # increment curr_x by the distance between the vertical lines
      grid << vertical_separator(curr_x, y + 1, y  + h) # add separator
    end

    # paint_grid uses a hash to assign values to keys.
    state.paint_grid ||= {"x" => x, "y" => y, "h" => h, "w" => w, "lines_h" => lines_h,
                          "lines_v" => lines_v, "dist_x" => dist_x,
                          "dist_y" => dist_y }

    return grid
  end

  # Checks if the user is keeping the mouse pressed down and sets the mouse_hold variable accordingly using boolean values.
  # If the mouse is up, the user cannot drag the mouse.
  def check_click
    if inputs.mouse.down #is mouse up or down?
      state.mouse_held = true # mouse is being held down
    elsif inputs.mouse.up # if mouse is up
    state.mouse_held = false # mouse is not being held down or dragged
      state.mouse_dragging = false
    end

    if state.mouse_held &&    # mouse needs to be down
      !inputs.mouse.click &&     # must not be first click
      ((inputs.mouse.previous_click.point.x - inputs.mouse.position.x).abs > 15) # Need to move 15 pixels before "drag"
      state.mouse_dragging = true
    end

    # If the user clicks their mouse inside the grid, the search_lines method is called with a click input type.
    if ((inputs.mouse.click) && (inputs.mouse.click.point.inside_rect? state.grid_border))
      search_lines(inputs.mouse.click.point, :click)

    # If the user drags their mouse inside the grid, the search_lines method is called with a drag input type.
    elsif ((state.mouse_dragging) && (inputs.mouse.position.inside_rect? state.grid_border))
      search_lines(inputs.mouse.position, :drag)
    end
  end

  # Sets the definition of a grid box and handles user input to fill in or clear grid boxes.
  def search_lines (point, input_type)
    point.x -= state.paint_grid["x"] # subtracts the value assigned to the "x" key in the paint_grid hash
    point.y -= state.paint_grid["y"] # subtracts the value assigned to the "y" key in the paint_grid hash

    # Remove code following the .floor and see what happens when you try to fill in grid squares
    point.x = (point.x / state.paint_grid["dist_x"]).floor * state.paint_grid["dist_x"]
    point.y = (point.y / state.paint_grid["dist_y"]).floor * state.paint_grid["dist_y"]

    point.x += state.paint_grid["x"]
    point.y += state.paint_grid["y"]

    # Sets definition of a grid box, meaning its x, y, width, and height.
    # Floor is called on the point.x and point.y variables.
    # Ceil method is called on values of the distance hash keys, setting the width and height of a box.
    grid_box = [ point.x.floor, point.y.floor, state.paint_grid["dist_x"].ceil, state.paint_grid["dist_y"].ceil ]

    if input_type == :click # if user clicks their mouse
      if state.filled_squares.include? grid_box # if grid box is already filled in
        state.filled_squares.delete grid_box # box is cleared and removed from filled_squares
      else
        state.filled_squares << grid_box # otherwise, box is filled in and added to filled_squares
      end
    elsif input_type == :drag # if user drags mouse
      unless state.filled_squares.include? grid_box # unless the grid box dragged over is already filled in
        state.filled_squares << grid_box # the box is filled in and added to filled_squares
      end
    end
  end

  # Creates and outputs a "Clear" button on the screen using a label and a border.
  # If the button is clicked, the filled squares are cleared, making the filled_squares collection empty.
  def draw_buttons
    x, y, w, h = 390, 50, 240, 50
    state.clear_button        ||= state.new_entity(:button_with_fade)

    # The x and y positions are set to display the label in the center of the button.
    # Try changing the first two parameters to simply x, y and see what happens to the text placement!
    state.clear_button.label  ||= [x + w.half, y + h.half + 10, "Clear", 0, 1] # placed in center of border
    state.clear_button.border ||= [x, y, w, h]

    # If the mouse is clicked inside the borders of the clear button,
    # the filled_squares collection is emptied and the squares are cleared.
    if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.clear_button.border)
      state.clear_button.clicked_at = inputs.mouse.click.created_at # time (frame) the click occurred
      state.filled_squares.clear
      inputs.mouse.previous_click = nil
    end

    outputs.labels << state.clear_button.label
    outputs.borders << state.clear_button.border

    # When the clear button is clicked, the color of the button changes
    # and the transparency changes, as well. If you change the time from
    # 0.25.seconds to 1.25.seconds or more, the change will last longer.
    if state.clear_button.clicked_at
      outputs.solids << [x, y, w, h, 0, 180, 80, 255 * state.clear_button.clicked_at.ease(0.25.seconds, :flip)]
    end
  end
end

$paint_app = PaintApp.new

def tick args
  $paint_app.inputs = args.inputs
  $paint_app.state = args.state
  $paint_app.grid = args.grid
  $paint_app.args = args
  $paint_app.outputs = args.outputs
  $paint_app.tick
  tick_instructions args, "How to create a simple paint app. CLICK and HOLD to draw."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Coordinate Systems - main.rb link

    # ./samples/05_mouse/04_coordinate_systems/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - args.inputs.mouse.click.position: Coordinates of the mouse's position on the screen.
   Unlike args.inputs.mouse.click.point, the mouse does not need to be pressed down for
   position to know the mouse's coordinates.
   For more information about the mouse, go to mygame/documentation/07-mouse.md.

 Reminders:

 - args.inputs.mouse.click: This property will be set if the mouse was clicked.

 - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

   In this sample app, string interpolation is used to show the current position of the mouse
   in a label.

 - args.outputs.labels: An array that generates a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.outputs.solids: An array that generates a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.lines: An array that generates a line.
   The parameters are [X, Y, X2, Y2, RED, GREEN, BLUE, ALPHA]
   For more information about lines, go to mygame/documentation/04-lines.md.

=end

# This sample app shows a coordinate system or grid. The user can move their mouse around the screen and the
# coordinates of their position on the screen will be displayed. Users can choose to view one quadrant or
# four quadrants by pressing the button.

def tick args

  # The addition and subtraction in the first two parameters of the label and solid
  # ensure that the outputs don't overlap each other. Try removing them and see what happens.
  pos = args.inputs.mouse.position # stores coordinates of mouse's position
  args.outputs.labels << [pos.x + 10, pos.y + 10, "#{pos}"] # outputs label of coordinates
  args.outputs.solids << [pos.x -  2, pos.y - 2, 5, 5] # outputs small blackk box placed where mouse is hovering

  button = [0, 0, 370, 50] # sets definition of toggle button
  args.outputs.borders << button # outputs button as border (not filled in)
  args.outputs.labels << [10, 35, "click here toggle coordinate system"] # label of button
  args.outputs.lines << [    0, -720,    0, 720] # vertical line dividing quadrants
  args.outputs.lines << [-1280,    0, 1280,   0] # horizontal line dividing quadrants

  if args.inputs.mouse.click # if the user clicks the mouse
    pos = args.inputs.mouse.click.point # pos's value is point where user clicked (coordinates)
    if pos.inside_rect? button # if the click occurred inside the button
      if args.grid.name == :bottom_left # if the grid shows bottom left as origin
        args.grid.origin_center! # origin will be shown in center
      else
        args.grid.origin_bottom_left! # otherwise, the view will change to show bottom left as origin
      end
    end
  end

  tick_instructions args, "Sample app shows the two supported coordinate systems in Game Toolkit."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Clicking Buttons - main.rb link

    # ./samples/05_mouse/05_clicking_buttons/app/main.rb
def tick args
  # create buttons
  args.state.buttons ||= [
    create_button(args, id: :button_1, row: 0, col: 0, text: "button 1"),
    create_button(args, id: :button_2, row: 1, col: 0, text: "button 2"),
    create_button(args, id: :clear,    row: 2, col: 0, text: "clear")
  ]

  # render button's border and label
  args.outputs.primitives << args.state.buttons.map do |b|
    b.primitives
  end

  # render center label if the text is set
  if args.state.center_label_text
    args.outputs.labels << { x: 640,
                             y: 360,
                             text: args.state.center_label_text,
                             alignment_enum: 1,
                             vertical_alignment_enum: 1 }
  end

  # if the mouse is clicked, see if the mouse click intersected
  # with a button
  if args.inputs.mouse.click
    button = args.state.buttons.find do |b|
      args.inputs.mouse.intersect_rect? b
    end

    # update the center label text based on button clicked
    case button.id
    when :button_1
      args.state.center_label_text = "button 1 was clicked"
    when :button_2
      args.state.center_label_text = "button 2 was clicked"
    when :clear
      args.state.center_label_text = nil
    end
  end
end

def create_button args, id:, row:, col:, text:;
  # args.layout.rect(row:, col:, w:, h:) is method that will
  # return a rectangle inside of a grid with 12 rows and 24 columns
  rect = args.layout.rect row: row, col: col, w: 3, h: 1

  # get senter of rect for label
  center = args.geometry.rect_center_point rect

  {
    id: id,
    x: rect.x,
    y: rect.y,
    w: rect.w,
    h: rect.h,
    primitives: [
      {
        x: rect.x,
        y: rect.y,
        w: rect.w,
        h: rect.h,
        primitive_marker: :border
      },
      {
        x: center.x,
        y: center.y,
        text: text,
        size_enum: -1,
        alignment_enum: 1,
        vertical_alignment_enum: 1,
        primitive_marker: :label
      }
    ]
  }
end

$gtk.reset

    Save Load link

    Reading Writing Files - main.rb link

    # ./samples/06_save_load/00_reading_writing_files/app/main.rb
# APIs covered:
#   args.gtk.write_file "file-1.txt", args.state.tick_count.to_s
#   args.gtk.append_file "file-1.txt", args.state.tick_count.to_s

#   stat = args.gtk.stat_file "file-1.txt"

#   contents = args.gtk.read_file "file-1.txt"

#   args.gtk.delete_file "file-1.txt"
#   args.gtk.delete_file_if_exist "file-1.txt"

#   root_files = args.gtk.list_files ""
#   app_files  = args.gtk.list_files "app"

def tick args
  # create buttons
  args.state.buttons ||= [
    create_button(args, id: :write_file_1,  row: 0, col: 0, text: "write file-1.txt"),
    create_button(args, id: :append_file_1, row: 1, col: 0, text: "append file-1.txt"),
    create_button(args, id: :delete_file_1, row: 2, col: 0, text: "delete file-1.txt"),

    create_button(args, id: :read_file_1,   row: 0, col: 3, text: "read file-1.txt"),
    create_button(args, id: :stat_file_1,   row: 1, col: 3, text: "stat file-1.txt"),
    create_button(args, id: :list_files,    row: 2, col: 3, text: "list files"),
  ]

  # render button's border and label
  args.outputs.primitives << args.state.buttons.map do |b|
    b.primitives
  end

  # render center label if the text is set
  if args.state.center_label_text
    long_string = args.state.center_label_text
    max_character_length = 80
    long_strings_split = args.string.wrapped_lines long_string, max_character_length
    line_height = 23
    offset = (long_strings_split.length / 2) * line_height
    args.outputs.labels << long_strings_split.map_with_index do |s, i|
      {
        x: 400,
        y: 60.from_top - (i * line_height),
        text: s
      }
    end
  end

  # if the mouse is clicked, see if the mouse click intersected
  # with a button
  if args.inputs.mouse.click
    button = args.state.buttons.find do |b|
      args.inputs.mouse.intersect_rect? b
    end

    # update the center label text based on button clicked
    case button.id
    when :write_file_1
      args.gtk.write_file("file-1.txt", args.state.tick_count.to_s + "\n")

      args.state.center_label_text = ""
      args.state.center_label_text += "* Success (#{args.state.tick_count}):\n"
      args.state.center_label_text += "  Click \"read file-1.txt\" to see the contents.\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "** Sample Code\n"
      args.state.center_label_text += "   args.gtk.write_file(\"file-1.txt\", args.state.tick_count.to_s + \"\\n\")\n"
    when :append_file_1
      args.gtk.append_file("file-1.txt", args.state.tick_count.to_s + "\n")

      args.state.center_label_text = ""
      args.state.center_label_text += "* Success (#{args.state.tick_count}):\n"
      args.state.center_label_text += "  Click \"read file-1.txt\" to see the contents.\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "** Sample Code\n"
      args.state.center_label_text += "   args.gtk.append_file(\"file-1.txt\", args.state.tick_count.to_s + \"\\n\")\n"
    when :stat_file_1
      stat = args.gtk.stat_file "file-1.txt"

      args.state.center_label_text = ""
      args.state.center_label_text += "* Stat File (#{args.state.tick_count})\n"
      args.state.center_label_text += "#{stat || "nil (file does not exist)"}"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "** Sample Code\n"
      args.state.center_label_text += "   args.gtk.stat_files(\"file-1.txt\")\n"
    when :read_file_1
      contents = args.gtk.read_file("file-1.txt")

      args.state.center_label_text = ""
      if contents
        args.state.center_label_text += "* Contents (#{args.state.tick_count}):\n"
        args.state.center_label_text += contents
        args.state.center_label_text += "\n"
        args.state.center_label_text += "** Sample Code\n"
        args.state.center_label_text += "   contents = args.gtk.read_file(\"file-1.txt\")\n"
      else
        args.state.center_label_text += "* Contents (#{args.state.tick_count}):\n"
        args.state.center_label_text += "Contents of file was nil. Click stat file-1.txt for file information."
        args.state.center_label_text += "\n"
        args.state.center_label_text += "** Sample Code\n"
        args.state.center_label_text += "   contents = args.gtk.read_file(\"file-1.txt\")\n"
      end
    when :delete_file_1
      args.state.center_label_text = ""

      if args.gtk.stat_file "file-1.txt"
        args.gtk.delete_file "file-1.txt"
        args.state.center_label_text += "* Delete File\n"
        args.state.center_label_text += "file-1.txt was deleted. Click \"list files\" or \"stat file-1.txt\" for more info."
        args.state.center_label_text += "\n"
        args.state.center_label_text += "\n"
        args.state.center_label_text += "** Sample Code\n"
        args.state.center_label_text += "   args.gtk.delete_file(\"file-1.txt\")\n"
      else
        args.state.center_label_text = ""
        args.state.center_label_text += "* Delete File\n"
        args.state.center_label_text += "File does not exist. Click \"write file-1.txt\" or \"append file-1.txt\" to create file."
        args.state.center_label_text += "\n"
        args.state.center_label_text += "\n"
        args.state.center_label_text += "** Sample Code\n"
        args.state.center_label_text += "   if args.gtk.stat_file(\"file-1.txt\") ...\n"
      end
    when :list_files
      root_files = args.gtk.list_files ""
      app_files  = args.gtk.list_files "app"

      args.state.center_label_text = ""
      args.state.center_label_text += "** Root Files (#{args.state.tick_count}):\n"
      args.state.center_label_text += root_files.join "\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "** App Files (#{args.state.tick_count}):\n"
      args.state.center_label_text += app_files.join "\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "\n"
      args.state.center_label_text += "** Sample Code\n"
      args.state.center_label_text += "   root_files = args.gtk.list_files(\"\")\n"
      args.state.center_label_text += "   app_files = args.gtk.list_files(\"app\")\n"
    end
  end
end

def create_button args, id:, row:, col:, text:;
  # args.layout.rect(row:, col:, w:, h:) is method that will
  # return a rectangle inside of a grid with 12 rows and 24 columns
  rect = args.layout.rect row: row, col: col, w: 3, h: 1

  # get senter of rect for label
  center = args.geometry.rect_center_point rect

  {
    id: id,
    x: rect.x,
    y: rect.y,
    w: rect.w,
    h: rect.h,
    primitives: [
      {
        x: rect.x,
        y: rect.y,
        w: rect.w,
        h: rect.h,
        primitive_marker: :border
      },
      {
        x: center.x,
        y: center.y,
        text: text,
        size_enum: -2,
        alignment_enum: 1,
        vertical_alignment_enum: 1,
        primitive_marker: :label
      }
    ]
  }
end

$gtk.reset

    Save Load Game - main.rb link

    # ./samples/06_save_load/01_save_load_game/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Symbol (:): Ruby object with a name and an internal ID. Symbols are useful
   because with a given symbol name, you can refer to the same object throughout
   a Ruby program.

   In this sample app, we're using symbols for our buttons. We have buttons that
   light fires, save, load, etc. Each of these buttons has a distinct symbol like
   :light_fire, :save_game, :load_game, etc.

 - to_sym: Returns the symbol corresponding to the given string; creates the symbol
   if it does not already exist.
   For example,
   'car'.to_sym
   would return the symbol :car.

 - last: Returns the last element of an array.

 Reminders:

 - num1.lesser(num2): finds the lower value of the given options.
   For example, in the statement
   a = 4.lesser(3)
   3 has a lower value than 4, which means that the value of a would be set to 3,
   but if the statement had been
   a = 4.lesser(5)
   4 has a lower value than 5, which means that the value of a would be set to 4.

 - num1.fdiv(num2): returns the float division (will have a decimal) of the two given numbers.
   For example, 5.fdiv(2) = 2.5 and 5.fdiv(5) = 1.0

 - String interpolation: uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - args.outputs.labels: An array. Values generate a label.
   Parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information, go to mygame/documentation/02-labels.md.

 - ARRAY#inside_rect?: An array with at least two values is considered a point. An array
   with at least four values is considered a rect. The inside_rect? function returns true
   or false depending on if the point is inside the rect.

=end

# This code allows users to perform different tasks, such as saving and loading the game.
# Users also have options to reset the game and light a fire.

class TextedBasedGame

  # Contains methods needed for game to run properly.
  # Increments tick count by 1 each time it runs (60 times in a single second)
  def tick
    default
    show_intro
    state.engine_tick_count += 1
    tick_fire
  end

  # Sets default values.
  # The ||= ensures that a variable's value is only set to the value following the = sign
  # if the value has not already been set before. Intialization happens only in the first frame.
  def default
    state.engine_tick_count ||= 0
    state.active_module     ||= :room
    state.fire_progress     ||= 0
    state.fire_ready_in     ||= 10
    state.previous_fire     ||= :dead
    state.fire              ||= :dead
  end

  def show_intro
    return unless state.engine_tick_count == 0 # return unless the game just started
    set_story_line "awake." # calls set_story_line method, sets to "awake"
  end

  # Sets story line.
  def set_story_line story_line
    state.story_line    = story_line # story line set to value of parameter
    state.active_module = :alert # active module set to alert
  end

  # Clears story line.
  def clear_storyline
    state.active_module = :none # active module set to none
    state.story_line = nil # story line is cleared, set to nil (or empty)
  end

  # Determines fire progress (how close the fire is to being ready to light).
  def tick_fire
    return if state.active_module == :alert # return if active module is alert
    state.fire_progress += 1 # increment fire progress
    # fire_ready_in is 10. The fire_progress is either the current value or 10, whichever has a lower value.
    state.fire_progress = state.fire_progress.lesser(state.fire_ready_in)
  end

  # Sets the value of fire (whether it is dead or roaring), and the story line
  def light_fire
    return unless fire_ready? # returns unless the fire is ready to be lit
    state.fire = :roaring # fire is lit, set to roaring
    state.fire_progress = 0 # the fire progress returns to 0, since the fire has been lit
    if state.fire != state.previous_fire
      set_story_line "the fire is #{state.fire}." # the story line is set using string interpolation
      state.previous_fire = state.fire
    end
  end

  # Checks if the fire is ready to be lit. Returns a boolean value.
  def fire_ready?
    # If fire_progress (value between 0 and 10) is equal to fire_ready_in (value of 10),
    # the fire is ready to be lit.
    state.fire_progress == state.fire_ready_in
  end

  # Divides the value of the fire_progress variable by 10 to determine how close the user is to
  # being able to light a fire.
  def light_fire_progress
    state.fire_progress.fdiv(10) # float division
  end

  # Defines fire as the state.fire variable.
  def fire
    state.fire
  end

  # Sets the title of the room.
  def room_title
    return "a room that is dark" if state.fire == :dead # room is dark if the fire is dead
    return "a room that is lit" # room is lit if the fire is not dead
  end

  # Sets the active_module to room.
  def go_to_room
    state.active_module = :room
  end

  # Defines active_module as the state.active_module variable.
  def active_module
    state.active_module
  end

  # Defines story_line as the state.story_line variable.
  def story_line
    state.story_line
  end

  # Update every 60 frames (or every second)
  def should_tick?
    state.tick_count.mod_zero?(60)
  end

  # Sets the value of the game state provider.
  def initialize game_state_provider
    @game_state_provider = game_state_provider
  end

  # Defines the game state.
  # Any variable prefixed with an @ symbol is an instance variable.
  def state
    @game_state_provider.state
  end

  # Saves the state of the game in a text file called game_state.txt.
  def save
    $gtk.serialize_state('game_state.txt', state)
  end

  # Loads the game state from the game_state.txt text file.
  # If the load is unsuccessful, the user is informed since the story line indicates the failure.
  def load
    parsed_state = $gtk.deserialize_state('game_state.txt')
    if !parsed_state
      set_story_line "no game to load. press save first."
    else
      $gtk.args.state = parsed_state
    end
  end

  # Resets the game.
  def reset
    $gtk.reset
  end
end

class TextedBasedGamePresenter
  attr_accessor :state, :outputs, :inputs

  # Creates empty collection called highlights.
  # Calls methods necessary to run the game.
  def tick
    state.layout.highlights ||= []
    game.tick if game.should_tick?
    render
    process_input
  end

  # Outputs a label of the tick count (passage of time) and calls all render methods.
  def render
    outputs.labels << [10, 30, state.tick_count]
    render_alert
    render_room
    render_highlights
  end

  # Outputs a label onto the screen that shows the story line, and also outputs a "close" button.
  def render_alert
    return unless game.active_module == :alert

    outputs.labels << [640, 480, game.story_line, 5, 1]  # outputs story line label
    outputs.primitives << button(:alert_dismiss, 490, 380, "close")  # positions "close" button under story line
  end

  def render_room
    return unless game.active_module == :room
    outputs.labels << [640, 700, game.room_title, 4, 1] # outputs room title label at top of screen

    # The parameters for these outputs are (symbol, x, y, text, value/percentage) and each has a y value
    # that positions it 60 pixels lower than the previous output.

    # outputs the light_fire_progress bar, uses light_fire_progress for its percentage (which changes bar's appearance)
    outputs.primitives << progress_bar(:light_fire, 490, 600, "light fire", game.light_fire_progress)
    outputs.primitives << button(       :save_game, 490, 540, "save") # outputs save button
    outputs.primitives << button(       :load_game, 490, 480, "load") # outputs load button
    outputs.primitives << button(      :reset_game, 490, 420, "reset") # outputs reset button
    outputs.labels << [640, 30, "the fire is #{game.fire}", 0, 1] # outputs fire label at bottom of screen
  end

  # Outputs a collection of highlights using an array to set their values, and also rejects certain values from the collection.
  def render_highlights
    state.layout.highlights.each do |h| # for each highlight in the collection
        h.lifetime -= 1 # decrease the value of its lifetime
      end

      outputs.solids << state.layout.highlights.map do |h| # outputs highlights collection
        [h.x, h.y, h.w, h.h, h.color, 255 * h.lifetime / h.max_lifetime] # sets definition for each highlight
        # transparency changes; divide lifetime by max_lifetime, multiply result by 255
      end

      # reject highlights from collection that have no remaining lifetime
      state.layout.highlights = state.layout.highlights.reject { |h| h.lifetime <= 0 }
  end

  # Checks whether or not a button was clicked.
  # Returns a boolean value.
  def process_input
    button = button_clicked? # calls button_clicked? method
  end

  # Returns a boolean value.
  # Finds the button that was clicked from the button list and determines what method to call.
  # Adds a highlight to the highlights collection.
  def button_clicked?
    return nil unless click_pos # return nil unless click_pos holds coordinates of mouse click
      button = @button_list.find do |k, v| # goes through button_list to find button clicked
        click_pos.inside_rect? v[:primitives].last.rect # was the mouse clicked inside the rect of button?
      end
      return unless button # return unless a button was clicked
      method_to_call = "#{button[0]}_clicked".to_sym # sets method_to_call to symbol (like :save_game or :load_game)
      if self.respond_to? method_to_call # returns true if self responds to the given method (method actually exists)
        border = button[1][:primitives].last # sets border definition using value of last key in button list hash

        # declares each highlight as a new entity, sets properties
        state.layout.highlights << state.new_entity(:highlight) do |h|
            h.x = border.x
            h.y = border.y
            h.w = border.w
            h.h = border.h
            h.max_lifetime = 10
            h.lifetime = h.max_lifetime
            h.color = [120, 120, 180] # sets color to shade of purple
          end

          self.send method_to_call # invoke method identified by symbol
        else # otherwise, if self doesn't respond to given method
          border = button[1][:primitives].last # sets border definition using value of last key in hash

          # declares each highlight as a new entity, sets properties
          state.layout.highlights << state.new_entity(:highlight) do |h|
            h.x = border.x
            h.y = border.y
            h.w = border.w
            h.h = border.h
            h.max_lifetime = 4 # different max_lifetime than the one set if respond_to? had been true
            h.lifetime = h.max_lifetime
            h.color = [120, 80, 80] # sets color to dark color
          end

          # instructions for users on how to add the missing method_to_call to the code
          puts "It looks like #{method_to_call} doesn't exists on TextedBasedGamePresenter. Please add this method:"
          puts "Just copy the code below and put it in the #{TextedBasedGamePresenter} class definition."
          puts ""
          puts "```"
          puts "class TextedBasedGamePresenter <--- find this class and put the method below in it"
          puts ""
          puts "  def #{method_to_call}"
          puts "    puts 'Yay that worked!'"
          puts "  end"
          puts ""
          puts "end <-- make sure to put the #{method_to_call} method in between the `class` word and the final `end` statement."
          puts "```"
          puts ""
      end
  end

  # Returns the position of the mouse when it is clicked.
  def click_pos
    return nil unless inputs.mouse.click # returns nil unless the mouse was clicked
    return inputs.mouse.click.point # returns location of mouse click (coordinates)
  end

  # Creates buttons for the button_list and sets their values using a hash (uses symbols as keys)
  def button id, x, y, text
    @button_list[id] ||= { # assigns values to hash keys
      id: id,
      text: text,
      primitives: [
        [x + 10, y + 30, text, 2, 0].label, # positions label inside border
        [x, y, 300, 50].border,             # sets definition of border
      ]
    }

    @button_list[id][:primitives] # returns label and border for buttons
  end

  # Creates a progress bar (used for lighting the fire) and sets its values.
  def progress_bar id, x, y, text, percentage
    @button_list[id] = { # assigns values to hash keys
      id: id,
      text: text,
      primitives: [
        [x, y, 300, 50, 100, 100, 100].solid, # sets definition for solid (which fills the bar with gray)
        [x + 10, y + 30, text, 2, 0].label, # sets definition for label, positions inside border
        [x, y, 300, 50].border, # sets definition of border
      ]
    }

    # Fills progress bar based on percentage. If the fire was ready to be lit (100%) and we multiplied by
    # 100, only 1/3 of the bar would only be filled in. 200 would cause only 2/3 to be filled in.
    @button_list[id][:primitives][0][2] = 300 * percentage
    @button_list[id][:primitives]
  end

  # Defines the game.
  def game
    @game
  end

  # Initalizes the game and creates an empty list of buttons.
  def initialize
    @game = TextedBasedGame.new self
    @button_list ||= {}
  end

  # Clears the storyline and takes the user to the room.
  def alert_dismiss_clicked
    game.clear_storyline
    game.go_to_room
  end

  # Lights the fire when the user clicks the "light fire" option.
  def light_fire_clicked
    game.light_fire
  end

  # Saves the game when the user clicks the "save" option.
  def save_game_clicked
    game.save
  end

  # Resets the game when the user clicks the "reset" option.
  def reset_game_clicked
    game.reset
  end

  # Loads the game when the user clicks the "load" option.
  def load_game_clicked
    game.load
  end
end

$text_based_rpg = TextedBasedGamePresenter.new

def tick args
  $text_based_rpg.state = args.state
  $text_based_rpg.outputs = args.outputs
  $text_based_rpg.inputs = args.inputs
  $text_based_rpg.tick
end

    Advanced Audio link

    Audio Mixer - main.rb link

    # ./samples/07_advanced_audio/01_audio_mixer/app/main.rb
# these are the properties that you can sent on args.audio
def spawn_new_sound args, name, path
  # Spawn randomly in an area that won't be covered by UI.
  screenx = (rand * 600.0) + 200.0
  screeny = (rand * 400.0) + 100.0

  id = new_sound_id! args
  # you can hang anything on the audio hashes you want, so we store the
  #  actual screen position in here for convenience.
  args.audio[id] = {
    name: name,
    input: path,
    screenx: screenx,
    screeny: screeny,
    x: ((screenx / 1279.0) * 2.0) - 1.0,  # scale to -1.0 - 1.0 range
    y: ((screeny / 719.0) * 2.0) - 1.0,   # scale to -1.0 - 1.0 range
    z: 0.0,
    gain: 1.0,
    pitch: 1.0,
    looping: true,
    paused: false
  }

  args.state.selected = id
end

# these are values you can change on the ~args.audio~ data structure
def input_panel args
  return unless args.state.panel
  return if args.state.dragging

  audio_entry = args.audio[args.state.selected]
  results = args.state.panel

  if args.state.mouse_state == :held && args.inputs.mouse.position.inside_rect?(results.pitch_slider_rect.rect)
    audio_entry.pitch = 2.0 * ((args.inputs.mouse.x - results.pitch_slider_rect.rect.x).to_f / (results.pitch_slider_rect.rect.w - 1.0))
  elsif args.state.mouse_state == :held && args.inputs.mouse.position.inside_rect?(results.playtime_slider_rect.rect)
    audio_entry.playtime = audio_entry.length_ * ((args.inputs.mouse.x - results.playtime_slider_rect.rect.x).to_f / (results.playtime_slider_rect.rect.w - 1.0))
  elsif args.state.mouse_state == :held && args.inputs.mouse.position.inside_rect?(results.gain_slider_rect.rect)
    audio_entry.gain = (args.inputs.mouse.x - results.gain_slider_rect.rect.x).to_f / (results.gain_slider_rect.rect.w - 1.0)
  elsif args.inputs.mouse.click && args.inputs.mouse.position.inside_rect?(results.looping_checkbox_rect.rect)
    audio_entry.looping = !audio_entry.looping
  elsif args.inputs.mouse.click && args.inputs.mouse.position.inside_rect?(results.paused_checkbox_rect.rect)
    audio_entry.paused = !audio_entry.paused
  elsif args.inputs.mouse.click && args.inputs.mouse.position.inside_rect?(results.delete_button_rect.rect)
    args.audio.delete args.state.selected
  end
end

def render_sources args
  args.outputs.primitives << args.audio.keys.map do |k|
    s = args.audio[k]

    isselected = (k == args.state.selected)

    color = isselected ? [ 0, 255, 0, 255 ] : [ 0, 0, 255, 255 ]
    [
      [s.screenx, s.screeny, args.state.boxsize, args.state.boxsize, *color].solid,

