Physics And Collisions - Collision With Object Removal - tests.rb

# ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/tests.rb
# For advanced users:
# You can put some quick verification tests here, any method
# that starts with the `test_` will be run when you save this file.

# Here is an example test and game

# To run the test: ./dragonruby mygame --eval app/tests.rb --no-tick

class MySuperHappyFunGame
  attr_gtk

  def tick
    outputs.solids << [100, 100, 300, 300]
  end
end

def test_universe args, assert
  game = MySuperHappyFunGame.new
  game.args = args
  game.tick
  assert.true!  args.outputs.solids.length == 1, "failure: a solid was not added after tick"
  assert.false! 1 == 2, "failure: some how, 1 equals 2, the world is ending"
  puts "test_universe completed successfully"
end

puts "running tests"
$gtk.reset 100
$gtk.log_level = :off
$gtk.tests.start

Physics And Collisions - Collision With Object Removal - vector2d.rb

# ./samples/04_physics_and_collisions/10_collision_with_object_removal/app/vector2d.rb

class Vector2d
  attr_accessor :x, :y

  def initialize x=0, y=0
    @x=x
    @y=y
  end

  #returns a vector multiplied by scalar x
  #x [float] scalar
  def mult x
    r = Vector2d.new(0,0)
    [email protected]*x
    [email protected]*x
    r
  end

  # vect [Vector2d] vector to copy
  def copy vect
    Vector2d.new(@x, @y)
  end

  #returns a new vector equivalent to this+vect
  #vect [Vector2d] vector to add to self
  def add vect
    Vector2d.new(@x+vect.x,@y+vect.y)
  end

  #returns a new vector equivalent to this-vect
  #vect [Vector2d] vector to subtract to self
  def sub vect
    Vector2d.new(@x-vect.c, @y-vect.y)
  end

  #return the magnitude of the vector
  def mag
    ((@x**2)+(@y**2))**0.5
  end

  #returns a new normalize version of the vector
  def normalize
    Vector2d.new(@x/mag, @y/mag)
  end

  #TODO delet?
  def distABS vect
    ((([email protected])**2+([email protected])**2)**0.5).abs()
  end
end

Mouse - Mouse Click - main.rb

# ./samples/05_mouse/01_mouse_click/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - product: Returns an array of all combinations of elements from all arrays.

   For example, [1,2].product([1,2]) would return the following array...
   [[1,1], [1,2], [2,1], [2,2]]
   More than two arrays can be given to product and it will still work,
   such as [1,2].product([1,2],[3,4]). What would product return in this case?

   Answer:
   [[1,1,3],[1,1,4],[1,2,3],[1,2,4],[2,1,3],[2,1,4],[2,2,3],[2,2,4]]

 - num1.fdiv(num2): Returns the float division (will have a decimal) of the two given numbers.
   For example, 5.fdiv(2) = 2.5 and 5.fdiv(5) = 1.0

 - yield: Allows you to call a method with a code block and yield to that block.

 Reminders:

 - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - args.inputs.mouse.click: This property will be set if the mouse was clicked.

 - Ternary operator (?): Will evaluate a statement (just like an if statement)
   and perform an action if the result is true or another action if it is false.

 - reject: Removes elements from a collection if they meet certain requirements.

 - args.outputs.borders: An array. The values generate a border.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
   For more information about borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.

=end

# This sample app is a classic game of Tic Tac Toe.

class TicTacToe
  attr_accessor :_, :state, :outputs, :inputs, :grid, :gtk

  # Starts the game with player x's turn and creates an array (to_a) for space combinations.
  # Calls methods necessary for the game to run properly.
  def tick
    state.current_turn ||= :x
    state.space_combinations = [-1, 0, 1].product([-1, 0, 1]).to_a
    render_board
    input_board
  end

  # Uses borders to create grid squares for the game's board. Also outputs the game pieces using labels.
  def render_board
    square_size = 80

    # Positions the game's board in the center of the screen.
    # Try removing what follows grid.w_half or grid.h_half and see how the position changes!
    board_left = grid.w_half - square_size * 1.5
    board_top  = grid.h_half - square_size * 1.5

    # At first glance, the add(1) looks pretty trivial. But if you remove it,
    # you'll see that the positioning of the board would be skewed without it!
    # Or if you put 2 in the parenthesis, the pieces will be placed in the wrong squares
    # due to the change in board placement.
    outputs.borders << all_spaces do |x, y, space| # outputs borders for all board spaces
      space.border ||= [
        board_left + x.add(1) * square_size, # space.border is initialized using this definition
        board_top  + y.add(1) * square_size,
        square_size,
        square_size
      ]
    end

    # Again, the calculations ensure that the piece is placed in the center of the grid square.
    # Remove the '- 20' and the piece will be placed at the top of the grid square instead of the center.
    outputs.labels << filled_spaces do |x, y, space| # put label in each filled space of board
          label board_left + x.add(1) * square_size + square_size.fdiv(2),
          board_top  + y.add(1) * square_size + square_size - 20,
          space.piece # text of label, either "x" or "o"
    end

    # Uses a label to output whether x or o won, or if a draw occurred.
    # If the game is ongoing, a label shows whose turn it currently is.
    outputs.labels << if state.x_won
                        label grid.w_half, grid.top - 80, "x won" # the '-80' positions the label 80 pixels lower than top
                      elsif state.o_won
                        label grid.w_half, grid.top - 80, "o won" # grid.w_half positions the label in the center horizontally
                      elsif state.draw
                        label grid.w_half, grid.top - 80, "a draw"
                      else # if no one won and the game is ongoing
                        label grid.w_half, grid.top - 80, "turn: #{state.current_turn}"
                      end
  end

  # Calls the methods responsible for handling user input and determining the winner.
  # Does nothing unless the mouse is clicked.
  def input_board
    return unless inputs.mouse.click
    input_place_piece
    input_restart_game
    determine_winner
  end

  # Handles user input for placing pieces on the board.
  def input_place_piece
    return if state.game_over

    # Checks to find the space that the mouse was clicked inside of, and makes sure the space does not already
    # have a piece in it.
    __, __, space = all_spaces.find do |__, __, space|
      inputs.mouse.click.point.inside_rect?(space.border) && !space.piece
    end

    # The piece that goes into the space belongs to the player whose turn it currently is.
    return unless space
    space.piece = state.current_turn

    # This ternary operator statement allows us to change the current player's turn.
    # If it is currently x's turn, it becomes o's turn. If it is not x's turn, it become's x's turn.
    state.current_turn = state.current_turn == :x ? :o : :x
  end

  # Resets the game.
  def input_restart_game
    return unless state.game_over
    gtk.reset
  end

  # Checks if x or o won the game.
  # If neither player wins and all nine squares are filled, a draw happens.
  # Once a player is chosen as the winner or a draw happens, the game is over.
  def determine_winner
    state.x_won = won? :x # evaluates to either true or false (boolean values)
    state.o_won = won? :o
    state.draw = true if filled_spaces.length == 9 && !state.x_won && !state.o_won
    state.game_over = state.x_won || state.o_won || state.draw
  end

  # Determines if a player won by checking if there is a horizontal match or vertical match.
  # Horizontal_match and vertical_match have boolean values. If either is true, the game has been won.
  def won? piece
    # performs action on all space combinations
    won = [[-1, 0, 1]].product([-1, 0, 1]).map do |xs, y|

      # Checks if the 3 grid spaces with the same y value (or same row) and
      # x values that are next to each other have pieces that belong to the same player.
      # Remember, the value of piece is equal to the current turn (which is the player).
      horizontal_match = state.spaces[xs[0]][y].piece == piece &&
                         state.spaces[xs[1]][y].piece == piece &&
                         state.spaces[xs[2]][y].piece == piece

      # Checks if the 3 grid spaces with the same x value (or same column) and
      # y values that are next to each other have pieces that belong to the same player.
      # The && represents an "and" statement: if even one part of the statement is false,
      # the entire statement evaluates to false.
      vertical_match = state.spaces[y][xs[0]].piece == piece &&
                       state.spaces[y][xs[1]].piece == piece &&
                       state.spaces[y][xs[2]].piece == piece

      horizontal_match || vertical_match # if either is true, true is returned
    end

    # Sees if there is a diagonal match, starting from the bottom left and ending at the top right.
    # Is added to won regardless of whether the statement is true or false.
    won << (state.spaces[-1][-1].piece == piece && # bottom left
            state.spaces[ 0][ 0].piece == piece && # center
            state.spaces[ 1][ 1].piece == piece)   # top right

    # Sees if there is a diagonal match, starting at the bottom right and ending at the top left
    # and is added to won.
    won << (state.spaces[ 1][-1].piece == piece && # bottom right
            state.spaces[ 0][ 0].piece == piece && # center
            state.spaces[-1][ 1].piece == piece)   # top left

    # Any false statements (meaning false diagonal matches) are rejected from won
    won.reject_false.any?
  end

  # Defines filled spaces on the board by rejecting all spaces that do not have game pieces in them.
  # The ! before a statement means "not". For example, we are rejecting any space combinations that do
  # NOT have pieces in them.
  def filled_spaces
    state.space_combinations
      .reject { |x, y| !state.spaces[x][y].piece } # reject spaces with no pieces in them
      .map do |x, y|
        if block_given?
          yield x, y, state.spaces[x][y]
        else
          [x, y, state.spaces[x][y]] # sets definition of space
        end
    end
  end

  # Defines all spaces on the board.
  def all_spaces
    if !block_given?
      state.space_combinations.map do |x, y|
        [x, y, state.spaces[x][y]] # sets definition of space
      end
    else # if a block is given (block_given? is true)
      state.space_combinations.map do |x, y|
        yield x, y, state.spaces[x][y] # yield if a block is given
      end
    end
  end

  # Sets values for a label, such as the position, value, size, alignment, and color.
  def label x, y, value
    [x, y + 10, value, 20, 1, 0, 0, 0]
  end
end

$tic_tac_toe = TicTacToe.new

def tick args
  $tic_tac_toe._       = args
  $tic_tac_toe.state   = args.state
  $tic_tac_toe.outputs = args.outputs
  $tic_tac_toe.inputs  = args.inputs
  $tic_tac_toe.grid    = args.grid
  $tic_tac_toe.gtk     = args.gtk
  $tic_tac_toe.tick
  tick_instructions args, "Sample app shows how to work with mouse clicks."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Mouse - Mouse Move - main.rb

# ./samples/05_mouse/02_mouse_move/app/main.rb
=begin

 Reminders:

 - num1.greater(num2): Returns the greater value.
   For example, if we have the command
   puts 4.greater(3)
   the number 4 would be printed to the console since it has a greater value than 3.
   Similar to lesser, which returns the lesser value.

 - find_all: Finds all elements of a collection that meet certain requirements.
   For example, in this sample app, we're using find_all to find all zombies that have intersected
   or hit the player's sprite since these zombies have been killed.

 - args.inputs.keyboard.key_down.KEY: Determines if a key is being held or pressed.
   Stores the frame the "down" event occurred.
   For more information about the keyboard, go to mygame/documentation/06-keyboard.md.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
   For more information about sprites, go to mygame/documentation/05-sprites.md.

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   When we want to create a new object, we can declare it as a new entity and then define
   its properties. (Remember, you can use state to define ANY property and it will
   be retained across frames.)

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - map: Ruby method used to transform data; used in arrays, hashes, and collections.
   Can be used to perform an action on every element of a collection, such as multiplying
   each element by 2 or declaring every element as a new entity.

 - sample: Chooses a random element from the array.

 - reject: Removes elements that meet certain requirements.
   In this sample app, we're removing/rejecting zombies that reach the center of the screen. We're also
   rejecting zombies that were killed more than 30 frames ago.

=end

# This sample app allows users to move around the screen in order to kill zombies. Zombies appear from every direction so the goal
# is to kill the zombies as fast as possible!

class ProtectThePuppiesFromTheZombies
  attr_accessor :grid, :inputs, :state, :outputs

  # Calls the methods necessary for the game to run properly.
  def tick
    defaults
    render
    calc
    input
  end

  # Sets default values for the zombies and for the player.
  # Initialization happens only in the first frame.
  def defaults
    state.flash_at               ||= 0
    state.zombie_min_spawn_rate  ||= 60
    state.zombie_spawn_countdown ||= random_spawn_countdown state.zombie_min_spawn_rate
    state.zombies                ||= []
    state.killed_zombies         ||= []

    # Declares player as a new entity and sets its properties.
    # The player begins the game in the center of the screen, not moving in any direction.
    state.player ||= state.new_entity(:player, { x: 640,
                                               y: 360,
                                               attack_angle: 0,
                                               dx: 0,
                                               dy: 0 })
  end

  # Outputs a gray background.
  # Calls the methods needed to output the player, zombies, etc onto the screen.
  def render
    outputs.solids << [grid.rect, 100, 100, 100]
    render_zombies
    render_killed_zombies
    render_player
    render_flash
  end

  # Outputs the zombies on the screen and sets values for the sprites, such as the position, width, height, and animation.
  def render_zombies
    outputs.sprites << state.zombies.map do |z| # performs action on all zombies in the collection
      z.sprite = [z.x, z.y, 4 * 3, 8 * 3, animation_sprite(z)].sprite # sets definition for sprite, calls animation_sprite method
      z.sprite
    end
  end

  # Outputs sprites of killed zombies, and displays a slash image to show that a zombie has been killed.
  def render_killed_zombies
    outputs.sprites << state.killed_zombies.map do |z| # performs action on all killed zombies in collection
      z.sprite = [z.x,
                  z.y,
                  4 * 3,
                  8 * 3,
                  animation_sprite(z, z.death_at), # calls animation_sprite method
                  0, # angle
                  255 * z.death_at.ease(30, :flip)].sprite # transparency of a zombie changes when they die
                  # change the value of 30 and see what happens when a zombie is killed

      # Sets values to output the slash over the zombie's sprite when a zombie is killed.
      # The slash is tilted 45 degrees from the angle of the player's attack.
      # Change the 3 inside scale_rect to 30 and the slash will be HUGE! Scale_rect positions
      # the slash over the killed zombie's sprite.
      [z.sprite, [z.sprite.rect, 'sprites/slash.png', 45 + state.player.attack_angle_on_click, z.sprite.a].scale_rect(3, 0.5, 0.5)]
    end
  end

  # Outputs the player sprite using the images in the sprites folder.
  def render_player
    state.player_sprite = [state.player.x,
                           state.player.y,
                          4 * 3,
                          8 * 3, "sprites/player-#{animation_index(state.player.created_at_elapsed)}.png"] # string interpolation
    outputs.sprites << state.player_sprite

    # Outputs a small red square that previews the angles that the player can attack in.
    # It can be moved in a perfect circle around the player to show possible movements.
    # Change the 60 in the parenthesis and see what happens to the movement of the red square.
    outputs.solids <<  [state.player.x + state.player.attack_angle.vector_x(60),
                        state.player.y + state.player.attack_angle.vector_y(60),
                        3, 3, 255, 0, 0]
  end

