• 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):