      {
        x: s.screenx + args.state.boxsize.half,
        y: s.screeny,
        text: s.name,
        r: 255,
        g: 255,
        b: 255,
        alignment_enum: 1
      }.label!
    ]
  end
end

def playtime_str t
  return "" unless t
  minutes = (t / 60.0).floor
  seconds = t - (minutes * 60.0).to_f
  return minutes.to_s + ':' + seconds.floor.to_s + ((seconds - seconds.floor).to_s + "000")[1..3]
end

def label_with_drop_shadow x, y, text
  [
    { x: x + 1, y: y + 1, text: text, vertical_alignment_enum: 1, alignment_enum: 1, r:   0, g:   0, b:   0 }.label!,
    { x: x + 2, y: y + 0, text: text, vertical_alignment_enum: 1, alignment_enum: 1, r:   0, g:   0, b:   0 }.label!,
    { x: x + 0, y: y + 1, text: text, vertical_alignment_enum: 1, alignment_enum: 1, r: 200, g: 200, b: 200 }.label!
  ]
end

def check_box opts = {}
  checkbox_template = opts.args.layout.rect(w: 0.5, h: 0.5, col: 2)
  final_rect = checkbox_template.center_inside_rect_y(opts.args.layout.rect(row: opts.row, col: opts.col))
  color = { r:   0, g:   0, b:   0 }
  color = { r: 255, g: 255, b: 255 } if opts.checked

  {
    rect: final_rect,
    primitives: [
      (final_rect.to_solid color)
    ]
  }
end

def progress_bar opts = {}
  outer_rect  = opts.args.layout.rect(row: opts.row, col: opts.col, w: 5, h: 1)
  color = opts.percentage * 255
  baseline_progress_bar = opts.args
                              .layout
                              .rect(w: 5, h: 0.5)

  final_rect = baseline_progress_bar.center_inside_rect(outer_rect)
  center = final_rect.rect_center_point

  {
    rect: final_rect,
    primitives: [
      final_rect.merge(r: color, g: color, b: color, a: 128).solid!,
      label_with_drop_shadow(center.x, center.y, opts.text)
    ]
  }
end

def panel_primitives args, audio_entry
  results = { primitives: [] }

  return results unless audio_entry

  # this uses DRGTK's layout apis to layout the controls
  # imagine the screen is split into equal cells (24 cells across, 12 cells up and down)
  # args.layout.rect returns a hash which we merge values with to create primitives
  # using args.layout.rect removes the need for pixel pushing

  # args.outputs.debug << args.layout.debug_primitives(r: 255, g: 255, b: 255)

  white_color = { r: 255, g: 255, b: 255 }
  label_style = white_color.merge(vertical_alignment_enum: 1)

  # panel background
  results.primitives << args.layout.rect(row: 0, col: 0, w: 7, h: 6, include_col_gutter: true, include_row_gutter: true)
                                   .border!(r: 255, g: 255, b: 255)

  # title
  results.primitives << args.layout.point(row: 0, col: 3.5, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text:           "Source #{args.state.selected} (#{args.audio[args.state.selected].name})",
                                          size_enum:      3,
                                          alignment_enum: 1)

  # seperator line
  results.primitives << args.layout.rect(row: 1, col: 0, w: 7, h: 0)
                                   .line!(white_color)

  # screen location
  results.primitives << args.layout.point(row: 1.0, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "screen:")

  results.primitives << args.layout.point(row: 1.0, col: 2, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "(#{audio_entry.screenx.to_i}, #{audio_entry.screeny.to_i})")

  # position
  results.primitives << args.layout.point(row: 1.5, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "position:")

  results.primitives << args.layout.point(row: 1.5, col: 2, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "(#{audio_entry[:x].round(5).to_s[0..6]}, #{audio_entry[:y].round(5).to_s[0..6]})")

  results.primitives << args.layout.point(row: 2.0, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "pitch:")

  results.pitch_slider_rect = progress_bar(row: 2.0, col: 2,
                                           percentage: audio_entry.pitch / 2.0,
                                           text: "#{audio_entry.pitch.to_sf}",
                                           args: args)

  results.primitives << results.pitch_slider_rect.primitives

  results.primitives << args.layout.point(row: 2.5, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "playtime:")

  results.playtime_slider_rect = progress_bar(args: args,
                                              row:  2.5,
                                              col:  2,
                                              percentage: (audio_entry.playtime || 1) / (audio_entry.length_ || 1),
                                              text: "#{playtime_str(audio_entry.playtime)} / #{playtime_str(audio_entry.length_)}")

  results.primitives << results.playtime_slider_rect.primitives

  results.primitives << args.layout.point(row: 3.0, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "gain:")

  results.gain_slider_rect = progress_bar(args: args,
                                          row:  3.0,
                                          col:  2,
                                          percentage: audio_entry.gain,
                                          text: "#{audio_entry.gain.to_sf}")

  results.primitives << results.gain_slider_rect.primitives


  results.primitives << args.layout.point(row: 3.5, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "looping:")

  checkbox_template = args.layout.rect(w: 0.5, h: 0.5, col: 2)

  results.looping_checkbox_rect = check_box(args: args, row: 3.5, col: 2, checked: audio_entry.looping)
  results.primitives << results.looping_checkbox_rect.primitives

  results.primitives << args.layout.point(row: 4.0, col: 0, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "paused:")

  checkbox_template = args.layout.rect(w: 0.5, h: 0.5, col: 2)

  results.paused_checkbox_rect = check_box(args: args, row: 4.0, col: 2, checked: !audio_entry.paused)
  results.primitives << results.paused_checkbox_rect.primitives

  results.delete_button_rect = { rect: args.layout.rect(row: 5, col: 0, w: 7, h: 1) }

  results.primitives << results.delete_button_rect.rect.to_solid(r: 180)

  results.primitives << args.layout.point(row: 5, col: 3.5, row_anchor: 0.5)
                                   .merge(label_style)
                                   .merge(text: "DELETE", alignment_enum: 1)

  return results
end

def render_panel args
  args.state.panel = nil
  audio_entry = args.audio[args.state.selected]
  return unless audio_entry

  mouse_down = (args.state.mouse_held >= 0)
  args.state.panel = panel_primitives args, audio_entry
  args.outputs.primitives << args.state.panel.primitives
end

def new_sound_id! args
  args.state.sound_id ||= 0
  args.state.sound_id  += 1
  args.state.sound_id
end

def render_launcher args
  args.outputs.primitives << args.state.spawn_sound_buttons.map(&:primitives)
end

def render_ui args
  render_launcher args
  render_panel args
end

def tick args
  defaults args
  render args
  input args
end

def input args
  if !args.audio[args.state.selected]
    args.state.selected = nil
    args.state.dragging = nil
  end

  # spawn button and node interaction
  if args.inputs.mouse.click
    spawn_sound_button = args.state.spawn_sound_buttons.find { |b| args.inputs.mouse.inside_rect? b.rect }

    audio_click_key, audio_click_value = args.audio.find do |k, v|
      args.inputs.mouse.inside_rect? [v.screenx, v.screeny, args.state.boxsize, args.state.boxsize]
    end

    if spawn_sound_button
      args.state.selected = nil
      spawn_new_sound args, spawn_sound_button.name, spawn_sound_button.path
    elsif audio_click_key
      args.state.selected = audio_click_key
    end
  end

  if args.state.mouse_state == :held && args.state.selected
    v = args.audio[args.state.selected]
    if args.inputs.mouse.inside_rect? [v.screenx, v.screeny, args.state.boxsize, args.state.boxsize]
      args.state.dragging = args.state.selected
    end

    if args.state.dragging
      s = args.audio[args.state.selected]
      # you can hang anything on the audio hashes you want, so we store the
      #  actual screen position so it doesn't scale weirdly vs your mouse.
      s.screenx = args.inputs.mouse.x - (args.state.boxsize / 2)
      s.screeny = args.inputs.mouse.y - (args.state.boxsize / 2)

      s.screeny = 50 if s.screeny < 50
      s.screeny = (719 - args.state.boxsize) if s.screeny > (719 - args.state.boxsize)
      s.screenx = 0 if s.screenx < 0
      s.screenx = (1279 - args.state.boxsize) if s.screenx > (1279 - args.state.boxsize)

      s.x = ((s.screenx / 1279.0) * 2.0) - 1.0  # scale to -1.0 - 1.0 range
      s.y = ((s.screeny / 719.0) * 2.0) - 1.0   # scale to -1.0 - 1.0 range
    end
  elsif args.state.mouse_state == :released
    args.state.dragging = nil
  end

  input_panel args
end

def defaults args
  args.state.mouse_state      ||= :released
  args.state.dragging_source  ||= false
  args.state.selected         ||= 0
  args.state.next_sound_index ||= 0
  args.state.boxsize          ||= 30
  args.state.sound_files      ||= [
    { name: :tada,   path: "sounds/tada.wav"   },
    { name: :splash, path: "sounds/splash.wav" },
    { name: :drum,   path: "sounds/drum.mp3"   },
    { name: :spring, path: "sounds/spring.wav" },
    { name: :music,  path: "sounds/music.ogg"  }
  ]

  # generate buttons based off the sound collection above
  args.state.spawn_sound_buttons ||= begin
    # create a group of buttons
    # column centered (using col_offset to calculate the column offset)
    # where each item is 2 columns apart
    rects = args.layout.rect_group row:   11,
                                   col_offset: {
                                     count: args.state.sound_files.length,
                                     w:     2
                                   },
                                   dcol:  2,
                                   w:     2,
                                   h:     1,
                                   group: args.state.sound_files

    # now that you have the rects
    # construct the metadata for the buttons
    rects.map do |rect|
      {
        rect: rect,
        name: rect.name,
        path: rect.path,
        primitives: [
          rect.to_border(r: 255, g: 255, b: 255),
          rect.to_label(x: rect.center_x,
                        y: rect.center_y,
                        text: "#{rect.name}",
                        alignment_enum: 1,
                        vertical_alignment_enum: 1,
                        r: 255, g: 255, b: 255)
        ]
      }
    end
  end

  if args.inputs.mouse.up
    args.state.mouse_state = :released
    args.state.dragging_source = false
  elsif args.inputs.mouse.down
    args.state.mouse_state = :held
  end

  args.outputs.background_color = [ 0, 0, 0, 255 ]
end

def render args
  render_ui args
  render_sources args
end

    Audio Mixer - server_ip_address.txt link

    # ./samples/07_advanced_audio/01_audio_mixer/app/server_ip_address.txt
192.168.1.65

    Sound Synthesis - main.rb link

    # ./samples/07_advanced_audio/02_sound_synthesis/app/main.rb
begin # region: top level tick methods
  def tick args
    defaults args
    render args
    input args
    process_audio_queue args
  end

  def defaults args
    args.state.sine_waves      ||= {}
    args.state.square_waves    ||= {}
    args.state.saw_tooth_waves ||= {}
    args.state.triangle_waves  ||= {}
    args.state.audio_queue     ||= []
    args.state.buttons         ||= [
      (frequency_buttons args),
      (sine_wave_note_buttons args),
      (bell_buttons args),
      (square_wave_note_buttons args),
      (saw_tooth_wave_note_buttons args),
      (triangle_wave_note_buttons args),
    ].flatten
  end

  def render args
    args.outputs.borders << args.state.buttons.map { |b| b[:border] }
    args.outputs.labels  << args.state.buttons.map { |b| b[:label]  }
  end

  def input args
    args.state.buttons.each do |b|
      if args.inputs.mouse.click && (args.inputs.mouse.click.inside_rect? b[:rect])
        parameter_string = (b.slice :frequency, :note, :octave).map { |k, v| "#{k}: #{v}" }.join ", "
        args.gtk.notify! "#{b[:method_to_call]} #{parameter_string}"
        send b[:method_to_call], args, b
      end
    end

    if args.inputs.mouse.click && (args.inputs.mouse.click.inside_rect? (args.layout.rect(row: 0).yield_self { |r| r.merge y: r.y + r.h.half, h: r.h.half }))
      args.gtk.openurl 'https://www.youtube.com/watch?v=zEzovM5jT-k&ab_channel=AmirRajan'
    end
  end

  def process_audio_queue args
    to_queue = args.state.audio_queue.find_all { |v| v[:queue_at] <= args.tick_count }
    args.state.audio_queue -= to_queue
    to_queue.each { |a| args.audio[a[:id]] = a }

    args.audio.find_all { |k, v| v[:decay_rate] }
      .each     { |k, v| v[:gain] -= v[:decay_rate] }

    sounds_to_stop = args.audio
                       .find_all { |k, v| v[:stop_at] && args.state.tick_count >= v[:stop_at] }
                       .map { |k, v| k }

    sounds_to_stop.each { |k| args.audio.delete k }
  end
end

begin # region: button definitions, ui layout, callback functions
  def button args, opts
    button_def = opts.merge rect: (args.layout.rect (opts.merge w: 2, h: 1))

    button_def[:border] = button_def[:rect].merge r: 0, g: 0, b: 0

    label_offset_x = 5
    label_offset_y = 30

    button_def[:label]  = button_def[:rect].merge text: opts[:text],
                                                  size_enum: -2.5,
                                                  x: button_def[:rect].x + label_offset_x,
                                                  y: button_def[:rect].y + label_offset_y

    button_def
  end

  def play_sine_wave args, sender
    queue_sine_wave args,
                    frequency: sender[:frequency],
                    duration: 1.seconds,
                    fade_out: true
  end

  def play_note args, sender
    method_to_call = :queue_sine_wave
    method_to_call = :queue_square_wave    if sender[:type] == :square
    method_to_call = :queue_saw_tooth_wave if sender[:type] == :saw_tooth
    method_to_call = :queue_triangle_wave  if sender[:type] == :triangle
    method_to_call = :queue_bell           if sender[:type] == :bell

    send method_to_call, args,
         frequency: (frequency_for note: sender[:note], octave: sender[:octave]),
         duration: 1.seconds,
         fade_out: true
  end

  def frequency_buttons args
    [
      (button args,
              row: 4.0, col: 0, text: "300hz",
              frequency: 300,
              method_to_call: :play_sine_wave),
      (button args,
              row: 5.0, col: 0, text: "400hz",
              frequency: 400,
              method_to_call: :play_sine_wave),
      (button args,
              row: 6.0, col: 0, text: "500hz",
              frequency: 500,
              method_to_call: :play_sine_wave),
    ]
  end

  def sine_wave_note_buttons args
    [
      (button args,
              row: 1.5, col: 2, text: "Sine C4",
              note: :c, octave: 4, type: :sine, method_to_call: :play_note),
      (button args,
              row: 2.5, col: 2, text: "Sine D4",
              note: :d, octave: 4, type: :sine, method_to_call: :play_note),
      (button args,
              row: 3.5, col: 2, text: "Sine E4",
              note: :e, octave: 4, type: :sine, method_to_call: :play_note),
      (button args,
              row: 4.5, col: 2, text: "Sine F4",
              note: :f, octave: 4, type: :sine, method_to_call: :play_note),
      (button args,
              row: 5.5, col: 2, text: "Sine G4",
              note: :g, octave: 4, type: :sine, method_to_call: :play_note),
      (button args,
              row: 6.5, col: 2, text: "Sine A5",
              note: :a, octave: 5, type: :sine, method_to_call: :play_note),
      (button args,
              row: 7.5, col: 2, text: "Sine B5",
              note: :b, octave: 5, type: :sine, method_to_call: :play_note),
      (button args,
              row: 8.5, col: 2, text: "Sine C5",
              note: :c, octave: 5, type: :sine, method_to_call: :play_note),
    ]
  end

  def square_wave_note_buttons args
    [
      (button args,
              row: 1.5, col: 6, text: "Square C4",
              note: :c, octave: 4, type: :square, method_to_call: :play_note),
      (button args,
              row: 2.5, col: 6, text: "Square D4",
              note: :d, octave: 4, type: :square, method_to_call: :play_note),
      (button args,
              row: 3.5, col: 6, text: "Square E4",
              note: :e, octave: 4, type: :square, method_to_call: :play_note),
      (button args,
              row: 4.5, col: 6, text: "Square F4",
              note: :f, octave: 4, type: :square, method_to_call: :play_note),
      (button args,
              row: 5.5, col: 6, text: "Square G4",
              note: :g, octave: 4, type: :square, method_to_call: :play_note),
      (button args,
              row: 6.5, col: 6, text: "Square A5",
              note: :a, octave: 5, type: :square, method_to_call: :play_note),
      (button args,
              row: 7.5, col: 6, text: "Square B5",
              note: :b, octave: 5, type: :square, method_to_call: :play_note),
      (button args,
              row: 8.5, col: 6, text: "Square C5",
              note: :c, octave: 5, type: :square, method_to_call: :play_note),
    ]
  end
  def saw_tooth_wave_note_buttons args
    [
      (button args,
              row: 1.5, col: 8, text: "Saw C4",
              note: :c, octave: 4, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 2.5, col: 8, text: "Saw D4",
              note: :d, octave: 4, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 3.5, col: 8, text: "Saw E4",
              note: :e, octave: 4, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 4.5, col: 8, text: "Saw F4",
              note: :f, octave: 4, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 5.5, col: 8, text: "Saw G4",
              note: :g, octave: 4, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 6.5, col: 8, text: "Saw A5",
              note: :a, octave: 5, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 7.5, col: 8, text: "Saw B5",
              note: :b, octave: 5, type: :saw_tooth, method_to_call: :play_note),
      (button args,
              row: 8.5, col: 8, text: "Saw C5",
              note: :c, octave: 5, type: :saw_tooth, method_to_call: :play_note),
    ]
  end

  def triangle_wave_note_buttons args
    [
      (button args,
              row: 1.5, col: 10, text: "Triangle C4",
              note: :c, octave: 4, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 2.5, col: 10, text: "Triangle D4",
              note: :d, octave: 4, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 3.5, col: 10, text: "Triangle E4",
              note: :e, octave: 4, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 4.5, col: 10, text: "Triangle F4",
              note: :f, octave: 4, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 5.5, col: 10, text: "Triangle G4",
              note: :g, octave: 4, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 6.5, col: 10, text: "Triangle A5",
              note: :a, octave: 5, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 7.5, col: 10, text: "Triangle B5",
              note: :b, octave: 5, type: :triangle, method_to_call: :play_note),
      (button args,
              row: 8.5, col: 10, text: "Triangle C5",
              note: :c, octave: 5, type: :triangle, method_to_call: :play_note),
    ]
  end

  def bell_buttons args
    [
      (button args,
              row: 1.5, col: 4, text: "Bell C4",
              note: :c, octave: 4, type: :bell, method_to_call: :play_note),
      (button args,
              row: 2.5, col: 4, text: "Bell D4",
              note: :d, octave: 4, type: :bell, method_to_call: :play_note),
      (button args,
              row: 3.5, col: 4, text: "Bell E4",
              note: :e, octave: 4, type: :bell, method_to_call: :play_note),
      (button args,
              row: 4.5, col: 4, text: "Bell F4",
              note: :f, octave: 4, type: :bell, method_to_call: :play_note),
      (button args,
              row: 5.5, col: 4, text: "Bell G4",
              note: :g, octave: 4, type: :bell, method_to_call: :play_note),
      (button args,
              row: 6.5, col: 4, text: "Bell A5",
              note: :a, octave: 5, type: :bell, method_to_call: :play_note),
      (button args,
              row: 7.5, col: 4, text: "Bell B5",
              note: :b, octave: 5, type: :bell, method_to_call: :play_note),
      (button args,
              row: 8.5, col: 4, text: "Bell C5",
              note: :c, octave: 5, type: :bell, method_to_call: :play_note),
    ]
  end
end

begin # region: wave generation
  begin # sine wave
    def defaults_sine_wave_for
      { frequency: 440, sample_rate: 48000 }
    end

    def sine_wave_for opts = {}
      opts = defaults_sine_wave_for.merge opts
      frequency   = opts[:frequency]
      sample_rate = opts[:sample_rate]
      period_size = (sample_rate.fdiv frequency).ceil
      period_size.map_with_index do |i|
        Math::sin((2.0 * Math::PI) / (sample_rate.to_f / frequency.to_f) * i)
      end.to_a
    end

    def defaults_queue_sine_wave
      { frequency: 440, duration: 60, gain: 1.0, fade_out: false, queue_in: 0 }
    end

    def queue_sine_wave args, opts = {}
      opts        = defaults_queue_sine_wave.merge opts
      frequency   = opts[:frequency]
      sample_rate = 48000

      sine_wave = sine_wave_for frequency: frequency, sample_rate: sample_rate
      args.state.sine_waves[frequency] ||= sine_wave_for frequency: frequency, sample_rate: sample_rate

      proc = lambda do
        generate_audio_data args.state.sine_waves[frequency], sample_rate
      end

      audio_state = new_audio_state args, opts
      audio_state[:input] = [1, sample_rate, proc]
      queue_audio args, audio_state: audio_state, wave: sine_wave
    end
  end

  begin # region: square wave
    def defaults_square_wave_for
      { frequency: 440, sample_rate: 48000 }
    end

    def square_wave_for opts = {}
      opts = defaults_square_wave_for.merge opts
      sine_wave = sine_wave_for opts
      sine_wave.map do |v|
        if v >= 0
          1.0
        else
          -1.0
        end
      end.to_a
    end

    def defaults_queue_square_wave
      { frequency: 440, duration: 60, gain: 0.3, fade_out: false, queue_in: 0 }
    end

    def queue_square_wave args, opts = {}
      opts        = defaults_queue_square_wave.merge opts
      frequency   = opts[:frequency]
      sample_rate = 48000

      square_wave = square_wave_for frequency: frequency, sample_rate: sample_rate
      args.state.square_waves[frequency] ||= square_wave_for frequency: frequency, sample_rate: sample_rate

      proc = lambda do
        generate_audio_data args.state.square_waves[frequency], sample_rate
      end

      audio_state = new_audio_state args, opts
      audio_state[:input] = [1, sample_rate, proc]
      queue_audio args, audio_state: audio_state, wave: square_wave
    end
  end

  begin # region: saw tooth wave
    def defaults_saw_tooth_wave_for
      { frequency: 440, sample_rate: 48000 }
    end

    def saw_tooth_wave_for opts = {}
      opts = defaults_saw_tooth_wave_for.merge opts
      sine_wave = sine_wave_for opts
      period_size = sine_wave.length
      sine_wave.map_with_index do |v, i|
        (((i % period_size).fdiv period_size) * 2) - 1
      end
    end

    def defaults_queue_saw_tooth_wave
      { frequency: 440, duration: 60, gain: 0.3, fade_out: false, queue_in: 0 }
    end

    def queue_saw_tooth_wave args, opts = {}
      opts        = defaults_queue_saw_tooth_wave.merge opts
      frequency   = opts[:frequency]
      sample_rate = 48000

      saw_tooth_wave = saw_tooth_wave_for frequency: frequency, sample_rate: sample_rate
      args.state.saw_tooth_waves[frequency] ||= saw_tooth_wave_for frequency: frequency, sample_rate: sample_rate

      proc = lambda do
        generate_audio_data args.state.saw_tooth_waves[frequency], sample_rate
      end

      audio_state = new_audio_state args, opts
      audio_state[:input] = [1, sample_rate, proc]
      queue_audio args, audio_state: audio_state, wave: saw_tooth_wave
    end
  end

  begin # region: triangle wave
    def defaults_triangle_wave_for
      { frequency: 440, sample_rate: 48000 }
    end

    def triangle_wave_for opts = {}
      opts = defaults_saw_tooth_wave_for.merge opts
      sine_wave = sine_wave_for opts
      period_size = sine_wave.length
      sine_wave.map_with_index do |v, i|
        ratio = (i.fdiv period_size)
        if ratio <= 0.5
          (ratio * 4) - 1
        else
          ratio -= 0.5
          1 - (ratio * 4)
        end
      end
    end

    def defaults_queue_triangle_wave
      { frequency: 440, duration: 60, gain: 1.0, fade_out: false, queue_in: 0 }
    end

    def queue_triangle_wave args, opts = {}
      opts        = defaults_queue_triangle_wave.merge opts
      frequency   = opts[:frequency]
      sample_rate = 48000

      triangle_wave = triangle_wave_for frequency: frequency, sample_rate: sample_rate
      args.state.triangle_waves[frequency] ||= triangle_wave_for frequency: frequency, sample_rate: sample_rate

      proc = lambda do
        generate_audio_data args.state.triangle_waves[frequency], sample_rate
      end

      audio_state = new_audio_state args, opts
      audio_state[:input] = [1, sample_rate, proc]
      queue_audio args, audio_state: audio_state, wave: triangle_wave
    end
  end

  begin # region: bell
    def defaults_queue_bell
      { frequency: 440, duration: 1.seconds, queue_in: 0 }
    end

    def queue_bell args, opts = {}
      (bell_to_sine_waves (defaults_queue_bell.merge opts)).each { |b| queue_sine_wave args, b }
    end

    def bell_harmonics
      [
        { frequency_ratio: 0.5, duration_ratio: 1.00 },
        { frequency_ratio: 1.0, duration_ratio: 0.80 },
        { frequency_ratio: 2.0, duration_ratio: 0.60 },
        { frequency_ratio: 3.0, duration_ratio: 0.40 },
        { frequency_ratio: 4.2, duration_ratio: 0.25 },
        { frequency_ratio: 5.4, duration_ratio: 0.20 },
        { frequency_ratio: 6.8, duration_ratio: 0.15 }
      ]
    end

    def defaults_bell_to_sine_waves
      { frequency: 440, duration: 1.seconds, queue_in: 0 }
    end

    def bell_to_sine_waves opts = {}
      opts = defaults_bell_to_sine_waves.merge opts
      bell_harmonics.map do |b|
        {
          frequency: opts[:frequency] * b[:frequency_ratio],
          duration:  opts[:duration] * b[:duration_ratio],
          queue_in:  opts[:queue_in],
          gain:      (1.fdiv bell_harmonics.length),
          fade_out:  true
        }
      end
    end
  end

  begin # audio entity construction
    def generate_audio_data sine_wave, sample_rate
      sample_size = (sample_rate.fdiv (1000.fdiv 60)).ceil
      copy_count  = (sample_size.fdiv sine_wave.length).ceil
      sine_wave * copy_count
    end

    def defaults_new_audio_state
      { frequency: 440, duration: 60, gain: 1.0, fade_out: false, queue_in: 0 }
    end

    def new_audio_state args, opts = {}
      opts        = defaults_new_audio_state.merge opts
      decay_rate  = 0
      decay_rate  = 1.fdiv(opts[:duration]) * opts[:gain] if opts[:fade_out]
      frequency   = opts[:frequency]
      sample_rate = 48000

      {
        id:               (new_id! args),
        frequency:        frequency,
        sample_rate:      48000,
        stop_at:          args.tick_count + opts[:queue_in] + opts[:duration],
        gain:             opts[:gain].to_f,
        queue_at:         args.state.tick_count + opts[:queue_in],
        decay_rate:       decay_rate,
        pitch:            1.0,
        looping:          true,
        paused:           false
      }
    end

    def queue_audio args, opts = {}
      graph_wave args, opts[:wave], opts[:audio_state][:frequency]
      args.state.audio_queue << opts[:audio_state]
    end

    def new_id! args
      args.state.audio_id ||= 0
      args.state.audio_id  += 1
    end

    def graph_wave args, wave, frequency
      if args.state.tick_count != args.state.graphed_at
        args.outputs.static_lines.clear
        args.outputs.static_sprites.clear
      end

      wave = wave

      r, g, b = frequency.to_i % 85,
                frequency.to_i % 170,
                frequency.to_i % 255

      starting_rect = args.layout.rect(row: 5, col: 13)
      x_scale    = 10
      y_scale    = 100
      max_points = 25

      points = wave
      if wave.length > max_points
        resolution = wave.length.idiv max_points
        points = wave.find_all.with_index { |y, i| (i % resolution == 0) }
      end

      args.outputs.static_lines << points.map_with_index do |y, x|
        next_y = points[x + 1]

        if next_y
          {
            x:  starting_rect.x + (x * x_scale),
            y:  starting_rect.y + starting_rect.h.half + y_scale * y,
            x2: starting_rect.x + ((x + 1) * x_scale),
            y2: starting_rect.y + starting_rect.h.half + y_scale * next_y,
            r:  r,
            g:  g,
            b:  b
          }
        end
      end

      args.outputs.static_sprites << points.map_with_index do |y, x|
        {
          x:  (starting_rect.x + (x * x_scale)) - 2,
          y:  (starting_rect.y + starting_rect.h.half + y_scale * y) - 2,
          w:  4,
          h:  4,
          path: 'sprites/square-white.png',
          r: r,
          g: g,
          b: b
        }
      end

      args.state.graphed_at = args.state.tick_count
    end
  end

  begin # region: musical note mapping
    def defaults_frequency_for
      { note: :a, octave: 5, sharp:  false, flat:   false }
    end

    def frequency_for opts = {}
      opts = defaults_frequency_for.merge opts
      octave_offset_multiplier  = opts[:octave] - 5
      note = note_frequencies_octave_5[opts[:note]]
      if octave_offset_multiplier < 0
        note = note * 1 / (octave_offset_multiplier.abs + 1)
      elsif octave_offset_multiplier > 0
        note = note * (octave_offset_multiplier.abs + 1) / 1
      end
      note
    end

    def note_frequencies_octave_5
      {
        a: 440.0,
        a_sharp: 466.16, b_flat: 466.16,
        b: 493.88,
        c: 523.25,
        c_sharp: 554.37, d_flat: 587.33,
        d: 587.33,
        d_sharp: 622.25, e_flat: 659.25,
        e: 659.25,
        f: 698.25,
        f_sharp: 739.99, g_flat: 739.99,
        g: 783.99,
        g_sharp: 830.61, a_flat: 830.61
      }
    end
  end
end

$gtk.reset

    Advanced Rendering link

    Labels With Wrapped Text - main.rb link

    # ./samples/07_advanced_rendering/00_labels_with_wrapped_text/app/main.rb
def tick args
  # defaults
  args.state.scroll_location  ||= 0
  args.state.textbox.messages ||= []
  args.state.textbox.scroll   ||= 0

  # render
  args.outputs.background_color = [0, 0, 0, 255]
  render_messages args
  render_instructions args

  # inputs
  if args.inputs.keyboard.key_down.one
    queue_message args, "Hello there neighbour! my name is mark, how is your day today?"
  end

  if args.inputs.keyboard.key_down.two
    queue_message args, "I'm doing great sir, actually I'm having a picnic today"
  end

  if args.inputs.keyboard.key_down.three
    queue_message args, "Well that sounds wonderful!"
  end

  if args.inputs.keyboard.key_down.home
    args.state.scroll_location = 1
  end

  if args.inputs.keyboard.key_down.delete
    clear_message_queue args
  end
end

def queue_message args, msg
  args.state.textbox.messages.concat msg.wrapped_lines 50
end

def clear_message_queue args
  args.state.textbox.messages = nil
  args.state.textbox.scroll = 0
end

def render_messages args
  args.outputs[:textbox].transient!
  args.outputs[:textbox].w = 400
  args.outputs[:textbox].h = 720

  args.outputs.primitives << args.state.textbox.messages.each_with_index.map do |s, idx|
    {
      x: 0,
      y: 20 * (args.state.textbox.messages.size - idx) + args.state.textbox.scroll * 20,
      text: s,
      size_enum: -3,
      alignment_enum: 0,
      r: 255, g:255, b: 255, a: 255
    }
  end

  args.outputs[:textbox].labels << args.state.textbox.messages.each_with_index.map do |s, idx|
    {
      x: 0,
      y: 20 * (args.state.textbox.messages.size - idx) + args.state.textbox.scroll * 20,
      text: s,
      size_enum: -3,
      alignment_enum: 0,
      r: 255, g:255, b: 255, a: 255
    }
  end

  args.outputs[:textbox].borders << [0, 0, args.outputs[:textbox].w, 720]

  args.state.textbox.scroll += args.inputs.mouse.wheel.y unless args.inputs.mouse.wheel.nil?

  if args.state.scroll_location > 0
    args.state.textbox.scroll = 0
    args.state.scroll_location = 0
  end

  args.outputs.sprites << [900, 0, args.outputs[:textbox].w, 720, :textbox]
end

def render_instructions args
  args.outputs.labels << [30,
                          30.from_top,
                          "press 1, 2, 3 to display messages, MOUSE WHEEL to scroll, HOME to go to top, BACKSPACE to delete.",
                          0, 255, 255]

  args.outputs.primitives << [0, 55.from_top, 1280, 30, :pixel, 0, 255, 0, 0, 0].sprite
end

    Rotating Label - main.rb link

    # ./samples/07_advanced_rendering/00_rotating_label/app/main.rb
def tick args
  # set the render target width and height to match the label
  args.outputs[:scene].transient!
  args.outputs[:scene].w = 220
  args.outputs[:scene].h = 30


  # make the background transparent
  args.outputs[:scene].background_color = [255, 255, 255, 0]

  # set the blendmode of the label to 0 (no blending)
  # center it inside of the scene
  # set the vertical_alignment_enum to 1 (center)
  args.outputs[:scene].labels  << { x: 0,
                                    y: 15,
                                    text: "label in render target",
                                    blendmode_enum: 0,
                                    vertical_alignment_enum: 1 }

  # add a border to the render target
  args.outputs[:scene].borders << { x: 0,
                                    y: 0,
                                    w: args.outputs[:scene].w,
                                    h: args.outputs[:scene].h }

  # add the rendertarget to the main output as a sprite
  args.outputs.sprites << { x: 640 - args.outputs[:scene].w.half,
                            y: 360 - args.outputs[:scene].h.half,
                            w: args.outputs[:scene].w,
                            h: args.outputs[:scene].h,
                            angle: args.state.tick_count,
                            path: :scene }
end

    Render Targets Clip Area - main.rb link

    # ./samples/07_advanced_rendering/01_render_targets_clip_area/app/main.rb
def tick args
  # define your state
  args.state.player ||= { x: 0, y: 0, w: 300, h: 300, path: "sprites/square/blue.png" }

  # controller input for player
  args.state.player.x += args.inputs.left_right * 5
  args.state.player.y += args.inputs.up_down * 5

  # create a render target that holds the
  # full view that you want to render

  # make the background transparent
  args.outputs[:clipped_area].background_color = [0, 0, 0, 0]

  # set the w/h to match the screen
  args.outputs[:clipped_area].w = 1280
  args.outputs[:clipped_area].h = 720

  # mark it as transient so that the render target
  # isn't cached (since we are going to be changing it every frame)
  args.outputs[:clipped_area].transient!