  # Renders flash as a solid. The screen turns white for 10 frames when a zombie is killed.
  def render_flash
    return if state.flash_at.elapsed_time > 10 # return if more than 10 frames have passed since flash.
    # Transparency gradually changes (or eases) during the 10 frames of flash.
    outputs.primitives << [grid.rect, 255, 255, 255, 255 * state.flash_at.ease(10, :flip)].solid
  end

  # Calls all methods necessary for performing calculations.
  def calc
    calc_spawn_zombie
    calc_move_zombies
    calc_player
    calc_kill_zombie
  end

  # Decreases the zombie spawn countdown by 1 if it has a value greater than 0.
  def calc_spawn_zombie
    if state.zombie_spawn_countdown > 0
      state.zombie_spawn_countdown -= 1
      return
    end

    # New zombies are created, positioned on the screen, and added to the zombies collection.
    state.zombies << state.new_entity(:zombie) do |z| # each zombie is declared a new entity
      if rand > 0.5
        z.x = grid.rect.w.randomize(:ratio) # random x position on screen (within grid scope)
        z.y = [-10, 730].sample # y position is set to either -10 or 730 (randomly chosen)
        # the possible values exceed the screen's scope so zombies appear to be coming from far away
      else
        z.x = [-10, 1290].sample # x position is set to either -10 or 1290 (randomly chosen)
        z.y = grid.rect.w.randomize(:ratio) # random y position on screen
      end
    end

    # Calls random_spawn_countdown method (determines how fast new zombies appear)
    state.zombie_spawn_countdown = random_spawn_countdown state.zombie_min_spawn_rate
    state.zombie_min_spawn_rate -= 1
    # set to either the current zombie_min_spawn_rate or 0, depending on which value is greater
    state.zombie_min_spawn_rate  = state.zombie_min_spawn_rate.greater(0)
  end

  # Moves all zombies towards the center of the screen.
  # All zombies that reach the center (640, 360) are rejected from the zombies collection and disappear.
  def calc_move_zombies
    state.zombies.each do |z| # for each zombie in the collection
      z.y = z.y.towards(360, 0.1) # move the zombie towards the center (640, 360) at a rate of 0.1
      z.x = z.x.towards(640, 0.1) # change 0.1 to 1.1 and see how much faster the zombies move to the center
    end
    state.zombies = state.zombies.reject { |z| z.y == 360 && z.x == 640 } # remove zombies that are in center
  end

  # Calculates the position and movement of the player on the screen.
  def calc_player
    state.player.x += state.player.dx # changes x based on dx (change in x)
    state.player.y += state.player.dy # changes y based on dy (change in y)

    state.player.dx *= 0.9 # scales dx down
    state.player.dy *= 0.9 # scales dy down

    # Compares player's x to 1280 to find lesser value, then compares result to 0 to find greater value.
    # This ensures that the player remains within the screen's scope.
    state.player.x = state.player.x.lesser(1280).greater(0)
    state.player.y = state.player.y.lesser(720).greater(0) # same with player's y
  end

  # Finds all zombies that intersect with the player's sprite. These zombies are removed from the zombies collection
  # and added to the killed_zombies collection since any zombie that intersects with the player is killed.
  def calc_kill_zombie

    # Find all zombies that intersect with the player. They are considered killed.
    killed_this_frame = state.zombies.find_all { |z| z.sprite.intersect_rect? state.player_sprite }
    state.zombies = state.zombies - killed_this_frame # remove newly killed zombies from zombies collection
    state.killed_zombies += killed_this_frame # add newly killed zombies to killed zombies

    if killed_this_frame.length > 0 # if atleast one zombie was killed in the frame
      state.flash_at = state.tick_count # flash_at set to the frame when the zombie was killed
    # Don't forget, the rendered flash lasts for 10 frames after the zombie is killed (look at render_flash method)
    end

    # Sets the tick_count (passage of time) as the value of the death_at variable for each killed zombie.
    # Death_at stores the frame a zombie was killed.
    killed_this_frame.each do |z|
      z.death_at = state.tick_count
    end

    # Zombies are rejected from the killed_zombies collection depending on when they were killed.
    # They are rejected if more than 30 frames have passed since their death.
    state.killed_zombies = state.killed_zombies.reject { |z| state.tick_count - z.death_at > 30 }
  end

  # Uses input from the user to move the player around the screen.
  def input

    # If the "a" key or left key is pressed, the x position of the player decreases.
    # Otherwise, if the "d" key or right key is pressed, the x position of the player increases.
    if inputs.keyboard.key_held.a || inputs.keyboard.key_held.left
      state.player.x -= 5
    elsif inputs.keyboard.key_held.d || inputs.keyboard.key_held.right
      state.player.x += 5
    end

    # If the "w" or up key is pressed, the y position of the player increases.
    # Otherwise, if the "s" or down key is pressed, the y position of the player decreases.
    if inputs.keyboard.key_held.w || inputs.keyboard.key_held.up
      state.player.y += 5
    elsif inputs.keyboard.key_held.s || inputs.keyboard.key_held.down
      state.player.y -= 5
    end

    # Sets the attack angle so the player can move and attack in the precise direction it wants to go.
    # If the mouse is moved, the attack angle is changed (based on the player's position and mouse position).
    # Attack angle also contributes to the position of red square.
    if inputs.mouse.moved
      state.player.attack_angle = inputs.mouse.position.angle_from [state.player.x, state.player.y]
    end

    if inputs.mouse.click && state.player.dx < 0.5 && state.player.dy < 0.5
      state.player.attack_angle_on_click = inputs.mouse.position.angle_from [state.player.x, state.player.y]
      state.player.attack_angle = state.player.attack_angle_on_click # player's attack angle is set
      state.player.dx = state.player.attack_angle.vector_x(25) # change in player's position
      state.player.dy = state.player.attack_angle.vector_y(25)
    end
  end

  # Sets the zombie spawn's countdown to a random number.
  # How fast zombies appear (change the 60 to 6 and too many zombies will appear at once!)
  def random_spawn_countdown minimum
    10.randomize(:ratio, :sign).to_i + 60
  end

  # Helps to iterate through the images in the sprites folder by setting the animation index.
  # 3 frames is how long to show an image, and 6 is how many images to flip through.
  def animation_index at
    at.idiv(3).mod(6)
  end

  # Animates the zombies by using the animation index to go through the images in the sprites folder.
  def animation_sprite zombie, at = nil
    at ||= zombie.created_at_elapsed # how long it is has been since a zombie was created
    index = animation_index at
    "sprites/zombie-#{index}.png" # string interpolation to iterate through images
  end
end

$protect_the_puppies_from_the_zombies = ProtectThePuppiesFromTheZombies.new

def tick args
  $protect_the_puppies_from_the_zombies.grid    = args.grid
  $protect_the_puppies_from_the_zombies.inputs  = args.inputs
  $protect_the_puppies_from_the_zombies.state    = args.state
  $protect_the_puppies_from_the_zombies.outputs = args.outputs
  $protect_the_puppies_from_the_zombies.tick
  tick_instructions args, "How to get the mouse position and translate it to an x, y position using .vector_x and .vector_y. CLICK to play."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Mouse - Mouse Move Paint App - main.rb

# ./samples/05_mouse/03_mouse_move_paint_app/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Floor: Method that returns an integer number smaller than or equal to the original with no decimal.

   For example, if we have a variable, a = 13.7, and we called floor on it, it would look like this...
   puts a.floor()
   which would print out 13.
   (There is also a ceil method, which returns an integer number greater than or equal to the original
   with no decimal. If we had called ceil on the variable a, the result would have been 14.)

 Reminders:

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.

   For example, if we have a "numbers" hash that stores numbers in English as the
   key and numbers in Spanish as the value, we'd have a hash that looks like this...
   numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
   and on it goes.

   Now if we wanted to find the corresponding value of the "one" key, we could say
   puts numbers["one"]
   which would print "uno" to the console.

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   In this sample app, new_entity is used to create a new button that clears the grid.
   (Remember, you can use state to define ANY property and it will be retained across frames.)

 - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.

 - args.inputs.mouse.click.point.created_at: The frame the mouse click occurred in.

 - args.outputs.labels: An array. The values in the array generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - ARRAY#inside_rect?: Returns true or false depending on if the point is inside the rect.

=end

# This sample app shows an empty grid that the user can paint on.
# To paint, the user must keep their mouse presssed and drag it around the grid.
# The "clear" button allows users to clear the grid so they can start over.

class PaintApp
  attr_accessor :inputs, :state, :outputs, :grid, :args

  # Runs methods necessary for the game to function properly.
  def tick
    print_title
    add_grid
    check_click
    draw_buttons
  end

  # Prints the title onto the screen by using a label.
  # Also separates the title from the grid with a line as a horizontal separator.
  def print_title
    args.outputs.labels << [ 640, 700, 'Paint!', 0, 1 ]
    outputs.lines << horizontal_separator(660, 0, 1280)
  end

  # Sets the starting position, ending position, and color for the horizontal separator.
  # The starting and ending positions have the same y values.
  def horizontal_separator y, x, x2
    [x, y, x2, y, 150, 150, 150]
  end

  # Sets the starting position, ending position, and color for the vertical separator.
  # The starting and ending positions have the same x values.
  def vertical_separator x, y, y2
    [x, y, x, y2, 150, 150, 150]
  end

  # Outputs a border and a grid containing empty squares onto the screen.
  def add_grid

    # Sets the x, y, height, and width of the grid.
    # There are 31 horizontal lines and 31 vertical lines in the grid.
    # Feel free to count them yourself before continuing!
    x, y, h, w = 640 - 500/2, 640 - 500, 500, 500 # calculations done so the grid appears in screen's center
    lines_h = 31
    lines_v = 31

    # Sets values for the grid's border, grid lines, and filled squares.
    # The filled_squares variable is initially set to an empty array.
    state.grid_border ||= [ x, y, h, w ] # definition of grid's outer border
    state.grid_lines ||= draw_grid(x, y, h, w, lines_h, lines_v) # calls draw_grid method
    state.filled_squares ||= [] # there are no filled squares until the user fills them in

    # Outputs the grid lines, border, and filled squares onto the screen.
    outputs.lines.concat state.grid_lines
    outputs.borders << state.grid_border
    outputs.solids << state.filled_squares
  end

  # Draws the grid by adding in vertical and horizontal separators.
  def draw_grid x, y, h, w, lines_h, lines_v

    # The grid starts off empty.
    grid = []

    # Calculates the placement and adds horizontal lines or separators into the grid.
    curr_y = y # start at the bottom of the box
    dist_y = h / (lines_h + 1) # finds distance to place horizontal lines evenly throughout 500 height of grid
    lines_h.times do
      curr_y += dist_y # increment curr_y by the distance between the horizontal lines
      grid << horizontal_separator(curr_y, x, x + w - 1) # add a separator into the grid
    end

    # Calculates the placement and adds vertical lines or separators into the grid.
    curr_x = x # now start at the left of the box
    dist_x = w / (lines_v + 1) # finds distance to place vertical lines evenly throughout 500 width of grid
    lines_v.times do
      curr_x += dist_x # increment curr_x by the distance between the vertical lines
      grid << vertical_separator(curr_x, y + 1, y  + h) # add separator
    end

    # paint_grid uses a hash to assign values to keys.
    state.paint_grid ||= {"x" => x, "y" => y, "h" => h, "w" => w, "lines_h" => lines_h,
                          "lines_v" => lines_v, "dist_x" => dist_x,
                          "dist_y" => dist_y }

    return grid
  end

  # Checks if the user is keeping the mouse pressed down and sets the mouse_hold variable accordingly using boolean values.
  # If the mouse is up, the user cannot drag the mouse.
  def check_click
    if inputs.mouse.down #is mouse up or down?
      state.mouse_held = true # mouse is being held down
    elsif inputs.mouse.up # if mouse is up
    state.mouse_held = false # mouse is not being held down or dragged
      state.mouse_dragging = false
    end

    if state.mouse_held &&    # mouse needs to be down
      !inputs.mouse.click &&     # must not be first click
      ((inputs.mouse.previous_click.point.x - inputs.mouse.position.x).abs > 15) # Need to move 15 pixels before "drag"
      state.mouse_dragging = true
    end

    # If the user clicks their mouse inside the grid, the search_lines method is called with a click input type.
    if ((inputs.mouse.click) && (inputs.mouse.click.point.inside_rect? state.grid_border))
      search_lines(inputs.mouse.click.point, :click)

    # If the user drags their mouse inside the grid, the search_lines method is called with a drag input type.
    elsif ((state.mouse_dragging) && (inputs.mouse.position.inside_rect? state.grid_border))
      search_lines(inputs.mouse.position, :drag)
    end
  end

  # Sets the definition of a grid box and handles user input to fill in or clear grid boxes.
  def search_lines (point, input_type)
    point.x -= state.paint_grid["x"] # subtracts the value assigned to the "x" key in the paint_grid hash
    point.y -= state.paint_grid["y"] # subtracts the value assigned to the "y" key in the paint_grid hash

    # Remove code following the .floor and see what happens when you try to fill in grid squares
    point.x = (point.x / state.paint_grid["dist_x"]).floor * state.paint_grid["dist_x"]
    point.y = (point.y / state.paint_grid["dist_y"]).floor * state.paint_grid["dist_y"]

    point.x += state.paint_grid["x"]
    point.y += state.paint_grid["y"]

    # Sets definition of a grid box, meaning its x, y, width, and height.
    # Floor is called on the point.x and point.y variables.
    # Ceil method is called on values of the distance hash keys, setting the width and height of a box.
    grid_box = [ point.x.floor, point.y.floor, state.paint_grid["dist_x"].ceil, state.paint_grid["dist_y"].ceil ]

    if input_type == :click # if user clicks their mouse
      if state.filled_squares.include? grid_box # if grid box is already filled in
        state.filled_squares.delete grid_box # box is cleared and removed from filled_squares
      else
        state.filled_squares << grid_box # otherwise, box is filled in and added to filled_squares
      end
    elsif input_type == :drag # if user drags mouse
      unless state.filled_squares.include? grid_box # unless the grid box dragged over is already filled in
        state.filled_squares << grid_box # the box is filled in and added to filled_squares
      end
    end
  end

  # Creates and outputs a "Clear" button on the screen using a label and a border.
  # If the button is clicked, the filled squares are cleared, making the filled_squares collection empty.
  def draw_buttons
    x, y, w, h = 390, 50, 240, 50
    state.clear_button        ||= state.new_entity(:button_with_fade)

    # The x and y positions are set to display the label in the center of the button.
    # Try changing the first two parameters to simply x, y and see what happens to the text placement!
    state.clear_button.label  ||= [x + w.half, y + h.half + 10, "Clear", 0, 1] # placed in center of border
    state.clear_button.border ||= [x, y, w, h]

    # If the mouse is clicked inside the borders of the clear button,
    # the filled_squares collection is emptied and the squares are cleared.
    if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.clear_button.border)
      state.clear_button.clicked_at = inputs.mouse.click.created_at # time (frame) the click occurred
      state.filled_squares.clear
      inputs.mouse.previous_click = nil
    end

    outputs.labels << state.clear_button.label
    outputs.borders << state.clear_button.border

    # When the clear button is clicked, the color of the button changes
    # and the transparency changes, as well. If you change the time from
    # 0.25.seconds to 1.25.seconds or more, the change will last longer.
    if state.clear_button.clicked_at
      outputs.solids << [x, y, w, h, 0, 180, 80, 255 * state.clear_button.clicked_at.ease(0.25.seconds, :flip)]
    end
  end
end

$paint_app = PaintApp.new

def tick args
  $paint_app.inputs = args.inputs
  $paint_app.state = args.state
  $paint_app.grid = args.grid
  $paint_app.args = args
  $paint_app.outputs = args.outputs
  $paint_app.tick
  tick_instructions args, "How to create a simple paint app. CLICK and HOLD to draw."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Mouse - Coordinate Systems - main.rb

# ./samples/05_mouse/04_coordinate_systems/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - args.inputs.mouse.click.position: Coordinates of the mouse's position on the screen.
   Unlike args.inputs.mouse.click.point, the mouse does not need to be pressed down for
   position to know the mouse's coordinates.
   For more information about the mouse, go to mygame/documentation/07-mouse.md.