  # render the player in the render target
  args.outputs[:clipped_area].sprites << args.state.player

  # render the player and clip area as borders to
  # keep track of where everything is at regardless of clip mode
  args.outputs.borders << args.state.player
  args.outputs.borders << { x: 540, y: 460, w: 200, h: 200 }

  # render the render target, but only the clipped area
  args.outputs.sprites << {
    # where to render the render target
    x: 540,
    y: 460,
    w: 200,
    h: 200,
    # what part of the render target to render
    source_x: 540,
    source_y: 460,
    source_w: 200,
    source_h: 200,
    # path of render target to render
    path: :clipped_area
  }

  # mini map
  args.outputs.borders << { x: 1280 - 160, y: 0, w: 160, h: 90 }
  args.outputs.sprites << { x: 1280 - 160, y: 0, w: 160, h: 90, path: :clipped_area }
end

$gtk.reset

    Render Targets Combining Sprites - main.rb link

    # ./samples/07_advanced_rendering/01_render_targets_combining_sprites/app/main.rb
# sample app shows how to use a render target to
# create a combined sprite
def tick args
  create_combined_sprite args

  # render the combined sprite
  # using its name :two_squares
  # have it move across the screen and rotate
  args.outputs.sprites << { x: args.state.tick_count % 1280,
                            y: 0,
                            w: 80,
                            h: 80,
                            angle: args.state.tick_count,
                            path: :two_squares }
end

def create_combined_sprite args
  # NOTE: you can have the construction of the combined
  #       sprite to happen every tick or only once (if the
  #       combined sprite never changes).
  #
  # if the combined sprite never changes, comment out the line
  # below to only construct it on the first frame and then
  # use the cached texture
  # return if args.state.tick_count != 0 # <---- guard clause to only construct on first frame and cache

  # define the dimensions of the combined sprite
  # the name of the combined sprite is :two_squares
  args.outputs[:two_squares].transient!
  args.outputs[:two_squares].w = 80
  args.outputs[:two_squares].h = 80

  # put a blue sprite within the combined sprite
  # who's width is "thin"
  args.outputs[:two_squares].sprites << {
    x: 40 - 10,
    y: 0,
    w: 20,
    h: 80,
    path: 'sprites/square/blue.png'
  }

  # put a red sprite within the combined sprite
  # who's height is "thin"
  args.outputs[:two_squares].sprites << {
    x: 0,
    y: 40 - 10,
    w: 80,
    h: 20,
    path: 'sprites/square/red.png'
  }
end

    Simple Render Targets - main.rb link

    # ./samples/07_advanced_rendering/01_simple_render_targets/app/main.rb
def tick args
  # args.outputs.render_targets are really really powerful.
  # They essentially allow you to create a sprite programmatically and cache the result.

  # Create a render_target of a :block and a :gradient on tick zero.
  if args.state.tick_count == 0
    args.render_target(:block).solids << [0, 0, 1280, 100]

    # The gradient is actually just a collection of black solids with increasing
    # opacities.
    args.render_target(:gradient).solids << 90.map_with_index do |x|
      50.map_with_index do |y|
        [x * 15, y * 15, 15, 15, 0, 0, 0, (x * 3).fdiv(255) * 255]
      end
    end
  end

  # Take the :block render_target and present it horizontally centered.
  # Use a subsection of the render_targetd specified by source_x,
  # source_y, source_w, source_h.
  args.outputs.sprites << { x: 0,
                            y: 310,
                            w: 1280,
                            h: 100,
                            path: :block,
                            source_x: 0,
                            source_y: 0,
                            source_w: 1280,
                            source_h: 100 }

  # After rendering :block, render gradient on top of :block.
  args.outputs.sprites << [0, 0, 1280, 720, :gradient]

  args.outputs.labels  << [1270, 710, args.gtk.current_framerate, 0, 2, 255, 255, 255]
  tick_instructions args, "Sample app shows how to use render_targets (programmatically create cached sprites)."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

$gtk.reset

    Coordinate Systems And Render Targets - main.rb link

    # ./samples/07_advanced_rendering/02_coordinate_systems_and_render_targets/app/main.rb
def tick args
  # every 4.5 seconds, swap between origin_bottom_left and origin_center
  args.state.origin_state ||= :bottom_left

  if args.state.tick_count.zmod? 270
    args.state.origin_state = if args.state.origin_state == :bottom_left
                                :center
                              else
                                :bottom_left
                              end
  end

  if args.state.origin_state == :bottom_left
    tick_origin_bottom_left args
  else
    tick_origin_center args
  end
end

def tick_origin_center args
  # set the coordinate system to origin_center
  args.grid.origin_center!
  args.outputs.labels <<  { x: 0, y: 100, text: "args.grid.origin_center! with sprite inside of a render target, centered at 0, 0", vertical_alignment_enum: 1, alignment_enum: 1 }

  # create a render target with a sprint in the center assuming the origin is center screen
  args.outputs[:scene].transient!
  args.outputs[:scene].sprites << { x: -50, y: -50, w: 100, h: 100, path: 'sprites/square/blue.png' }
  args.outputs.sprites << { x: -640, y: -360, w: 1280, h: 720, path: :scene }
end

def tick_origin_bottom_left args
  args.grid.origin_bottom_left!
  args.outputs.labels <<  { x: 640, y: 360 + 100, text: "args.grid.origin_bottom_left! with sprite inside of a render target, centered at 640, 360", vertical_alignment_enum: 1, alignment_enum: 1 }

  # create a render target with a sprint in the center assuming the origin is bottom left
  args.outputs[:scene].transient!
  args.outputs[:scene].sprites << { x: 640 - 50, y: 360 - 50, w: 100, h: 100, path: 'sprites/square/blue.png' }
  args.outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :scene }
end

    Render Targets Thick Lines - main.rb link

    # ./samples/07_advanced_rendering/02_render_targets_thick_lines/app/main.rb
# Sample app shows how you can use render targets to create arbitrary shapes like a thicker line
def tick args
  args.state.line_cache ||= {}
  args.outputs.primitives << thick_line(args,
                                        args.state.line_cache,
                                        x: 0, y: 0, x2: 640, y2: 360, thickness: 3).merge(r: 0, g: 0, b: 0)
end

def thick_line args, cache, line
  line_length = Math.sqrt((line.x2 - line.x)**2 + (line.y2 - line.y)**2)
  name = "line-sprite-#{line_length}-#{line.thickness}"
  cached_line = cache[name]
  line_angle = Math.atan2(line.y2 - line.y1, line.x2 - line.x1) * 180 / Math::PI
  if cached_line
    perpendicular_angle = (line_angle + 90) % 360
    return cached_line.sprite.merge(x: line.x - perpendicular_angle.vector_x * (line.thickness / 2),
                                    y: line.y - perpendicular_angle.vector_y * (line.thickness / 2),
                                    angle: line_angle)
  end

  cache[name] = {
    line: line,
    thickness: line.thickness,
    sprite: {
      w: line_length,
      h: line.thickness,
      path: name,
      angle_anchor_x: 0,
      angle_anchor_y: 0
    }
  }

  args.outputs[name].w = line_length
  args.outputs[name].h = line.thickness
  args.outputs[name].solids << { x: 0, y: 0, w: line_length, h: line.thickness, r: 255, g: 255, b: 255 }
  return thick_line args, cache, line
end

    Render Targets With Tile Manipulation - main.rb link

    # ./samples/07_advanced_rendering/02_render_targets_with_tile_manipulation/app/main.rb
# This sample is meant to show you how to do that dripping transition thing
#  at the start of the original Doom. Most of this file is here to animate
#  a scene to wipe away; the actual wipe effect is in the last 20 lines or
#  so.

$gtk.reset   # reset all game state if reloaded.

def circle_of_blocks pass, xoffset, yoffset, angleoffset, blocksize, distance
  numblocks = 10

  for i in 1..numblocks do
    angle = ((360 / numblocks) * i) + angleoffset
    radians = angle * (Math::PI / 180)
    x = (xoffset + (distance * Math.cos(radians))).round
    y = (yoffset + (distance * Math.sin(radians))).round
    pass.solids << [ x, y, blocksize, blocksize, 255, 255, 0 ]
  end
end

def draw_scene args, pass
  pass.solids << [0, 360, 1280, 360, 0, 0, 200]
  pass.solids << [0, 0, 1280, 360, 0, 127, 0]

  blocksize = 100
  angleoffset = args.state.tick_count * 2.5
  centerx = (1280 - blocksize) / 2
  centery = (720 - blocksize) / 2

  circle_of_blocks pass, centerx, centery, angleoffset, blocksize * 2, 500
  circle_of_blocks pass, centerx, centery, angleoffset, blocksize, 325
  circle_of_blocks pass, centerx, centery, angleoffset, blocksize / 2, 200
  circle_of_blocks pass, centerx, centery, angleoffset, blocksize / 4, 100
end

def tick args
  segments = 160

  # On the first tick, initialize some stuff.
  if !args.state.yoffsets
    args.state.baseyoff = 0
    args.state.yoffsets = []
    for i in 0..segments do
      args.state.yoffsets << rand * 100
    end
  end

  # Just draw some random stuff for a few seconds.
  args.state.static_debounce ||= 60 * 2.5
  if args.state.static_debounce > 0
    last_frame = args.state.static_debounce == 1
    target = last_frame ? args.render_target(:last_frame) : args.outputs
    draw_scene args, target
    args.state.static_debounce -= 1
    return unless last_frame
  end

  # build up the wipe...

  # this is the thing we're wiping to.
  args.outputs.sprites << [ 0, 0, 1280, 720, 'dragonruby.png' ]

  return if (args.state.baseyoff > (1280 + 100))  # stop when done sliding

  segmentw = 1280 / segments

  x = 0
  for i in 0..segments do
    yoffset = 0
    if args.state.yoffsets[i] < args.state.baseyoff
      yoffset = args.state.baseyoff - args.state.yoffsets[i]
    end

    # (720 - yoffset) flips the coordinate system, (- 720) adjusts for the height of the segment.
    args.outputs.sprites << [ x, (720 - yoffset) - 720, segmentw, 720, 'last_frame', 0, 255, 255, 255, 255, x, 0, segmentw, 720 ]
    x += segmentw
  end

  args.state.baseyoff += 4

  tick_instructions args, "Sample app shows an advanced usage of render_target."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Render Target Viewports - main.rb link

    # ./samples/07_advanced_rendering/03_render_target_viewports/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   For example, if we want to create a new button, we would declare it as a new entity and
   then define its properties. (Remember, you can use state to define ANY property and it will
   be retained across frames.)

   If you have a solar system and you're creating args.state.sun and setting its image path to an
   image in the sprites folder, you would do the following:
   (See samples/99_sample_nddnug_workshop for more details.)

   args.state.sun ||= args.state.new_entity(:sun) do |s|
   s.path = 'sprites/sun.png'
   end

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

   For example, if we have a variable
   name = "Ruby"
   then the line
   puts "How are you, #{name}?"
   would print "How are you, Ruby?" to the console.
   (Remember, string interpolation only works with double quotes!)

 - Ternary operator (?): Similar to if statement; first evalulates whether a statement is
   true or false, and then executes a command depending on that result.
   For example, if we had a variable
   grade = 75
   and used the ternary operator in the command
   pass_or_fail = grade > 65 ? "pass" : "fail"
   then the value of pass_or_fail would be "pass" since grade's value was greater than 65.

 Reminders:

 - args.grid.(left|right|top|bottom): Pixel value for the boundaries of the virtual
   720 p screen (Dragon Ruby Game Toolkits's virtual resolution is always 1280x720).

 - Numeric#shift_(left|right|up|down): Shifts the Numeric in the correct direction
   by adding or subracting.

 - ARRAY#inside_rect?: An array with at least two values is considered a point. An array
   with at least four values is considered a rect. The inside_rect? function returns true
   or false depending on if the point is inside the rect.

 - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.

 - args.inputs.mouse.click: This property will be set if the mouse was clicked.
   For more information about the mouse, go to mygame/documentation/07-mouse.md.

 - args.inputs.keyboard.key_up.KEY: The value of the properties will be set
   to the frame  that the key_up event occurred (the frame correlates
   to args.state.tick_count).
   For more information about the keyboard, go to mygame/documentation/06-keyboard.md.

 - args.state.labels:
   The parameters for a label are
   1. the position (x, y)
   2. the text
   3. the size
   4. the alignment
   5. the color (red, green, and blue saturations)
   6. the alpha (or transparency)
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.state.lines:
   The parameters for a line are
   1. the starting position (x, y)
   2. the ending position (x2, y2)
   3. the color (red, green, and blue saturations)
   4. the alpha (or transparency)
   For more information about lines, go to mygame/documentation/04-lines.md.

 - args.state.solids (and args.state.borders):
   The parameters for a solid (or border) are
   1. the position (x, y)
   2. the width (w)
   3. the height (h)
   4. the color (r, g, b)
   5. the alpha (or transparency)
   For more information about solids and borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.state.sprites:
   The parameters for a sprite are
   1. the position (x, y)
   2. the width (w)
   3. the height (h)
   4. the image path
   5. the angle
   6. the alpha (or transparency)
   For more information about sprites, go to mygame/documentation/05-sprites.md.
=end

# This sample app shows different objects that can be used when making games, such as labels,
# lines, sprites, solids, buttons, etc. Each demo section shows how these objects can be used.

# Also note that state.tick_count refers to the passage of time, or current frame.

class TechDemo
  attr_accessor :inputs, :state, :outputs, :grid, :args

  # Calls all methods necessary for the app to run properly.
  def tick
    labels_tech_demo
    lines_tech_demo
    solids_tech_demo
    borders_tech_demo
    sprites_tech_demo
    keyboards_tech_demo
    controller_tech_demo
    mouse_tech_demo
    point_to_rect_tech_demo
    rect_to_rect_tech_demo
    button_tech_demo
    export_game_state_demo
    window_state_demo
    render_seperators
  end

  # Shows output of different kinds of labels on the screen
  def labels_tech_demo
    outputs.labels << [grid.left.shift_right(5), grid.top.shift_down(5), "This is a label located at the top left."]
    outputs.labels << [grid.left.shift_right(5), grid.bottom.shift_up(30), "This is a label located at the bottom left."]
    outputs.labels << [ 5, 690, "Labels (x, y, text, size, align, r, g, b, a)"]
    outputs.labels << [ 5, 660, "Smaller label.",  -2]
    outputs.labels << [ 5, 630, "Small label.",    -1]
    outputs.labels << [ 5, 600, "Medium label.",    0]
    outputs.labels << [ 5, 570, "Large label.",     1]
    outputs.labels << [ 5, 540, "Larger label.",    2]
    outputs.labels << [300, 660, "Left aligned.",    0, 2]
    outputs.labels << [300, 640, "Center aligned.",  0, 1]
    outputs.labels << [300, 620, "Right aligned.",   0, 0]
    outputs.labels << [175, 595, "Red Label.",       0, 0, 255,   0,   0]
    outputs.labels << [175, 575, "Green Label.",     0, 0,   0, 255,   0]
    outputs.labels << [175, 555, "Blue Label.",      0, 0,   0,   0, 255]
    outputs.labels << [175, 535, "Faded Label.",     0, 0,   0,   0,   0, 128]
  end

  # Shows output of lines on the screen
  def lines_tech_demo
    outputs.labels << [5, 500, "Lines (x, y, x2, y2, r, g, b, a)"]
    outputs.lines  << [5, 450, 100, 450]
    outputs.lines  << [5, 430, 300, 430]
    outputs.lines  << [5, 410, 300, 410, state.tick_count % 255, 0, 0, 255] # red saturation changes
    outputs.lines  << [5, 390 - state.tick_count % 25, 300, 390, 0, 0, 0, 255] # y position changes
    outputs.lines  << [5 + state.tick_count % 200, 360, 300, 360, 0, 0, 0, 255] # x position changes
  end

  # Shows output of different kinds of solids on the screen
  def solids_tech_demo
    outputs.labels << [  5, 350, "Solids (x, y, w, h, r, g, b, a)"]
    outputs.solids << [ 10, 270, 50, 50]
    outputs.solids << [ 70, 270, 50, 50, 0, 0, 0]
    outputs.solids << [130, 270, 50, 50, 255, 0, 0]
    outputs.solids << [190, 270, 50, 50, 255, 0, 0, 128]
    outputs.solids << [250, 270, 50, 50, 0, 0, 0, 128 + state.tick_count % 128] # transparency changes
  end

  # Shows output of different kinds of borders on the screen
  # The parameters for a border are the same as the parameters for a solid
  def borders_tech_demo
    outputs.labels <<  [  5, 260, "Borders (x, y, w, h, r, g, b, a)"]
    outputs.borders << [ 10, 180, 50, 50]
    outputs.borders << [ 70, 180, 50, 50, 0, 0, 0]
    outputs.borders << [130, 180, 50, 50, 255, 0, 0]
    outputs.borders << [190, 180, 50, 50, 255, 0, 0, 128]
    outputs.borders << [250, 180, 50, 50, 0, 0, 0, 128 + state.tick_count % 128] # transparency changes
  end

  # Shows output of different kinds of sprites on the screen
  def sprites_tech_demo
    outputs.labels <<  [   5, 170, "Sprites (x, y, w, h, path, angle, a)"]
    outputs.sprites << [  10, 40, 128, 101, 'dragonruby.png']
    outputs.sprites << [ 150, 40, 128, 101, 'dragonruby.png', state.tick_count % 360] # angle changes
    outputs.sprites << [ 300, 40, 128, 101, 'dragonruby.png', 0, state.tick_count % 255] # transparency changes
  end

  # Holds size, alignment, color (black), and alpha (transparency) parameters
  # Using small_font as a parameter accounts for all remaining parameters
  # so they don't have to be repeatedly typed
  def small_font
    [-2, 0, 0, 0, 0, 255]
  end

  # Sets position of each row
  # Converts given row value to pixels that DragonRuby understands
  def row_to_px row_number

    # Row 0 starts 5 units below the top of the grid.
    # Each row afterward is 20 units lower.
    grid.top.shift_down(5).shift_down(20 * row_number)
  end

  # Uses labels to output current game time (passage of time), and whether or not "h" was pressed
  # If "h" is pressed, the frame is output when the key_up event occurred
  def keyboards_tech_demo
    outputs.labels << [460, row_to_px(0), "Current game time: #{state.tick_count}", small_font]
    outputs.labels << [460, row_to_px(2), "Keyboard input: inputs.keyboard.key_up.h", small_font]
    outputs.labels << [460, row_to_px(3), "Press \"h\" on the keyboard.", small_font]

    if inputs.keyboard.key_up.h # if "h" key_up event occurs
      state.h_pressed_at = state.tick_count # frame it occurred is stored
    end

    # h_pressed_at is initially set to false, and changes once the user presses the "h" key.
    state.h_pressed_at ||= false

    if state.h_pressed_at # if h is pressed (pressed_at has a frame number and is no longer false)
      outputs.labels << [460, row_to_px(4), "\"h\" was pressed at time: #{state.h_pressed_at}", small_font]
    else # otherwise, label says "h" was never pressed
      outputs.labels << [460, row_to_px(4), "\"h\" has never been pressed.", small_font]
    end

    # border around keyboard input demo section
    outputs.borders << [455, row_to_px(5), 360, row_to_px(2).shift_up(5) - row_to_px(5)]
  end

  # Sets definition for a small label
  # Makes it easier to position labels in respect to the position of other labels
  def small_label x, row, message
    [x, row_to_px(row), message, small_font]
  end

  # Uses small labels to show whether the "a" button on the controller is down, held, or up.
  # y value of each small label is set by calling the row_to_px method
  def controller_tech_demo
    x = 460
    outputs.labels << small_label(x, 6, "Controller one input: inputs.controller_one")
    outputs.labels << small_label(x, 7, "Current state of the \"a\" button.")
    outputs.labels << small_label(x, 8, "Check console window for more info.")

    if inputs.controller_one.key_down.a # if "a" is in "down" state
      outputs.labels << small_label(x, 9, "\"a\" button down: #{inputs.controller_one.key_down.a}")
      puts "\"a\" button down at #{inputs.controller_one.key_down.a}" # prints frame the event occurred
    elsif inputs.controller_one.key_held.a # if "a" is held down
      outputs.labels << small_label(x, 9, "\"a\" button held: #{inputs.controller_one.key_held.a}")
    elsif inputs.controller_one.key_up.a # if "a" is in up state
      outputs.labels << small_label(x, 9, "\"a\" button up: #{inputs.controller_one.key_up.a}")
      puts "\"a\" key up at #{inputs.controller_one.key_up.a}"
    else # if no event has occurred
      outputs.labels << small_label(x, 9, "\"a\" button state is nil.")
    end

    # border around controller input demo section
    outputs.borders << [455, row_to_px(10), 360, row_to_px(6).shift_up(5) - row_to_px(10)]
  end

  # Outputs when the mouse was clicked, as well as the coordinates on the screen
  # of where the click occurred
  def mouse_tech_demo
    x = 460

    outputs.labels << small_label(x, 11, "Mouse input: inputs.mouse")

    if inputs.mouse.click # if click has a value and is not nil
      state.last_mouse_click = inputs.mouse.click # coordinates of click are stored
    end

    if state.last_mouse_click # if mouse is clicked (has coordinates as value)
      # outputs the time (frame) the click occurred, as well as how many frames have passed since the event
      outputs.labels << small_label(x, 12, "Mouse click happened at: #{state.last_mouse_click.created_at}, #{state.last_mouse_click.created_at_elapsed}")
      # outputs coordinates of click
      outputs.labels << small_label(x, 13, "Mouse click location: #{state.last_mouse_click.point.x}, #{state.last_mouse_click.point.y}")
    else # otherwise if the mouse has not been clicked
      outputs.labels << small_label(x, 12, "Mouse click has not occurred yet.")
      outputs.labels << small_label(x, 13, "Please click mouse.")
    end
  end

  # Outputs whether a mouse click occurred inside or outside of a box
  def point_to_rect_tech_demo
    x = 460

    outputs.labels << small_label(x, 15, "Click inside the blue box maybe ---->")

    box = [765, 370, 50, 50, 0, 0, 170] # blue box
    outputs.borders << box

    if state.last_mouse_click # if the mouse was clicked
      if state.last_mouse_click.point.inside_rect? box # if mouse clicked inside box
        outputs.labels << small_label(x, 16, "Mouse click happened inside the box.")
      else # otherwise, if mouse was clicked outside the box
        outputs.labels << small_label(x, 16, "Mouse click happened outside the box.")
      end
    else # otherwise, if was not clicked at all
      outputs.labels << small_label(x, 16, "Mouse click has not occurred yet.") # output if the mouse was not clicked
    end

    # border around mouse input demo section
    outputs.borders << [455, row_to_px(14), 360, row_to_px(11).shift_up(5) - row_to_px(14)]
  end

  # Outputs a red box onto the screen. A mouse click from the user inside of the red box will output
  # a smaller box. If two small boxes are inside of the red box, it will be determined whether or not
  # they intersect.
  def rect_to_rect_tech_demo
    x = 460

    outputs.labels << small_label(x, 17.5, "Click inside the red box below.") # label with instructions
    red_box = [460, 250, 355, 90, 170, 0, 0] # definition of the red box
    outputs.borders << red_box # output as a border (not filled in)

    # If the mouse is clicked inside the red box, two collision boxes are created.
    if inputs.mouse.click
      if inputs.mouse.click.point.inside_rect? red_box
        if !state.box_collision_one # if the collision_one box does not yet have a definition
          # Subtracts 25 from the x and y positions of the click point in order to make the click point the center of the box.
          # You can try deleting the subtraction to see how it impacts the box placement.
          state.box_collision_one = [inputs.mouse.click.point.x - 25, inputs.mouse.click.point.y - 25, 50, 50, 180, 0,   0, 180]  # sets definition
        elsif !state.box_collision_two # if collision_two does not yet have a definition
          state.box_collision_two = [inputs.mouse.click.point.x - 25, inputs.mouse.click.point.y - 25, 50, 50,   0, 0, 180, 180] # sets definition
        else
          state.box_collision_one = nil # both boxes are empty
          state.box_collision_two = nil
        end
      end
    end

    # If collision boxes exist, they are output onto screen inside the red box as solids
    if state.box_collision_one
      outputs.solids << state.box_collision_one
    end

    if state.box_collision_two
      outputs.solids << state.box_collision_two
    end

    # Outputs whether or not the two collision boxes intersect.
    if state.box_collision_one && state.box_collision_two # if both collision_boxes are defined (and not nil or empty)
      if state.box_collision_one.intersect_rect? state.box_collision_two # if the two boxes intersect
        outputs.labels << small_label(x, 23.5, 'The boxes intersect.')
      else # otherwise, if the two boxes do not intersect
        outputs.labels << small_label(x, 23.5, 'The boxes do not intersect.')
      end
    else
      outputs.labels << small_label(x, 23.5, '--') # if the two boxes are not defined (are nil or empty), this label is output
    end
  end

  # Creates a button and outputs it onto the screen using labels and borders.
  # If the button is clicked, the color changes to make it look faded.
  def button_tech_demo
    x, y, w, h = 460, 160, 300, 50
    state.button        ||= state.new_entity(:button_with_fade)

    # Adds w.half to x and h.half + 10 to y in order to display the text inside the button's borders.
    state.button.label  ||= [x + w.half, y + h.half + 10, "click me and watch me fade", 0, 1]
    state.button.border ||= [x, y, w, h]

    if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.button.border) # if mouse is clicked, and clicked inside button's border
      state.button.clicked_at = inputs.mouse.click.created_at # stores the time the click occurred
    end

    outputs.labels << state.button.label
    outputs.borders << state.button.border

    if state.button.clicked_at # if button was clicked (variable has a value and is not nil)

      # The appearance of the button changes for 0.25 seconds after the time the button is clicked at.
      # The color changes (rgb is set to 0, 180, 80) and the transparency gradually changes.
      # Change 0.25 to 1.25 and notice that the transparency takes longer to return to normal.
      outputs.solids << [x, y, w, h, 0, 180, 80, 255 * state.button.clicked_at.ease(0.25.seconds, :flip)]
    end
  end

  # Creates a new button by declaring it as a new entity, and sets values.
  def new_button_prefab x, y, message
    w, h = 300, 50
    button        = state.new_entity(:button_with_fade)
    button.label  = [x + w.half, y + h.half + 10, message, 0, 1] # '+ 10' keeps label's text within button's borders
    button.border = [x, y, w, h] # sets border definition
    button
  end

  # If the mouse has been clicked and the click's location is inside of the button's border, that means
  # that the button has been clicked. This method returns a boolean value.
  def button_clicked? button
    inputs.mouse.click && inputs.mouse.click.point.inside_rect?(button.border)
  end

  # Determines if button was clicked, and changes its appearance if it is clicked
  def tick_button_prefab button
    outputs.labels << button.label # outputs button's label and border
    outputs.borders << button.border

    if button_clicked? button # if button is clicked
      button.clicked_at = inputs.mouse.click.created_at # stores the time that the button was clicked
    end

    if button.clicked_at # if clicked_at has a frame value and is not nil
      # button is output; color changes and transparency changes for 0.25 seconds after click occurs
      outputs.solids << [button.border.x, button.border.y, button.border.w, button.border.h,
                         0, 180, 80, 255 * button.clicked_at.ease(0.25.seconds, :flip)] # transparency changes for 0.25 seconds
    end
  end

  # Exports the app's game state if the export button is clicked.
  def export_game_state_demo
    state.export_game_state_button ||= new_button_prefab(460, 100, "click to export app state")
    tick_button_prefab(state.export_game_state_button) # calls method to output button
    if button_clicked? state.export_game_state_button # if the export button is clicked
      args.gtk.export! "Exported from clicking the export button in the tech demo." # the export occurs
    end
  end

  # The mouse and keyboard focus are set to "yes" when the Dragonruby window is the active window.
  def window_state_demo
    m = $gtk.args.inputs.mouse.has_focus ? 'Y' : 'N' # ternary operator (similar to if statement)
    k = $gtk.args.inputs.keyboard.has_focus ? 'Y' : 'N'
    outputs.labels << [460, 20, "mouse focus: #{m}   keyboard focus: #{k}", small_font]
  end

  #Sets values for the horizontal separator (divides demo sections)
  def horizontal_seperator y, x, x2
    [x, y, x2, y, 150, 150, 150]
  end

  #Sets the values for the vertical separator (divides demo sections)
  def vertical_seperator x, y, y2
    [x, y, x, y2, 150, 150, 150]
  end

  # Outputs vertical and horizontal separators onto the screen to separate each demo section.
  def render_seperators
    outputs.lines << horizontal_seperator(505, grid.left, 445)
    outputs.lines << horizontal_seperator(353, grid.left, 445)
    outputs.lines << horizontal_seperator(264, grid.left, 445)
    outputs.lines << horizontal_seperator(174, grid.left, 445)

    outputs.lines << vertical_seperator(445, grid.top, grid.bottom)

    outputs.lines << horizontal_seperator(690, 445, 820)
    outputs.lines << horizontal_seperator(426, 445, 820)

    outputs.lines << vertical_seperator(820, grid.top, grid.bottom)
  end
end

$tech_demo = TechDemo.new

def tick args
  $tech_demo.inputs = args.inputs
  $tech_demo.state = args.state
  $tech_demo.grid = args.grid
  $tech_demo.args = args
  $tech_demo.outputs = args.render_target(:mini_map)
  $tech_demo.outputs.transient = true
  $tech_demo.tick
  args.outputs.labels  << [830, 715, "Render target:", [-2, 0, 0, 0, 0, 255]]
  args.outputs.sprites << [0, 0, 1280, 720, :mini_map]
  args.outputs.sprites << [830, 300, 675, 379, :mini_map]
  tick_instructions args, "Sample app shows all the rendering apis available."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

    Render Primitive Hierarchies - main.rb link

    # ./samples/07_advanced_rendering/04_render_primitive_hierarchies/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Nested array: An array whose individual elements are also arrays; useful for
   storing groups of similar data.  Also called multidimensional arrays.

   In this sample app, we see nested arrays being used in object definitions.
   Notice the parameters for solids, listed below. Parameters 1-3 set the
   definition for the rect, and parameter 4 sets the definition of the color.

   Instead of having a solid definition that looks like this,
   [X, Y, W, H, R, G, B]
   we can separate it into two separate array definitions in one, like this
   [[X, Y, W, H], [R, G, B]]
   and both options work fine in defining our solid (or any object).

 - Collections: Lists of data; useful for organizing large amounts of data.
   One element of a collection could be an array (which itself contains many elements).
   For example, a collection that stores two solid objects would look like this:
   [
    [100, 100, 50, 50, 0, 0, 0],
    [100, 150, 50, 50, 255, 255, 255]
   ]
   If this collection was added to args.outputs.solids, two solids would be output
   next to each other, one black and one white.
   Nested arrays can be used in collections, as you will see in this sample app.

 Reminders:

 - args.outputs.solids: An array. The values generate a solid.
   The parameters for a solid are
   1. The position on the screen (x, y)
   2. The width (w)
   3. The height (h)
   4. The color (r, g, b) (if a color is not assigned, the object's default color will be black)
   NOTE: THE PARAMETERS ARE THE SAME FOR BORDERS!

   Here is an example of a (red) border or solid definition:
   [100, 100, 400, 500, 255, 0, 0]
   It will be a solid or border depending on if it is added to args.outputs.solids or args.outputs.borders.
   For more information about solids and borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters for sprites are
   1. The position on the screen (x, y)
   2. The width (w)
   3. The height (h)
   4. The image path (p)

   Here is an example of a sprite definition:
   [100, 100, 400, 500, 'sprites/dragonruby.png']
   For more information about sprites, go to mygame/documentation/05-sprites.md.

=end

# This code demonstrates the creation and output of objects like sprites, borders, and solids
# If filled in, they are solids
# If hollow, they are borders
# If images, they are sprites

# Solids are added to args.outputs.solids
# Borders are added to args.outputs.borders
# Sprites are added to args.outputs.sprites

# The tick method runs 60 frames every second.
# Your game is going to happen under this one function.
def tick args
  border_as_solid_and_solid_as_border args
  sprite_as_border_or_solids args
  collection_of_borders_and_solids args
  collection_of_sprites args
end

# Shows a border being output onto the screen as a border and a solid
# Also shows how colors can be set
def border_as_solid_and_solid_as_border args
  border = [0, 0, 50, 50]
  args.outputs.borders << border
  args.outputs.solids  << border

  # Red, green, blue saturations (last three parameters) can be any number between 0 and 255
  border_with_color = [0, 100, 50, 50, 255, 0, 0]
  args.outputs.borders << border_with_color
  args.outputs.solids  << border_with_color

  border_with_nested_color = [0, 200, 50, 50, [0, 255, 0]] # nested color
  args.outputs.borders << border_with_nested_color
  args.outputs.solids  << border_with_nested_color

  border_with_nested_rect = [[0, 300, 50, 50], 0, 0, 255] # nested rect
  args.outputs.borders << border_with_nested_rect
  args.outputs.solids  << border_with_nested_rect

  border_with_nested_color_and_rect = [[0, 400, 50, 50], [255, 0, 255]] # nested rect and color
  args.outputs.borders << border_with_nested_color_and_rect
  args.outputs.solids  << border_with_nested_color_and_rect
end

# Shows a sprite output onto the screen as a sprite, border, and solid
# Demonstrates that all three outputs appear differently on screen
def sprite_as_border_or_solids args
  sprite = [100, 0, 50, 50, 'sprites/ship.png']
  args.outputs.sprites << sprite

  # Sprite_as_border variable has same parameters (excluding position) as above object,
  # but will appear differently on screen because it is added to args.outputs.borders
  sprite_as_border = [100, 100, 50, 50, 'sprites/ship.png']
  args.outputs.borders << sprite_as_border

  # Sprite_as_solid variable has same parameters (excluding position) as above object,
  # but will appear differently on screen because it is added to args.outputs.solids
  sprite_as_solid = [100, 200, 50, 50, 'sprites/ship.png']
  args.outputs.solids << sprite_as_solid
end

# Holds and outputs a collection of borders and a collection of solids
# Collections are created by using arrays to hold parameters of each individual object
def collection_of_borders_and_solids args
  collection_borders = [
    [
      [200,  0, 50, 50],                    # black border
      [200,  100, 50, 50, 255, 0, 0],       # red border
      [200,  200, 50, 50, [0, 255, 0]],     # nested color
    ],
    [[200, 300, 50, 50], 0, 0, 255],        # nested rect
    [[200, 400, 50, 50], [255, 0, 255]]     # nested rect and nested color
  ]

  args.outputs.borders << collection_borders

  collection_solids = [
    [
      [[300, 300, 50, 50], 0, 0, 255],      # nested rect
      [[300, 400, 50, 50], [255, 0, 255]]   # nested rect and nested color
    ],
    [300,  0, 50, 50],
    [300,  100, 50, 50, 255, 0, 0],
    [300,  200, 50, 50, [0, 255, 0]],       # nested color
  ]

  args.outputs.solids << collection_solids
end

# Holds and outputs a collection of sprites by adding it to args.outputs.sprites
# Also outputs a collection with same parameters (excluding position) by adding
# it to args.outputs.solids and another to args.outputs.borders
def collection_of_sprites args
  sprites_collection = [
    [
      [400, 0, 50, 50, 'sprites/ship.png'],
      [400, 100, 50, 50, 'sprites/ship.png'],
    ],
    [400, 200, 50, 50, 'sprites/ship.png']
  ]

  args.outputs.sprites << sprites_collection

  args.outputs.solids << [
    [500, 0, 50, 50, 'sprites/ship.png'],
    [500, 100, 50, 50, 'sprites/ship.png'],
    [[[500, 200, 50, 50, 'sprites/ship.png']]]
  ]

  args.outputs.borders << [
    [
      [600, 0, 50, 50, 'sprites/ship.png'],
      [600, 100, 50, 50, 'sprites/ship.png'],
    ],
    [600, 200, 50, 50, 'sprites/ship.png']
  ]
end

    Render Primitives As Hash - main.rb link

    # ./samples/07_advanced_rendering/05_render_primitives_as_hash/app/main.rb
=begin

 Reminders:

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.

   For example, if we have a "numbers" hash that stores numbers in English as the
   key and numbers in Spanish as the value, we'd have a hash that looks like this...
   numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
   and on it goes.

   Now if we wanted to find the corresponding value of the "one" key, we could say
   puts numbers["one"]
   which would print "uno" to the console.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
   For more information about sprites, go to mygame/documentation/05-sprites.md.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.outputs.solids: An array. The values generate a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.borders: An array. The values generate a border.
   The parameters are the same as a solid.
   For more information about borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.lines: An array. The values generate a line.
   The parameters are [X1, Y1, X2, Y2, RED, GREEN, BLUE]
   For more information about labels, go to mygame/documentation/02-labels.md.

=end

# This sample app demonstrates how hashes can be used to output different kinds of objects.

def tick args
  args.state.angle ||= 0 # initializes angle to 0
  args.state.angle  += 1 # increments angle by 1 every frame (60 times a second)

  # Outputs sprite using a hash
  args.outputs.sprites << {
    x: 30,                          # sprite position
    y: 550,
    w: 128,                         # sprite size
    h: 101,
    path: "dragonruby.png",         # image path
    angle: args.state.angle,        # angle
    a: 255,                         # alpha (transparency)
    r: 255,                         # color saturation
    g: 255,
    b: 255,
    tile_x:  0,                     # sprite sub division/tile
    tile_y:  0,
    tile_w: -1,
    tile_h: -1,
    flip_vertically: false,         # don't flip sprite
    flip_horizontally: false,
    angle_anchor_x: 0.5,            # rotation center set to middle
    angle_anchor_y: 0.5
  }

  # Outputs label using a hash
  args.outputs.labels << {
    x:              200,                 # label position
    y:              550,
    text:           "dragonruby",        # label text
    size_enum:      2,
    alignment_enum: 1,
    r:              155,                 # color saturation
    g:              50,
    b:              50,
    a:              255,                 # transparency
    font:           "fonts/manaspc.ttf"  # font style; without mentioned file, label won't output correctly
  }

  # Outputs solid using a hash
  # [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
  args.outputs.solids << {
    x: 400,                         # position
    y: 550,
    w: 160,                         # size
    h:  90,
    r: 120,                         # color saturation
    g:  50,
    b:  50,
    a: 255                          # transparency
  }

  # Outputs border using a hash
  # Same parameters as a solid
  args.outputs.borders << {
    x: 600,
    y: 550,
    w: 160,
    h:  90,
    r: 120,
    g:  50,
    b:  50,
    a: 255
  }

  # Outputs line using a hash
  args.outputs.lines << {
    x:  900,                        # starting position
    y:  550,
    x2: 1200,                       # ending position
    y2: 550,
    r:  120,                        # color saturation
    g:   50,
    b:   50,
    a:  255                         # transparency
  }

  # Outputs sprite as a primitive using a hash
  args.outputs.primitives << {
    x: 30,                          # position
    y: 200,
    w: 128,                         # size
    h: 101,
    path: "dragonruby.png",         # image path
    angle: args.state.angle,        # angle
    a: 255,                         # transparency
    r: 255,                         # color saturation
    g: 255,
    b: 255,
    tile_x:  0,                     # sprite sub division/tile
    tile_y:  0,
    tile_w: -1,
    tile_h: -1,
    flip_vertically: false,         # don't flip
    flip_horizontally: false,
    angle_anchor_x: 0.5,            # rotation center set to middle
    angle_anchor_y: 0.5
  }.sprite!

  # Outputs label as primitive using a hash
  args.outputs.primitives << {
    x:         200,                 # position
    y:         200,
    text:      "dragonruby",        # text
    size:      2,
    alignment: 1,
    r:         155,                 # color saturation
    g:         50,
    b:         50,
    a:         255,                 # transparency
    font:      "fonts/manaspc.ttf"  # font style
  }.label!

  # Outputs solid as primitive using a hash
  args.outputs.primitives << {
    x: 400,                         # position
    y: 200,
    w: 160,                         # size
    h:  90,
    r: 120,                         # color saturation
    g:  50,
    b:  50,
    a: 255                          # transparency
  }.solid!

  # Outputs border as primitive using a hash
  # Same parameters as solid
  args.outputs.primitives << {
    x: 600,                         # position
    y: 200,
    w: 160,                         # size
    h:  90,
    r: 120,                         # color saturation
    g:  50,
    b:  50,
    a: 255                          # transparency
  }.border!

  # Outputs line as primitive using a hash
  args.outputs.primitives << {
    x:  900,                        # starting position
    y:  200,
    x2: 1200,                       # ending position
    y2: 200,
    r:  120,                        # color saturation
    g:   50,
    b:   50,
    a:  255                         # transparency
  }.line!
end

    Buttons As Render Targets - main.rb link

    # ./samples/07_advanced_rendering/06_buttons_as_render_targets/app/main.rb
def tick args
  # create a texture/render_target that's composed of a border and a label
  create_button args, :hello_world_button, "Hello World", 500, 50

  # two button primitives using the hello_world_button render_target
  args.state.buttons ||= [
    # one button at the top
    { id: :top_button, x: 640 - 250, y: 80.from_top, w: 500, h: 50, path: :hello_world_button },

    # another button at the buttom, upside down, and flipped horizontally
    { id: :bottom_button, x: 640 - 250, y: 30, w: 500, h: 50, path: :hello_world_button, angle: 180, flip_horizontally: true },
  ]

  # check if a mouse click occurred
  if args.inputs.mouse.click
    # check to see if any of the buttons were intersected
    # and set the selected button if so
    args.state.selected_button = args.state.buttons.find { |b| b.intersect_rect? args.inputs.mouse }
  end

  # render the buttons
  args.outputs.sprites << args.state.buttons

  # if there was a selected button, print it's id
  if args.state.selected_button
    args.outputs.labels << { x: 30, y: 30.from_top, text: "#{args.state.selected_button.id} was clicked." }
  end
end

def create_button args, id, text, w, h
  # render_targets only need to be created once, we use the the id to determine if the texture
  # has already been created
  args.state.created_buttons ||= {}
  return if args.state.created_buttons[id]

  # if the render_target hasn't been created, then generate it and store it in the created_buttons cache
  args.state.created_buttons[id] = { created_at: args.state.tick_count, id: id, w: w, h: h, text: text }

  # define the w/h of the texture
  args.outputs[id].w = w
  args.outputs[id].h = h

  # create a border
  args.outputs[id].borders << { x: 0, y: 0, w: w, h: h }

  # create a label centered vertically and horizontally within the texture
  args.outputs[id].labels << { x: w / 2, y: h / 2, text: text, vertical_alignment_enum: 1, alignment_enum: 1 }
end

    Pixel Arrays - main.rb link

    # ./samples/07_advanced_rendering/06_pixel_arrays/app/main.rb
def tick args
  args.state.posinc ||= 1
  args.state.pos ||= 0
  args.state.rotation ||= 0

  dimension = 10  # keep it small and let the GPU scale it when rendering the sprite.

  # Set up our "scanner" pixel array and fill it with black pixels.
  args.pixel_array(:scanner).width = dimension
  args.pixel_array(:scanner).height = dimension
  args.pixel_array(:scanner).pixels.fill(0xFF000000, 0, dimension * dimension)  # black, full alpha

  # Draw a green line that bounces up and down the sprite.
  args.pixel_array(:scanner).pixels.fill(0xFF00FF00, dimension * args.state.pos, dimension)  # green, full alpha

  # Adjust position for next frame.
  args.state.pos += args.state.posinc
  if args.state.posinc > 0 && args.state.pos >= dimension
    args.state.posinc = -1
    args.state.pos = dimension - 1
  elsif args.state.posinc < 0 && args.state.pos < 0
    args.state.posinc = 1
    args.state.pos = 1
  end

  # New/changed pixel arrays get uploaded to the GPU before we render
  #  anything. At that point, they can be scaled, rotated, and otherwise
  #  used like any other sprite.
  w = 100
  h = 100
  x = (1280 - w) / 2
  y = (720 - h) / 2
  args.outputs.background_color = [64, 0, 128]
  args.outputs.primitives << [x, y, w, h, :scanner, args.state.rotation].sprite
  args.state.rotation += 1

  args.outputs.primitives << args.gtk.current_framerate_primitives
end


$gtk.reset

    Pixel Arrays From File - main.rb link

    # ./samples/07_advanced_rendering/06_pixel_arrays_from_file/app/main.rb
def tick args
  args.state.rotation ||= 0

  # on load, get pixels from png and load it into a pixel array
  if args.state.tick_count == 0
    pixel_array = args.gtk.get_pixels 'sprites/square/blue.png'
    args.pixel_array(:square).w = pixel_array.w
    args.pixel_array(:square).h = pixel_array.h
    pixel_array.pixels.each_with_index do |p, i|
      args.pixel_array(:square).pixels[i] = p
    end
  end

  w = 100
  h = 100
  x = (1280 - w) / 2
  y = (720 - h) / 2
  args.outputs.background_color = [64, 0, 128]
  # render the pixel array by name
  args.outputs.primitives << { x: x, y: y, w: w, h: h, path: :square, angle: args.state.rotation }
  args.state.rotation += 1

  args.outputs.primitives << args.gtk.current_framerate_primitives
end

$gtk.reset

    Shake Camera - main.rb link

    # ./samples/07_advanced_rendering/07_shake_camera/app/main.rb
# Demo of camera shake
# Hold space to shake and release to stop

class ScreenShake
  attr_gtk

  def tick
    defaults
    calc_camera

    outputs.labels << { x: 600, y: 400, text: "Hold Space!" }

    # Add outputs to :scene
    outputs[:scene].transient!
    outputs[:scene].sprites << { x: 100, y: 100,          w: 80, h: 80, path: 'sprites/square/blue.png' }
    outputs[:scene].sprites << { x: 200, y: 300.from_top, w: 80, h: 80, path: 'sprites/square/blue.png' }
    outputs[:scene].sprites << { x: 900, y: 200,          w: 80, h: 80, path: 'sprites/square/blue.png' }

    # Describe how to render :scene
    outputs.sprites << { x: 0 - state.camera.x_offset,
                         y: 0 - state.camera.y_offset,
                         w: 1280,
                         h: 720,
                         angle: state.camera.angle,
                         path: :scene }
  end

  def defaults
    state.camera.trauma ||= 0
    state.camera.angle ||= 0
    state.camera.x_offset ||= 0
    state.camera.y_offset ||= 0
  end

  def calc_camera
    if inputs.keyboard.key_held.space
      state.camera.trauma += 0.02
    end

    next_camera_angle = 180.0 / 20.0 * state.camera.trauma**2
    next_offset       = 100.0 * state.camera.trauma**2

    # Ensure that the camera angle always switches from
    # positive to negative and vice versa
    # which gives the effect of shaking back and forth
    state.camera.angle = state.camera.angle > 0 ?
                           next_camera_angle * -1 :
                           next_camera_angle

    state.camera.x_offset = next_offset.randomize(:sign, :ratio)
    state.camera.y_offset = next_offset.randomize(:sign, :ratio)

    # Gracefully degrade trauma
    state.camera.trauma *= 0.95
  end
end

def tick args
  $screen_shake ||= ScreenShake.new
  $screen_shake.args = args
  $screen_shake.tick
end

    Simple Camera - main.rb link

    # ./samples/07_advanced_rendering/07_simple_camera/app/main.rb
def tick args
  # variables you can play around with
  args.state.world.w      ||= 1280
  args.state.world.h      ||= 720

  args.state.player.x     ||= 0
  args.state.player.y     ||= 0
  args.state.player.size  ||= 32

  args.state.enemy.x      ||= 700
  args.state.enemy.y      ||= 700
  args.state.enemy.size   ||= 16

  args.state.camera.x                ||= 640
  args.state.camera.y                ||= 300
  args.state.camera.scale            ||= 1.0
  args.state.camera.show_empty_space ||= :yes

  # instructions
  args.outputs.primitives << { x: 0, y:  80.from_top, w: 360, h: 80, r: 0, g: 0, b: 0, a: 128 }.solid!
  args.outputs.primitives << { x: 10, y: 10.from_top, text: "arrow keys to move around", r: 255, g: 255, b: 255}.label!
  args.outputs.primitives << { x: 10, y: 30.from_top, text: "+/- to change zoom of camera", r: 255, g: 255, b: 255}.label!
  args.outputs.primitives << { x: 10, y: 50.from_top, text: "tab to change camera edge behavior", r: 255, g: 255, b: 255}.label!

  # render scene
  args.outputs[:scene].transient!
  args.outputs[:scene].w = args.state.world.w
  args.outputs[:scene].h = args.state.world.h

  args.outputs[:scene].solids << { x: 0, y: 0, w: args.state.world.w, h: args.state.world.h, r: 20, g: 60, b: 80 }
  args.outputs[:scene].solids << { x: args.state.player.x, y: args.state.player.y,
                                   w: args.state.player.size, h: args.state.player.size, r: 80, g: 155, b: 80 }
  args.outputs[:scene].solids << { x: args.state.enemy.x, y: args.state.enemy.y,
                                   w: args.state.enemy.size, h: args.state.enemy.size, r: 155, g: 80, b: 80 }

  # render camera
  scene_position = calc_scene_position args
  args.outputs.sprites << { x: scene_position.x,
                            y: scene_position.y,
                            w: scene_position.w,
                            h: scene_position.h,
                            path: :scene }

  # move player
  if args.inputs.directional_angle
    args.state.player.x += args.inputs.directional_angle.vector_x * 5
    args.state.player.y += args.inputs.directional_angle.vector_y * 5
    args.state.player.x  = args.state.player.x.clamp(0, args.state.world.w - args.state.player.size)
    args.state.player.y  = args.state.player.y.clamp(0, args.state.world.h - args.state.player.size)
  end

  # +/- to zoom in and out
  if args.inputs.keyboard.plus && args.state.tick_count.zmod?(3)
    args.state.camera.scale += 0.05
  elsif args.inputs.keyboard.hyphen && args.state.tick_count.zmod?(3)
    args.state.camera.scale -= 0.05
  elsif args.inputs.keyboard.key_down.tab
    if args.state.camera.show_empty_space == :yes
      args.state.camera.show_empty_space = :no
    else
      args.state.camera.show_empty_space = :yes
    end
  end

  args.state.camera.scale = args.state.camera.scale.greater(0.1)
end

def calc_scene_position args
  result = { x: args.state.camera.x - (args.state.player.x * args.state.camera.scale),
             y: args.state.camera.y - (args.state.player.y * args.state.camera.scale),
             w: args.state.world.w * args.state.camera.scale,
             h: args.state.world.h * args.state.camera.scale,
             scale: args.state.camera.scale }

  return result if args.state.camera.show_empty_space == :yes

  if result.w < args.grid.w
    result.merge!(x: (args.grid.w - result.w).half)
  elsif (args.state.player.x * result.scale) < args.grid.w.half
    result.merge!(x: 10)
  elsif (result.x + result.w) < args.grid.w
    result.merge!(x: - result.w + (args.grid.w - 10))
  end

  if result.h < args.grid.h
    result.merge!(y: (args.grid.h - result.h).half)
  elsif (result.y) > 10
    result.merge!(y: 10)
  elsif (result.y + result.h) < args.grid.h
    result.merge!(y: - result.h + (args.grid.h - 10))
  end

  result
end

    Simple Camera Multiple Targets - main.rb link

    # ./samples/07_advanced_rendering/07_simple_camera_multiple_targets/app/main.rb
def tick args
  args.outputs.background_color = [0, 0, 0]

  # variables you can play around with
  args.state.world.w                ||= 1280
  args.state.world.h                ||= 720
  args.state.target_hero            ||= :hero_1
  args.state.target_hero_changed_at ||= -30
  args.state.hero_size              ||= 32

  # initial state of heros and camera
  args.state.hero_1 ||= { x: 100, y: 100 }
  args.state.hero_2 ||= { x: 100, y: 600 }
  args.state.camera ||= { x: 640, y: 360, scale: 1.0 }

  # render instructions
  args.outputs.primitives << { x: 0,  y: 80.from_top, w: 360, h: 80, r: 0, g: 0, b: 0, a: 128 }.solid!
  args.outputs.primitives << { x: 10, y: 10.from_top, text: "+/- to change zoom of camera", r: 255, g: 255, b: 255}.label!
  args.outputs.primitives << { x: 10, y: 30.from_top, text: "arrow keys to move target hero", r: 255, g: 255, b: 255}.label!
  args.outputs.primitives << { x: 10, y: 50.from_top, text: "space to cycle target hero", r: 255, g: 255, b: 255}.label!

  # render scene
  args.outputs[:scene].transient!
  args.outputs[:scene].w = args.state.world.w
  args.outputs[:scene].h = args.state.world.h

  # render world
  args.outputs[:scene].solids << { x: 0, y: 0, w: args.state.world.w, h: args.state.world.h, r: 20, g: 60, b: 80 }

  # render hero_1
  args.outputs[:scene].solids << { x: args.state.hero_1.x, y: args.state.hero_1.y,
                                   w: args.state.hero_size, h: args.state.hero_size, r: 255, g: 155, b: 80 }

  # render hero_2
  args.outputs[:scene].solids << { x: args.state.hero_2.x, y: args.state.hero_2.y,
                                   w: args.state.hero_size, h: args.state.hero_size, r: 155, g: 255, b: 155 }

  # render scene relative to camera
  scene_position = calc_scene_position args

  args.outputs.sprites << { x: scene_position.x,
                            y: scene_position.y,
                            w: scene_position.w,
                            h: scene_position.h,
                            path: :scene }

  # mini map
  args.outputs.borders << { x: 10,
                            y: 10,
                            w: args.state.world.w.idiv(8),
                            h: args.state.world.h.idiv(8),
                            r: 255,
                            g: 255,
                            b: 255 }
  args.outputs.sprites << { x: 10,
                            y: 10,
                            w: args.state.world.w.idiv(8),
                            h: args.state.world.h.idiv(8),
                            path: :scene }

  # cycle target hero
  if args.inputs.keyboard.key_down.space
    if args.state.target_hero == :hero_1
      args.state.target_hero = :hero_2
    else
      args.state.target_hero = :hero_1
    end
    args.state.target_hero_changed_at = args.state.tick_count
  end

  # move target hero
  hero_to_move = if args.state.target_hero == :hero_1
                   args.state.hero_1
                 else
                   args.state.hero_2
                 end

  if args.inputs.directional_angle
    hero_to_move.x += args.inputs.directional_angle.vector_x * 5
    hero_to_move.y += args.inputs.directional_angle.vector_y * 5
    hero_to_move.x  = hero_to_move.x.clamp(0, args.state.world.w - hero_to_move.size)
    hero_to_move.y  = hero_to_move.y.clamp(0, args.state.world.h - hero_to_move.size)
  end

  # +/- to zoom in and out
  if args.inputs.keyboard.plus && args.state.tick_count.zmod?(3)
    args.state.camera.scale += 0.05
  elsif args.inputs.keyboard.hyphen && args.state.tick_count.zmod?(3)
    args.state.camera.scale -= 0.05
  end

  args.state.camera.scale = 0.1 if args.state.camera.scale < 0.1
end

def other_hero args
  if args.state.target_hero == :hero_1
    return args.state.hero_2
  else
    return args.state.hero_1
  end
end

def calc_scene_position args
  target_hero = if args.state.target_hero == :hero_1
                  args.state.hero_1
                else
                  args.state.hero_2
                end

  other_hero = if args.state.target_hero == :hero_1
                 args.state.hero_2
               else
                 args.state.hero_1
               end

  # calculate the lerp percentage based on the time since the target hero changed
  lerp_percentage = args.easing.ease args.state.target_hero_changed_at,
                                     args.state.tick_count,
                                     30,
                                     :smooth_stop_quint,
                                     :flip

  # calculate the angle and distance between the target hero and the other hero
  angle_to_other_hero = args.geometry.angle_to target_hero, other_hero

  # calculate the distance between the target hero and the other hero
  distance_to_other_hero = args.geometry.distance target_hero, other_hero

  # the camera position is the target hero position plus the angle and distance to the other hero (lerped)
  { x: args.state.camera.x - (target_hero.x + (angle_to_other_hero.vector_x * distance_to_other_hero * lerp_percentage)) * args.state.camera.scale,
    y: args.state.camera.y - (target_hero.y + (angle_to_other_hero.vector_y * distance_to_other_hero * lerp_percentage)) * args.state.camera.scale,
    w: args.state.world.w * args.state.camera.scale,
    h: args.state.world.h * args.state.camera.scale }
end

    Splitscreen Camera - main.rb link

    # ./samples/07_advanced_rendering/08_splitscreen_camera/app/main.rb
class CameraMovement
  attr_accessor :state, :inputs, :outputs, :grid

  #==============================================================================================
  #Serialize
  def serialize
    {state: state, inputs: inputs, outputs: outputs, grid: grid }
  end

  def inspect
    serialize.to_s
  end

  def to_s
    serialize.to_s
  end

  #==============================================================================================
  #Tick
  def tick
    defaults
    calc
    render
    input
  end

  #==============================================================================================
  #Default functions
  def defaults
    outputs[:scene].transient!
    outputs[:scene].background_color = [0,0,0]
    state.trauma ||= 0.0
    state.trauma_power ||= 2
    state.player_cyan ||= new_player_cyan
    state.player_magenta ||= new_player_magenta
    state.camera_magenta ||= new_camera_magenta
    state.camera_cyan ||= new_camera_cyan
    state.camera_center ||= new_camera_center
    state.room ||= new_room
  end

  def default_player x, y, w, h, sprite_path
    state.new_entity(:player,
                     { x: x,
                       y: y,
                       dy: 0,
                       dx: 0,
                       w: w,
                       h: h,
                       damage: 0,
                       dead: false,
                       orientation: "down",
                       max_alpha: 255,
                       sprite_path: sprite_path})
  end

  def default_floor_tile x, y, w, h, sprite_path
    state.new_entity(:room,
                     { x: x,
                       y: y,
                       w: w,
                       h: h,
                       sprite_path: sprite_path})
  end

  def default_camera x, y, w, h
    state.new_entity(:camera,
                     { x: x,
                       y: y,
                       dx: 0,
                       dy: 0,
                       w: w,
                       h: h})
  end

  def new_player_cyan
    default_player(0, 0, 64, 64,
                   "sprites/player/player_#{state.player_cyan.orientation}_standing.png")
  end

  def new_player_magenta
    default_player(64, 0, 64, 64,
                   "sprites/player/player_#{state.player_magenta.orientation}_standing.png")
  end

  def new_camera_magenta
    default_camera(0,0,720,720)
  end

  def new_camera_cyan
    default_camera(0,0,720,720)
  end

  def new_camera_center
    default_camera(0,0,1280,720)
  end


  def new_room
    default_floor_tile(0,0,1024,1024,'sprites/rooms/camera_room.png')
  end