 Reminders:

 - args.inputs.mouse.click: This property will be set if the mouse was clicked.

 - args.inputs.mouse.click.point.(x|y): The x and y location of the mouse.

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

   In this sample app, string interpolation is used to show the current position of the mouse
   in a label.

 - args.outputs.labels: An array that generates a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.outputs.solids: An array that generates a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.lines: An array that generates a line.
   The parameters are [X, Y, X2, Y2, RED, GREEN, BLUE, ALPHA]
   For more information about lines, go to mygame/documentation/04-lines.md.

=end

# This sample app shows a coordinate system or grid. The user can move their mouse around the screen and the
# coordinates of their position on the screen will be displayed. Users can choose to view one quadrant or
# four quadrants by pressing the button.

def tick args

  # The addition and subtraction in the first two parameters of the label and solid
  # ensure that the outputs don't overlap each other. Try removing them and see what happens.
  pos = args.inputs.mouse.position # stores coordinates of mouse's position
  args.outputs.labels << [pos.x + 10, pos.y + 10, "#{pos}"] # outputs label of coordinates
  args.outputs.solids << [pos.x -  2, pos.y - 2, 5, 5] # outputs small blackk box placed where mouse is hovering

  button = [0, 0, 370, 50] # sets definition of toggle button
  args.outputs.borders << button # outputs button as border (not filled in)
  args.outputs.labels << [10, 35, "click here toggle coordinate system"] # label of button
  args.outputs.lines << [    0, -720,    0, 720] # vertical line dividing quadrants
  args.outputs.lines << [-1280,    0, 1280,   0] # horizontal line dividing quadrants

  if args.inputs.mouse.click # if the user clicks the mouse
    pos = args.inputs.mouse.click.point # pos's value is point where user clicked (coordinates)
    if pos.inside_rect? button # if the click occurred inside the button
      if args.grid.name == :bottom_left # if the grid shows bottom left as origin
        args.grid.origin_center! # origin will be shown in center
      else
        args.grid.origin_bottom_left! # otherwise, the view will change to show bottom left as origin
      end
    end
  end

  tick_instructions args, "Sample app shows the two supported coordinate systems in Game Toolkit."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Save Load - Save Load Game - main.rb

# ./samples/06_save_load/01_save_load_game/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Symbol (:): Ruby object with a name and an internal ID. Symbols are useful
   because with a given symbol name, you can refer to the same object throughout
   a Ruby program.

   In this sample app, we're using symbols for our buttons. We have buttons that
   light fires, save, load, etc. Each of these buttons has a distinct symbol like
   :light_fire, :save_game, :load_game, etc.

 - to_sym: Returns the symbol corresponding to the given string; creates the symbol
   if it does not already exist.
   For example,
   'car'.to_sym
   would return the symbol :car.

 - last: Returns the last element of an array.

 Reminders:

 - num1.lesser(num2): finds the lower value of the given options.
   For example, in the statement
   a = 4.lesser(3)
   3 has a lower value than 4, which means that the value of a would be set to 3,
   but if the statement had been
   a = 4.lesser(5)
   4 has a lower value than 5, which means that the value of a would be set to 4.

 - num1.fdiv(num2): returns the float division (will have a decimal) of the two given numbers.
   For example, 5.fdiv(2) = 2.5 and 5.fdiv(5) = 1.0

 - String interpolation: uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - args.outputs.labels: An array. Values generate a label.
   Parameters are [X, Y, TEXT, SIZE, ALIGN, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information, go to mygame/documentation/02-labels.md.

 - ARRAY#inside_rect?: An array with at least two values is considered a point. An array
   with at least four values is considered a rect. The inside_rect? function returns true
   or false depending on if the point is inside the rect.

=end

# This code allows users to perform different tasks, such as saving and loading the game.
# Users also have options to reset the game and light a fire.

class TextedBasedGame

  # Contains methods needed for game to run properly.
  # Increments tick count by 1 each time it runs (60 times in a single second)
  def tick
    default
    show_intro
    state.engine_tick_count += 1
    tick_fire
  end

  # Sets default values.
  # The ||= ensures that a variable's value is only set to the value following the = sign
  # if the value has not already been set before. Intialization happens only in the first frame.
  def default
    state.engine_tick_count ||= 0
    state.active_module     ||= :room
    state.fire_progress     ||= 0
    state.fire_ready_in     ||= 10
    state.previous_fire     ||= :dead
    state.fire              ||= :dead
  end

  def show_intro
    return unless state.engine_tick_count == 0 # return unless the game just started
    set_story_line "awake." # calls set_story_line method, sets to "awake"
  end

  # Sets story line.
  def set_story_line story_line
    state.story_line    = story_line # story line set to value of parameter
    state.active_module = :alert # active module set to alert
  end

  # Clears story line.
  def clear_storyline
    state.active_module = :none # active module set to none
    state.story_line = nil # story line is cleared, set to nil (or empty)
  end

  # Determines fire progress (how close the fire is to being ready to light).
  def tick_fire
    return if state.active_module == :alert # return if active module is alert
    state.fire_progress += 1 # increment fire progress
    # fire_ready_in is 10. The fire_progress is either the current value or 10, whichever has a lower value.
    state.fire_progress = state.fire_progress.lesser(state.fire_ready_in)
  end

  # Sets the value of fire (whether it is dead or roaring), and the story line
  def light_fire
    return unless fire_ready? # returns unless the fire is ready to be lit
    state.fire = :roaring # fire is lit, set to roaring
    state.fire_progress = 0 # the fire progress returns to 0, since the fire has been lit
    if state.fire != state.previous_fire
      set_story_line "the fire is #{state.fire}." # the story line is set using string interpolation
      state.previous_fire = state.fire
    end
  end

  # Checks if the fire is ready to be lit. Returns a boolean value.
  def fire_ready?
    # If fire_progress (value between 0 and 10) is equal to fire_ready_in (value of 10),
    # the fire is ready to be lit.
    state.fire_progress == state.fire_ready_in
  end

  # Divides the value of the fire_progress variable by 10 to determine how close the user is to
  # being able to light a fire.
  def light_fire_progress
    state.fire_progress.fdiv(10) # float division
  end

  # Defines fire as the state.fire variable.
  def fire
    state.fire
  end

  # Sets the title of the room.
  def room_title
    return "a room that is dark" if state.fire == :dead # room is dark if the fire is dead
    return "a room that is lit" # room is lit if the fire is not dead
  end

  # Sets the active_module to room.
  def go_to_room
    state.active_module = :room
  end

  # Defines active_module as the state.active_module variable.
  def active_module
    state.active_module
  end

  # Defines story_line as the state.story_line variable.
  def story_line
    state.story_line
  end

  # Update every 60 frames (or every second)
  def should_tick?
    state.tick_count.mod_zero?(60)
  end

  # Sets the value of the game state provider.
  def initialize game_state_provider
    @game_state_provider = game_state_provider
  end

  # Defines the game state.
  # Any variable prefixed with an @ symbol is an instance variable.
  def state
    @game_state_provider.state
  end

  # Saves the state of the game in a text file called game_state.txt.
  def save
    $gtk.serialize_state('game_state.txt', state)
  end

  # Loads the game state from the game_state.txt text file.
  # If the load is unsuccessful, the user is informed since the story line indicates the failure.
  def load
    parsed_state = $gtk.deserialize_state('game_state.txt')
    if !parsed_state
      set_story_line "no game to load. press save first."
    else
      $gtk.args.state = parsed_state
    end
  end

  # Resets the game.
  def reset
    $gtk.reset
  end
end

class TextedBasedGamePresenter
  attr_accessor :state, :outputs, :inputs

  # Creates empty collection called highlights.
  # Calls methods necessary to run the game.
  def tick
    state.layout.highlights ||= []
    game.tick if game.should_tick?
    render
    process_input
  end

  # Outputs a label of the tick count (passage of time) and calls all render methods.
  def render
    outputs.labels << [10, 30, state.tick_count]
    render_alert
    render_room
    render_highlights
  end

  # Outputs a label onto the screen that shows the story line, and also outputs a "close" button.
  def render_alert
    return unless game.active_module == :alert

    outputs.labels << [640, 480, game.story_line, 5, 1]  # outputs story line label
    outputs.primitives << button(:alert_dismiss, 490, 380, "close")  # positions "close" button under story line
  end

  def render_room
    return unless game.active_module == :room
    outputs.labels << [640, 700, game.room_title, 4, 1] # outputs room title label at top of screen

    # The parameters for these outputs are (symbol, x, y, text, value/percentage) and each has a y value
    # that positions it 60 pixels lower than the previous output.

    # outputs the light_fire_progress bar, uses light_fire_progress for its percentage (which changes bar's appearance)
    outputs.primitives << progress_bar(:light_fire, 490, 600, "light fire", game.light_fire_progress)
    outputs.primitives << button(       :save_game, 490, 540, "save") # outputs save button
    outputs.primitives << button(       :load_game, 490, 480, "load") # outputs load button
    outputs.primitives << button(      :reset_game, 490, 420, "reset") # outputs reset button
    outputs.labels << [640, 30, "the fire is #{game.fire}", 0, 1] # outputs fire label at bottom of screen
  end

  # Outputs a collection of highlights using an array to set their values, and also rejects certain values from the collection.
  def render_highlights
    state.layout.highlights.each do |h| # for each highlight in the collection
        h.lifetime -= 1 # decrease the value of its lifetime
      end

      outputs.solids << state.layout.highlights.map do |h| # outputs highlights collection
        [h.x, h.y, h.w, h.h, h.color, 255 * h.lifetime / h.max_lifetime] # sets definition for each highlight
        # transparency changes; divide lifetime by max_lifetime, multiply result by 255
      end

      # reject highlights from collection that have no remaining lifetime
      state.layout.highlights = state.layout.highlights.reject { |h| h.lifetime <= 0 }
  end

  # Checks whether or not a button was clicked.
  # Returns a boolean value.
  def process_input
    button = button_clicked? # calls button_clicked? method
  end

  # Returns a boolean value.
  # Finds the button that was clicked from the button list and determines what method to call.
  # Adds a highlight to the highlights collection.
  def button_clicked?
    return nil unless click_pos # return nil unless click_pos holds coordinates of mouse click
      button = @button_list.find do |k, v| # goes through button_list to find button clicked
        click_pos.inside_rect? v[:primitives].last.rect # was the mouse clicked inside the rect of button?
      end
      return unless button # return unless a button was clicked
      method_to_call = "#{button[0]}_clicked".to_sym # sets method_to_call to symbol (like :save_game or :load_game)
      if self.respond_to? method_to_call # returns true if self responds to the given method (method actually exists)
        border = button[1][:primitives].last # sets border definition using value of last key in button list hash

        # declares each highlight as a new entity, sets properties
        state.layout.highlights << state.new_entity(:highlight) do |h|
            h.x = border.x
            h.y = border.y
            h.w = border.w
            h.h = border.h
            h.max_lifetime = 10
            h.lifetime = h.max_lifetime
            h.color = [120, 120, 180] # sets color to shade of purple
          end

          self.send method_to_call # invoke method identified by symbol
        else # otherwise, if self doesn't respond to given method
          border = button[1][:primitives].last # sets border definition using value of last key in hash

          # declares each highlight as a new entity, sets properties
          state.layout.highlights << state.new_entity(:highlight) do |h|
            h.x = border.x
            h.y = border.y
            h.w = border.w
            h.h = border.h
            h.max_lifetime = 4 # different max_lifetime than the one set if respond_to? had been true
            h.lifetime = h.max_lifetime
            h.color = [120, 80, 80] # sets color to dark color
          end

          # instructions for users on how to add the missing method_to_call to the code
          puts "It looks like #{method_to_call} doesn't exists on TextedBasedGamePresenter. Please add this method:"
          puts "Just copy the code below and put it in the #{TextedBasedGamePresenter} class definition."
          puts ""
          puts "```"
          puts "class TextedBasedGamePresenter <--- find this class and put the method below in it"
          puts ""
          puts "  def #{method_to_call}"
          puts "    puts 'Yay that worked!'"
          puts "  end"
          puts ""
          puts "end <-- make sure to put the #{method_to_call} method in between the `class` word and the final `end` statement."
          puts "```"
          puts ""
      end
  end

  # Returns the position of the mouse when it is clicked.
  def click_pos
    return nil unless inputs.mouse.click # returns nil unless the mouse was clicked
    return inputs.mouse.click.point # returns location of mouse click (coordinates)
  end

  # Creates buttons for the button_list and sets their values using a hash (uses symbols as keys)
  def button id, x, y, text
    @button_list[id] ||= { # assigns values to hash keys
      id: id,
      text: text,
      primitives: [
        [x + 10, y + 30, text, 2, 0].label, # positions label inside border
        [x, y, 300, 50].border,             # sets definition of border
      ]
    }

    @button_list[id][:primitives] # returns label and border for buttons
  end

  # Creates a progress bar (used for lighting the fire) and sets its values.
  def progress_bar id, x, y, text, percentage
    @button_list[id] = { # assigns values to hash keys
      id: id,
      text: text,
      primitives: [
        [x, y, 300, 50, 100, 100, 100].solid, # sets definition for solid (which fills the bar with gray)
        [x + 10, y + 30, text, 2, 0].label, # sets definition for label, positions inside border
        [x, y, 300, 50].border, # sets definition of border
      ]
    }

    # Fills progress bar based on percentage. If the fire was ready to be lit (100%) and we multiplied by
    # 100, only 1/3 of the bar would only be filled in. 200 would cause only 2/3 to be filled in.
    @button_list[id][:primitives][0][2] = 300 * percentage
    @button_list[id][:primitives]
  end

  # Defines the game.
  def game
    @game
  end

  # Initalizes the game and creates an empty list of buttons.
  def initialize
    @game = TextedBasedGame.new self
    @button_list ||= {}
  end

  # Clears the storyline and takes the user to the room.
  def alert_dismiss_clicked
    game.clear_storyline
    game.go_to_room
  end

  # Lights the fire when the user clicks the "light fire" option.
  def light_fire_clicked
    game.light_fire
  end

  # Saves the game when the user clicks the "save" option.
  def save_game_clicked
    game.save
  end

  # Resets the game when the user clicks the "reset" option.
  def reset_game_clicked
    game.reset
  end

  # Loads the game when the user clicks the "load" option.
  def load_game_clicked
    game.load
  end
end

$text_based_rpg = TextedBasedGamePresenter.new

def tick args
  $text_based_rpg.state = args.state
  $text_based_rpg.outputs = args.outputs
  $text_based_rpg.inputs = args.inputs
  $text_based_rpg.tick
end

Advanced Rendering - Simple Render Targets - main.rb

# ./samples/07_advanced_rendering/01_simple_render_targets/app/main.rb
def tick args
  # args.outputs.render_targets are really really powerful.
  # They essentially allow you to create a sprite programmatically and cache the result.