  #==============================================================================================
  #Calculation functions
  def calc
    calc_camera_magenta
    calc_camera_cyan
    calc_camera_center
    calc_player_cyan
    calc_player_magenta
    calc_trauma_decay
  end

  def center_camera_tolerance
    return Math.sqrt(((state.player_magenta.x - state.player_cyan.x) ** 2) +
              ((state.player_magenta.y - state.player_cyan.y) ** 2)) > 640
  end

  def calc_player_cyan
    state.player_cyan.x += state.player_cyan.dx
    state.player_cyan.y += state.player_cyan.dy
  end

  def calc_player_magenta
    state.player_magenta.x += state.player_magenta.dx
    state.player_magenta.y += state.player_magenta.dy
  end

  def calc_camera_center
    timeScale = 1
    midX = (state.player_magenta.x + state.player_cyan.x)/2
    midY = (state.player_magenta.y + state.player_cyan.y)/2
    targetX = midX - state.camera_center.w/2
    targetY = midY - state.camera_center.h/2
    state.camera_center.x += (targetX - state.camera_center.x) * 0.1 * timeScale
    state.camera_center.y += (targetY - state.camera_center.y) * 0.1 * timeScale
  end


  def calc_camera_magenta
    timeScale = 1
    targetX = state.player_magenta.x + state.player_magenta.w - state.camera_magenta.w/2
    targetY = state.player_magenta.y + state.player_magenta.h - state.camera_magenta.h/2
    state.camera_magenta.x += (targetX - state.camera_magenta.x) * 0.1 * timeScale
    state.camera_magenta.y += (targetY - state.camera_magenta.y) * 0.1 * timeScale
  end

  def calc_camera_cyan
    timeScale = 1
    targetX = state.player_cyan.x + state.player_cyan.w - state.camera_cyan.w/2
    targetY = state.player_cyan.y + state.player_cyan.h - state.camera_cyan.h/2
    state.camera_cyan.x += (targetX - state.camera_cyan.x) * 0.1 * timeScale
    state.camera_cyan.y += (targetY - state.camera_cyan.y) * 0.1 * timeScale
  end

  def calc_player_quadrant angle
    if angle < 45 and angle > -45 and state.player_cyan.x < state.player_magenta.x
      return 1
    elsif angle < 45 and angle > -45 and state.player_cyan.x > state.player_magenta.x
      return 3
    elsif (angle > 45 or angle < -45) and state.player_cyan.y < state.player_magenta.y
      return 2
    elsif (angle > 45 or angle < -45) and state.player_cyan.y > state.player_magenta.y
      return 4
    end
  end

  def calc_camera_shake
    state.trauma
  end

  def calc_trauma_decay
    state.trauma = state.trauma * 0.9
  end

  def calc_random_float_range(min, max)
    rand * (max-min) + min
  end

  #==============================================================================================
  #Render Functions
  def render
    render_floor
    render_player_cyan
    render_player_magenta
    if center_camera_tolerance
      render_split_camera_scene
    else
      render_camera_center_scene
    end
  end

  def render_player_cyan
    outputs[:scene].sprites << {x: state.player_cyan.x,
                                y: state.player_cyan.y,
                                w: state.player_cyan.w,
                                h: state.player_cyan.h,
                                path: "sprites/player/player_#{state.player_cyan.orientation}_standing.png",
                                r: 0,
                                g: 255,
                                b: 255}
  end

  def render_player_magenta
    outputs[:scene].sprites << {x: state.player_magenta.x,
                                y: state.player_magenta.y,
                                w: state.player_magenta.w,
                                h: state.player_magenta.h,
                                path: "sprites/player/player_#{state.player_magenta.orientation}_standing.png",
                                r: 255,
                                g: 0,
                                b: 255}
  end

  def render_floor
    outputs[:scene].sprites << [state.room.x, state.room.y,
                                state.room.w, state.room.h,
                                state.room.sprite_path]
  end

  def render_camera_center_scene
    zoomFactor = 1
    outputs[:scene].width = state.room.w
    outputs[:scene].height = state.room.h

    maxAngle = 10.0
    maxOffset = 20.0
    angle = maxAngle * calc_camera_shake * calc_random_float_range(-1,1)
    offsetX = 32 - (maxOffset * calc_camera_shake * calc_random_float_range(-1,1))
    offsetY = 32 - (maxOffset * calc_camera_shake * calc_random_float_range(-1,1))

    outputs.sprites << {x: (-state.camera_center.x - offsetX)/zoomFactor,
                        y: (-state.camera_center.y - offsetY)/zoomFactor,
                        w: outputs[:scene].width/zoomFactor,
                        h: outputs[:scene].height/zoomFactor,
                        path: :scene,
                        angle: angle,
                        source_w: -1,
                        source_h: -1}
    outputs.labels << [128,64,"#{state.trauma.round(1)}",8,2,255,0,255,255]
  end

  def render_split_camera_scene
     outputs[:scene].width = state.room.w
     outputs[:scene].height = state.room.h
     render_camera_magenta_scene
     render_camera_cyan_scene

     angle = Math.atan((state.player_magenta.y - state.player_cyan.y)/(state.player_magenta.x- state.player_cyan.x)) * 180/Math::PI
     output_split_camera angle

  end

  def render_camera_magenta_scene
     zoomFactor = 1
     offsetX = 32
     offsetY = 32

     outputs[:scene_magenta].transient!
     outputs[:scene_magenta].sprites << {x: (-state.camera_magenta.x*2),
                                         y: (-state.camera_magenta.y),
                                         w: outputs[:scene].width*2,
                                         h: outputs[:scene].height,
                                         path: :scene}

  end

  def render_camera_cyan_scene
    zoomFactor = 1
    offsetX = 32
    offsetY = 32
    outputs[:scene_cyan].transient!
    outputs[:scene_cyan].sprites << {x: (-state.camera_cyan.x*2),
                                     y: (-state.camera_cyan.y),
                                     w: outputs[:scene].width*2,
                                     h: outputs[:scene].height,
                                     path: :scene}
  end

  def output_split_camera angle
    #TODO: Clean this up!
    quadrant = calc_player_quadrant angle
    outputs.labels << [128,64,"#{quadrant}",8,2,255,0,255,255]
    if quadrant == 1
      set_camera_attributes(w: 640, h: 720, m_x: 640, m_y: 0, c_x: 0, c_y: 0)

    elsif quadrant == 2
      set_camera_attributes(w: 1280, h: 360, m_x: 0, m_y: 360, c_x: 0, c_y: 0)

    elsif quadrant == 3
      set_camera_attributes(w: 640, h: 720, m_x: 0, m_y: 0, c_x: 640, c_y: 0)

    elsif quadrant == 4
      set_camera_attributes(w: 1280, h: 360, m_x: 0, m_y: 0, c_x: 0, c_y: 360)

    end
  end

  def set_camera_attributes(w: 0, h: 0, m_x: 0, m_y: 0, c_x: 0, c_y: 0)
    state.camera_cyan.w = w + 64
    state.camera_cyan.h = h + 64
    outputs[:scene_cyan].width = (w) * 2
    outputs[:scene_cyan].height = h

    state.camera_magenta.w = w + 64
    state.camera_magenta.h = h + 64
    outputs[:scene_magenta].width = (w) * 2
    outputs[:scene_magenta].height = h
    outputs.sprites << {x: m_x,
                        y: m_y,
                        w: w,
                        h: h,
                        path: :scene_magenta}
    outputs.sprites << {x: c_x,
                        y: c_y,
                        w: w,
                        h: h,
                        path: :scene_cyan}
  end

  def add_trauma amount
    state.trauma = [state.trauma + amount, 1.0].min
  end

  def remove_trauma amount
    state.trauma = [state.trauma - amount, 0.0].max
  end
  #==============================================================================================
  #Input functions
  def input
    input_move_cyan
    input_move_magenta

    if inputs.keyboard.key_down.t
      add_trauma(0.5)
    elsif inputs.keyboard.key_down.y
      remove_trauma(0.1)
    end
  end

  def input_move_cyan
    if inputs.keyboard.key_held.up
      state.player_cyan.dy = 5
      state.player_cyan.orientation = "up"
    elsif inputs.keyboard.key_held.down
      state.player_cyan.dy = -5
      state.player_cyan.orientation = "down"
    else
      state.player_cyan.dy *= 0.8
    end
    if inputs.keyboard.key_held.left
      state.player_cyan.dx = -5
      state.player_cyan.orientation = "left"
    elsif inputs.keyboard.key_held.right
      state.player_cyan.dx = 5
      state.player_cyan.orientation = "right"
    else
      state.player_cyan.dx *= 0.8
    end

    outputs.labels << [128,512,"#{state.player_cyan.x.round()}",8,2,0,255,255,255]
    outputs.labels << [128,480,"#{state.player_cyan.y.round()}",8,2,0,255,255,255]
  end

  def input_move_magenta
    if inputs.keyboard.key_held.w
      state.player_magenta.dy = 5
      state.player_magenta.orientation = "up"
    elsif inputs.keyboard.key_held.s
      state.player_magenta.dy = -5
      state.player_magenta.orientation = "down"
    else
      state.player_magenta.dy *= 0.8
    end
    if inputs.keyboard.key_held.a
      state.player_magenta.dx = -5
      state.player_magenta.orientation = "left"
    elsif inputs.keyboard.key_held.d
      state.player_magenta.dx = 5
      state.player_magenta.orientation = "right"
    else
      state.player_magenta.dx *= 0.8
    end

    outputs.labels << [128,360,"#{state.player_magenta.x.round()}",8,2,255,0,255,255]
    outputs.labels << [128,328,"#{state.player_magenta.y.round()}",8,2,255,0,255,255]
  end
end

$camera_movement = CameraMovement.new

def tick args
  args.outputs.background_color = [0,0,0]
  $camera_movement.inputs  = args.inputs
  $camera_movement.outputs = args.outputs
  $camera_movement.state   = args.state
  $camera_movement.grid    = args.grid
  $camera_movement.tick
end

    Z Targeting Camera - main.rb link

    # ./samples/07_advanced_rendering/09_z_targeting_camera/app/main.rb
class Game
  attr_gtk

  def tick
    defaults
    render
    input
    calc
  end

  def defaults
    outputs.background_color = [219, 208, 191]
    player.x        ||= 634
    player.y        ||= 153
    player.angle    ||= 90
    player.distance ||= arena_radius
    target.x        ||= 634
    target.y        ||= 359
  end

  def render
    outputs[:scene].transient!
    outputs[:scene].sprites << ([0, 0, 933, 700, 'sprites/arena.png'].center_inside_rect grid.rect)
    outputs[:scene].sprites << target_sprite
    outputs[:scene].sprites << player_sprite
    outputs.sprites << scene
  end

  def target_sprite
    {
      x: target.x, y: target.y,
      w: 10, h: 10,
      path: 'sprites/square/black.png'
    }.anchor_rect 0.5, 0.5
  end

  def input
    if inputs.up && player.distance > 30
      player.distance -= 2
    elsif inputs.down && player.distance < 200
      player.distance += 2
    end

    player.angle += inputs.left_right * -1
  end

  def calc
    player.x = target.x + ((player.angle *  1).vector_x player.distance)
    player.y = target.y + ((player.angle * -1).vector_y player.distance)
  end

  def player_sprite
    {
      x: player.x,
      y: player.y,
      w: 50,
      h: 100,
      path: 'sprites/player.png',
      angle: (player.angle * -1) + 90
    }.anchor_rect 0.5, 0
  end

  def center_map
    { x: 634, y: 359 }
  end

  def zoom_factor_single
    2 - ((args.geometry.distance player, center_map).fdiv arena_radius)
  end

  def zoom_factor
    zoom_factor_single ** 2
  end

  def arena_radius
    206
  end

  def scene
    {
      x:    (640 - player.x) + (640 - (640 * zoom_factor)),
      y:    (360 - player.y - (75 * zoom_factor)) + (320 - (320 * zoom_factor)),
      w:    1280 * zoom_factor,
      h:     720 * zoom_factor,
      path: :scene,
      angle: player.angle - 90,
      angle_anchor_x: (player.x.fdiv 1280),
      angle_anchor_y: (player.y.fdiv 720)
    }
  end

  def player
    state.player
  end

  def target
    state.target
  end
end

def tick args
  $game ||= Game.new
  $game.args = args
  $game.tick
end

$gtk.reset

    Camera And Large Map - main.rb link

    # ./samples/07_advanced_rendering/10_camera_and_large_map/app/main.rb
def tick args
  # you want to make sure all of your pngs are a maximum size of 1280x1280
  # low-end android devices and machines with underpowered GPUs are unable to
  # load very large textures.

  # this sample app creates 640x640 tiles of a 6400x6400 pixel png and displays them
  # on the screen relative to the player's position

  # tile creation process
  create_tiles_if_needed args

  # if tiles are already present the show map
  display_tiles args
end

def display_tiles args
  # set the player's starting location
  args.state.player ||= {
    x:  0,
    y:  0,
    w: 40,
    h: 40,
    path: "sprites/square/blue.png"
  }

  # if all tiles have been created, then we are
  # in "displaying_tiles" mode
  if args.state.displaying_tiles
    # create a render target that can hold 9 640x640 tiles
    args.outputs[:scene].transient!
    args.outputs[:scene].background_color = [0, 0, 0, 0]
    args.outputs[:scene].w = 1920
    args.outputs[:scene].h = 1920

    # allow player to be moved with arrow keys
    args.state.player.x += args.inputs.left_right * 10
    args.state.player.y += args.inputs.up_down * 10

    # given the player's location, return a collection of primitives
    # to render that are within the 1920x1920 viewport
    args.outputs[:scene].primitives << tiles_in_viewport(args)

    # place the player in the center of the render_target
    args.outputs[:scene].primitives << {
      x: 960 - 20,
      y: 960 - 20,
      w: 40,
      h: 40,
      path: "sprites/square/blue.png"
    }

    # center the 1920x1920 render target within the 1280x720 window
    args.outputs.sprites << {
      x: -320,
      y: -600,
      w: 1920,
      h: 1920,
      path: :scene
    }
  end
end

def tiles_in_viewport args
  state = args.state
  # define the size of each tile
  tile_size = 640

  # determine what tile the player is on
  tile_player_is_on = { x: state.player.x.idiv(tile_size), y: state.player.y.idiv(tile_size) }

  # calculate the x and y offset of the player so that tiles are positioned correctly
  offset_x = 960 - (state.player.x - (tile_player_is_on.x * tile_size))
  offset_y = 960 - (state.player.y - (tile_player_is_on.y * tile_size))

  primitives = []

  # get 9 tiles in total (the tile the player is on and the 8 surrounding tiles)

  # center tile
  primitives << (tile_in_viewport size:       tile_size,
                                  from_row:   tile_player_is_on.y,
                                  from_col:   tile_player_is_on.x,
                                  offset_row: 0,
                                  offset_col: 0,
                                  dy:         offset_y,
                                  dx:         offset_x)

  # tile to the right
  primitives << (tile_in_viewport size:       tile_size,
                                  from_row:   tile_player_is_on.y,
                                  from_col:   tile_player_is_on.x,
                                  offset_row: 0,
                                  offset_col: 1,
                                  dy:         offset_y,
                                  dx:         offset_x)
  # tile to the left
  primitives << (tile_in_viewport size:        tile_size,
                                  from_row:    tile_player_is_on.y,
                                  from_col:    tile_player_is_on.x,
                                  offset_row:  0,
                                  offset_col: -1,
                                  dy:          offset_y,
                                  dx:          offset_x)

  # tile directly above
  primitives << (tile_in_viewport size:       tile_size,
                                  from_row:   tile_player_is_on.y,
                                  from_col:   tile_player_is_on.x,
                                  offset_row: 1,
                                  offset_col: 0,
                                  dy:         offset_y,
                                  dx:         offset_x)
  # tile directly below
  primitives << (tile_in_viewport size:         tile_size,
                                  from_row:     tile_player_is_on.y,
                                  from_col:     tile_player_is_on.x,
                                  offset_row:  -1,
                                  offset_col:   0,
                                  dy:           offset_y,
                                  dx:           offset_x)
  # tile up and to the left
  primitives << (tile_in_viewport size:        tile_size,
                                  from_row:    tile_player_is_on.y,
                                  from_col:    tile_player_is_on.x,
                                  offset_row:  1,
                                  offset_col: -1,
                                  dy:          offset_y,
                                  dx:          offset_x)

  # tile up and to the right
  primitives << (tile_in_viewport size:       tile_size,
                                  from_row:   tile_player_is_on.y,
                                  from_col:   tile_player_is_on.x,
                                  offset_row: 1,
                                  offset_col: 1,
                                  dy:         offset_y,
                                  dx:         offset_x)

  # tile down and to the left
  primitives << (tile_in_viewport size:        tile_size,
                                  from_row:    tile_player_is_on.y,
                                  from_col:    tile_player_is_on.x,
                                  offset_row: -1,
                                  offset_col: -1,
                                  dy:          offset_y,
                                  dx:          offset_x)

  # tile down and to the right
  primitives << (tile_in_viewport size:        tile_size,
                                  from_row:    tile_player_is_on.y,
                                  from_col:    tile_player_is_on.x,
                                  offset_row: -1,
                                  offset_col:  1,
                                  dy:          offset_y,
                                  dx:          offset_x)

  primitives
end

def tile_in_viewport size:, from_row:, from_col:, offset_row:, offset_col:, dy:, dx:;
  x = size * offset_col + dx
  y = size * offset_row + dy

  return nil if (from_row + offset_row) < 0
  return nil if (from_row + offset_row) > 9

  return nil if (from_col + offset_col) < 0
  return nil if (from_col + offset_col) > 9

  # return the tile sprite, a border demarcation, and label of which tile x and y
  [
    {
      x: x,
      y: y,
      w: size,
      h: size,
      path: "sprites/tile-#{from_col + offset_col}-#{from_row + offset_row}.png",
    },
    {
      x: x,
      y: y,
      w: size,
      h: size,
      r: 255,
      primitive_marker: :border,
    },
    {
      x: x + size / 2 - 150,
      y: y + size / 2 - 25,
      w: 300,
      h: 50,
      primitive_marker: :solid,
      r: 0,
      g: 0,
      b: 0,
      a: 128
    },
    {
      x: x + size / 2,
      y: y + size / 2,
      text: "tile #{from_col + offset_col}, #{from_row + offset_row}",
      alignment_enum: 1,
      vertical_alignment_enum: 1,
      size_enum: 2,
      r: 255,
      g: 255,
      b: 255
    },
  ]
end

def create_tiles_if_needed args
  # We are going to use args.outputs.screenshots to generate tiles of a
  # png of size 6400x6400 called sprites/large.png.
  if !args.gtk.stat_file("sprites/tile-9-9.png") && !args.state.creating_tiles
    args.state.displaying_tiles = false
    args.outputs.labels << {
      x: 960,
      y: 360,
      text: "Press enter to generate tiles of sprites/large.png.",
      alignment_enum: 1,
      vertical_alignment_enum: 1
    }
  elsif !args.state.creating_tiles
    args.state.displaying_tiles = true
  end

  # pressing enter will start the tile creation process
  if args.inputs.keyboard.key_down.enter && !args.state.creating_tiles
    args.state.displaying_tiles = false
    args.state.creating_tiles = true
    args.state.tile_clock = 0
  end

  # the tile creation process renders an area of sprites/large.png
  # to the screen and takes a screenshot of it every half second
  # until all tiles are generated.
  # once all tiles are generated a map viewport will be rendered that
  # stitches tiles together.
  if args.state.creating_tiles
    args.state.tile_x ||= 0
    args.state.tile_y ||= 0

    # render a sub-square of the large png.
    args.outputs.sprites << {
      x: 0,
      y: 0,
      w: 640,
      h: 640,
      source_x: args.state.tile_x * 640,
      source_y: args.state.tile_y * 640,
      source_w: 640,
      source_h: 640,
      path: "sprites/large.png"
    }

    # determine tile file name
    tile_path = "sprites/tile-#{args.state.tile_x}-#{args.state.tile_y}.png"

    args.outputs.labels << {
      x: 960,
      y: 320,
      text: "Generating #{tile_path}",
      alignment_enum: 1,
      vertical_alignment_enum: 1
    }

    # take a screenshot on frames divisible by 29
    if args.state.tile_clock.zmod?(29)
      args.outputs.screenshots << {
        x: 0,
        y: 0,
        w: 640,
        h: 640,
        path: tile_path,
        a: 255
      }
    end

    # increment tile to render on frames divisible by 30 (half a second)
    # (one frame is allotted to take screenshot)
    if args.state.tile_clock.zmod?(30)
      args.state.tile_x += 1
      if args.state.tile_x >= 10
        args.state.tile_x  = 0
        args.state.tile_y += 1
      end

      # once all of tile tiles are created, begin displaying map
      if args.state.tile_y >= 10
        args.state.creating_tiles = false
        args.state.displaying_tiles = true
      end
    end

    args.state.tile_clock += 1
  end
end

$gtk.reset

    Blend Modes - main.rb link

    # ./samples/07_advanced_rendering/11_blend_modes/app/main.rb
$gtk.reset

def draw_blendmode args, mode
  w = 160
  h = w
  args.state.x += (1280-w) / (args.state.blendmodes.length + 1)
  x = args.state.x
  y = (720 - h) / 2
  s = 'sprites/blue-feathered.png'
  args.outputs.sprites << { blendmode_enum: mode.value, x: x, y: y, w: w, h: h, path: s }
  args.outputs.labels << [x + (w/2), y, mode.name.to_s, 1, 1, 255, 255, 255]
end

def tick args

  # Different blend modes do different things, depending on what they
  # blend against (in this case, the pixels of the background color).
  args.state.bg_element ||= 1
  args.state.bg_color ||= 255
  args.state.bg_color_direction ||= 1
  bg_r = (args.state.bg_element == 1) ? args.state.bg_color : 0
  bg_g = (args.state.bg_element == 2) ? args.state.bg_color : 0
  bg_b = (args.state.bg_element == 3) ? args.state.bg_color : 0
  args.state.bg_color += args.state.bg_color_direction
  if (args.state.bg_color_direction > 0) && (args.state.bg_color >= 255)
    args.state.bg_color_direction = -1
    args.state.bg_color = 255
  elsif (args.state.bg_color_direction < 0) && (args.state.bg_color <= 0)
    args.state.bg_color_direction = 1
    args.state.bg_color = 0
    args.state.bg_element += 1
    if args.state.bg_element >= 4
      args.state.bg_element = 1
    end
  end

  args.outputs.background_color = [ bg_r, bg_g, bg_b, 255 ]

  args.state.blendmodes ||= [
    { name: :none,  value: 0 },
    { name: :blend, value: 1 },
    { name: :add,   value: 2 },
    { name: :mod,   value: 3 },
    { name: :mul,   value: 4 }
  ]

  args.state.x = 0  # reset this, draw_blendmode will increment it.
  args.state.blendmodes.each { |blendmode| draw_blendmode args, blendmode }
end

    Render Target Noclear - main.rb link

    # ./samples/07_advanced_rendering/12_render_target_noclear/app/main.rb
def tick args
  args.state.x ||= 500
  args.state.y ||= 350
  args.state.xinc ||= 7
  args.state.yinc ||= 7
  args.state.bgcolor ||= 1
  args.state.bginc ||= 1

  # clear the render target on the first tick, and then never again. Draw
  #  another box to it every tick, accumulating over time.
  clear_target = (args.state.tick_count == 0) || (args.inputs.keyboard.key_down.space)
  args.render_target(:accumulation).transient = true
  args.render_target(:accumulation).background_color = [ 0, 0, 0, 0 ];
  args.render_target(:accumulation).clear_before_render = clear_target
  args.render_target(:accumulation).solids << [args.state.x, args.state.y, 25, 25, 255, 0, 0, 255];
  args.state.x += args.state.xinc
  args.state.y += args.state.yinc
  args.state.bgcolor += args.state.bginc

  # animation upkeep...change where we draw the next box and what color the
  #  window background will be.
  if args.state.xinc > 0 && args.state.x >= 1280
    args.state.xinc = -7
  elsif args.state.xinc < 0 && args.state.x < 0
    args.state.xinc = 7
  end

  if args.state.yinc > 0 && args.state.y >= 720
    args.state.yinc = -7
  elsif args.state.yinc < 0 && args.state.y < 0
    args.state.yinc = 7
  end

  if args.state.bginc > 0 && args.state.bgcolor >= 255
    args.state.bginc = -1
  elsif args.state.bginc < 0 && args.state.bgcolor <= 0
    args.state.bginc = 1
  end

  # clear the screen to a shade of blue and draw the render target, which
  #  is not clearing every frame, on top of it. Note that you can NOT opt to
  #  skip clearing the screen, only render targets. The screen clears every
  #  frame; double-buffering would prevent correct updates between frames.
  args.outputs.background_color = [ 0, 0, args.state.bgcolor, 255 ]
  args.outputs.sprites << [ 0, 0, 1280, 720, :accumulation ]
end

$gtk.reset

    Lighting - main.rb link

    # ./samples/07_advanced_rendering/13_lighting/app/main.rb
def calc args
  args.state.swinging_light_sign     ||= 1
  args.state.swinging_light_start_at ||= 0
  args.state.swinging_light_duration ||= 300
  args.state.swinging_light_perc       = args.state
                                             .swinging_light_start_at
                                             .ease_spline_extended args.state.tick_count,
                                                                   args.state.swinging_light_duration,
                                                                   [
                                                                     [0.0, 1.0, 1.0, 1.0],
                                                                     [1.0, 1.0, 1.0, 0.0]
                                                                   ]
  args.state.max_swing_angle ||= 45

  if args.state.swinging_light_start_at.elapsed_time > args.state.swinging_light_duration
    args.state.swinging_light_start_at = args.state.tick_count
    args.state.swinging_light_sign *= -1
  end

  args.state.swinging_light_angle = 360 + ((args.state.max_swing_angle * args.state.swinging_light_perc) * args.state.swinging_light_sign)
end

def render args
  args.outputs.background_color = [0, 0, 0]

  # render scene
  args.outputs[:scene].transient!
  args.outputs[:scene].sprites << { x:        0, y:   0, w: 1280, h: 720, path: :pixel }
  args.outputs[:scene].sprites << { x: 640 - 40, y: 100, w:   80, h:  80, path: 'sprites/square/blue.png' }
  args.outputs[:scene].sprites << { x: 640 - 40, y: 200, w:   80, h:  80, path: 'sprites/square/blue.png' }
  args.outputs[:scene].sprites << { x: 640 - 40, y: 300, w:   80, h:  80, path: 'sprites/square/blue.png' }
  args.outputs[:scene].sprites << { x: 640 - 40, y: 400, w:   80, h:  80, path: 'sprites/square/blue.png' }
  args.outputs[:scene].sprites << { x: 640 - 40, y: 500, w:   80, h:  80, path: 'sprites/square/blue.png' }

  # render light
  swinging_light_w = 1100
  args.outputs[:lights].transient!
  args.outputs[:lights].background_color = [0, 0, 0, 0]
  args.outputs[:lights].sprites << { x: 640 - swinging_light_w.half,
                                     y: -1300,
                                     w: swinging_light_w,
                                     h: 3000,
                                     angle_anchor_x: 0.5,
                                     angle_anchor_y: 1.0,
                                     path: "sprites/lights/mask.png",
                                     angle: args.state.swinging_light_angle }

  args.outputs[:lights].sprites << { x: args.inputs.mouse.x - 400,
                                     y: args.inputs.mouse.y - 400,
                                     w: 800,
                                     h: 800,
                                     path: "sprites/lights/mask.png" }

  # merge unlighted scene with lights
  args.outputs[:lighted_scene].transient!
  args.outputs[:lighted_scene].sprites << { x: 0, y: 0, w: 1280, h: 720, path: :lights, blendmode_enum: 0 }
  args.outputs[:lighted_scene].sprites << { blendmode_enum: 2, x: 0, y: 0, w: 1280, h: 720, path: :scene }

  # output lighted scene to main canvas
  args.outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :lighted_scene }

  # render lights and scene render_targets as a mini map
  args.outputs.debug  << { x: 16,      y: (16 + 90).from_top, w: 160, h: 90, r: 255, g: 255, b: 255 }.solid!
  args.outputs.debug  << { x: 16,      y: (16 + 90).from_top, w: 160, h: 90, path: :lights }
  args.outputs.debug  << { x: 16 + 80, y: (16 + 90 + 8).from_top, text: ":lights render_target", r: 255, g: 255, b: 255, size_enum: -3, alignment_enum: 1 }

  args.outputs.debug  << { x: 16 + 160 + 16,      y: (16 + 90).from_top, w: 160, h: 90, r: 255, g: 255, b: 255 }.solid!
  args.outputs.debug  << { x: 16 + 160 + 16,      y: (16 + 90).from_top, w: 160, h: 90, path: :scene }
  args.outputs.debug  << { x: 16 + 160 + 16 + 80, y: (16 + 90 + 8).from_top, text: ":scene render_target", r: 255, g: 255, b: 255, size_enum: -3, alignment_enum: 1 }
end

def tick args
  render args
  calc args
end

$gtk.reset

    Triangles - main.rb link

    # ./samples/07_advanced_rendering/14_triangles/app/main.rb
def tick args
  args.outputs.labels << {
    x: 640,
    y: 30.from_top,
    text: "Triangle rendering is available in Indie and Pro versions (ignored in Standard Edition).",
    alignment_enum: 1
  }

  dragonruby_logo_width  = 128
  dragonruby_logo_height = 101

  row_0 = 400
  row_1 = 250

  col_0 = 384 - dragonruby_logo_width.half + dragonruby_logo_width * 0
  col_1 = 384 - dragonruby_logo_width.half + dragonruby_logo_width * 1
  col_2 = 384 - dragonruby_logo_width.half + dragonruby_logo_width * 2
  col_3 = 384 - dragonruby_logo_width.half + dragonruby_logo_width * 3
  col_4 = 384 - dragonruby_logo_width.half + dragonruby_logo_width * 4

  # row 0
  args.outputs.solids << make_triangle(
    col_0,
    row_0,
    col_0 + dragonruby_logo_width.half,
    row_0 + dragonruby_logo_height,
    col_0 + dragonruby_logo_width.half + dragonruby_logo_width.half,
    row_0,
    0, 128, 128,
    128
  )

  args.outputs.solids << {
    x:  col_1,
    y:  row_0,
    x2: col_1 + dragonruby_logo_width.half,
    y2: row_0 + dragonruby_logo_height,
    x3: col_1 + dragonruby_logo_width,
    y3: row_0,
  }

  args.outputs.sprites << {
    x:  col_2,
    y:  row_0,
    w:  dragonruby_logo_width,
    h:  dragonruby_logo_height,
    path: 'dragonruby.png'
  }

  args.outputs.sprites << {
    x:  col_3,
    y:  row_0,
    x2: col_3 + dragonruby_logo_width.half,
    y2: row_0 + dragonruby_logo_height,
    x3: col_3 + dragonruby_logo_width,
    y3: row_0,
    path: 'dragonruby.png',
    source_x:  0,
    source_y:  0,
    source_x2: dragonruby_logo_width.half,
    source_y2: dragonruby_logo_height,
    source_x3: dragonruby_logo_width,
    source_y3: 0
  }

  args.outputs.sprites << TriangleLogo.new(x:  col_4,
                                           y:  row_0,
                                           x2: col_4 + dragonruby_logo_width.half,
                                           y2: row_0 + dragonruby_logo_height,
                                           x3: col_4 + dragonruby_logo_width,
                                           y3: row_0,
                                           path: 'dragonruby.png',
                                           source_x:  0,
                                           source_y:  0,
                                           source_x2: dragonruby_logo_width.half,
                                           source_y2: dragonruby_logo_height,
                                           source_x3: dragonruby_logo_width,
                                           source_y3: 0)