  # Create a render_target of a :block and a :gradient on tick zero.
  if args.state.tick_count == 0
    args.render_target(:block).solids << [0, 0, 1280, 100]

    # The gradient is actually just a collection of black solids with increasing
    # opacities.
    args.render_target(:gradient).solids << 90.map_with_index do |x|
      50.map_with_index do |y|
        [x * 15, y * 15, 15, 15, 0, 0, 0, (x * 3).fdiv(255) * 255]
      end
    end
  end

  # Take the :block render_target and present it horizontally centered.
  # Use a subsection of the render_targetd specified by source_x,
  # source_y, source_w, source_h.
  args.outputs.sprites << { x: 0,
                            y: 310,
                            w: 1280,
                            h: 100,
                            path: :block,
                            source_x: 0,
                            source_y: 0,
                            source_w: 1280,
                            source_h: 100 }

  # After rendering :block, render gradient on top of :block.
  args.outputs.sprites << [0, 0, 1280, 720, :gradient]

  args.outputs.labels  << [1270, 710, args.gtk.current_framerate, 0, 2, 255, 255, 255]
  tick_instructions args, "Sample app shows how to use render_targets (programmatically create cached sprites)."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

$gtk.reset

Advanced Rendering - Render Targets With Tile Manipulation - main.rb

# ./samples/07_advanced_rendering/02_render_targets_with_tile_manipulation/app/main.rb
# This sample is meant to show you how to do that dripping transition thing
#  at the start of the original Doom. Most of this file is here to animate
#  a scene to wipe away; the actual wipe effect is in the last 20 lines or
#  so.

$gtk.reset   # reset all game state if reloaded.

def circle_of_blocks pass, xoffset, yoffset, angleoffset, blocksize, distance
  numblocks = 10

  for i in 1..numblocks do
    angle = ((360 / numblocks) * i) + angleoffset
    radians = angle * (Math::PI / 180)
    x = (xoffset + (distance * Math.cos(radians))).round
    y = (yoffset + (distance * Math.sin(radians))).round
    pass.solids << [ x, y, blocksize, blocksize, 255, 255, 0 ]
  end
end

def draw_scene args, pass
  pass.solids << [0, 360, 1280, 360, 0, 0, 200]
  pass.solids << [0, 0, 1280, 360, 0, 127, 0]

  blocksize = 100
  angleoffset = args.state.tick_count * 2.5
  centerx = (1280 - blocksize) / 2
  centery = (720 - blocksize) / 2

  circle_of_blocks pass, centerx, centery, angleoffset, blocksize * 2, 500
  circle_of_blocks pass, centerx, centery, angleoffset, blocksize, 325
  circle_of_blocks pass, centerx, centery, angleoffset, blocksize / 2, 200
  circle_of_blocks pass, centerx, centery, angleoffset, blocksize / 4, 100
end

def tick args
  segments = 160

  # On the first tick, initialize some stuff.
  if !args.state.yoffsets
    args.state.baseyoff = 0
    args.state.yoffsets = []
    for i in 0..segments do
      args.state.yoffsets << rand * 100
    end
  end

  # Just draw some random stuff for a few seconds.
  args.state.static_debounce ||= 60 * 2.5
  if args.state.static_debounce > 0
    last_frame = args.state.static_debounce == 1
    target = last_frame ? args.render_target(:last_frame) : args.outputs
    draw_scene args, target
    args.state.static_debounce -= 1
    return unless last_frame
  end

  # build up the wipe...

  # this is the thing we're wiping to.
  args.outputs.sprites << [ 0, 0, 1280, 720, 'dragonruby.png' ]

  return if (args.state.baseyoff > (1280 + 100))  # stop when done sliding

  segmentw = 1280 / segments

  x = 0
  for i in 0..segments do
    yoffset = 0
    if args.state.yoffsets[i] < args.state.baseyoff
      yoffset = args.state.baseyoff - args.state.yoffsets[i]
    end

    # (720 - yoffset) flips the coordinate system, (- 720) adjusts for the height of the segment.
    args.outputs.sprites << [ x, (720 - yoffset) - 720, segmentw, 720, 'last_frame', 0, 255, 255, 255, 255, x, 0, segmentw, 720 ]
    x += segmentw
  end

  args.state.baseyoff += 4

  tick_instructions args, "Sample app shows an advanced usage of render_target."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Advanced Rendering - Render Target Viewports - main.rb

# ./samples/07_advanced_rendering/03_render_target_viewports/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   For example, if we want to create a new button, we would declare it as a new entity and
   then define its properties. (Remember, you can use state to define ANY property and it will
   be retained across frames.)

   If you have a solar system and you're creating args.state.sun and setting its image path to an
   image in the sprites folder, you would do the following:
   (See samples/99_sample_nddnug_workshop for more details.)

   args.state.sun ||= args.state.new_entity(:sun) do |s|
   s.path = 'sprites/sun.png'
   end

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

   For example, if we have a variable
   name = "Ruby"
   then the line
   puts "How are you, #{name}?"
   would print "How are you, Ruby?" to the console.
   (Remember, string interpolation only works with double quotes!)

 - Ternary operator (?): Similar to if statement; first evalulates whether a statement is
   true or false, and then executes a command depending on that result.
   For example, if we had a variable
   grade = 75
   and used the ternary operator in the command
   pass_or_fail = grade > 65 ? "pass" : "fail"
   then the value of pass_or_fail would be "pass" since grade's value was greater than 65.

 Reminders:

 - args.grid.(left|right|top|bottom): Pixel value for the boundaries of the virtual
   720 p screen (Dragon Ruby Game Toolkits's virtual resolution is always 1280x720).

 - Numeric#shift_(left|right|up|down): Shifts the Numeric in the correct direction
   by adding or subracting.

 - ARRAY#inside_rect?: An array with at least two values is considered a point. An array
   with at least four values is considered a rect. The inside_rect? function returns true
   or false depending on if the point is inside the rect.

 - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.

 - args.inputs.mouse.click: This property will be set if the mouse was clicked.
   For more information about the mouse, go to mygame/documentation/07-mouse.md.

 - args.inputs.keyboard.key_up.KEY: The value of the properties will be set
   to the frame  that the key_up event occurred (the frame correlates
   to args.state.tick_count).
   For more information about the keyboard, go to mygame/documentation/06-keyboard.md.

 - args.state.labels:
   The parameters for a label are
   1. the position (x, y)
   2. the text
   3. the size
   4. the alignment
   5. the color (red, green, and blue saturations)
   6. the alpha (or transparency)
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.state.lines:
   The parameters for a line are
   1. the starting position (x, y)
   2. the ending position (x2, y2)
   3. the color (red, green, and blue saturations)
   4. the alpha (or transparency)
   For more information about lines, go to mygame/documentation/04-lines.md.

 - args.state.solids (and args.state.borders):
   The parameters for a solid (or border) are
   1. the position (x, y)
   2. the width (w)
   3. the height (h)
   4. the color (r, g, b)
   5. the alpha (or transparency)
   For more information about solids and borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.state.sprites:
   The parameters for a sprite are
   1. the position (x, y)
   2. the width (w)
   3. the height (h)
   4. the image path
   5. the angle
   6. the alpha (or transparency)
   For more information about sprites, go to mygame/documentation/05-sprites.md.
=end

# This sample app shows different objects that can be used when making games, such as labels,
# lines, sprites, solids, buttons, etc. Each demo section shows how these objects can be used.

# Also note that state.tick_count refers to the passage of time, or current frame.

class TechDemo
  attr_accessor :inputs, :state, :outputs, :grid, :args

  # Calls all methods necessary for the app to run properly.
  def tick
    labels_tech_demo
    lines_tech_demo
    solids_tech_demo
    borders_tech_demo
    sprites_tech_demo
    keyboards_tech_demo
    controller_tech_demo
    mouse_tech_demo
    point_to_rect_tech_demo
    rect_to_rect_tech_demo
    button_tech_demo
    export_game_state_demo
    window_state_demo
    render_seperators
  end

  # Shows output of different kinds of labels on the screen
  def labels_tech_demo
    outputs.labels << [grid.left.shift_right(5), grid.top.shift_down(5), "This is a label located at the top left."]
    outputs.labels << [grid.left.shift_right(5), grid.bottom.shift_up(30), "This is a label located at the bottom left."]
    outputs.labels << [ 5, 690, "Labels (x, y, text, size, align, r, g, b, a)"]
    outputs.labels << [ 5, 660, "Smaller label.",  -2]
    outputs.labels << [ 5, 630, "Small label.",    -1]
    outputs.labels << [ 5, 600, "Medium label.",    0]
    outputs.labels << [ 5, 570, "Large label.",     1]
    outputs.labels << [ 5, 540, "Larger label.",    2]
    outputs.labels << [300, 660, "Left aligned.",    0, 2]
    outputs.labels << [300, 640, "Center aligned.",  0, 1]
    outputs.labels << [300, 620, "Right aligned.",   0, 0]
    outputs.labels << [175, 595, "Red Label.",       0, 0, 255,   0,   0]
    outputs.labels << [175, 575, "Green Label.",     0, 0,   0, 255,   0]
    outputs.labels << [175, 555, "Blue Label.",      0, 0,   0,   0, 255]
    outputs.labels << [175, 535, "Faded Label.",     0, 0,   0,   0,   0, 128]
  end

  # Shows output of lines on the screen
  def lines_tech_demo
    outputs.labels << [5, 500, "Lines (x, y, x2, y2, r, g, b, a)"]
    outputs.lines  << [5, 450, 100, 450]
    outputs.lines  << [5, 430, 300, 430]
    outputs.lines  << [5, 410, 300, 410, state.tick_count % 255, 0, 0, 255] # red saturation changes
    outputs.lines  << [5, 390 - state.tick_count % 25, 300, 390, 0, 0, 0, 255] # y position changes
    outputs.lines  << [5 + state.tick_count % 200, 360, 300, 360, 0, 0, 0, 255] # x position changes
  end

  # Shows output of different kinds of solids on the screen
  def solids_tech_demo
    outputs.labels << [  5, 350, "Solids (x, y, w, h, r, g, b, a)"]
    outputs.solids << [ 10, 270, 50, 50]
    outputs.solids << [ 70, 270, 50, 50, 0, 0, 0]
    outputs.solids << [130, 270, 50, 50, 255, 0, 0]
    outputs.solids << [190, 270, 50, 50, 255, 0, 0, 128]
    outputs.solids << [250, 270, 50, 50, 0, 0, 0, 128 + state.tick_count % 128] # transparency changes
  end

  # Shows output of different kinds of borders on the screen
  # The parameters for a border are the same as the parameters for a solid
  def borders_tech_demo
    outputs.labels <<  [  5, 260, "Borders (x, y, w, h, r, g, b, a)"]
    outputs.borders << [ 10, 180, 50, 50]
    outputs.borders << [ 70, 180, 50, 50, 0, 0, 0]
    outputs.borders << [130, 180, 50, 50, 255, 0, 0]
    outputs.borders << [190, 180, 50, 50, 255, 0, 0, 128]
    outputs.borders << [250, 180, 50, 50, 0, 0, 0, 128 + state.tick_count % 128] # transparency changes
  end

  # Shows output of different kinds of sprites on the screen
  def sprites_tech_demo
    outputs.labels <<  [   5, 170, "Sprites (x, y, w, h, path, angle, a)"]
    outputs.sprites << [  10, 40, 128, 101, 'dragonruby.png']
    outputs.sprites << [ 150, 40, 128, 101, 'dragonruby.png', state.tick_count % 360] # angle changes
    outputs.sprites << [ 300, 40, 128, 101, 'dragonruby.png', 0, state.tick_count % 255] # transparency changes
  end

  # Holds size, alignment, color (black), and alpha (transparency) parameters
  # Using small_font as a parameter accounts for all remaining parameters
  # so they don't have to be repeatedly typed
  def small_font
    [-2, 0, 0, 0, 0, 255]
  end

  # Sets position of each row
  # Converts given row value to pixels that DragonRuby understands
  def row_to_px row_number

    # Row 0 starts 5 units below the top of the grid.
    # Each row afterward is 20 units lower.
    grid.top.shift_down(5).shift_down(20 * row_number)
  end

  # Uses labels to output current game time (passage of time), and whether or not "h" was pressed
  # If "h" is pressed, the frame is output when the key_up event occurred
  def keyboards_tech_demo
    outputs.labels << [460, row_to_px(0), "Current game time: #{state.tick_count}", small_font]
    outputs.labels << [460, row_to_px(2), "Keyboard input: inputs.keyboard.key_up.h", small_font]
    outputs.labels << [460, row_to_px(3), "Press \"h\" on the keyboard.", small_font]

    if inputs.keyboard.key_up.h # if "h" key_up event occurs
      state.h_pressed_at = state.tick_count # frame it occurred is stored
    end

    # h_pressed_at is initially set to false, and changes once the user presses the "h" key.
    state.h_pressed_at ||= false

    if state.h_pressed_at # if h is pressed (pressed_at has a frame number and is no longer false)
      outputs.labels << [460, row_to_px(4), "\"h\" was pressed at time: #{state.h_pressed_at}", small_font]
    else # otherwise, label says "h" was never pressed
      outputs.labels << [460, row_to_px(4), "\"h\" has never been pressed.", small_font]
    end

    # border around keyboard input demo section
    outputs.borders << [455, row_to_px(5), 360, row_to_px(2).shift_up(5) - row_to_px(5)]
  end

  # Sets definition for a small label
  # Makes it easier to position labels in respect to the position of other labels
  def small_label x, row, message
    [x, row_to_px(row), message, small_font]
  end

  # Uses small labels to show whether the "a" button on the controller is down, held, or up.
  # y value of each small label is set by calling the row_to_px method
  def controller_tech_demo
    x = 460
    outputs.labels << small_label(x, 6, "Controller one input: inputs.controller_one")
    outputs.labels << small_label(x, 7, "Current state of the \"a\" button.")
    outputs.labels << small_label(x, 8, "Check console window for more info.")