  # row 1
  args.outputs.primitives << make_triangle(
    col_0,
    row_1,
    col_0 + dragonruby_logo_width.half,
    row_1 + dragonruby_logo_height,
    col_0 + dragonruby_logo_width,
    row_1,
    0, 128, 128,
    args.state.tick_count.to_radians.sin_r.abs * 255
  )

  args.outputs.primitives << {
    x:  col_1,
    y:  row_1,
    x2: col_1 + dragonruby_logo_width.half,
    y2: row_1 + dragonruby_logo_height,
    x3: col_1 + dragonruby_logo_width,
    y3: row_1,
    r:  0, g: 0, b: 0, a: args.state.tick_count.to_radians.sin_r.abs * 255
  }

  args.outputs.sprites << {
    x:  col_2,
    y:  row_1,
    w:  dragonruby_logo_width,
    h:  dragonruby_logo_height,
    path: 'dragonruby.png',
    source_x:  0,
    source_y:  0,
    source_w:  dragonruby_logo_width,
    source_h:  dragonruby_logo_height.half +
               dragonruby_logo_height.half * Math.sin(args.state.tick_count.to_radians).abs,
  }

  args.outputs.primitives << {
    x:  col_3,
    y:  row_1,
    x2: col_3 + dragonruby_logo_width.half,
    y2: row_1 + dragonruby_logo_height,
    x3: col_3 + dragonruby_logo_width,
    y3: row_1,
    path: 'dragonruby.png',
    source_x:  0,
    source_y:  0,
    source_x2: dragonruby_logo_width.half,
    source_y2: dragonruby_logo_height.half +
               dragonruby_logo_height.half * Math.sin(args.state.tick_count.to_radians).abs,
    source_x3: dragonruby_logo_width,
    source_y3: 0
  }

  args.outputs.primitives << TriangleLogo.new(x:  col_4,
                                              y:  row_1,
                                              x2: col_4 + dragonruby_logo_width.half,
                                              y2: row_1 + dragonruby_logo_height,
                                              x3: col_4 + dragonruby_logo_width,
                                              y3: row_1,
                                              path: 'dragonruby.png',
                                              source_x:  0,
                                              source_y:  0,
                                              source_x2: dragonruby_logo_width.half,
                                              source_y2: dragonruby_logo_height.half +
                                                         dragonruby_logo_height.half * Math.sin(args.state.tick_count.to_radians).abs,
                                              source_x3: dragonruby_logo_width,
                                              source_y3: 0)
end

def make_triangle *opts
  x, y, x2, y2, x3, y3, r, g, b, a = opts
  {
    x: x, y: y, x2: x2, y2: y2, x3: x3, y3: y3,
    r: r || 0,
    g: g || 0,
    b: b || 0,
    a: a || 255
  }
end

class TriangleLogo
  attr_sprite

  def initialize x:, y:, x2:, y2:, x3:, y3:, path:, source_x:, source_y:, source_x2:, source_y2:, source_x3:, source_y3:;
    @x         = x
    @y         = y
    @x2        = x2
    @y2        = y2
    @x3        = x3
    @y3        = y3
    @path      = path
    @source_x  = source_x
    @source_y  = source_y
    @source_x2 = source_x2
    @source_y2 = source_y2
    @source_x3 = source_x3
    @source_y3 = source_y3
  end
end

    Triangles Trapezoid - main.rb link

    # ./samples/07_advanced_rendering/15_triangles_trapezoid/app/main.rb
def tick args
  args.outputs.labels << {
    x: 640,
    y: 30.from_top,
    text: "Triangle rendering is available in Indie and Pro versions (ignored in Standard Edition).",
    alignment_enum: 1
  }

  transform_scale = ((args.state.tick_count / 3).sin.abs ** 5).half
  args.outputs.sprites << [
    { x:         600,
      y:         320,
      x2:        600,
      y2:        400,
      x3:        640,
      y3:        360,
      path:      "sprites/square/blue.png",
      source_x:  0,
      source_y:  0,
      source_x2: 0,
      source_y2: 80,
      source_x3: 40,
      source_y3: 40 },
    { x:         600,
      y:         400,
      x2:        680,
      y2:        (400 - 80 * transform_scale).round,
      x3:        640,
      y3:        360,
      path:      "sprites/square/blue.png",
      source_x:  0,
      source_y:  80,
      source_x2: 80,
      source_y2: 80,
      source_x3: 40,
      source_y3: 40 },
    { x:         640,
      y:         360,
      x2:        680,
      y2:        (400 - 80 * transform_scale).round,
      x3:        680,
      y3:        (320 + 80 * transform_scale).round,
      path:      "sprites/square/blue.png",
      source_x:  40,
      source_y:  40,
      source_x2: 80,
      source_y2: 80,
      source_x3: 80,
      source_y3: 0 },
    { x:         600,
      y:         320,
      x2:        640,
      y2:        360,
      x3:        680,
      y3:        (320 + 80 * transform_scale).round,
      path:      "sprites/square/blue.png",
      source_x:  0,
      source_y:  0,
      source_x2: 40,
      source_y2: 40,
      source_x3: 80,
      source_y3: 0 }
  ]
end

    Camera Space World Space Simple - main.rb link

    # ./samples/07_advanced_rendering/16_camera_space_world_space_simple/app/main.rb
def tick args
  # camera must have the following properties (x, y, and scale)
  args.state.camera ||= {
    x: 0,
    y: 0,
    scale: 1
  }

  args.state.camera.x += args.inputs.left_right * 10 * args.state.camera.scale
  args.state.camera.y += args.inputs.up_down * 10 * args.state.camera.scale

  # generate 500 shapes with random positions
  args.state.objects ||= 500.map do
    {
      x: -2000 + rand(4000),
      y: -2000 + rand(4000),
      w: 16,
      h: 16,
      path: 'sprites/square/blue.png'
    }
  end

  # "i" to zoom in, "o" to zoom out
  if args.inputs.keyboard.key_down.i || args.inputs.keyboard.key_down.equal_sign || args.inputs.keyboard.key_down.plus
    args.state.camera.scale += 0.1
  elsif args.inputs.keyboard.key_down.o || args.inputs.keyboard.key_down.minus
    args.state.camera.scale -= 0.1
    args.state.camera.scale = 0.1 if args.state.camera.scale < 0.1
  end

  # "zero" to reset zoom and camera
  if args.inputs.keyboard.key_down.zero
    args.state.camera.scale = 1
    args.state.camera.x = 0
    args.state.camera.y = 0
  end

  # if mouse is clicked
  if args.inputs.mouse.click
    # convert the mouse to world space and delete any objects that intersect with the mouse
    rect = Camera.to_world_space args.state.camera, args.inputs.mouse
    args.state.objects.reject! { |o| rect.intersect_rect? o }
  end

  # "r" to reset
  if args.inputs.keyboard.key_down.r
    $gtk.reset_next_tick
  end

  # define scene
  args.outputs[:scene].transient!
  args.outputs[:scene].w = Camera::WORLD_SIZE
  args.outputs[:scene].h = Camera::WORLD_SIZE

  # render diagonals and background of scene
  args.outputs[:scene].lines << { x: 0, y: 0, x2: 1500, y2: 1500, r: 0, g: 0, b: 0, a: 255 }
  args.outputs[:scene].lines << { x: 0, y: 1500, x2: 1500, y2: 0, r: 0, g: 0, b: 0, a: 255 }
  args.outputs[:scene].solids << { x: 0, y: 0, w: 1500, h: 1500, a: 128 }

  # find all objects to render
  objects_to_render = Camera.find_all_intersect_viewport args.state.camera, args.state.objects

  # for objects that were found, convert the rect to screen coordinates and place them in scene
  args.outputs[:scene].sprites << objects_to_render.map { |o| Camera.to_screen_space args.state.camera, o }

  # render scene to screen
  args.outputs.sprites << { **Camera.viewport, path: :scene }

  # render instructions
  args.outputs.sprites << { x: 0, y: 110.from_top, w: 1280, h: 110, path: :pixel, r: 0, g: 0, b: 0, a: 128 }
  label_style = { r: 255, g: 255, b: 255, anchor_y: 0.5 }
  args.outputs.labels << { x: 30, y: 30.from_top, text: "Arrow keys to move around. I and O Keys to zoom in and zoom out (0 to reset camera, R to reset everything).", **label_style }
  args.outputs.labels << { x: 30, y: 60.from_top, text: "Click square to remove from world.", **label_style }
  args.outputs.labels << { x: 30, y: 90.from_top, text: "Mouse locationin world: #{(Camera.to_world_space args.state.camera, args.inputs.mouse).to_sf}", **label_style }
end

# helper methods to create a camera and go to and from screen space and world space
class Camera
  SCREEN_WIDTH = 1280
  SCREEN_HEIGHT = 720
  WORLD_SIZE = 1500
  WORLD_SIZE_HALF = WORLD_SIZE / 2
  OFFSET_X = (SCREEN_WIDTH - WORLD_SIZE) / 2
  OFFSET_Y = (SCREEN_HEIGHT - WORLD_SIZE) / 2

  class << self
    # given a rect in screen space, converts the rect to world space
    def to_world_space camera, rect
      rect_x = rect.x
      rect_y = rect.y
      rect_w = rect.w || 0
      rect_h = rect.h || 0
      x = (rect_x - WORLD_SIZE_HALF + camera.x * camera.scale - OFFSET_X) / camera.scale
      y = (rect_y - WORLD_SIZE_HALF + camera.y * camera.scale - OFFSET_Y) / camera.scale
      w = rect_w / camera.scale
      h = rect_h / camera.scale
      rect.merge x: x, y: y, w: w, h: h
    end

    # given a rect in world space, converts the rect to screen space
    def to_screen_space camera, rect
      rect_x = rect.x
      rect_y = rect.y
      rect_w = rect.w || 0
      rect_h = rect.h || 0
      x = rect_x * camera.scale - camera.x * camera.scale + WORLD_SIZE_HALF
      y = rect_y * camera.scale - camera.y * camera.scale + WORLD_SIZE_HALF
      w = rect_w * camera.scale
      h = rect_h * camera.scale
      rect.merge x: x, y: y, w: w, h: h
    end

    # viewport of the scene
    def viewport
      {
        x: OFFSET_X,
        y: OFFSET_Y,
        w: 1500,
        h: 1500
      }
    end

    # viewport in the context of the world
    def viewport_world camera
      to_world_space camera, viewport
    end

    # helper method to find objects within viewport
    def find_all_intersect_viewport camera, os
      Geometry.find_all_intersect_rect viewport_world(camera), os
    end
  end
end

$gtk.reset

    Camera Space World Space Simple Grid Map - main.rb link

    # ./samples/07_advanced_rendering/16_camera_space_world_space_simple_grid_map/app/main.rb
def tick args
  defaults args
  calc args
  render args
end

def defaults args
  tile_size = 100
  tiles_per_row = 32
  number_of_rows = 32
  number_of_tiles = tiles_per_row * number_of_rows

  # generate map tiles
  args.state.tiles ||= number_of_tiles.map_with_index do |i|
    row = i.idiv(tiles_per_row)
    col = i.mod(tiles_per_row)
    {
      x: row * tile_size,
      y: col * tile_size,
      w: tile_size,
      h: tile_size,
      path: 'sprites/square/blue.png'
    }
  end

  center_map = {
    x: tiles_per_row.idiv(2) * tile_size,
    y: number_of_rows.idiv(2) * tile_size,
    w: 1,
    h: 1
  }

  args.state.center_tile ||= args.state.tiles.find { |o| o.intersect_rect? center_map }
  args.state.selected_tile ||= args.state.center_tile

  # camera must have the following properties (x, y, and scale)
  if !args.state.camera
    args.state.camera = {
      x: 0,
      y: 0,
      scale: 1,
      target_x: 0,
      target_y: 0,
      target_scale: 1
    }

    args.state.camera.target_x = args.state.selected_tile.x + args.state.selected_tile.w.half
    args.state.camera.target_y = args.state.selected_tile.y + args.state.selected_tile.h.half
    args.state.camera.x = args.state.camera.target_x
    args.state.camera.y = args.state.camera.target_y
  end
end

def calc args
  calc_inputs args
  calc_camera args
end

def calc_inputs args
  # "i" to zoom in, "o" to zoom out
  if args.inputs.keyboard.key_down.i || args.inputs.keyboard.key_down.equal_sign || args.inputs.keyboard.key_down.plus
    args.state.camera.target_scale += 0.1 * args.state.camera.scale
  elsif args.inputs.keyboard.key_down.o || args.inputs.keyboard.key_down.minus
    args.state.camera.target_scale -= 0.1 * args.state.camera.scale
    args.state.camera.target_scale = 0.1 if args.state.camera.scale < 0.1
  end

  # "zero" to reset zoom and camera
  if args.inputs.keyboard.key_down.zero
    args.state.camera.target_scale = 1
    args.state.selected_tile = args.state.center_tile
  end

  # if mouse is clicked
  if args.inputs.mouse.click
    # convert the mouse to world space and delete any tiles that intersect with the mouse
    rect = Camera.to_world_space args.state.camera, args.inputs.mouse
    selected_tile = args.state.tiles.find { |o| rect.intersect_rect? o }
    if selected_tile
      args.state.selected_tile = selected_tile
      args.state.camera.target_scale = 1
    end
  end

  # "r" to reset
  if args.inputs.keyboard.key_down.r
    $gtk.reset_next_tick
  end
end

def calc_camera args
  args.state.camera.target_x = args.state.selected_tile.x + args.state.selected_tile.w.half
  args.state.camera.target_y = args.state.selected_tile.y + args.state.selected_tile.h.half
  dx = args.state.camera.target_x - args.state.camera.x
  dy = args.state.camera.target_y - args.state.camera.y
  ds = args.state.camera.target_scale - args.state.camera.scale
  args.state.camera.x += dx * 0.1 * args.state.camera.scale
  args.state.camera.y += dy * 0.1 * args.state.camera.scale
  args.state.camera.scale += ds * 0.1
end

def render args
  args.outputs.background_color = [0, 0, 0]

  # define scene
  args.outputs[:scene].transient!
  args.outputs[:scene].w = Camera::WORLD_SIZE
  args.outputs[:scene].h = Camera::WORLD_SIZE
  args.outputs[:scene].background_color = [0, 0, 0, 0]

  # render diagonals and background of scene
  args.outputs[:scene].lines << { x: 0, y: 0, x2: 1500, y2: 1500, r: 0, g: 0, b: 0, a: 255 }
  args.outputs[:scene].lines << { x: 0, y: 1500, x2: 1500, y2: 0, r: 0, g: 0, b: 0, a: 255 }
  args.outputs[:scene].solids << { x: 0, y: 0, w: 1500, h: 1500, a: 128 }

  # find all tiles to render
  objects_to_render = Camera.find_all_intersect_viewport args.state.camera, args.state.tiles

  # convert mouse to world space to see if it intersects with any tiles (hover color)
  mouse_in_world = Camera.to_world_space args.state.camera, args.inputs.mouse

  # for tiles that were found, convert the rect to screen coordinates and place them in scene
  args.outputs[:scene].sprites << objects_to_render.map do |o|
    if o == args.state.selected_tile
      tile_to_render = o.merge path: 'sprites/square/green.png'
    elsif o.intersect_rect? mouse_in_world
      tile_to_render = o.merge path: 'sprites/square/orange.png'
    else
      tile_to_render = o.merge path: 'sprites/square/blue.png'
    end

    Camera.to_screen_space args.state.camera, tile_to_render
  end

  # render scene to screen
  args.outputs.sprites << { **Camera.viewport, path: :scene }

  # render instructions
  args.outputs.sprites << { x: 0, y: 110.from_top, w: 1280, h: 110, path: :pixel, r: 0, g: 0, b: 0, a: 200 }
  label_style = { r: 255, g: 255, b: 255, anchor_y: 0.5 }
  args.outputs.labels << { x: 30, y: 30.from_top, text: "I/O or +/- keys to zoom in and zoom out (0 to reset camera, R to reset everything).", **label_style }
  args.outputs.labels << { x: 30, y: 60.from_top, text: "Click to center on square.", **label_style }
  args.outputs.labels << { x: 30, y: 90.from_top, text: "Mouse location in world: #{(Camera.to_world_space args.state.camera, args.inputs.mouse).to_sf}", **label_style }
end

# helper methods to create a camera and go to and from screen space and world space
class Camera
  SCREEN_WIDTH = 1280
  SCREEN_HEIGHT = 720
  WORLD_SIZE = 1500
  WORLD_SIZE_HALF = WORLD_SIZE / 2
  OFFSET_X = (SCREEN_WIDTH - WORLD_SIZE) / 2
  OFFSET_Y = (SCREEN_HEIGHT - WORLD_SIZE) / 2

  class << self
    # given a rect in screen space, converts the rect to world space
    def to_world_space camera, rect
      rect_x = rect.x
      rect_y = rect.y
      rect_w = rect.w || 0
      rect_h = rect.h || 0
      x = (rect_x - WORLD_SIZE_HALF + camera.x * camera.scale - OFFSET_X) / camera.scale
      y = (rect_y - WORLD_SIZE_HALF + camera.y * camera.scale - OFFSET_Y) / camera.scale
      w = rect_w / camera.scale
      h = rect_h / camera.scale
      rect.merge x: x, y: y, w: w, h: h
    end

    # given a rect in world space, converts the rect to screen space
    def to_screen_space camera, rect
      rect_x = rect.x
      rect_y = rect.y
      rect_w = rect.w || 0
      rect_h = rect.h || 0
      x = rect_x * camera.scale - camera.x * camera.scale + WORLD_SIZE_HALF
      y = rect_y * camera.scale - camera.y * camera.scale + WORLD_SIZE_HALF
      w = rect_w * camera.scale
      h = rect_h * camera.scale
      rect.merge x: x, y: y, w: w, h: h
    end

    # viewport of the scene
    def viewport
      {
        x: OFFSET_X,
        y: OFFSET_Y,
        w: WORLD_SIZE,
        h: WORLD_SIZE
      }
    end

    # viewport in the context of the world
    def viewport_world camera
      to_world_space camera, viewport
    end

    # helper method to find objects within viewport
    def find_all_intersect_viewport camera, os
      Geometry.find_all_intersect_rect viewport_world(camera), os
    end
  end
end

$gtk.reset

    Matrix And Triangles 2d - main.rb link

    # ./samples/07_advanced_rendering/16_matrix_and_triangles_2d/app/main.rb
include MatrixFunctions

def tick args
  args.state.square_one_sprite = { x:        0,
                                   y:        0,
                                   w:        100,
                                   h:        100,
                                   path:     "sprites/square/blue.png",
                                   source_x: 0,
                                   source_y: 0,
                                   source_w: 80,
                                   source_h: 80 }

  args.state.square_two_sprite = { x:        0,
                                   y:        0,
                                   w:        100,
                                   h:        100,
                                   path:     "sprites/square/red.png",
                                   source_x: 0,
                                   source_y: 0,
                                   source_w: 80,
                                   source_h: 80 }

  args.state.square_one        = sprite_to_triangles args.state.square_one_sprite
  args.state.square_two        = sprite_to_triangles args.state.square_two_sprite
  args.state.camera.x        ||= 0
  args.state.camera.y        ||= 0
  args.state.camera.zoom     ||= 1
  args.state.camera.rotation ||= 0

  zmod = 1
  move_multiplier = 1
  dzoom = 0.01

  if args.state.tick_count.zmod? zmod
    args.state.camera.x += args.inputs.left_right * -1 * move_multiplier
    args.state.camera.y += args.inputs.up_down * -1 * move_multiplier
  end

  if args.inputs.keyboard.i
    args.state.camera.zoom += dzoom
  elsif args.inputs.keyboard.o
    args.state.camera.zoom -= dzoom
  end

  args.state.camera.zoom = args.state.camera.zoom.clamp(0.25, 10)

  args.outputs.sprites << triangles_mat3_mul(args.state.square_one,
                                             mat3_translate(-50, -50),
                                             mat3_rotate(args.state.tick_count),
                                             mat3_translate(0, 0),
                                             mat3_translate(args.state.camera.x, args.state.camera.y),
                                             mat3_scale(args.state.camera.zoom),
                                             mat3_translate(640, 360))

  args.outputs.sprites << triangles_mat3_mul(args.state.square_two,
                                             mat3_translate(-50, -50),
                                             mat3_rotate(args.state.tick_count),
                                             mat3_translate(100, 100),
                                             mat3_translate(args.state.camera.x, args.state.camera.y),
                                             mat3_scale(args.state.camera.zoom),
                                             mat3_translate(640, 360))

  mouse_coord = vec3 args.inputs.mouse.x,
                     args.inputs.mouse.y,
                     1

  mouse_coord = mul mouse_coord,
                    mat3_translate(-640, -360),
                    mat3_scale(args.state.camera.zoom),
                    mat3_translate(-args.state.camera.x, -args.state.camera.y)

  args.outputs.lines  << { x: 640, y:   0, h:  720 }
  args.outputs.lines  << { x:   0, y: 360, w: 1280 }
  args.outputs.labels << { x: 30, y: 60.from_top, text: "x: #{args.state.camera.x.to_sf} y: #{args.state.camera.y.to_sf} z: #{args.state.camera.zoom.to_sf}" }
  args.outputs.labels << { x: 30, y: 90.from_top, text: "Mouse: #{mouse_coord.x.to_sf} #{mouse_coord.y.to_sf}" }
  args.outputs.labels << { x: 30,
                           y: 30.from_top,
                           text: "W,A,S,D to move. I, O to zoom. Triangles is a Indie/Pro Feature and will be ignored in Standard." }
end

def sprite_to_triangles sprite
  [
    {
      x:         sprite.x,                          y:  sprite.y,
      x2:        sprite.x,                          y2: sprite.y + sprite.h,
      x3:        sprite.x + sprite.w,               y3: sprite.y + sprite.h,
      source_x:  sprite.source_x,                   source_y:  sprite.source_y,
      source_x2: sprite.source_x,                   source_y2: sprite.source_y + sprite.source_h,
      source_x3: sprite.source_x + sprite.source_w, source_y3: sprite.source_y + sprite.source_h,
      path:      sprite.path
    },
    {
      x:  sprite.x,                                 y:  sprite.y,
      x2: sprite.x + sprite.w,                      y2: sprite.y + sprite.h,
      x3: sprite.x + sprite.w,                      y3: sprite.y,
      source_x:  sprite.source_x,                   source_y:  sprite.source_y,
      source_x2: sprite.source_x + sprite.source_w, source_y2: sprite.source_y + sprite.source_h,
      source_x3: sprite.source_x + sprite.source_w, source_y3: sprite.source_y,
      path:      sprite.path
    }
  ]
end

def mat3_translate dx, dy
  mat3 1, 0, dx,
       0, 1, dy,
       0, 0,  1
end

def mat3_rotate angle_d
  angle_r = angle_d.to_radians
  mat3 Math.cos(angle_r), -Math.sin(angle_r), 0,
       Math.sin(angle_r),  Math.cos(angle_r), 0,
                       0,                  0, 1
end

def mat3_scale scale
  mat3 scale,     0, 0,
           0, scale, 0,
           0,     0, 1
end

def triangles_mat3_mul triangles, *matrices
  triangles.map { |triangle| triangle_mat3_mul triangle, *matrices }
end

def triangle_mat3_mul triangle, *matrices
  result = [
    (vec3 triangle.x,  triangle.y,  1),
    (vec3 triangle.x2, triangle.y2, 1),
    (vec3 triangle.x3, triangle.y3, 1)
  ].map do |coord|
    mul coord, *matrices
  end

  {
    **triangle,
    x:  result[0].x,
    y:  result[0].y,
    x2: result[1].x,
    y2: result[1].y,
    x3: result[2].x,
    y3: result[2].y,
  }
rescue Exception => e
  pretty_print triangle
  pretty_print result
  pretty_print matrices
  puts "#{matrices}"
  raise e
end

    Matrix And Triangles 3d - main.rb link

    # ./samples/07_advanced_rendering/16_matrix_and_triangles_3d/app/main.rb
include MatrixFunctions

def tick args
  args.outputs.labels << { x: 0,
                           y: 30.from_top,
                           text: "W,A,S,D to move. Q,E,U,O to turn, I,K for elevation. Triangles is a Indie/Pro Feature and will be ignored in Standard.",
                           alignment_enum: 1 }

  args.grid.origin_center!

  args.state.cam_x ||= 0.00
  if args.inputs.keyboard.left
    args.state.cam_x += 0.01
  elsif args.inputs.keyboard.right
    args.state.cam_x -= 0.01
  end

  args.state.cam_y ||= 0.00
  if args.inputs.keyboard.i
    args.state.cam_y += 0.01
  elsif args.inputs.keyboard.k
    args.state.cam_y -= 0.01
  end

  args.state.cam_z ||= 6.5
  if args.inputs.keyboard.s
    args.state.cam_z += 0.1
  elsif args.inputs.keyboard.w
    args.state.cam_z -= 0.1
  end

  args.state.cam_angle_y ||= 0
  if args.inputs.keyboard.q
    args.state.cam_angle_y += 0.25
  elsif args.inputs.keyboard.e
    args.state.cam_angle_y -= 0.25
  end

  args.state.cam_angle_x ||= 0
  if args.inputs.keyboard.u
    args.state.cam_angle_x += 0.1
  elsif args.inputs.keyboard.o
    args.state.cam_angle_x -= 0.1
  end

  # model A
  args.state.a = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.a_world = mul_world args,
                                 args.state.a,
                                 (translate -0.25, -0.25, 0),
                                 (translate  0, 0, 0.25),
                                 (rotate_x args.state.tick_count)

  args.state.a_camera = mul_cam args, args.state.a_world
  args.state.a_projected = mul_perspective args, args.state.a_camera
  render_projection args, args.state.a_projected

  # model B
  args.state.b = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.b_world = mul_world args,
                                 args.state.b,
                                 (translate -0.25, -0.25, 0),
                                 (translate  0, 0, -0.25),
                                 (rotate_x args.state.tick_count)

  args.state.b_camera = mul_cam args, args.state.b_world
  args.state.b_projected = mul_perspective args, args.state.b_camera
  render_projection args, args.state.b_projected

  # model C
  args.state.c = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.c_world = mul_world args,
                                 args.state.c,
                                 (translate -0.25, -0.25, 0),
                                 (rotate_y 90),
                                 (translate -0.25,  0, 0),
                                 (rotate_x args.state.tick_count)

  args.state.c_camera = mul_cam args, args.state.c_world
  args.state.c_projected = mul_perspective args, args.state.c_camera
  render_projection args, args.state.c_projected

  # model D
  args.state.d = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.d_world = mul_world args,
                                 args.state.d,
                                 (translate -0.25, -0.25, 0),
                                 (rotate_y 90),
                                 (translate  0.25,  0, 0),
                                 (rotate_x args.state.tick_count)

  args.state.d_camera = mul_cam args, args.state.d_world
  args.state.d_projected = mul_perspective args, args.state.d_camera
  render_projection args, args.state.d_projected

  # model E
  args.state.e = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.e_world = mul_world args,
                                 args.state.e,
                                 (translate -0.25, -0.25, 0),
                                 (rotate_x 90),
                                 (translate  0,  0.25, 0),
                                 (rotate_x args.state.tick_count)

  args.state.e_camera = mul_cam args, args.state.e_world
  args.state.e_projected = mul_perspective args, args.state.e_camera
  render_projection args, args.state.e_projected

  # model E
  args.state.f = [
    [vec4(0, 0, 0, 1),   vec4(0.5, 0, 0, 1),   vec4(0, 0.5, 0, 1)],
    [vec4(0.5, 0, 0, 1), vec4(0.5, 0.5, 0, 1), vec4(0, 0.5, 0, 1)]
  ]

  # model to world
  args.state.f_world = mul_world args,
                                 args.state.f,
                                 (translate -0.25, -0.25, 0),
                                 (rotate_x 90),
                                 (translate  0,  -0.25, 0),
                                 (rotate_x args.state.tick_count)

  args.state.f_camera = mul_cam args, args.state.f_world
  args.state.f_projected = mul_perspective args, args.state.f_camera
  render_projection args, args.state.f_projected

  # render_debug args, args.state.a, args.state.a_transform, args.state.a_projected
  # args.outputs.labels << { x: -630, y:  10.from_top,  text: "x:         #{args.state.cam_x.to_sf} -> #{( args.state.cam_x * 1000 ).to_sf}" }
  # args.outputs.labels << { x: -630, y:  30.from_top,  text: "y:         #{args.state.cam_y.to_sf} -> #{( args.state.cam_y * 1000 ).to_sf}" }
  # args.outputs.labels << { x: -630, y:  50.from_top,  text: "z:         #{args.state.cam_z.fdiv(10).to_sf} -> #{( args.state.cam_z * 100 ).to_sf}" }
end

def mul_world args, model, *mul_def
  model.map do |vecs|
    vecs.map do |vec|
      mul vec,
          *mul_def
    end
  end
end

def mul_cam args, world_vecs
  world_vecs.map do |vecs|
    vecs.map do |vec|
      mul vec,
          (translate -args.state.cam_x, args.state.cam_y, -args.state.cam_z),
          (rotate_y args.state.cam_angle_y),
          (rotate_x args.state.cam_angle_x)
    end
  end
end

def mul_perspective args, camera_vecs
  camera_vecs.map do |vecs|
    vecs.map do |vec|
      perspective vec
    end
  end
end

def render_debug args, model, transform, projected
  args.outputs.labels << { x: -630, y:  10.from_top,  text: "model:     #{vecs_to_s model[0]}" }
  args.outputs.labels << { x: -630, y:  30.from_top,  text: "           #{vecs_to_s model[1]}" }
  args.outputs.labels << { x: -630, y:  50.from_top,  text: "transform: #{vecs_to_s transform[0]}" }
  args.outputs.labels << { x: -630, y:  70.from_top,  text: "           #{vecs_to_s transform[1]}" }
  args.outputs.labels << { x: -630, y:  90.from_top,  text: "projected: #{vecs_to_s projected[0]}" }
  args.outputs.labels << { x: -630, y: 110.from_top,  text: "           #{vecs_to_s projected[1]}" }
end

def render_projection args, projection
  p0 = projection[0]
  args.outputs.sprites << {
    x:  p0[0].x,   y: p0[0].y,
    x2: p0[1].x,  y2: p0[1].y,
    x3: p0[2].x,  y3: p0[2].y,
    source_x:   0, source_y:   0,
    source_x2: 80, source_y2:  0,
    source_x3:  0, source_y3: 80,
    a: 40,
    # r: 128, g: 128, b: 128,
    path: 'sprites/square/blue.png'
  }

  p1 = projection[1]
  args.outputs.sprites << {
    x:  p1[0].x,   y: p1[0].y,
    x2: p1[1].x,  y2: p1[1].y,
    x3: p1[2].x,  y3: p1[2].y,
    source_x:  80, source_y:   0,
    source_x2: 80, source_y2: 80,
    source_x3:  0, source_y3: 80,
    a: 40,
    # r: 128, g: 128, b: 128,
    path: 'sprites/square/blue.png'
  }
end

def perspective vec
  left   = -1.0
  right  =  1.0
  bottom = -1.0
  top    =  1.0
  near   =  300.0
  far    =  1000.0
  sx = 2 * near / (right - left)
  sy = 2 * near / (top - bottom)
  c2 = - (far + near) / (far - near)
  c1 = 2 * near * far / (near - far)
  tx = -near * (left + right) / (right - left)
  ty = -near * (bottom + top) / (top - bottom)

  p = mat4 sx, 0, 0, tx,
           0, sy, 0, ty,
           0, 0, c2, c1,
           0, 0, -1, 0

  r = mul vec, p
  r.x *= r.z / r.w / 100
  r.y *= r.z / r.w / 100
  r
end

def mat_scale scale
  mat4 scale,     0,     0,   0,
           0, scale,     0,   0,
           0,     0, scale,   0,
           0,     0,     0,   1
end

def rotate_y angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4  cos_t,  0, sin_t, 0,
         0,      1, 0,     0,
         -sin_t, 0, cos_t, 0,
         0,      0, 0,     1)
end

def rotate_z angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4 cos_t, -sin_t, 0, 0,
        sin_t,  cos_t, 0, 0,
        0,      0,     1, 0,
        0,      0,     0, 1)
end

def translate dx, dy, dz
  mat4 1, 0, 0, dx,
       0, 1, 0, dy,
       0, 0, 1, dz,
       0, 0, 0,  1
end


def rotate_x angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4  1,     0,      0, 0,
         0, cos_t, -sin_t, 0,
         0, sin_t,  cos_t, 0,
         0,     0,      0, 1)
end

def vecs_to_s vecs
  vecs.map do |vec|
    "[#{vec.x.to_sf} #{vec.y.to_sf} #{vec.z.to_sf}]"
  end.join " "
end