    if inputs.controller_one.key_down.a # if "a" is in "down" state
      outputs.labels << small_label(x, 9, "\"a\" button down: #{inputs.controller_one.key_down.a}")
      puts "\"a\" button down at #{inputs.controller_one.key_down.a}" # prints frame the event occurred
    elsif inputs.controller_one.key_held.a # if "a" is held down
      outputs.labels << small_label(x, 9, "\"a\" button held: #{inputs.controller_one.key_held.a}")
    elsif inputs.controller_one.key_up.a # if "a" is in up state
      outputs.labels << small_label(x, 9, "\"a\" button up: #{inputs.controller_one.key_up.a}")
      puts "\"a\" key up at #{inputs.controller_one.key_up.a}"
    else # if no event has occurred
      outputs.labels << small_label(x, 9, "\"a\" button state is nil.")
    end

    # border around controller input demo section
    outputs.borders << [455, row_to_px(10), 360, row_to_px(6).shift_up(5) - row_to_px(10)]
  end

  # Outputs when the mouse was clicked, as well as the coordinates on the screen
  # of where the click occurred
  def mouse_tech_demo
    x = 460

    outputs.labels << small_label(x, 11, "Mouse input: inputs.mouse")

    if inputs.mouse.click # if click has a value and is not nil
      state.last_mouse_click = inputs.mouse.click # coordinates of click are stored
    end

    if state.last_mouse_click # if mouse is clicked (has coordinates as value)
      # outputs the time (frame) the click occurred, as well as how many frames have passed since the event
      outputs.labels << small_label(x, 12, "Mouse click happened at: #{state.last_mouse_click.created_at}, #{state.last_mouse_click.created_at_elapsed}")
      # outputs coordinates of click
      outputs.labels << small_label(x, 13, "Mouse click location: #{state.last_mouse_click.point.x}, #{state.last_mouse_click.point.y}")
    else # otherwise if the mouse has not been clicked
      outputs.labels << small_label(x, 12, "Mouse click has not occurred yet.")
      outputs.labels << small_label(x, 13, "Please click mouse.")
    end
  end

  # Outputs whether a mouse click occurred inside or outside of a box
  def point_to_rect_tech_demo
    x = 460

    outputs.labels << small_label(x, 15, "Click inside the blue box maybe ---->")

    box = [765, 370, 50, 50, 0, 0, 170] # blue box
    outputs.borders << box

    if state.last_mouse_click # if the mouse was clicked
      if state.last_mouse_click.point.inside_rect? box # if mouse clicked inside box
        outputs.labels << small_label(x, 16, "Mouse click happened inside the box.")
      else # otherwise, if mouse was clicked outside the box
        outputs.labels << small_label(x, 16, "Mouse click happened outside the box.")
      end
    else # otherwise, if was not clicked at all
      outputs.labels << small_label(x, 16, "Mouse click has not occurred yet.") # output if the mouse was not clicked
    end

    # border around mouse input demo section
    outputs.borders << [455, row_to_px(14), 360, row_to_px(11).shift_up(5) - row_to_px(14)]
  end

  # Outputs a red box onto the screen. A mouse click from the user inside of the red box will output
  # a smaller box. If two small boxes are inside of the red box, it will be determined whether or not
  # they intersect.
  def rect_to_rect_tech_demo
    x = 460

    outputs.labels << small_label(x, 17.5, "Click inside the red box below.") # label with instructions
    red_box = [460, 250, 355, 90, 170, 0, 0] # definition of the red box
    outputs.borders << red_box # output as a border (not filled in)

    # If the mouse is clicked inside the red box, two collision boxes are created.
    if inputs.mouse.click
      if inputs.mouse.click.point.inside_rect? red_box
        if !state.box_collision_one # if the collision_one box does not yet have a definition
          # Subtracts 25 from the x and y positions of the click point in order to make the click point the center of the box.
          # You can try deleting the subtraction to see how it impacts the box placement.
          state.box_collision_one = [inputs.mouse.click.point.x - 25, inputs.mouse.click.point.y - 25, 50, 50, 180, 0,   0, 180]  # sets definition
        elsif !state.box_collision_two # if collision_two does not yet have a definition
          state.box_collision_two = [inputs.mouse.click.point.x - 25, inputs.mouse.click.point.y - 25, 50, 50,   0, 0, 180, 180] # sets definition
        else
          state.box_collision_one = nil # both boxes are empty
          state.box_collision_two = nil
        end
      end
    end

    # If collision boxes exist, they are output onto screen inside the red box as solids
    if state.box_collision_one
      outputs.solids << state.box_collision_one
    end

    if state.box_collision_two
      outputs.solids << state.box_collision_two
    end

    # Outputs whether or not the two collision boxes intersect.
    if state.box_collision_one && state.box_collision_two # if both collision_boxes are defined (and not nil or empty)
      if state.box_collision_one.intersect_rect? state.box_collision_two # if the two boxes intersect
        outputs.labels << small_label(x, 23.5, 'The boxes intersect.')
      else # otherwise, if the two boxes do not intersect
        outputs.labels << small_label(x, 23.5, 'The boxes do not intersect.')
      end
    else
      outputs.labels << small_label(x, 23.5, '--') # if the two boxes are not defined (are nil or empty), this label is output
    end
  end

  # Creates a button and outputs it onto the screen using labels and borders.
  # If the button is clicked, the color changes to make it look faded.
  def button_tech_demo
    x, y, w, h = 460, 160, 300, 50
    state.button        ||= state.new_entity(:button_with_fade)

    # Adds w.half to x and h.half + 10 to y in order to display the text inside the button's borders.
    state.button.label  ||= [x + w.half, y + h.half + 10, "click me and watch me fade", 0, 1]
    state.button.border ||= [x, y, w, h]

    if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.button.border) # if mouse is clicked, and clicked inside button's border
      state.button.clicked_at = inputs.mouse.click.created_at # stores the time the click occurred
    end

    outputs.labels << state.button.label
    outputs.borders << state.button.border

    if state.button.clicked_at # if button was clicked (variable has a value and is not nil)

      # The appearance of the button changes for 0.25 seconds after the time the button is clicked at.
      # The color changes (rgb is set to 0, 180, 80) and the transparency gradually changes.
      # Change 0.25 to 1.25 and notice that the transparency takes longer to return to normal.
      outputs.solids << [x, y, w, h, 0, 180, 80, 255 * state.button.clicked_at.ease(0.25.seconds, :flip)]
    end
  end

  # Creates a new button by declaring it as a new entity, and sets values.
  def new_button_prefab x, y, message
    w, h = 300, 50
    button        = state.new_entity(:button_with_fade)
    button.label  = [x + w.half, y + h.half + 10, message, 0, 1] # '+ 10' keeps label's text within button's borders
    button.border = [x, y, w, h] # sets border definition
    button
  end

  # If the mouse has been clicked and the click's location is inside of the button's border, that means
  # that the button has been clicked. This method returns a boolean value.
  def button_clicked? button
    inputs.mouse.click && inputs.mouse.click.point.inside_rect?(button.border)
  end

  # Determines if button was clicked, and changes its appearance if it is clicked
  def tick_button_prefab button
    outputs.labels << button.label # outputs button's label and border
    outputs.borders << button.border

    if button_clicked? button # if button is clicked
      button.clicked_at = inputs.mouse.click.created_at # stores the time that the button was clicked
    end

    if button.clicked_at # if clicked_at has a frame value and is not nil
      # button is output; color changes and transparency changes for 0.25 seconds after click occurs
      outputs.solids << [button.border.x, button.border.y, button.border.w, button.border.h,
                         0, 180, 80, 255 * button.clicked_at.ease(0.25.seconds, :flip)] # transparency changes for 0.25 seconds
    end
  end

  # Exports the app's game state if the export button is clicked.
  def export_game_state_demo
    state.export_game_state_button ||= new_button_prefab(460, 100, "click to export app state")
    tick_button_prefab(state.export_game_state_button) # calls method to output button
    if button_clicked? state.export_game_state_button # if the export button is clicked
      args.gtk.export! "Exported from clicking the export button in the tech demo." # the export occurs
    end
  end

  # The mouse and keyboard focus are set to "yes" when the Dragonruby window is the active window.
  def window_state_demo
    m = $gtk.args.inputs.mouse.has_focus ? 'Y' : 'N' # ternary operator (similar to if statement)
    k = $gtk.args.inputs.keyboard.has_focus ? 'Y' : 'N'
    outputs.labels << [460, 20, "mouse focus: #{m}   keyboard focus: #{k}", small_font]
  end

  #Sets values for the horizontal separator (divides demo sections)
  def horizontal_seperator y, x, x2
    [x, y, x2, y, 150, 150, 150]
  end

  #Sets the values for the vertical separator (divides demo sections)
  def vertical_seperator x, y, y2
    [x, y, x, y2, 150, 150, 150]
  end

  # Outputs vertical and horizontal separators onto the screen to separate each demo section.
  def render_seperators
    outputs.lines << horizontal_seperator(505, grid.left, 445)
    outputs.lines << horizontal_seperator(353, grid.left, 445)
    outputs.lines << horizontal_seperator(264, grid.left, 445)
    outputs.lines << horizontal_seperator(174, grid.left, 445)

    outputs.lines << vertical_seperator(445, grid.top, grid.bottom)

    outputs.lines << horizontal_seperator(690, 445, 820)
    outputs.lines << horizontal_seperator(426, 445, 820)

    outputs.lines << vertical_seperator(820, grid.top, grid.bottom)
  end
end

$tech_demo = TechDemo.new

def tick args
  $tech_demo.inputs = args.inputs
  $tech_demo.state = args.state
  $tech_demo.grid = args.grid
  $tech_demo.args = args
  $tech_demo.outputs = args.render_target(:mini_map)
  $tech_demo.tick
  args.outputs.labels  << [830, 715, "Render target:", [-2, 0, 0, 0, 0, 255]]
  args.outputs.sprites << [0, 0, 1280, 720, :mini_map]
  args.outputs.sprites << [830, 300, 675, 379, :mini_map]
  tick_instructions args, "Sample app shows all the rendering apis available."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Advanced Rendering - Render Primitive Hierarchies - main.rb

# ./samples/07_advanced_rendering/04_render_primitive_hierarchies/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - Nested array: An array whose individual elements are also arrays; useful for
   storing groups of similar data.  Also called multidimensional arrays.

   In this sample app, we see nested arrays being used in object definitions.
   Notice the parameters for solids, listed below. Parameters 1-3 set the
   definition for the rect, and parameter 4 sets the definition of the color.

   Instead of having a solid definition that looks like this,
   [X, Y, W, H, R, G, B]
   we can separate it into two separate array definitions in one, like this
   [[X, Y, W, H], [R, G, B]]
   and both options work fine in defining our solid (or any object).

 - Collections: Lists of data; useful for organizing large amounts of data.
   One element of a collection could be an array (which itself contains many elements).
   For example, a collection that stores two solid objects would look like this:
   [
    [100, 100, 50, 50, 0, 0, 0],
    [100, 150, 50, 50, 255, 255, 255]
   ]
   If this collection was added to args.outputs.solids, two solids would be output
   next to each other, one black and one white.
   Nested arrays can be used in collections, as you will see in this sample app.

 Reminders:

 - args.outputs.solids: An array. The values generate a solid.
   The parameters for a solid are
   1. The position on the screen (x, y)
   2. The width (w)
   3. The height (h)
   4. The color (r, g, b) (if a color is not assigned, the object's default color will be black)
   NOTE: THE PARAMETERS ARE THE SAME FOR BORDERS!

   Here is an example of a (red) border or solid definition:
   [100, 100, 400, 500, 255, 0, 0]
   It will be a solid or border depending on if it is added to args.outputs.solids or args.outputs.borders.
   For more information about solids and borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters for sprites are
   1. The position on the screen (x, y)
   2. The width (w)
   3. The height (h)
   4. The image path (p)

   Here is an example of a sprite definition:
   [100, 100, 400, 500, 'sprites/dragonruby.png']
   For more information about sprites, go to mygame/documentation/05-sprites.md.

=end

# This code demonstrates the creation and output of objects like sprites, borders, and solids
# If filled in, they are solids
# If hollow, they are borders
# If images, they are sprites

# Solids are added to args.outputs.solids
# Borders are added to args.outputs.borders
# Sprites are added to args.outputs.sprites

# The tick method runs 60 frames every second.
# Your game is going to happen under this one function.
def tick args
  border_as_solid_and_solid_as_border args
  sprite_as_border_or_solids args
  collection_of_borders_and_solids args
  collection_of_sprites args
end

# Shows a border being output onto the screen as a border and a solid
# Also shows how colors can be set
def border_as_solid_and_solid_as_border args
  border = [0, 0, 50, 50]
  args.outputs.borders << border
  args.outputs.solids  << border

  # Red, green, blue saturations (last three parameters) can be any number between 0 and 255
  border_with_color = [0, 100, 50, 50, 255, 0, 0]
  args.outputs.borders << border_with_color
  args.outputs.solids  << border_with_color

  border_with_nested_color = [0, 200, 50, 50, [0, 255, 0]] # nested color
  args.outputs.borders << border_with_nested_color
  args.outputs.solids  << border_with_nested_color

  border_with_nested_rect = [[0, 300, 50, 50], 0, 0, 255] # nested rect
  args.outputs.borders << border_with_nested_rect
  args.outputs.solids  << border_with_nested_rect

  border_with_nested_color_and_rect = [[0, 400, 50, 50], [255, 0, 255]] # nested rect and color
  args.outputs.borders << border_with_nested_color_and_rect
  args.outputs.solids  << border_with_nested_color_and_rect
end

# Shows a sprite output onto the screen as a sprite, border, and solid
# Demonstrates that all three outputs appear differently on screen
def sprite_as_border_or_solids args
  sprite = [100, 0, 50, 50, 'sprites/ship.png']
  args.outputs.sprites << sprite

  # Sprite_as_border variable has same parameters (excluding position) as above object,
  # but will appear differently on screen because it is added to args.outputs.borders
  sprite_as_border = [100, 100, 50, 50, 'sprites/ship.png']
  args.outputs.borders << sprite_as_border

  # Sprite_as_solid variable has same parameters (excluding position) as above object,
  # but will appear differently on screen because it is added to args.outputs.solids
  sprite_as_solid = [100, 200, 50, 50, 'sprites/ship.png']
  args.outputs.solids << sprite_as_solid
end

# Holds and outputs a collection of borders and a collection of solids
# Collections are created by using arrays to hold parameters of each individual object
def collection_of_borders_and_solids args
  collection_borders = [
    [
      [200,  0, 50, 50],                    # black border
      [200,  100, 50, 50, 255, 0, 0],       # red border
      [200,  200, 50, 50, [0, 255, 0]],     # nested color
    ],
    [[200, 300, 50, 50], 0, 0, 255],        # nested rect
    [[200, 400, 50, 50], [255, 0, 255]]     # nested rect and nested color
  ]

  args.outputs.borders << collection_borders

  collection_solids = [
    [
      [[300, 300, 50, 50], 0, 0, 255],      # nested rect
      [[300, 400, 50, 50], [255, 0, 255]]   # nested rect and nested color
    ],
    [300,  0, 50, 50],
    [300,  100, 50, 50, 255, 0, 0],
    [300,  200, 50, 50, [0, 255, 0]],       # nested color
  ]

  args.outputs.solids << collection_solids
end

# Holds and outputs a collection of sprites by adding it to args.outputs.sprites
# Also outputs a collection with same parameters (excluding position) by adding
# it to args.outputs.solids and another to args.outputs.borders
def collection_of_sprites args
  sprites_collection = [
    [
      [400, 0, 50, 50, 'sprites/ship.png'],
      [400, 100, 50, 50, 'sprites/ship.png'],
    ],
    [400, 200, 50, 50, 'sprites/ship.png']
  ]

  args.outputs.sprites << sprites_collection

  args.outputs.solids << [
    [500, 0, 50, 50, 'sprites/ship.png'],
    [500, 100, 50, 50, 'sprites/ship.png'],
    [[[500, 200, 50, 50, 'sprites/ship.png']]]
  ]

  args.outputs.borders << [
    [
      [600, 0, 50, 50, 'sprites/ship.png'],
      [600, 100, 50, 50, 'sprites/ship.png'],
    ],
    [600, 200, 50, 50, 'sprites/ship.png']
  ]
end

Advanced Rendering - Render Primitives As Hash - main.rb

# ./samples/07_advanced_rendering/05_render_primitives_as_hash/app/main.rb
=begin

 Reminders:

 - Hashes: Collection of unique keys and their corresponding values. The value can be found
   using their keys.

   For example, if we have a "numbers" hash that stores numbers in English as the
   key and numbers in Spanish as the value, we'd have a hash that looks like this...
   numbers = { "one" => "uno", "two" => "dos", "three" => "tres" }
   and on it goes.

   Now if we wanted to find the corresponding value of the "one" key, we could say
   puts numbers["one"]
   which would print "uno" to the console.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters are [X, Y, WIDTH, HEIGHT, PATH, ANGLE, ALPHA, RED, GREEN, BLUE]
   For more information about sprites, go to mygame/documentation/05-sprites.md.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.outputs.solids: An array. The values generate a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.borders: An array. The values generate a border.
   The parameters are the same as a solid.
   For more information about borders, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.lines: An array. The values generate a line.
   The parameters are [X1, Y1, X2, Y2, RED, GREEN, BLUE]
   For more information about labels, go to mygame/documentation/02-labels.md.

=end

# This sample app demonstrates how hashes can be used to output different kinds of objects.

def tick args
  args.state.angle ||= 0 # initializes angle to 0
  args.state.angle  += 1 # increments angle by 1 every frame (60 times a second)

  # Outputs sprite using a hash
  args.outputs.sprites << {
    x: 30,                          # sprite position
    y: 550,
    w: 128,                         # sprite size
    h: 101,
    path: "dragonruby.png",         # image path
    angle: args.state.angle,        # angle
    a: 255,                         # alpha (transparency)
    r: 255,                         # color saturation
    g: 255,
    b: 255,
    tile_x:  0,                     # sprite sub division/tile
    tile_y:  0,
    tile_w: -1,
    tile_h: -1,
    flip_vertically: false,         # don't flip sprite
    flip_horizontally: false,
    angle_anchor_x: 0.5,            # rotation center set to middle
    angle_anchor_y: 0.5
  }

  # Outputs label using a hash
  args.outputs.labels << {
    x:              200,                 # label position
    y:              550,
    text:           "dragonruby",        # label text
    size_enum:      2,
    alignment_enum: 1,
    r:              155,                 # color saturation
    g:              50,
    b:              50,
    a:              255,                 # transparency
    font:           "fonts/manaspc.ttf"  # font style; without mentioned file, label won't output correctly
  }

  # Outputs solid using a hash
  # [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE, ALPHA]
  args.outputs.solids << {
    x: 400,                         # position
    y: 550,
    w: 160,                         # size
    h:  90,
    r: 120,                         # color saturation
    g:  50,
    b:  50,
    a: 255                          # transparency
  }

  # Outputs border using a hash
  # Same parameters as a solid
  args.outputs.borders << {
    x: 600,
    y: 550,
    w: 160,
    h:  90,
    r: 120,
    g:  50,
    b:  50,
    a: 255
  }

  # Outputs line using a hash
  args.outputs.lines << {
    x:  900,                        # starting position
    y:  550,
    x2: 1200,                       # ending position
    y2: 550,
    r:  120,                        # color saturation
    g:   50,
    b:   50,
    a:  255                         # transparency
  }

  # Outputs sprite as a primitive using a hash
  args.outputs.primitives << {
    x: 30,                          # position
    y: 200,
    w: 128,                         # size
    h: 101,
    path: "dragonruby.png",         # image path
    angle: args.state.angle,        # angle
    a: 255,                         # transparency
    r: 255,                         # color saturation
    g: 255,
    b: 255,
    tile_x:  0,                     # sprite sub division/tile
    tile_y:  0,
    tile_w: -1,
    tile_h: -1,
    flip_vertically: false,         # don't flip
    flip_horizontally: false,
    angle_anchor_x: 0.5,            # rotation center set to middle
    angle_anchor_y: 0.5
  }.sprite

  # Outputs label as primitive using a hash
  args.outputs.primitives << {
    x:         200,                 # position
    y:         200,
    text:      "dragonruby",        # text
    size:      2,
    alignment: 1,
    r:         155,                 # color saturation
    g:         50,
    b:         50,
    a:         255,                 # transparency
    font:      "fonts/manaspc.ttf"  # font style
  }.label

  # Outputs solid as primitive using a hash
  args.outputs.primitives << {
    x: 400,                         # position
    y: 200,
    w: 160,                         # size
    h:  90,
    r: 120,                         # color saturation
    g:  50,
    b:  50,
    a: 255                          # transparency
  }.solid

  # Outputs border as primitive using a hash
  # Same parameters as solid
  args.outputs.primitives << {
    x: 600,                         # position
    y: 200,
    w: 160,                         # size
    h:  90,
    r: 120,                         # color saturation
    g:  50,
    b:  50,
    a: 255                          # transparency
  }.border

  # Outputs line as primitive using a hash
  args.outputs.primitives << {
    x:  900,                        # starting position
    y:  200,
    x2: 1200,                       # ending position
    y2: 200,
    r:  120,                        # color saturation
    g:   50,
    b:   50,
    a:  255                         # transparency
  }.line
end

Advanced Rendering - Pixel Arrays - main.rb

# ./samples/07_advanced_rendering/06_pixel_arrays/app/main.rb
$gtk.reset

def tick args
  args.state.posinc ||= 1
  args.state.pos ||= 0
  args.state.rotation ||= 0

  dimension = 10  # keep it small and let the GPU scale it when rendering the sprite.

  # Set up our "scanner" pixel array and fill it with black pixels.
  args.pixel_array(:scanner).width = dimension
  args.pixel_array(:scanner).height = dimension
  args.pixel_array(:scanner).pixels.fill(0xFF000000, 0, dimension * dimension)  # black, full alpha

  # Draw a green line that bounces up and down the sprite.
  args.pixel_array(:scanner).pixels.fill(0xFF00FF00, dimension * args.state.pos, dimension)  # green, full alpha

  # Adjust position for next frame.
  args.state.pos += args.state.posinc
  if args.state.posinc > 0 && args.state.pos >= dimension
    args.state.posinc = -1
    args.state.pos = dimension - 1
  elsif args.state.posinc < 0 && args.state.pos < 0
    args.state.posinc = 1
    args.state.pos = 1
  end

  # New/changed pixel arrays get uploaded to the GPU before we render
  #  anything. At that point, they can be scaled, rotated, and otherwise
  #  used like any other sprite.
  w = 100
  h = 100
  x = (1280 - w) / 2
  y = (720 - h) / 2
  args.outputs.background_color = [64, 0, 128]
  args.outputs.primitives << [x, y, w, h, :scanner, args.state.rotation].sprite
  args.state.rotation += 1

  args.outputs.primitives << args.gtk.current_framerate_primitives
end

Advanced Rendering - Simple Camera - main.rb

# ./samples/07_advanced_rendering/07_simple_camera/app/main.rb
def tick args
  # variables you can play around with
  args.state.world.w      ||= 1280
  args.state.world.h      ||= 720

  args.state.player.x     ||= 0
  args.state.player.y     ||= 0
  args.state.player.size  ||= 32

  args.state.enemy.x      ||= 700
  args.state.enemy.y      ||= 700
  args.state.enemy.size   ||= 16

  args.state.camera.x                ||= 640
  args.state.camera.y                ||= 300
  args.state.camera.scale            ||= 1.0
  args.state.camera.show_empty_space ||= :yes

  # instructions
  args.outputs.primitives << { x: 0, y:  80.from_top, w: 360, h: 80, r: 0, g: 0, b: 0, a: 128 }.solid
  args.outputs.primitives << { x: 10, y: 10.from_top, text: "arrow keys to move around", r: 255, g: 255, b: 255}.label
  args.outputs.primitives << { x: 10, y: 30.from_top, text: "+/- to change zoom of camera", r: 255, g: 255, b: 255}.label
  args.outputs.primitives << { x: 10, y: 50.from_top, text: "tab to change camera edge behavior", r: 255, g: 255, b: 255}.label

  # render scene
  args.outputs[:scene].w = args.state.world.w
  args.outputs[:scene].h = args.state.world.h

  args.outputs[:scene].solids << { x: 0, y: 0, w: args.state.world.w, h: args.state.world.h, r: 20, g: 60, b: 80 }
  args.outputs[:scene].solids << { x: args.state.player.x, y: args.state.player.y,
                                   w: args.state.player.size, h: args.state.player.size, r: 80, g: 155, b: 80 }
  args.outputs[:scene].solids << { x: args.state.enemy.x, y: args.state.enemy.y,
                                   w: args.state.enemy.size, h: args.state.enemy.size, r: 155, g: 80, b: 80 }

  # render camera
  scene_position = calc_scene_position args
  args.outputs.sprites << { x: scene_position.x,
                            y: scene_position.y,
                            w: scene_position.w,
                            h: scene_position.h,
                            path: :scene }

  # move player
  if args.inputs.directional_angle
    args.state.player.x += args.inputs.directional_angle.vector_x * 5
    args.state.player.y += args.inputs.directional_angle.vector_y * 5
    args.state.player.x  = args.state.player.x.clamp(0, args.state.world.w - args.state.player.size)
    args.state.player.y  = args.state.player.y.clamp(0, args.state.world.h - args.state.player.size)
  end

  # +/- to zoom in and out
  if args.inputs.keyboard.plus && args.state.tick_count.zmod?(3)
    args.state.camera.scale += 0.05
  elsif args.inputs.keyboard.hyphen && args.state.tick_count.zmod?(3)
    args.state.camera.scale -= 0.05
  elsif args.inputs.keyboard.key_down.tab
    if args.state.camera.show_empty_space == :yes
      args.state.camera.show_empty_space = :no
    else
      args.state.camera.show_empty_space = :yes
    end
  end

  args.state.camera.scale = args.state.camera.scale.greater(0.1)
end

def calc_scene_position args
  result = { x: args.state.camera.x - (args.state.player.x * args.state.camera.scale),
             y: args.state.camera.y - (args.state.player.y * args.state.camera.scale),
             w: args.state.world.w * args.state.camera.scale,
             h: args.state.world.h * args.state.camera.scale,
             scale: args.state.camera.scale }

  return result if args.state.camera.show_empty_space == :yes

  if result.w < args.grid.w
    result.merge!(x: (args.grid.w - result.w).half)
  elsif (args.state.player.x * result.scale) < args.grid.w.half
    result.merge!(x: 10)
  elsif (result.x + result.w) < args.grid.w
    result.merge!(x: - result.w + (args.grid.w - 10))
  end

  if result.h < args.grid.h
    result.merge!(y: (args.grid.h - result.h).half)
  elsif (result.y) > 10
    result.merge!(y: 10)
  elsif (result.y + result.h) < args.grid.h
    result.merge!(y: - result.h + (args.grid.h - 10))
  end

  result
end

Advanced Rendering - Splitscreen Camera - main.rb

# ./samples/07_advanced_rendering/08_splitscreen_camera/app/main.rb
class CameraMovement
  attr_accessor :state, :inputs, :outputs, :grid

  #==============================================================================================
  #Serialize
  def serialize
    {state: state, inputs: inputs, outputs: outputs, grid: grid }
  end

  def inspect
    serialize.to_s
  end

  def to_s
    serialize.to_s
  end

  #==============================================================================================
  #Tick
  def tick
    defaults
    calc
    render
    input
  end

  #==============================================================================================
  #Default functions
  def defaults
    outputs[:scene].background_color = [0,0,0]
    state.trauma ||= 0.0
    state.trauma_power ||= 2
    state.player_cyan ||= new_player_cyan
    state.player_magenta ||= new_player_magenta
    state.camera_magenta ||= new_camera_magenta
    state.camera_cyan ||= new_camera_cyan
    state.camera_center ||= new_camera_center
    state.room ||= new_room
  end

  def default_player x, y, w, h, sprite_path
    state.new_entity(:player,
                     { x: x,
                       y: y,
                       dy: 0,
                       dx: 0,
                       w: w,
                       h: h,
                       damage: 0,
                       dead: false,
                       orientation: "down",
                       max_alpha: 255,
                       sprite_path: sprite_path})
  end

  def default_floor_tile x, y, w, h, sprite_path
    state.new_entity(:room,
                     { x: x,
                       y: y,
                       w: w,
                       h: h,
                       sprite_path: sprite_path})
  end

  def default_camera x, y, w, h
    state.new_entity(:camera,
                     { x: x,
                       y: y,
                       dx: 0,
                       dy: 0,
                       w: w,
                       h: h})
  end

  def new_player_cyan
    default_player(0, 0, 64, 64,
                   "sprites/player/player_#{state.player_cyan.orientation}_standing.png")
  end

  def new_player_magenta
    default_player(64, 0, 64, 64,
                   "sprites/player/player_#{state.player_magenta.orientation}_standing.png")
  end

  def new_camera_magenta
    default_camera(0,0,720,720)
  end

  def new_camera_cyan
    default_camera(0,0,720,720)
  end

  def new_camera_center
    default_camera(0,0,1280,720)
  end

  def new_room
    default_floor_tile(0,0,1024,1024,'sprites/rooms/camera_room.png')
  end