    Matrix Camera Space World Space - main.rb link

    # ./samples/07_advanced_rendering/16_matrix_camera_space_world_space/app/main.rb
# sample app shows how to translate between screen and world coordinates using matrix multiplication
class Game
  attr_gtk

  def tick
    defaults
    input
    calc
    render
  end

  def defaults
    return if state.tick_count != 0

    # define the size of the world
    state.world_size = 1280

    # initialize the camera
    state.camera = {
      x: 0,
      y: 0,
      zoom: 1
    }

    # initialize entities: place entities randomly in the world
    state.entities = 200.map do
      {
        x: (rand * state.world_size - 100).to_i * (rand > 0.5 ? 1 : -1),
        y: (rand * state.world_size - 100).to_i * (rand > 0.5 ? 1 : -1),
        w: 32,
        h: 32,
        angle: 0,
        path: "sprites/square/blue.png",
        rotation_speed: rand * 5
      }
    end

    # backdrop for the world
    state.backdrop = { x: -state.world_size,
                       y: -state.world_size,
                       w: state.world_size * 2,
                       h: state.world_size * 2,
                       r: 200,
                       g: 100,
                       b: 0,
                       a: 128,
                       path: :pixel }

    # rect representing the screen
    state.screen_rect = { x: 0, y: 0, w: 1280, h: 720 }

    # update the camera matricies (initial state)
    update_matricies!
  end

  # if the camera is ever changed, recompute the matricies that are used
  # to translate between screen and world coordinates. we want to cache
  # the resolved matrix for speed
  def update_matricies!
    # camera space is defined with three matricies
    # every entity is:
    # - offset by the location of the camera
    # - scaled
    # - then centered on the screen
    state.to_camera_space_matrix = MatrixFunctions.mul(mat3_translate(state.camera.x, state.camera.y),
                                                       mat3_scale(state.camera.zoom),
                                                       mat3_translate(640, 360))

    # world space is defined based off the camera matricies but inverted:
    # every entity is:
    # - uncentered from the screen
    # - unscaled
    # - offset by the location of the camera in the opposite direction
    state.to_world_space_matrix = MatrixFunctions.mul(mat3_translate(-640, -360),
                                                      mat3_scale(1.0 / state.camera.zoom),
                                                      mat3_translate(-state.camera.x, -state.camera.y))

    # the viewport is computed by taking the screen rect and moving it into world space.
    # what entities get rendered is based off of the viewport
    state.viewport = rect_mul_matrix(state.screen_rect, state.to_world_space_matrix)
  end

  def input
    # if the camera is changed, invalidate/recompute the translation matricies
    should_update_matricies = false

    # + and - keys zoom in and out
    if inputs.keyboard.equal_sign || inputs.keyboard.plus || inputs.mouse.wheel && inputs.mouse.wheel.y > 0
      state.camera.zoom += 0.01 * state.camera.zoom
      should_update_matricies = true
    elsif inputs.keyboard.minus || inputs.mouse.wheel && inputs.mouse.wheel.y < 0
      state.camera.zoom -= 0.01 * state.camera.zoom
      should_update_matricies = true
    end

    # clamp the zoom to a minimum of 0.25
    if state.camera.zoom < 0.25
      state.camera.zoom = 0.25
      should_update_matricies = true
    end

    # left and right keys move the camera left and right
    if inputs.left_right != 0
      state.camera.x += -1 * (inputs.left_right * 10) * state.camera.zoom
      should_update_matricies = true
    end

    # up and down keys move the camera up and down
    if inputs.up_down != 0
      state.camera.y += -1 * (inputs.up_down * 10) * state.camera.zoom
      should_update_matricies = true
    end

    # reset the camera to the default position
    if inputs.keyboard.key_down.zero
      state.camera.x = 0
      state.camera.y = 0
      state.camera.zoom = 1
      should_update_matricies = true
    end

    # if the update matricies flag is set, recompute the matricies
    update_matricies! if should_update_matricies
  end

  def calc
    # rotate all the entities by their rotation speed
    # and reset their hovered state
    state.entities.each do |entity|
      entity.hovered = false
      entity.angle += entity.rotation_speed
    end

    # find all the entities that are hovered by the mouse and update their state back to hovered
    mouse_in_world = rect_to_world_coordinates inputs.mouse.rect
    hovered_entities = geometry.find_all_intersect_rect mouse_in_world, state.entities
    hovered_entities.each { |entity| entity.hovered = true }
  end

  def render
    # create a render target to represent the camera's viewport
    outputs[:scene].transient!
    outputs[:scene].w = state.world_size
    outputs[:scene].h = state.world_size

    # render the backdrop
    outputs[:scene].primitives << rect_to_screen_coordinates(state.backdrop)

    # get all entities that are within the camera's viewport
    entities_to_render = geometry.find_all_intersect_rect state.viewport, state.entities

    # render all the entities within the viewport
    outputs[:scene].primitives << entities_to_render.map do |entity|
      r = rect_to_screen_coordinates entity

      # change the color of the entity if it's hovered
      r.merge!(path: "sprites/square/red.png") if entity.hovered

      r
    end

    # render the camera's viewport
    outputs.sprites << {
      x: 0,
      y: 0,
      w: state.world_size,
      h: state.world_size,
      path: :scene
    }

    # show a label that shows the mouse's screen and world coordinates
    outputs.labels << { x: 30, y: 30.from_top, text: "#{gtk.current_framerate.to_sf}" }

    mouse_in_world = rect_to_world_coordinates inputs.mouse.rect

    outputs.labels << {
      x: 30,
      y: 55.from_top,
      text: "Screen Coordinates: #{inputs.mouse.x}, #{inputs.mouse.y}",
    }

    outputs.labels << {
      x: 30,
      y: 80.from_top,
      text: "World Coordinates: #{mouse_in_world.x.to_sf}, #{mouse_in_world.y.to_sf}",
    }
  end

  def rect_to_screen_coordinates rect
    rect_mul_matrix rect, state.to_camera_space_matrix
  end

  def rect_to_world_coordinates rect
    rect_mul_matrix rect, state.to_world_space_matrix
  end

  def rect_mul_matrix rect, matrix
    # the bottom left and top right corners of the rect
    # are multiplied by the matrix to get the new coordinates
    bottom_left = MatrixFunctions.mul (MatrixFunctions.vec3 rect.x, rect.y, 1), matrix
    top_right   = MatrixFunctions.mul (MatrixFunctions.vec3 rect.x + rect.w, rect.y + rect.h, 1), matrix

    # with the points of the rect recomputed, reconstruct the rect
    rect.merge x: bottom_left.x,
               y: bottom_left.y,
               w: top_right.x - bottom_left.x,
               h: top_right.y - bottom_left.y
  end

  # this is the definition of how to move a point in 2d space using a matrix
  def mat3_translate x, y
    MatrixFunctions.mat3 1, 0, x,
                         0, 1, y,
                         0, 0, 1
  end

  # this is the definition of how to scale a point in 2d space using a matrix
  def mat3_scale scale
    MatrixFunctions.mat3 scale, 0, 0,
                         0, scale, 0,
                         0,     0, 1
  end
end

$game = Game.new

def tick args
  $game.args = args
  $game.tick
end

$gtk.reset

    Matrix Cubeworld - main.rb link

    # ./samples/07_advanced_rendering/16_matrix_cubeworld/app/main.rb
require 'app/modeling-api.rb'

include MatrixFunctions

def tick args
  args.outputs.labels << { x: 0,
                           y: 30.from_top,
                           text: "W,A,S,D to move. Mouse to look. Triangles is a Indie/Pro Feature and will be ignored in Standard.",
                           alignment_enum: 1 }

  args.grid.origin_center!

  args.state.cam_y ||= 0.00
  if args.inputs.keyboard.i
    args.state.cam_y += 0.01
  elsif args.inputs.keyboard.k
    args.state.cam_y -= 0.01
  end

  args.state.cam_angle_y ||= 0
  if args.inputs.keyboard.q
    args.state.cam_angle_y += 0.25
  elsif args.inputs.keyboard.e
    args.state.cam_angle_y -= 0.25
  end

  args.state.cam_angle_x ||= 0
  if args.inputs.keyboard.u
    args.state.cam_angle_x += 0.1
  elsif args.inputs.keyboard.o
    args.state.cam_angle_x -= 0.1
  end

  if args.inputs.mouse.has_focus
    y_change_rate = (args.inputs.mouse.x / 640) ** 2
    if args.inputs.mouse.x < 0
      args.state.cam_angle_y -= 0.8 * y_change_rate
    else
      args.state.cam_angle_y += 0.8 * y_change_rate
    end

    x_change_rate = (args.inputs.mouse.y / 360) ** 2
    if args.inputs.mouse.y < 0
      args.state.cam_angle_x += 0.8 * x_change_rate
    else
      args.state.cam_angle_x -= 0.8 * x_change_rate
    end
  end

  args.state.cam_z ||= 6.4
  if args.inputs.keyboard.up
    point_1 = { x: 0, y: 0.02 }
    point_r = args.geometry.rotate_point point_1, args.state.cam_angle_y
    args.state.cam_x -= point_r.x
    args.state.cam_z -= point_r.y
  elsif args.inputs.keyboard.down
    point_1 = { x: 0, y: -0.02 }
    point_r = args.geometry.rotate_point point_1, args.state.cam_angle_y
    args.state.cam_x -= point_r.x
    args.state.cam_z -= point_r.y
  end

  args.state.cam_x ||= 0.00
  if args.inputs.keyboard.right
    point_1 = { x: -0.02, y: 0 }
    point_r = args.geometry.rotate_point point_1, args.state.cam_angle_y
    args.state.cam_x -= point_r.x
    args.state.cam_z -= point_r.y
  elsif args.inputs.keyboard.left
    point_1 = { x:  0.02, y: 0 }
    point_r = args.geometry.rotate_point point_1, args.state.cam_angle_y
    args.state.cam_x -= point_r.x
    args.state.cam_z -= point_r.y
  end


  if args.inputs.keyboard.key_down.r || args.inputs.keyboard.key_down.zero
    args.state.cam_x = 0.00
    args.state.cam_y = 0.00
    args.state.cam_z = 1.00
    args.state.cam_angle_y = 0
    args.state.cam_angle_x = 0
  end

  if !args.state.models
    args.state.models = []
    25.times do
      args.state.models.concat new_random_cube
    end
  end

  args.state.models.each do |m|
    render_triangles args, m
  end

  args.outputs.lines << { x:   0, y: -50, h: 100, a: 80 }
  args.outputs.lines << { x: -50, y:   0, w: 100, a: 80 }
end

def mul_triangles model, *mul_def
  combined = mul mul_def
  model.map do |vecs|
    vecs.map do |vec|
      mul vec, *combined
    end
  end
end

def mul_cam args, world_vecs
  mul_triangles world_vecs,
                (translate -args.state.cam_x, -args.state.cam_y, -args.state.cam_z),
                (rotate_y args.state.cam_angle_y),
                (rotate_x args.state.cam_angle_x)
end

def mul_perspective camera_vecs
  camera_vecs.map do |vecs|
    r = vecs.map do |vec|
      perspective vec
    end

    r if r[0] && r[1] && r[2]
  end.reject_nil
end

def render_debug args, model, transform, projected
  args.outputs.labels << { x: -630, y:  10.from_top,  text: "model:     #{vecs_to_s model[0]}" }
  args.outputs.labels << { x: -630, y:  30.from_top,  text: "           #{vecs_to_s model[1]}" }
  args.outputs.labels << { x: -630, y:  50.from_top,  text: "transform: #{vecs_to_s transform[0]}" }
  args.outputs.labels << { x: -630, y:  70.from_top,  text: "           #{vecs_to_s transform[1]}" }
  args.outputs.labels << { x: -630, y:  90.from_top,  text: "projected: #{vecs_to_s projected[0]}" }
  args.outputs.labels << { x: -630, y: 110.from_top,  text: "           #{vecs_to_s projected[1]}" }
end

def render_triangles args, triangles
  camera_space = mul_cam args, triangles
  projection = mul_perspective camera_space

  args.outputs.sprites << projection.map_with_index do |i, index|
    if i
      {
        x:  i[0].x,   y: i[0].y,
        x2: i[1].x,  y2: i[1].y,
        x3: i[2].x,  y3: i[2].y,
        source_x:   0, source_y:   0,
        source_x2: 80, source_y2:  0,
        source_x3:  0, source_y3: 80,
        r: 128, g: 128, b: 128,
        a: 80 + 128 * 1 / (index + 1),
        path: :pixel
      }
    end
  end
end

def perspective vec
  left   =  100.0
  right  = -100.0
  bottom =  100.0
  top    = -100.0
  near   =  3000.0
  far    =  8000.0
  sx = 2 * near / (right - left)
  sy = 2 * near / (top - bottom)
  c2 = - (far + near) / (far - near)
  c1 = 2 * near * far / (near - far)
  tx = -near * (left + right) / (right - left)
  ty = -near * (bottom + top) / (top - bottom)

  p = mat4 sx, 0, 0, tx,
           0, sy, 0, ty,
           0, 0, c2, c1,
           0, 0, -1, 0

  r = mul vec, p
  return nil if r.w < 0
  r.x *= r.z / r.w / 100
  r.y *= r.z / r.w / 100
  r
end

def mat_scale scale
  mat4 scale,     0,     0,   0,
           0, scale,     0,   0,
           0,     0, scale,   0,
           0,     0,     0,   1
end

def rotate_y angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4  cos_t,  0, sin_t, 0,
         0,      1, 0,     0,
         -sin_t, 0, cos_t, 0,
         0,      0, 0,     1)
end

def rotate_z angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4 cos_t, -sin_t, 0, 0,
        sin_t,  cos_t, 0, 0,
        0,      0,     1, 0,
        0,      0,     0, 1)
end

def translate dx, dy, dz
  mat4 1, 0, 0, dx,
       0, 1, 0, dy,
       0, 0, 1, dz,
       0, 0, 0,  1
end


def rotate_x angle_d
  cos_t = Math.cos angle_d.to_radians
  sin_t = Math.sin angle_d.to_radians
  (mat4  1,     0,      0, 0,
         0, cos_t, -sin_t, 0,
         0, sin_t,  cos_t, 0,
         0,     0,      0, 1)
end

def vecs_to_s vecs
  vecs.map do |vec|
    "[#{vec.x.to_sf} #{vec.y.to_sf} #{vec.z.to_sf}]"
  end.join " "
end

def new_random_cube
  cube_w = rand * 0.2 + 0.1
  cube_h = rand * 0.2 + 0.1
  randx = rand * 2.0 * [1, -1].sample
  randy = rand * 2.0
  randz = rand * 5   * [1, -1].sample

  cube = [
    square do
      scale x: cube_w, y: cube_h
      translate x: -cube_w / 2, y: -cube_h / 2
      rotate_x 90
      translate y: -cube_h / 2
      translate x: randx, y: randy, z: randz
    end,
    square do
      scale x: cube_w, y: cube_h
      translate x: -cube_w / 2, y: -cube_h / 2
      rotate_x 90
      translate y:  cube_h / 2
      translate x: randx, y: randy, z: randz
    end,
    square do
      scale x: cube_h, y: cube_h
      translate x: -cube_h / 2, y: -cube_h / 2
      rotate_y 90
      translate x: -cube_w / 2
      translate x: randx, y: randy, z: randz
    end,
    square do
      scale x: cube_h, y: cube_h
      translate x: -cube_h / 2, y: -cube_h / 2
      rotate_y 90
      translate x:  cube_w / 2
      translate x: randx, y: randy, z: randz
    end,
    square do
      scale x: cube_w, y: cube_h
      translate x: -cube_w / 2, y: -cube_h / 2
      translate z: -cube_h / 2
      translate x: randx, y: randy, z: randz
    end,
    square do
      scale x: cube_w, y: cube_h
      translate x: -cube_w / 2, y: -cube_h / 2
      translate z:  cube_h / 2
      translate x: randx, y: randy, z: randz
    end
  ]

  cube
end

$gtk.reset

    Matrix Cubeworld - modeling-api.rb link

    # ./samples/07_advanced_rendering/16_matrix_cubeworld/app/modeling-api.rb
class ModelingApi
  attr :matricies

  def initialize
    @matricies = []
  end

  def scale x: 1, y: 1, z: 1
    @matricies << scale_matrix(x: x, y: y, z: z)
    if block_given?
      yield
      @matricies << scale_matrix(x: -x, y: -y, z: -z)
    end
  end

  def translate x: 0, y: 0, z: 0
    @matricies << translate_matrix(x: x, y: y, z: z)
    if block_given?
      yield
      @matricies << translate_matrix(x: -x, y: -y, z: -z)
    end
  end

  def rotate_x x
    @matricies << rotate_x_matrix(x)
    if block_given?
      yield
      @matricies << rotate_x_matrix(-x)
    end
  end

  def rotate_y y
    @matricies << rotate_y_matrix(y)
    if block_given?
      yield
      @matricies << rotate_y_matrix(-y)
    end
  end

  def rotate_z z
    @matricies << rotate_z_matrix(z)
    if block_given?
      yield
      @matricies << rotate_z_matrix(-z)
    end
  end

  def scale_matrix x:, y:, z:;
    mat4 x, 0, 0, 0,
         0, y, 0, 0,
         0, 0, z, 0,
         0, 0, 0, 1
  end

  def translate_matrix x:, y:, z:;
    mat4 1, 0, 0, x,
         0, 1, 0, y,
         0, 0, 1, z,
         0, 0, 0, 1
  end

  def rotate_y_matrix angle_d
    cos_t = Math.cos angle_d.to_radians
    sin_t = Math.sin angle_d.to_radians
    (mat4  cos_t,  0, sin_t, 0,
           0,      1, 0,     0,
           -sin_t, 0, cos_t, 0,
           0,      0, 0,     1)
  end

  def rotate_z_matrix angle_d
    cos_t = Math.cos angle_d.to_radians
    sin_t = Math.sin angle_d.to_radians
    (mat4 cos_t, -sin_t, 0, 0,
          sin_t,  cos_t, 0, 0,
          0,      0,     1, 0,
          0,      0,     0, 1)
  end

  def rotate_x_matrix angle_d
    cos_t = Math.cos angle_d.to_radians
    sin_t = Math.sin angle_d.to_radians
    (mat4  1,     0,      0, 0,
           0, cos_t, -sin_t, 0,
           0, sin_t,  cos_t, 0,
           0,     0,      0, 1)
  end

  def __mul_triangles__ model, *mul_def
    model.map do |vecs|
      vecs.map do |vec|
        mul vec,
            *mul_def
      end
    end
  end
end

def square &block
  square_verticies = [
    [vec4(0, 0, 0, 1),   vec4(1.0, 0, 0, 1),   vec4(0, 1.0, 0, 1)],
    [vec4(1.0, 0, 0, 1), vec4(1.0, 1.0, 0, 1), vec4(0, 1.0, 0, 1)]
  ]

  m = ModelingApi.new
  m.instance_eval &block if block
  m.__mul_triangles__ square_verticies, *m.matricies
end

    Override Core Rendering - main.rb link

    # ./samples/07_advanced_rendering/17_override_core_rendering/app/main.rb
class GTK::Runtime
  # You can completely override how DR renders by defining this method
  # It is strongly recommend that you do not do this unless you know what you're doing.
  def primitives pass
    # fn.each_send pass.solids,            self, :draw_solid
    # fn.each_send pass.static_solids,     self, :draw_solid
    # fn.each_send pass.sprites,           self, :draw_sprite
    # fn.each_send pass.static_sprites,    self, :draw_sprite
    # fn.each_send pass.primitives,        self, :draw_primitive
    # fn.each_send pass.static_primitives, self, :draw_primitive
    fn.each_send pass.labels,            self, :draw_label
    fn.each_send pass.static_labels,     self, :draw_label
    # fn.each_send pass.lines,             self, :draw_line
    # fn.each_send pass.static_lines,      self, :draw_line
    # fn.each_send pass.borders,           self, :draw_border
    # fn.each_send pass.static_borders,    self, :draw_border

    # if !self.production
    #   fn.each_send pass.debug,           self, :draw_primitive
    #   fn.each_send pass.static_debug,    self, :draw_primitive
    # end

    # fn.each_send pass.reserved,          self, :draw_primitive
    # fn.each_send pass.static_reserved,   self, :draw_primitive
  end
end

def tick args
  args.outputs.labels << { x: 30, y: 30, text: "primitives function defined, only labels rendered" }
  args.outputs.sprites << { x: 100, y: 100, w: 100, h: 100, path: "dragonruby.png" }
end

    Layouts - main.rb link

    # ./samples/07_advanced_rendering/18_layouts/app/main.rb
def tick args
  args.outputs.solids << args.layout.rect(row: 0,
                                          col: 0,
                                          w: 24,
                                          h: 12,
                                          include_row_gutter: true,
                                          include_col_gutter: true).merge(b: 255, a: 80)
  render_row_examples args
  render_column_examples args
  render_max_width_max_height_examples args
  render_points_with_anchored_label_examples args
  render_centered_rect_examples args
  render_rect_group_examples args
end

def render_row_examples args
  # rows (light blue)
  args.outputs.labels << args.layout.rect(row: 1, col: 6 + 3).merge(text: "row examples", anchor_x: 0.5, anchor_y: 0.5)
  4.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row, col: 6, w: 1, h: 1).merge(**light_blue)
  end

  2.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row * 2, col: 6 + 1, w: 1, h: 2).merge(**light_blue)
  end

  4.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row, col: 6 + 2, w: 2, h: 1).merge(**light_blue)
  end

  2.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row * 2, col: 6 + 4, w: 2, h: 2).merge(**light_blue)
  end
end

def render_column_examples args
  # columns (yellow)
  yellow = { r: 255, g: 255, b: 128 }
  args.outputs.labels << args.layout.rect(row: 1, col: 12 + 3).merge(text: "column examples", anchor_x: 0.5, anchor_y: 0.5)
  6.times do |col|
    args.outputs.solids << args.layout.rect(row: 0, col: 12 + col, w: 1, h: 1).merge(**yellow)
  end

  3.times do |col|
    args.outputs.solids << args.layout.rect(row: 1, col: 12 + col * 2, w: 2, h: 1).merge(**yellow)
  end

  6.times do |col|
    args.outputs.solids << args.layout.rect(row: 2, col: 12 + col, w: 1, h: 2).merge(**yellow)
  end
end

def render_max_width_max_height_examples args
  # max width/height baseline (transparent green)
  args.outputs.labels << args.layout.rect(row: 4, col: 12).merge(text: "max width/height examples", anchor_x: 0.5, anchor_y: 0.5)
  args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 24, h: 2).merge(a: 64, **green)

  # max height
  args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 24, h: 2, max_height: 1).merge(a: 64, **green)

  # max width
  args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 24, h: 2, max_width: 12).merge(a: 64, **green)
end

def render_points_with_anchored_label_examples args
  # labels relative to rects
  label_color = { r: 0, g: 0, b: 0 }

  # labels realtive to point, achored at 0.0, 0.0
  args.outputs.borders << args.layout.rect(row: 6, col: 3, w: 6, h: 5)
  args.outputs.labels << args.layout.rect(row: 6, col: 3, w: 6, h: 1).center.merge(text: "layout.point anchored to 0.0, 0.0", anchor_x: 0.5, anchor_y: 0.5, size_px: 15)
  grey = { r: 128, g: 128, b: 128 }
  args.outputs.solids << args.layout.rect(row: 7, col: 4.5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 7, col: 4.5, row_anchor: 1.0, col_anchor: 0.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)

  args.outputs.solids << args.layout.rect(row: 7, col: 5.5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 7, col: 5.5, row_anchor: 1.0, col_anchor: 0.5).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)

  args.outputs.solids << args.layout.rect(row: 7, col: 6.5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 7, col: 6.5, row_anchor: 1.0, col_anchor: 1.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)

  args.outputs.solids << args.layout.rect(row: 8, col: 4.5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 8, col: 4.5, row_anchor: 0.5, col_anchor: 0.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)

  args.outputs.solids << args.layout.rect(row: 8, col: 5.5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 8, col: 5.5, row_anchor: 0.5, col_anchor: 0.5).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)

  args.outputs.solids << args.layout.rect(row: 8, col: 6.5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 8, col: 6.5, row_anchor: 0.5, col_anchor: 1.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)

  args.outputs.solids << args.layout.rect(row: 9, col: 4.5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 9, col: 4.5, row_anchor: 0.0, col_anchor: 0.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)

  args.outputs.solids << args.layout.rect(row: 9, col: 5.5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 9, col: 5.5, row_anchor: 0.0, col_anchor: 0.5).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)

  args.outputs.solids << args.layout.rect(row: 9, col: 6.5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 9, col: 6.5, row_anchor: 0.0, col_anchor: 1.0).merge(text: "[x]", anchor_x: 0.5, anchor_y: 0.5, **label_color)
end

def render_centered_rect_examples args
  # centering rects
  args.outputs.borders << args.layout.rect(row: 6, col: 9, w: 6, h: 5)
  args.outputs.labels << args.layout.rect(row: 6, col: 9, w: 6, h: 1).center.merge(text: "layout.rect centered inside another rect", anchor_x: 0.5, anchor_y: 0.5, size_px: 15)
  outer_rect = args.layout.rect(row: 7, col: 10.5, w: 3, h: 3)

  # render outer rect
  args.outputs.solids << outer_rect.merge(**light_blue)

  # # center a yellow rect with w and h of two
  args.outputs.solids << args.layout.rect_center(
    args.layout.rect(w: 1, h: 5), # inner rect
    outer_rect, # outer rect
  ).merge(**yellow)

  # # center a black rect with w three h of one
  args.outputs.solids << args.layout.rect_center(
    args.layout.rect(w: 5, h: 1), # inner rect
    outer_rect, # outer rect
  )
end

def render_rect_group_examples args
  args.outputs.labels << args.layout.rect(row: 6, col: 15, w: 6, h: 1).center.merge(text: "layout.rect_group usage", anchor_x: 0.5, anchor_y: 0.5, size_px: 15)
  args.outputs.borders << args.layout.rect(row: 6, col: 15, w: 6, h: 5)

  horizontal_markers = [
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
  ]

  args.outputs.solids << args.layout.rect_group(row: 7,
                                                col: 15,
                                                dcol: 1,
                                                w: 1,
                                                h: 1,
                                                group: horizontal_markers)

  vertical_markers = [
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 }
  ]

  args.outputs.solids << args.layout.rect_group(row: 7,
                                                col: 15,
                                                drow: 1,
                                                w: 1,
                                                h: 1,
                                                group: vertical_markers)

  colors = [
    { r:   0, g:   0, b:   0 },
    { r:  50, g:  50, b:  50 },
    { r: 100, g: 100, b: 100 },
    { r: 150, g: 150, b: 150 },
    { r: 200, g: 200, b: 200 },
    { r: 250, g: 250, b: 250 },
  ]

  args.outputs.solids << args.layout.rect_group(row: 8,
                                                col: 15,
                                                dcol: 1,
                                                w: 1,
                                                h: 1,
                                                group: colors)
end

def light_blue
  { r: 128, g: 255, b: 255 }
end

def yellow
  { r: 255, g: 255, b: 128 }
end

def green
  { r: 0, g: 128, b: 80 }
end

def white
  { r: 255, g: 255, b: 255 }
end

def label_color
  { r: 0, g: 0, b: 0 }
end

$gtk.reset

    Advanced Rendering Hd link

    Hd Labels - main.rb link

    # ./samples/07_advanced_rendering_hd/01_hd_labels/app/main.rb
def tick args
  args.state.output_cycle ||= :top_level

  args.outputs.background_color = [0, 0, 0]
  args.outputs.solids << [0, 0, 1280, 720, 255, 255, 255]
  if args.state.output_cycle == :top_level
    render_main args
  else
    render_scene args
  end

  # cycle between labels in top level args.outputs
  # and labels inside of render target
  if args.state.tick_count.zmod? 300
    if args.state.output_cycle == :top_level
      args.state.output_cycle = :render_target
    else
      args.state.output_cycle = :top_level
    end
  end
end

def render_main args
  # center line
  args.outputs.lines   << { x:   0, y: 360, x2: 1280, y2: 360 }
  args.outputs.lines   << { x: 640, y:   0, x2:  640, y2: 720 }

  # horizontal ruler
  args.outputs.lines   << { x:   0, y: 370, x2: 1280, y2: 370 }
  args.outputs.lines   << { x:   0, y: 351, x2: 1280, y2: 351 }

  # vertical ruler
  args.outputs.lines   << { x:  575, y: 0, x2: 575, y2: 720 }
  args.outputs.lines   << { x:  701, y: 0, x2: 701, y2: 720 }

  args.outputs.sprites << { x: 640 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square/blue.png", a: 128 }
  args.outputs.labels  << { x:  640, y:   0, text: "(bottom)",  alignment_enum: 1, vertical_alignment_enum: 0 }
  args.outputs.labels  << { x:  640, y: 425, text: "top_level", alignment_enum: 1, vertical_alignment_enum: 1 }
  args.outputs.labels  << { x:  640, y: 720, text: "(top)",     alignment_enum: 1, vertical_alignment_enum: 2 }
  args.outputs.labels  << { x:    0, y: 360, text: "(left)",    alignment_enum: 0, vertical_alignment_enum: 1 }
  args.outputs.labels  << { x: 1280, y: 360, text: "(right)",   alignment_enum: 2, vertical_alignment_enum: 1 }
end

def render_scene args
  args.outputs[:scene].transient!
  args.outputs[:scene].background_color = [255, 255, 255, 0]