  #==============================================================================================
  #Calculation functions
  def calc
    calc_camera_magenta
    calc_camera_cyan
    calc_camera_center
    calc_player_cyan
    calc_player_magenta
    calc_trauma_decay
  end

  def center_camera_tolerance
    return Math.sqrt(((state.player_magenta.x - state.player_cyan.x) ** 2) +
              ((state.player_magenta.y - state.player_cyan.y) ** 2)) > 640
  end

  def calc_player_cyan
    state.player_cyan.x += state.player_cyan.dx
    state.player_cyan.y += state.player_cyan.dy
  end

  def calc_player_magenta
    state.player_magenta.x += state.player_magenta.dx
    state.player_magenta.y += state.player_magenta.dy
  end

  def calc_camera_center
    timeScale = 1
    midX = (state.player_magenta.x + state.player_cyan.x)/2
    midY = (state.player_magenta.y + state.player_cyan.y)/2
    targetX = midX - state.camera_center.w/2
    targetY = midY - state.camera_center.h/2
    state.camera_center.x += (targetX - state.camera_center.x) * 0.1 * timeScale
    state.camera_center.y += (targetY - state.camera_center.y) * 0.1 * timeScale
  end


  def calc_camera_magenta
    timeScale = 1
    targetX = state.player_magenta.x + state.player_magenta.w - state.camera_magenta.w/2
    targetY = state.player_magenta.y + state.player_magenta.h - state.camera_magenta.h/2
    state.camera_magenta.x += (targetX - state.camera_magenta.x) * 0.1 * timeScale
    state.camera_magenta.y += (targetY - state.camera_magenta.y) * 0.1 * timeScale
  end

  def calc_camera_cyan
    timeScale = 1
    targetX = state.player_cyan.x + state.player_cyan.w - state.camera_cyan.w/2
    targetY = state.player_cyan.y + state.player_cyan.h - state.camera_cyan.h/2
    state.camera_cyan.x += (targetX - state.camera_cyan.x) * 0.1 * timeScale
    state.camera_cyan.y += (targetY - state.camera_cyan.y) * 0.1 * timeScale
  end

  def calc_player_quadrant angle
    if angle < 45 and angle > -45 and state.player_cyan.x < state.player_magenta.x
      return 1
    elsif angle < 45 and angle > -45 and state.player_cyan.x > state.player_magenta.x
      return 3
    elsif (angle > 45 or angle < -45) and state.player_cyan.y < state.player_magenta.y
      return 2
    elsif (angle > 45 or angle < -45) and state.player_cyan.y > state.player_magenta.y
      return 4
    end
  end

  def calc_camera_shake
    state.trauma
  end

  def calc_trauma_decay
    state.trauma = state.trauma * 0.9
  end

  def calc_random_float_range(min, max)
    rand * (max-min) + min
  end

  #==============================================================================================
  #Render Functions
  def render
    render_floor
    render_player_cyan
    render_player_magenta
    if center_camera_tolerance
      render_split_camera_scene
    else
      render_camera_center_scene
    end
  end

  def render_player_cyan
    outputs[:scene].sprites << {x: state.player_cyan.x,
                                y: state.player_cyan.y,
                                w: state.player_cyan.w,
                                h: state.player_cyan.h,
                                path: "sprites/player/player_#{state.player_cyan.orientation}_standing.png",
                                r: 0,
                                g: 255,
                                b: 255}
  end

  def render_player_magenta
    outputs[:scene].sprites << {x: state.player_magenta.x,
                                y: state.player_magenta.y,
                                w: state.player_magenta.w,
                                h: state.player_magenta.h,
                                path: "sprites/player/player_#{state.player_magenta.orientation}_standing.png",
                                r: 255,
                                g: 0,
                                b: 255}
  end

  def render_floor
    outputs[:scene].sprites << [state.room.x, state.room.y,
                                state.room.w, state.room.h,
                                state.room.sprite_path]
  end

  def render_camera_center_scene
    zoomFactor = 1
    outputs[:scene].width = state.room.w
    outputs[:scene].height = state.room.h

    maxAngle = 10.0
    maxOffset = 20.0
    angle = maxAngle * calc_camera_shake * calc_random_float_range(-1,1)
    offsetX = 32 - (maxOffset * calc_camera_shake * calc_random_float_range(-1,1))
    offsetY = 32 - (maxOffset * calc_camera_shake * calc_random_float_range(-1,1))

    outputs.sprites << {x: (-state.camera_center.x - offsetX)/zoomFactor,
                        y: (-state.camera_center.y - offsetY)/zoomFactor,
                        w: outputs[:scene].width/zoomFactor,
                        h: outputs[:scene].height/zoomFactor,
                        path: :scene,
                        angle: angle,
                        source_w: -1,
                        source_h: -1}
    outputs.labels << [128,64,"#{state.trauma.round(1)}",8,2,255,0,255,255]
  end

  def render_split_camera_scene
     outputs[:scene].width = state.room.w
     outputs[:scene].height = state.room.h
     render_camera_magenta_scene
     render_camera_cyan_scene

     angle = Math.atan((state.player_magenta.y - state.player_cyan.y)/(state.player_magenta.x- state.player_cyan.x)) * 180/Math::PI
     output_split_camera angle

  end

  def render_camera_magenta_scene
     zoomFactor = 1
     offsetX = 32
     offsetY = 32

     outputs[:scene_magenta].sprites << {x: (-state.camera_magenta.x*2),
                                         y: (-state.camera_magenta.y),
                                         w: outputs[:scene].width*2,
                                         h: outputs[:scene].height,
                                         path: :scene}

  end

  def render_camera_cyan_scene
    zoomFactor = 1
    offsetX = 32
    offsetY = 32
    outputs[:scene_cyan].sprites << {x: (-state.camera_cyan.x*2),
                                     y: (-state.camera_cyan.y),
                                     w: outputs[:scene].width*2,
                                     h: outputs[:scene].height,
                                     path: :scene}
  end

  def output_split_camera angle
    #TODO: Clean this up!
    quadrant = calc_player_quadrant angle
    outputs.labels << [128,64,"#{quadrant}",8,2,255,0,255,255]
    if quadrant == 1
      set_camera_attributes(w: 640, h: 720, m_x: 640, m_y: 0, c_x: 0, c_y: 0)

    elsif quadrant == 2
      set_camera_attributes(w: 1280, h: 360, m_x: 0, m_y: 360, c_x: 0, c_y: 0)

    elsif quadrant == 3
      set_camera_attributes(w: 640, h: 720, m_x: 0, m_y: 0, c_x: 640, c_y: 0)

    elsif quadrant == 4
      set_camera_attributes(w: 1280, h: 360, m_x: 0, m_y: 0, c_x: 0, c_y: 360)

    end
  end

  def set_camera_attributes(w: 0, h: 0, m_x: 0, m_y: 0, c_x: 0, c_y: 0)
    state.camera_cyan.w = w + 64
    state.camera_cyan.h = h + 64
    outputs[:scene_cyan].width = (w) * 2
    outputs[:scene_cyan].height = h

    state.camera_magenta.w = w + 64
    state.camera_magenta.h = h + 64
    outputs[:scene_magenta].width = (w) * 2
    outputs[:scene_magenta].height = h
    outputs.sprites << {x: m_x,
                        y: m_y,
                        w: w,
                        h: h,
                        path: :scene_magenta}
    outputs.sprites << {x: c_x,
                        y: c_y,
                        w: w,
                        h: h,
                        path: :scene_cyan}
  end

  def add_trauma amount
    state.trauma = [state.trauma + amount, 1.0].min
  end

  def remove_trauma amount
    state.trauma = [state.trauma - amount, 0.0].max
  end
  #==============================================================================================
  #Input functions
  def input
    input_move_cyan
    input_move_magenta

    if inputs.keyboard.key_down.t
      add_trauma(0.5)
    elsif inputs.keyboard.key_down.y
      remove_trauma(0.1)
    end
  end

  def input_move_cyan
    if inputs.keyboard.key_held.up
      state.player_cyan.dy = 5
      state.player_cyan.orientation = "up"
    elsif inputs.keyboard.key_held.down
      state.player_cyan.dy = -5
      state.player_cyan.orientation = "down"
    else
      state.player_cyan.dy *= 0.8
    end
    if inputs.keyboard.key_held.left
      state.player_cyan.dx = -5
      state.player_cyan.orientation = "left"
    elsif inputs.keyboard.key_held.right
      state.player_cyan.dx = 5
      state.player_cyan.orientation = "right"
    else
      state.player_cyan.dx *= 0.8
    end

    outputs.labels << [128,512,"#{state.player_cyan.x.round()}",8,2,0,255,255,255]
    outputs.labels << [128,480,"#{state.player_cyan.y.round()}",8,2,0,255,255,255]
  end

  def input_move_magenta
    if inputs.keyboard.key_held.w
      state.player_magenta.dy = 5
      state.player_magenta.orientation = "up"
    elsif inputs.keyboard.key_held.s
      state.player_magenta.dy = -5
      state.player_magenta.orientation = "down"
    else
      state.player_magenta.dy *= 0.8
    end
    if inputs.keyboard.key_held.a
      state.player_magenta.dx = -5
      state.player_magenta.orientation = "left"
    elsif inputs.keyboard.key_held.d
      state.player_magenta.dx = 5
      state.player_magenta.orientation = "right"
    else
      state.player_magenta.dx *= 0.8
    end

    outputs.labels << [128,360,"#{state.player_magenta.x.round()}",8,2,255,0,255,255]
    outputs.labels << [128,328,"#{state.player_magenta.y.round()}",8,2,255,0,255,255]
  end
end

$camera_movement = CameraMovement.new

def tick args
  args.outputs.background_color = [0,0,0]
  $camera_movement.inputs  = args.inputs
  $camera_movement.outputs = args.outputs
  $camera_movement.state   = args.state
  $camera_movement.grid    = args.grid
  $camera_movement.tick
end

Advanced Rendering - Z Targeting Camera - main.rb

# ./samples/07_advanced_rendering/09_z_targeting_camera/app/main.rb
class Game
  attr_gtk

  def tick
    defaults
    render
    input
    calc
  end

  def defaults
    outputs.background_color = [219, 208, 191]
    player.x        ||= 634
    player.y        ||= 153
    player.angle    ||= 90
    player.distance ||= arena_radius
    target.x        ||= 634
    target.y        ||= 359
  end

  def render
    outputs[:scene].sprites << ([0, 0, 933, 700, 'sprites/arena.png'].center_inside_rect grid.rect)
    outputs[:scene].sprites << target_sprite
    outputs[:scene].sprites << player_sprite
    outputs.sprites << scene
  end

  def target_sprite
    {
      x: target.x, y: target.y,
      w: 10, h: 10,
      path: 'sprites/square/black.png'
    }.anchor_rect 0.5, 0.5
  end

  def input
    if inputs.up && player.distance > 30
      player.distance -= 2
    elsif inputs.down && player.distance < 200
      player.distance += 2
    end

    player.angle += inputs.left_right * -1
  end

  def calc
    player.x = target.x + ((player.angle *  1).vector_x player.distance)
    player.y = target.y + ((player.angle * -1).vector_y player.distance)
  end

  def player_sprite
    {
      x: player.x,
      y: player.y,
      w: 50,
      h: 100,
      path: 'sprites/player.png',
      angle: (player.angle * -1) + 90
    }.anchor_rect 0.5, 0
  end

  def center_map
    { x: 634, y: 359 }
  end

  def zoom_factor_single
    2 - ((args.geometry.distance player, center_map).fdiv arena_radius)
  end

  def zoom_factor
    zoom_factor_single ** 2
  end

  def arena_radius
    206
  end

  def scene
    {
      x:    (640 - player.x) + (640 - (640 * zoom_factor)),
      y:    (360 - player.y - (75 * zoom_factor)) + (320 - (320 * zoom_factor)),
      w:    1280 * zoom_factor,
      h:     720 * zoom_factor,
      path: :scene,
      angle: player.angle - 90,
      angle_anchor_x: (player.x.fdiv 1280),
      angle_anchor_y: (player.y.fdiv 720)
    }
  end

  def player
    state.player
  end

  def target
    state.target
  end
end

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

$gtk.reset

Tweening Lerping Easing Functions - Easing Functions - main.rb

# ./samples/08_tweening_lerping_easing_functions/01_easing_functions/app/main.rb
def tick args
  # STOP! Watch the following presentation first!!!!
  # Math for Game Programmers: Fast and Funky 1D Nonlinear Transformations
  # https://www.youtube.com/watch?v=mr5xkf6zSzk

  # You've watched the talk, yes? YES???

  # define starting and ending points of properties to animate
  args.state.target_x = 1180
  args.state.target_y = 620
  args.state.target_w = 100
  args.state.target_h = 100
  args.state.starting_x = 0
  args.state.starting_y = 0
  args.state.starting_w = 300
  args.state.starting_h = 300

  # define start time and duration of animation
  args.state.start_animate_at = 3.seconds # this is the same as writing 60 * 5 (or 300)
  args.state.duration = 2.seconds # this is the same as writing 60 * 2 (or 120)

  # define type of animations
  # Here are all the options you have for values you can put in the array:
  # :identity, :quad, :cube, :quart, :quint, :flip

  # Linear is defined as:
  # [:identity]
  #
  # Smooth start variations are:
  # [:quad]
  # [:cube]
  # [:quart]
  # [:quint]

  # Linear reversed, and smooth stop are the same as the animations defined above, but reversed:
  # [:flip, :identity]
  # [:flip, :quad, :flip]
  # [:flip, :cube, :flip]
  # [:flip, :quart, :flip]
  # [:flip, :quint, :flip]

  # You can also do custom definitions. See the bottom of the file details
  # on how to do that. I've defined a couple for you:
  # [:smoothest_start]
  # [:smoothest_stop]

  # CHANGE THIS LINE TO ONE OF THE LINES ABOVE TO SEE VARIATIONS
  args.state.animation_type = [:identity]
  # args.state.animation_type = [:quad]
  # args.state.animation_type = [:cube]
  # args.state.animation_type = [:quart]
  # args.state.animation_type = [:quint]
  # args.state.animation_type = [:flip, :identity]
  # args.state.animation_type = [:flip, :quad, :flip]
  # args.state.animation_type = [:flip, :cube, :flip]
  # args.state.animation_type = [:flip, :quart, :flip]
  # args.state.animation_type = [:flip, :quint, :flip]
  # args.state.animation_type = [:smoothest_start]
  # args.state.animation_type = [:smoothest_stop]

  # THIS IS WHERE THE MAGIC HAPPENS!
  # Numeric#ease
  progress = args.state.start_animate_at.ease(args.state.duration, args.state.animation_type)

  # Numeric#ease needs to called:
  # 1. On the number that represents the point in time you want to start, and takes two parameters:
  #   a. The first parameter is how long the animation should take.
  #   b. The second parameter represents the functions that need to be called.
  #
  # For example, if I wanted an animate to start 3 seconds in, and last for 10 seconds,
  # and I want to animation to start fast and end slow, I would do:
  # (60 * 3).ease(60 * 10, :flip, :quint, :flip)

  #        initial value           delta to the final value
  calc_x = args.state.starting_x + (args.state.target_x - args.state.starting_x) * progress
  calc_y = args.state.starting_y + (args.state.target_y - args.state.starting_y) * progress
  calc_w = args.state.starting_w + (args.state.target_w - args.state.starting_w) * progress
  calc_h = args.state.starting_h + (args.state.target_h - args.state.starting_h) * progress

  args.outputs.solids << [calc_x, calc_y, calc_w, calc_h, 0, 0, 0]