  # center line
  args.outputs[:scene].lines   << { x:   0, y: 360, x2: 1280, y2: 360 }
  args.outputs[:scene].lines   << { x: 640, y:   0, x2:  640, y2: 720 }

  # horizontal ruler
  args.outputs[:scene].lines   << { x:   0, y: 370, x2: 1280, y2: 370 }
  args.outputs[:scene].lines   << { x:   0, y: 351, x2: 1280, y2: 351 }

  # vertical ruler
  args.outputs[:scene].lines   << { x:  575, y: 0, x2: 575, y2: 720 }
  args.outputs[:scene].lines   << { x:  701, y: 0, x2: 701, y2: 720 }

  args.outputs[:scene].sprites << { x: 640 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square/blue.png", a: 128, blendmode_enum: 0 }
  args.outputs[:scene].labels  << { x:  640, y:   0, text: "(bottom)",      alignment_enum: 1, vertical_alignment_enum: 0, blendmode_enum: 0 }
  args.outputs[:scene].labels  << { x:  640, y: 425, text: "render target", alignment_enum: 1, vertical_alignment_enum: 1, blendmode_enum: 0 }
  args.outputs[:scene].labels  << { x:  640, y: 720, text: "(top)",         alignment_enum: 1, vertical_alignment_enum: 2, blendmode_enum: 0 }
  args.outputs[:scene].labels  << { x:    0, y: 360, text: "(left)",        alignment_enum: 0, vertical_alignment_enum: 1, blendmode_enum: 0 }
  args.outputs[:scene].labels  << { x: 1280, y: 360, text: "(right)",       alignment_enum: 2, vertical_alignment_enum: 1, blendmode_enum: 0 }

  args.outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :scene }
end

    Texture Atlases - main.rb link

    # ./samples/07_advanced_rendering_hd/02_texture_atlases/app/main.rb
# With HD mode enabled. DragonRuby will automatically use HD sprites given the following
# naming convention (assume we are using a sprite called =player.png=):
#
# | Name  | Resolution | File Naming Convention        |
# |-------+------------+-------------------------------|
# | 720p  |   1280x720 | =player.png=                  |
# | HD+   |   1600x900 | [email protected]=              |
# | 1080p |  1920x1080 | [email protected]=              |
# | 1440p |  2560x1440 | [email protected]=              |
# | 1800p |  3200x1800 | [email protected]=              |
# | 4k    |  3200x2160 | [email protected]=              |
# | 5k    |  6400x2880 | [email protected]=              |

# Note: Review the sample app's game_metadata.txt file for what configurations are enabled.

def tick args
  args.outputs.background_color = [0, 0, 0]
  args.outputs.borders << { x: 0, y: 0, w: 1280, h: 720, r: 255, g: 255, b: 255 }

  args.outputs.labels << { x: 30, y: 30.from_top, text: "render scale: #{args.grid.native_scale}", r: 255, g: 255, b: 255 }
  args.outputs.labels << { x: 30, y: 60.from_top, text: "render scale: #{args.grid.native_scale_enum}", r: 255, g: 255, b: 255 }

  args.outputs.sprites << { x: -640 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x: -320 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }

  args.outputs.sprites << { x:    0 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  320 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  640 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  960 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x: 1280 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }

  args.outputs.sprites << { x: 1600 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x: 1920 - 50, y: 360 - 50, w: 100, h: 100, path: "sprites/square.png" }

  args.outputs.sprites << { x:  640 - 50, y:          720, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  640 - 50, y: 100.from_top, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  640 - 50, y:     360 - 50, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  640 - 50, y:            0, w: 100, h: 100, path: "sprites/square.png" }
  args.outputs.sprites << { x:  640 - 50, y:         -100, w: 100, h: 100, path: "sprites/square.png" }
end

    Allscreen Properties - main.rb link

    # ./samples/07_advanced_rendering_hd/03_allscreen_properties/app/main.rb
def tick args
  label_style = { r: 255, g: 255, b: 255, size_enum: 4 }
  args.outputs.background_color = [0, 0, 0]
  args.outputs.borders << { x: 0, y: 0, w: 1280, h: 720, r: 255, g: 255, b: 255 }

  args.outputs.labels << { x: 10, y:  10.from_top, text: "native_scale:       #{args.grid.native_scale}", **label_style }
  args.outputs.labels << { x: 10, y:  40.from_top, text: "native_scale_enum:  #{args.grid.native_scale_enum}",  **label_style }
  args.outputs.labels << { x: 10, y:  70.from_top, text: "hd_offset_x:        #{args.grid.hd_offset_x}", **label_style }
  args.outputs.labels << { x: 10, y: 100.from_top, text: "hd_offset_y:        #{args.grid.hd_offset_y}", **label_style }

  if (args.state.tick_count % 500) < 250
    args.outputs.labels << { x: 10, y: 130.from_top, text: "cropped to:         grid", **label_style }

    args.outputs.sprites << { x:        0,
                              y:        0,
                              w:        1280,
                              h:        720,
                              source_x: 2000 - 640,
                              source_y: 2000 - 320,
                              source_w: 1280,
                              source_h: 720,
                              path: "sprites/world.png" }
  else
    args.outputs.labels << { x: 10, y: 130.from_top, text: "cropped to:         allscreen", **label_style }

    args.outputs.sprites << { x:        0    - args.grid.hd_offset_x,
                              y:        0    - args.grid.hd_offset_y,
                              w:        1280 + args.grid.hd_offset_x * 2,
                              h:        720  + args.grid.hd_offset_y * 2,
                              source_x: 2000 - 640 - args.grid.hd_offset_x,
                              source_y: 2000 - 320 - args.grid.hd_offset_y,
                              source_w: 1280 + args.grid.hd_offset_x * 2,
                              source_h: 720  + args.grid.hd_offset_y * 2,
                              path:     "sprites/world.png" }

    args.outputs.sprites << { x:        0    - args.grid.hd_offset_x,
                              y:        0    - args.grid.hd_offset_y,
                              w:        1280 + args.grid.hd_offset_x * 2,
                              h:        720  + args.grid.hd_offset_y * 2,
                              source_x: 2000 - 640 - args.grid.hd_offset_x,
                              source_y: 2000 - 320 - args.grid.hd_offset_y,
                              source_w: 1280 + args.grid.hd_offset_x * 2,
                              source_h: 720  + args.grid.hd_offset_y * 2,
                              path:     "sprites/world.png" }
  end

  args.outputs.sprites << { x: 0, y: 0.from_top - 165, w: 410, h: 165, r: 0, g: 0, b: 0, a: 200, path: :pixel }
end

    Layouts And Portrait Mode - main.rb link

    # ./samples/07_advanced_rendering_hd/04_layouts_and_portrait_mode/app/main.rb
def tick args
  args.outputs.solids << args.layout.rect(row: 0, col: 0, w: 12, h: 24, include_row_gutter: true, include_col_gutter: true).merge(b: 255, a: 80)

  # rows (light blue)
  light_blue = { r: 128, g: 255, b: 255 }
  args.outputs.labels << args.layout.rect(row: 1, col: 3).merge(text: "row examples", vertical_alignment_enum: 1, alignment_enum: 1)
  4.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row, col: 0, w: 1, h: 1).merge(**light_blue)
  end

  2.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row * 2, col: 1, w: 1, h: 2).merge(**light_blue)
  end

  4.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row, col: 2, w: 2, h: 1).merge(**light_blue)
  end

  2.map_with_index do |row|
    args.outputs.solids << args.layout.rect(row: row * 2, col: 4, w: 2, h: 2).merge(**light_blue)
  end

  # columns (yellow)
  yellow = { r: 255, g: 255, b: 128 }
  args.outputs.labels << args.layout.rect(row: 1, col: 9).merge(text: "column examples", vertical_alignment_enum: 1, alignment_enum: 1)
  6.times do |col|
    args.outputs.solids << args.layout.rect(row: 0, col: 6 + col, w: 1, h: 1).merge(**yellow)
  end

  3.times do |col|
    args.outputs.solids << args.layout.rect(row: 1, col: 6 + col * 2, w: 2, h: 1).merge(**yellow)
  end

  6.times do |col|
    args.outputs.solids << args.layout.rect(row: 2, col: 6 + col, w: 1, h: 2).merge(**yellow)
  end

  # max width/height baseline (transparent green)
  green = { r: 0, g: 128, b: 80 }
  args.outputs.labels << args.layout.rect(row: 4, col: 6).merge(text: "max width/height examples", vertical_alignment_enum: 1, alignment_enum: 1)
  args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 12, h: 2).merge(a: 64, **green)

  # max height
  args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 12, h: 2, max_height: 1).merge(a: 64, **green)

  # max width
  args.outputs.solids << args.layout.rect(row: 4, col: 0, w: 12, h: 2, max_width: 6).merge(a: 64, **green)

  # labels relative to rects
  label_color = { r: 0, g: 0, b: 0 }
  white = { r: 232, g: 232, b: 232 }

  # labels realtive to point, achored at 0.0, 0.0
  args.outputs.labels << args.layout.rect(row: 5.5, col: 6).merge(text: "labels using args.layout.point anchored to 0.0, 0.0", vertical_alignment_enum: 1, alignment_enum: 1)
  grey = { r: 128, g: 128, b: 128 }
  args.outputs.solids << args.layout.rect(row: 7, col: 4).merge(**grey)
  args.outputs.labels << args.layout.point(row: 7, col: 4, row_anchor: 1.0, col_anchor: 0.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 7, col: 5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 7, col: 5, row_anchor: 1.0, col_anchor: 0.5).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 7, col: 6).merge(**grey)
  args.outputs.labels << args.layout.point(row: 7, col: 6, row_anchor: 1.0, col_anchor: 1.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 8, col: 4).merge(**grey)
  args.outputs.labels << args.layout.point(row: 8, col: 4, row_anchor: 0.5, col_anchor: 0.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 8, col: 5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 8, col: 5, row_anchor: 0.5, col_anchor: 0.5).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 8, col: 6).merge(**grey)
  args.outputs.labels << args.layout.point(row: 8, col: 6, row_anchor: 0.5, col_anchor: 1.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 9, col: 4).merge(**grey)
  args.outputs.labels << args.layout.point(row: 9, col: 4, row_anchor: 0.0, col_anchor: 0.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 9, col: 5).merge(**grey)
  args.outputs.labels << args.layout.point(row: 9, col: 5, row_anchor: 0.0, col_anchor: 0.5).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  args.outputs.solids << args.layout.rect(row: 9, col: 6).merge(**grey)
  args.outputs.labels << args.layout.point(row: 9, col: 6, row_anchor: 0.0, col_anchor: 1.0).merge(text: "[x]", alignment_enum: 1, vertical_alignment_enum: 1, **label_color)

  # centering rects
  args.outputs.labels << args.layout.rect(row: 10.5, col: 6).merge(text: "layout.rect centered inside another layout.rect", vertical_alignment_enum: 1, alignment_enum: 1)
  outer_rect = args.layout.rect(row: 12, col: 4, w: 3, h: 3)

  # render outer rect
  args.outputs.solids << outer_rect.merge(**light_blue)

  # center a yellow rect with w and h of two
  args.outputs.solids << args.layout.rect_center(
    args.layout.rect(w: 1, h: 5), # inner rect
    outer_rect, # outer rect
  ).merge(**yellow)

  # center a black rect with w three h of one
  args.outputs.solids << args.layout.rect_center(
    args.layout.rect(w: 5, h: 1), # inner rect
    outer_rect, # outer rect
  )

  args.outputs.labels << args.layout.rect(row: 16.5, col: 6).merge(text: "layout.rect_group usage", vertical_alignment_enum: 1, alignment_enum: 1)

  horizontal_markers = [
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 }
  ]

  args.outputs.solids << args.layout.rect_group(row: 18,
                                                dcol: 1,
                                                w: 1,
                                                h: 1,
                                                group: horizontal_markers)

  vertical_markers = [
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 },
    { r: 0, g: 0, b: 0 }
  ]

  args.outputs.solids << args.layout.rect_group(row: 18,
                                                drow: 1,
                                                w: 1,
                                                h: 1,
                                                group: vertical_markers)

  colors = [
    { r:   0, g:   0, b:   0 },
    { r:  50, g:  50, b:  50 },
    { r: 100, g: 100, b: 100 },
    { r: 150, g: 150, b: 150 },
    { r: 200, g: 200, b: 200 },
  ]

  args.outputs.solids << args.layout.rect_group(row: 19,
                                                col: 1,
                                                dcol: 2,
                                                w: 2,
                                                h: 1,
                                                group: colors)

  args.outputs.solids << args.layout.rect_group(row: 19,
                                                col: 1,
                                                drow: 1,
                                                w: 2,
                                                h: 1,
                                                group: colors)
end

$gtk.reset

    Tweening Lerping Easing Functions link

    Easing Functions - main.rb link

    # ./samples/08_tweening_lerping_easing_functions/01_easing_functions/app/main.rb
def tick args
  # STOP! Watch the following presentation first!!!!
  # Math for Game Programmers: Fast and Funky 1D Nonlinear Transformations
  # https://www.youtube.com/watch?v=mr5xkf6zSzk

  # You've watched the talk, yes? YES???

  # define starting and ending points of properties to animate
  args.state.target_x = 1180
  args.state.target_y = 620
  args.state.target_w = 100
  args.state.target_h = 100
  args.state.starting_x = 0
  args.state.starting_y = 0
  args.state.starting_w = 300
  args.state.starting_h = 300

  # define start time and duration of animation
  args.state.start_animate_at = 3.seconds # this is the same as writing 60 * 5 (or 300)
  args.state.duration = 2.seconds # this is the same as writing 60 * 2 (or 120)

  # define type of animations
  # Here are all the options you have for values you can put in the array:
  # :identity, :quad, :cube, :quart, :quint, :flip

  # Linear is defined as:
  # [:identity]
  #
  # Smooth start variations are:
  # [:quad]
  # [:cube]
  # [:quart]
  # [:quint]

  # Linear reversed, and smooth stop are the same as the animations defined above, but reversed:
  # [:flip, :identity]
  # [:flip, :quad, :flip]
  # [:flip, :cube, :flip]
  # [:flip, :quart, :flip]
  # [:flip, :quint, :flip]

  # You can also do custom definitions. See the bottom of the file details
  # on how to do that. I've defined a couple for you:
  # [:smoothest_start]
  # [:smoothest_stop]

  # CHANGE THIS LINE TO ONE OF THE LINES ABOVE TO SEE VARIATIONS
  args.state.animation_type = [:identity]
  # args.state.animation_type = [:quad]
  # args.state.animation_type = [:cube]
  # args.state.animation_type = [:quart]
  # args.state.animation_type = [:quint]
  # args.state.animation_type = [:flip, :identity]
  # args.state.animation_type = [:flip, :quad, :flip]
  # args.state.animation_type = [:flip, :cube, :flip]
  # args.state.animation_type = [:flip, :quart, :flip]
  # args.state.animation_type = [:flip, :quint, :flip]
  # args.state.animation_type = [:smoothest_start]
  # args.state.animation_type = [:smoothest_stop]

  # THIS IS WHERE THE MAGIC HAPPENS!
  # Numeric#ease
  progress = args.state.start_animate_at.ease(args.state.duration, args.state.animation_type)

  # Numeric#ease needs to called:
  # 1. On the number that represents the point in time you want to start, and takes two parameters:
  #   a. The first parameter is how long the animation should take.
  #   b. The second parameter represents the functions that need to be called.
  #
  # For example, if I wanted an animate to start 3 seconds in, and last for 10 seconds,
  # and I want to animation to start fast and end slow, I would do:
  # (60 * 3).ease(60 * 10, :flip, :quint, :flip)

  #        initial value           delta to the final value
  calc_x = args.state.starting_x + (args.state.target_x - args.state.starting_x) * progress
  calc_y = args.state.starting_y + (args.state.target_y - args.state.starting_y) * progress
  calc_w = args.state.starting_w + (args.state.target_w - args.state.starting_w) * progress
  calc_h = args.state.starting_h + (args.state.target_h - args.state.starting_h) * progress

  args.outputs.solids << [calc_x, calc_y, calc_w, calc_h, 0, 0, 0]

  # count down
  count_down = args.state.start_animate_at - args.state.tick_count
  if count_down > 0
    args.outputs.labels << [640, 375, "Running: #{args.state.animation_type} in...", 3, 1]
    args.outputs.labels << [640, 345, "%.2f" % count_down.fdiv(60), 3, 1]
  elsif progress >= 1
    args.outputs.labels << [640, 360, "Click screen to reset.", 3, 1]
    if args.inputs.click
      $gtk.reset
    end
  end
end

# $gtk.reset

# you can make own variations of animations using this
module Easing
  # you have access to all the built in functions: identity, flip, quad, cube, quart, quint
  def self.smoothest_start x
    quad(quint(x))
  end

  def self.smoothest_stop x
    flip(quad(quint(flip(x))))
  end

  # this is the source for the existing easing functions
  def self.identity x
    x
  end

  def self.flip x
    1 - x
  end

  def self.quad x
    x * x
  end

  def self.cube x
    x * x * x
  end

  def self.quart x
    x * x * x * x * x
  end

  def self.quint x
    x * x * x * x * x * x
  end
end

    Cubic Bezier - main.rb link

    # ./samples/08_tweening_lerping_easing_functions/02_cubic_bezier/app/main.rb
def tick args
  args.outputs.background_color = [33, 33, 33]
  args.outputs.lines << bezier(100, 100,
                               100, 620,
                               1180, 620,
                               1180, 100,
                               0)

  args.outputs.lines << bezier(100, 100,
                               100, 620,
                               1180, 620,
                               1180, 100,
                               20)
end


def bezier x1, y1, x2, y2, x3, y3, x4, y4, step
  step ||= 0
  color = [200, 200, 200]
  points = points_for_bezier [x1, y1], [x2, y2], [x3, y3], [x4, y4], step

  points.each_cons(2).map do |p1, p2|
    [p1, p2, color]
  end
end

def points_for_bezier p1, p2, p3, p4, step
  points = []
  if step == 0
    [p1, p2, p3, p4]
  else
    t_step = 1.fdiv(step + 1)
    t = 0
    t += t_step
    points = []
    while t < 1
      points << [
        b_for_t(p1.x, p2.x, p3.x, p4.x, t),
        b_for_t(p1.y, p2.y, p3.y, p4.y, t),
      ]
      t += t_step
    end

    [
      p1,
      *points,
      p4
    ]
  end
end

def b_for_t v0, v1, v2, v3, t
  pow(1 - t, 3) * v0 +
  3 * pow(1 - t, 2) * t * v1 +
  3 * (1 - t) * pow(t, 2) * v2 +
  pow(t, 3) * v3
end

def pow n, to
  n ** to
end

    Easing Using Spline - main.rb link

    # ./samples/08_tweening_lerping_easing_functions/03_easing_using_spline/app/main.rb
def tick args
  args.state.duration = 10.seconds
  args.state.spline = [
    [0.0, 0.33, 0.66, 1.0],
    [1.0, 1.0,  1.0,  1.0],
    [1.0, 0.66, 0.33, 0.0],
  ]

  args.state.simulation_tick = args.state.tick_count % args.state.duration
  progress = 0.ease_spline_extended args.state.simulation_tick, args.state.duration, args.state.spline
  args.outputs.borders << args.grid.rect
  args.outputs.solids << [20 + 1240 * progress,
                          20 +  680 * progress,
                          20, 20].anchor_rect(0.5, 0.5)
  args.outputs.labels << [10,
                          710,
                          "perc: #{"%.2f" % (args.state.simulation_tick / args.state.duration)} t: #{args.state.simulation_tick}"]
end

    Pulsing Button - main.rb link

    # ./samples/08_tweening_lerping_easing_functions/04_pulsing_button/app/main.rb
# game concept from: https://youtu.be/Tz-AinJGDIM

# This class encapsulates the logic of a button that pulses when clicked.
# It is used in the StartScene and GameOverScene classes.
class PulseButton
  # a block is passed into the constructor and is called when the button is clicked,
  # and after the pulse animation is complete
  def initialize rect, text, &on_click
    @rect = rect
    @text = text
    @on_click = on_click
    @pulse_animation_spline = [[0.0, 0.90, 1.0, 1.0], [1.0, 0.10, 0.0, 0.0]]
    @duration = 10
  end

  # the button is ticked every frame and check to see if the mouse
  # intersects the button's bounding box.
  # if it does, then pertinent information is stored in the @clicked_at variable
  # which is used to calculate the pulse animation
  def tick tick_count, mouse
    @tick_count = tick_count

    if @clicked_at && @clicked_at.elapsed_time > @duration
      @clicked_at = nil
      @on_click.call
    end

    return if !mouse.click
    return if !mouse.inside_rect? @rect
    @clicked_at = tick_count
  end

  # this function returns an array of primitives that can be rendered
  def prefab easing
    # calculate the percentage of the pulse animation that has completed
    # and use the percentage to compute the size and position of the button
    perc = if @clicked_at
             easing.ease_spline @clicked_at, @tick_count, @duration, @pulse_animation_spline
           else
             0
           end

    rect = { x: @rect.x - 50 * perc / 2,
             y: @rect.y - 50 * perc / 2,
             w: @rect.w + 50 * perc,
             h: @rect.h + 50 * perc }

    point = { x: @rect.x + @rect.w / 2, y: @rect.y + @rect.h / 2 }
    [
      { **rect, path: :pixel },
      { **point, text: @text, size_px: 32, anchor_x: 0.5, anchor_y: 0.5 }
    ]
  end
end

class Game
  attr_gtk

  def initialize args
    self.args = args
    @pulse_button ||= PulseButton.new({ x: 640 - 100, y: 360 - 50, w: 200, h: 100 }, 'Click Me!') do
      $gtk.notify! "Animation complete and block invoked!"
    end
  end

  def tick
    @pulse_button.tick state.tick_count, inputs.mouse
    outputs.primitives << @pulse_button.prefab(easing)
  end
end

def tick args
  $game ||= Game.new args
  $game.args = args
  $game.tick
end

    Scene Transitions - main.rb link

    # ./samples/08_tweening_lerping_easing_functions/05_scene_transitions/app/main.rb
# This sample app shows a more advanced implementation of scenes:
# 1. "Scene 1" has a label on it that says "I am scene ONE. Press enter to go to scene TWO."
# 2. "Scene 2" has a label on it that says "I am scene TWO. Press enter to go to scene ONE."
# 3. When the game starts, Scene 1 is presented.
# 4. When the player presses enter, the scene transitions to Scene 2 (fades out Scene 1 over half a second, then fades in Scene 2 over half a second).
# 5. When the player presses enter again, the scene transitions to Scene 1 (fades out Scene 2 over half a second, then fades in Scene 1 over half a second).
# 6. During the fade transitions, spamming the enter key is ignored (scenes don't accept a transition/respond to the enter key until the current transition is completed).
class SceneOne
  attr_gtk

  def tick
    outputs[:scene].transient!
    outputs[:scene].labels << { x: 640,
                                y: 360,
                                text: "I am scene ONE. Press enter to go to scene TWO.",
                                alignment_enum: 1,
                                vertical_alignment_enum: 1 }

    state.next_scene = :scene_two if inputs.keyboard.key_down.enter
  end
end

class SceneTwo
  attr_gtk

  def tick
    outputs[:scene].transient!
    outputs[:scene].labels << { x: 640,
                                y: 360,
                                text: "I am scene TWO. Press enter to go to scene ONE.",
                                alignment_enum: 1,
                                vertical_alignment_enum: 1 }

    state.next_scene = :scene_one if inputs.keyboard.key_down.enter
  end
end

class RootScene
  attr_gtk

  def initialize
    @scene_one = SceneOne.new
    @scene_two = SceneTwo.new
  end

  def tick
    defaults
    render
    tick_scene
  end

  def defaults
    set_current_scene! :scene_one if state.tick_count == 0
    state.scene_transition_duration ||= 30
  end

  def render
    a = if state.transition_scene_at
          255 * state.transition_scene_at.ease(state.scene_transition_duration, :flip)
        elsif state.current_scene_at
          255 * state.current_scene_at.ease(state.scene_transition_duration)
        else
          255
        end

    outputs.sprites << { x: 0, y: 0, w: 1280, h: 720, path: :scene, a: a }
  end

  def tick_scene
    current_scene = state.current_scene

    @current_scene.args = args
    @current_scene.tick

    if current_scene != state.current_scene
      raise "state.current_scene changed mid tick from #{current_scene} to #{state.current_scene}. To change scenes, set state.next_scene."
    end

    if state.next_scene && state.next_scene != state.transition_scene && state.next_scene != state.current_scene
      state.transition_scene_at = state.tick_count
      state.transition_scene = state.next_scene
    end

    if state.transition_scene_at && state.transition_scene_at.elapsed_time >= state.scene_transition_duration
      set_current_scene! state.transition_scene
    end

    state.next_scene = nil
  end

  def set_current_scene! id
    return if state.current_scene == id
    state.current_scene = id
    state.current_scene_at = state.tick_count
    state.transition_scene = nil
    state.transition_scene_at = nil

    if state.current_scene == :scene_one
      @current_scene = @scene_one
    elsif state.current_scene == :scene_two
      @current_scene = @scene_two
    end
  end
end

def tick args
  $game ||= RootScene.new
  $game.args = args
  $game.tick
end

    Animation Queues - main.rb link

    # ./samples/08_tweening_lerping_easing_functions/06_animation_queues/app/main.rb
# here's how to create a "fire and forget" sprite animation queue
def tick args
  args.outputs.labels << { x: 640,
                           y: 360,
                           text: "Click anywhere on the screen.",
                           alignment_enum: 1,
                           vertical_alignment_enum: 1 }

  # initialize the queue to an empty array
  args.state.fade_out_queue ||=[]

  # if the mouse is click, add a sprite to the fire and forget
  # queue to be processed
  if args.inputs.mouse.click
    args.state.fade_out_queue << {
      x: args.inputs.mouse.x - 20,
      y: args.inputs.mouse.y - 20,
      w: 40,
      h: 40,
      path: "sprites/square/blue.png"
    }
  end

  # process the queue
  args.state.fade_out_queue.each do |item|
    # default the alpha value if it isn't specified
    item.a ||= 255

    # decrement the alpha by 5 each frame
    item.a -= 5
  end

  # remove the item if it's completely faded out
  args.state.fade_out_queue.reject! { |item| item.a <= 0 }

  # render the sprites in the queue
  args.outputs.sprites << args.state.fade_out_queue
end

    Animation Queues Advanced - main.rb link

    # ./samples/08_tweening_lerping_easing_functions/07_animation_queues_advanced/app/main.rb
# sample app shows how to perform a fire and forget animation when a collision occurs
def tick args
  defaults args
  spawn_bullets args
  calc_bullets args
  render args
end

def defaults args
  # place a player on the far left with sprite and hp information
  args.state.player ||= { x: 100, y: 360 - 50, w: 100, h: 100, path: "sprites/square/blue.png", hp: 30 }
  # create an array of bullets
  args.state.bullets ||= []
  # create a queue for handling bullet explosions
  args.state.explosion_queue ||= []
end

def spawn_bullets args
  # span a bullet in a random location on the far right every half second
  return if !args.state.tick_count.zmod? 30
  args.state.bullets << {
    x: 1280 - 100,
    y: rand(720 - 100),
    w: 100,
    h: 100,
    path: "sprites/square/red.png"
  }
end

def calc_bullets args
  # for each bullet
  args.state.bullets.each do |b|
    # move it to the left by 20 pixels
    b.x -= 20

    # determine if the bullet collides with the player
    if b.intersect_rect? args.state.player
      # decrement the player's health if it does
      args.state.player.hp -= 1
      # mark the bullet as exploded
      b.exploded = true

      # queue the explosion by adding it to the explosion queue
      args.state.explosion_queue << b.merge(exploded_at: args.state.tick_count)
    end
  end

  # remove bullets that have exploded so they wont be rendered
  args.state.bullets.reject! { |b| b.exploded }

  # remove animations from the animation queue that have completed
  # frame index will return nil once the animation has completed
  args.state.explosion_queue.reject! { |e| !e.exploded_at.frame_index(7, 4, false) }
end

def render args
  # render the player's hp above the sprite
  args.outputs.labels << {
    x: args.state.player.x + 50,
    y: args.state.player.y + 110,
    text: "#{args.state.player.hp}",
    alignment_enum: 1,
    vertical_alignment_enum: 0
  }

  # render the player
  args.outputs.sprites << args.state.player

  # render the bullets
  args.outputs.sprites << args.state.bullets

  # process the animation queue
  args.outputs.sprites << args.state.explosion_queue.map do |e|
    number_of_frames = 7
    hold_each_frame_for = 4
    repeat_animation = false
    # use the exploded_at property and the frame_index function to determine when the animation should start
    frame_index = e.exploded_at.frame_index(number_of_frames, hold_each_frame_for, repeat_animation)
    # take the explosion primitive and set the path variariable
    e.merge path: "sprites/misc/explosion-#{frame_index}.png"
  end
end

    Cutscenes - main.rb link

    # ./samples/08_tweening_lerping_easing_functions/08_cutscenes/app/main.rb
# sample app shows how you can user a queue/callback mechanism to create cutscenes
class Game
  attr_gtk

  def initialize
    # this class controls the cutscene orchestration
    @tick_queue = TickQueue.new
  end

  def tick
    @tick_queue.args = args
    state.player ||= { x: 0, y: 0, w: 100, h: 100, path: :pixel, r: 0, g: 255, b: 0 }
    state.fade_to_black ||= 0
    state.back_and_forth_count ||= 0

    # if the mouse is clicked, start the cutscene
    if inputs.mouse.click && !state.cutscene_started
      start_cutscene
    end

    outputs.primitives << state.player
    outputs.primitives << { x: 0, y: 0, w: 1280, h: 720, path: :pixel, r: 0, g: 0, b: 0, a: state.fade_to_black }
    @tick_queue.tick
  end

  def start_cutscene
    # don't start the cutscene if it's already started
    return if state.cutscene_started
    state.cutscene_started = true

    # start the cutscene by moving right
    queue_move_to_right_side
  end

  def queue_move_to_right_side
    # use the tick queue mechanism to kick off the player moving right
    @tick_queue.queue_tick state.tick_count do |args, entry|
      state.player.x += 30
      # once the player is done moving right, stage the next step of the cutscene (moving left)
      if state.player.x + state.player.w > 1280
        state.player.x = 1280 - state.player.w
        queue_move_to_left_side

        # marke the queued tick entry as complete so it doesn't get run again
        entry.complete!
      end
    end
  end

  def queue_move_to_left_side
    # use the tick queue mechanism to kick off the player moving right
    @tick_queue.queue_tick state.tick_count do |args, entry|
      args.state.player.x -= 30
      # once the player id done moving left, decide on whether they should move right again or fade to black
      # the decision point is based on the number of times the player has moved left and right
      if args.state.player.x < 0
        state.player.x = 0
        args.state.back_and_forth_count += 1
        if args.state.back_and_forth_count < 3
          # if they haven't moved left and right 3 times, move them right again
          queue_move_to_right_side
        else
          # if they have moved left and right 3 times, fade to black
          queue_fade_to_black
        end

        # marke the queued t