  # count down
  count_down = args.state.start_animate_at - args.state.tick_count
  if count_down > 0
    args.outputs.labels << [640, 375, "Running: #{args.state.animation_type} in...", 3, 1]
    args.outputs.labels << [640, 345, "%.2f" % count_down.fdiv(60), 3, 1]
  elsif progress >= 1
    args.outputs.labels << [640, 360, "Click screen to reset.", 3, 1]
    if args.inputs.click
      $gtk.reset
    end
  end
end

# $gtk.reset

# you can make own variations of animations using this
module Easing
  # you have access to all the built in functions: identity, flip, quad, cube, quart, quint
  def self.smoothest_start x
    quad(quint(x))
  end

  def self.smoothest_stop x
    flip(quad(quint(flip(x))))
  end

  # this is the source for the existing easing functions
  def self.identity x
    x
  end

  def self.flip x
    1 - x
  end

  def self.quad x
    x * x
  end

  def self.cube x
    x * x * x
  end

  def self.quart x
    x * x * x * x * x
  end

  def self.quint x
    x * x * x * x * x * x
  end
end

Tweening Lerping Easing Functions - Cubic Bezier - main.rb

# ./samples/08_tweening_lerping_easing_functions/02_cubic_bezier/app/main.rb
def tick args
  args.outputs.background_color = [33, 33, 33]
  args.outputs.lines << bezier(100, 100,
                               100, 620,
                               1180, 620,
                               1180, 100,
                               0)

  args.outputs.lines << bezier(100, 100,
                               100, 620,
                               1180, 620,
                               1180, 100,
                               20)
end


def bezier x1, y1, x2, y2, x3, y3, x4, y4, step
  step ||= 0
  color = [200, 200, 200]
  points = points_for_bezier [x1, y1], [x2, y2], [x3, y3], [x4, y4], step

  points.each_cons(2).map do |p1, p2|
    [p1, p2, color]
  end
end

def points_for_bezier p1, p2, p3, p4, step
  points = []
  if step == 0
    [p1, p2, p3, p4]
  else
    t_step = 1.fdiv(step + 1)
    t = 0
    t += t_step
    points = []
    while t < 1
      points << [
        b_for_t(p1.x, p2.x, p3.x, p4.x, t),
        b_for_t(p1.y, p2.y, p3.y, p4.y, t),
      ]
      t += t_step
    end

    [
      p1,
      *points,
      p4
    ]
  end
end

def b_for_t v0, v1, v2, v3, t
  pow(1 - t, 3) * v0 +
  3 * pow(1 - t, 2) * t * v1 +
  3 * (1 - t) * pow(t, 2) * v2 +
  pow(t, 3) * v3
end

def pow n, to
  n ** to
end

Tweening Lerping Easing Functions - Easing Using Spline - main.rb

# ./samples/08_tweening_lerping_easing_functions/03_easing_using_spline/app/main.rb
def tick args
  args.state.duration = 10.seconds
  args.state.spline = [
    [0.0, 0.33, 0.66, 1.0],
    [1.0, 1.0,  1.0,  1.0],
    [1.0, 0.66, 0.33, 0.0],
  ]

  args.state.simulation_tick = args.state.tick_count % args.state.duration
  progress = 0.ease_spline_extended args.state.simulation_tick, args.state.duration, args.state.spline
  args.outputs.borders << args.grid.rect
  args.outputs.solids << [20 + 1240 * progress,
                          20 +  680 * progress,
                          20, 20].anchor_rect(0.5, 0.5)
  args.outputs.labels << [10,
                          710,
                          "perc: #{"%.2f" % (args.state.simulation_tick / args.state.duration)} t: #{args.state.simulation_tick}"]
end

Tweening Lerping Easing Functions - Parametric Enemy Movement - main.rb

# ./samples/08_tweening_lerping_easing_functions/04_parametric_enemy_movement/app/main.rb
def new_star args
  { x: 1280.randomize(:ratio),
    starting_y: 800,
    distance_to_travel: 900 + 100.randomize(:ratio),
    duration: 100.randomize(:ratio) + 60,
    created_at: args.state.tick_count,
    max_alpha: 128.randomize(:ratio) + 128,
    b: 255.randomize(:ratio),
    g: 200.randomize(:ratio),
    w: 1.randomize(:ratio) + 1,
    h: 1.randomize(:ratio) + 1 }
end

def new_enemy args
  { x: 1280.randomize(:ratio),
    starting_y: 800,
    distance_to_travel: -900,
    duration: 60.randomize(:ratio) + 180,
    created_at: args.state.tick_count,
    w: 32,
    h: 32,
    fire_rate: (30.randomize(:ratio) + (60 - args.state.score)).to_i }
end

def new_bullet args, starting_x, starting_y, enemy_speed
  { x: starting_x,
    starting_y: starting_y,
    distance_to_travel: -900,
    created_at: args.state.tick_count,
    duration: 900 / (enemy_speed.abs + 2.0 + (5.0 * args.state.score.fdiv(100))).abs,
    w: 5,
    h: 5 }
end

def new_player_bullet args, starting_x, starting_y, player_speed
  { x: starting_x,
    starting_y: starting_y,
    distance_to_travel: 900,
    created_at: args.state.tick_count,
    duration: 900 / (player_speed + 2.0),
    w: 5,
    h: 5 }
end

def defaults args
  args.outputs.background_color  = [0, 0, 0]
  args.state.score             ||= 0
  args.state.stars             ||= []
  args.state.enemies           ||= []
  args.state.bullets           ||= []
  args.state.player_bullets    ||= []
  args.state.max_stars           = 50
  args.state.max_enemies         = 10
  args.state.player.x          ||= 640
  args.state.player.y          ||= 100
  args.state.player.w          ||= 32
  args.state.player.h          ||= 32

  if args.state.tick_count == 0
    args.state.stars.clear
    args.state.max_stars.times do
      s = new_star args
      s[:created_at] += s[:duration].randomize(:ratio)
      args.state.stars << s
    end
  end

  if args.state.tick_count == 0
    args.state.enemies.clear
    args.state.max_enemies.times do
      s = new_enemy args
      s[:created_at] += s[:duration].randomize(:ratio)
      args.state.enemies << s
    end
  end
end

def input args
  if args.inputs.keyboard.left
    args.state.player.x -= 5
  elsif args.inputs.keyboard.right
    args.state.player.x += 5
  end

  if args.inputs.keyboard.up
    args.state.player.y += 5
  elsif args.inputs.keyboard.down
    args.state.player.y -= 5
  end

  if args.inputs.keyboard.key_down.space
    args.state.player_bullets << new_player_bullet(args,
                                                   args.state.player.x + args.state.player.w.half,
                                                   args.state.player.y + args.state.player.h, 5)
  end

  args.state.player.y = args.state.player.y.greater(0).lesser(720 - args.state.player.w)
  args.state.player.x = args.state.player.x.greater(0).lesser(1280 - args.state.player.h)
end

def completed? entity
  (entity[:created_at] + entity[:duration]).elapsed_time > 0
end

def calc_stars args
  if (stars_to_add = args.state.max_stars - args.state.stars.length) > 0
    stars_to_add.times { args.state.stars << new_star(args) }
  end
  args.state.stars = args.state.stars.reject { |s| completed? s }
end

def move_enemies args
  if (enemies_to_add = args.state.max_enemies - args.state.enemies.length) > 0
    enemies_to_add.times { args.state.enemies << new_enemy(args) }
  end

  args.state.enemies = args.state.enemies.reject { |s| completed? s }
end

def move_bullets args
  args.state.enemies.each do |e|
    if args.state.tick_count.mod_zero?(e[:fire_rate])
      args.state.bullets << new_bullet(args, e[:x] + e[:w].half, current_y(e), e[:distance_to_travel] / e[:duration])
    end
  end

  args.state.bullets = args.state.bullets.reject { |s| completed? s }
  args.state.player_bullets = args.state.player_bullets.reject { |s| completed? s }
end

def intersect? entity_one, entity_two
  entity_one.merge(y: current_y(entity_one))
            .intersect_rect? entity_two.merge(y: current_y(entity_two))
end

def kill args
  bullets_hitting_enemies = []
  dead_bullets = []
  dead_enemies = []

  args.state.player_bullets.each do |b|
    args.state.enemies.each do |e|
      if intersect? b, e
        dead_bullets << b
        dead_enemies << e
      end
    end
  end

  args.state.score += dead_enemies.length

  args.state.player_bullets.reject! { |b| dead_bullets.include? b }
  args.state.enemies.reject! { |e| dead_enemies.include? e }

  dead = args.state.bullets.any? do |b|
    [args.state.player.x,
     args.state.player.y,
     args.state.player.w,
     args.state.player.h].intersect_rect? b.merge(y: current_y(b))
  end
  return unless dead
  args.gtk.reset
  defaults args
end

def calc args
  calc_stars args
  move_enemies args
  move_bullets args
  kill args
end

def current_y entity
  entity[:starting_y] + (entity[:distance_to_travel] * entity[:created_at].ease(entity[:duration], :identity))
end

def render args
  args.outputs.solids << args.state.stars.map do |s|
    [s[:x],
     current_y(s),
     s[:w], s[:h], 0, s[:g], s[:b], s[:max_alpha] * s[:created_at].ease(20, :identity)]
  end

  args.outputs.borders << args.state.enemies.map do |s|
    [s[:x],
     current_y(s),
     s[:w], s[:h], 255, 0, 0]
  end

  args.outputs.borders << args.state.bullets.map do |b|
    [b[:x],
     current_y(b),
     b[:w], b[:h], 255, 0, 0]
  end

  args.outputs.borders << args.state.player_bullets.map do |b|
    [b[:x],
     current_y(b),
     b[:w], b[:h], 255, 255, 255]
  end

  args.borders << [args.state.player.x,
                   args.state.player.y,
                   args.state.player.w,
                   args.state.player.h, 255, 255, 255]
end

def tick args
  defaults args
  input args
  calc args
  render args
end

Performance - Sprites As Hash - main.rb

# ./samples/09_performance/01_sprites_as_hash/app/main.rb

# Sprites represented as Hashes using the queue ~args.outputs.sprites~
# code up, but are the "slowest" to render.
# The reason for this is the access of the key in the Hash and also
# because the data args.outputs.sprites is cleared every tick.
def random_x args
  (args.grid.w.randomize :ratio) * -1
end

def random_y args
  (args.grid.h.randomize :ratio) * -1
end

def random_speed
  1 + (4.randomize :ratio)
end

def new_star args
  {
    x: (random_x args),
    y: (random_y args),
    w: 4, h: 4, path: 'sprites/tiny-star.png',
    s: random_speed
  }
end

def move_star args, star
  star.x += star[:s]
  star.y += star[:s]
  if star.x > args.grid.w || star.y > args.grid.h
    star.x = (random_x args)
    star.y = (random_y args)
    star[:s] = random_speed
  end
end

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

  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    puts "* INFO - Please specify the number of sprites to render."
    args.gtk.console.set_command "reset_with count: 100"
  end

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| new_star args }
  end

  # update
  args.state.stars.each { |s| move_star args, s }

  # render
  args.outputs.sprites << args.state.stars
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Sprites As Entities - main.rb

# ./samples/09_performance/02_sprites_as_entities/app/main.rb
# Sprites represented as Entities using the queue ~args.outputs.sprites~
# yields nicer access apis over Hashes, but require a bit more code upfront.
# The hash sample has to use star[:s] to get the speed of the star, but
# an entity can use .s instead.
def random_x args
  (args.grid.w.randomize :ratio) * -1
end

def random_y args
  (args.grid.h.randomize :ratio) * -1
end

def random_speed
  1 + (4.randomize :ratio)
end

def new_star args
  args.state.new_entity :star, {
    x: (random_x args),
    y: (random_y args),
    w: 4, h: 4,
    path: 'sprites/tiny-star.png',
    s: random_speed
  }
end

def move_star args, star
  star.x += star.s
  star.y += star.s
  if star.x > args.grid.w || star.y > args.grid.h
    star.x = (random_x args)
    star.y = (random_y args)
    star.s = random_speed
  end
end

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

  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    puts "* INFO - Please specify the number of sprites to render."
    args.gtk.console.set_command "reset_with count: 100"
  end

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| new_star args }
  end

  # update
  args.state.stars.each { |s| move_star args, s }

  # render
  args.outputs.sprites << args.state.stars
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Sprites As Strict Entities - main.rb

# ./samples/09_performance/03_sprites_as_strict_entities/app/main.rb
# Sprites represented as StrictEntities using the queue ~args.outputs.sprites~
# yields apis access similar to Entities, but all properties that can be set on the
# entity must be predefined with a default value. Strict entities do not support the
# addition of new properties after the fact. They are more performant than OpenEntities
# because of this constraint.
def random_x args
  (args.grid.w.randomize :ratio) * -1
end

def random_y args
  (args.grid.h.randomize :ratio) * -1
end

def random_speed
  1 + (4.randomize :ratio)
end

def new_star args
  args.state.new_entity_strict(:star,
                               x: (random_x args),
                               y: (random_y args),
                               w: 4, h: 4,
                               path: 'sprites/tiny-star.png',
                               s: random_speed) do |entity|
    # invoke attr_sprite so that it responds to
    # all properties that are required to render a sprite
    entity.attr_sprite
  end
end

def move_star args, star
  star.x += star.s
  star.y += star.s
  if star.x > args.grid.w || star.y > args.grid.h
    star.x = (random_x args)
    star.y = (random_y args)
    star.s = random_speed
  end
end

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

  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    puts "* INFO - Please specify the number of sprites to render."
    args.gtk.console.set_command "reset_with count: 100"
  end

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| new_star args }
  end

  # update
  args.state.stars.each { |s| move_star args, s }

  # render
  args.outputs.sprites << args.state.stars
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Sprites As Classes - main.rb

# ./samples/09_performance/04_sprites_as_classes/app/main.rb
# Sprites represented as Classes using the queue ~args.outputs.sprites~.
# gives you full control of property declaration and method invocation.
# They are more performant than OpenEntities and StrictEntities, but more code upfront.
class Star
  attr_sprite

  def initialize grid
    @grid = grid
    @x = (rand @grid.w) * -1
    @y = (rand @grid.h) * -1
    @w    = 4
    @h    = 4
    @s    = 1 + (4.randomize :ratio)
    @path = 'sprites/tiny-star.png'
  end

  def move
    @x += @s
    @y += @s
    @x = (rand @grid.w) * -1 if @x > @grid.right
    @y = (rand @grid.h) * -1 if @y > @grid.top
  end
end

# calls methods needed for game to run properly
def tick args
  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    args.gtk.console.set_command "reset_with count: 100"
  end

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| Star.new args.grid }
  end

  # update
  args.state.stars.each(&:move)

  # render
  args.outputs.sprites << args.state.stars
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Static Sprites As Classes - main.rb

# ./samples/09_performance/05_static_sprites_as_classes/app/main.rb
# Sprites represented as Classes using the queue ~args.outputs.static_sprites~.
# bypasses the queue behavior of ~args.outputs.sprites~. All instances are held
# by reference. You get better performance, but you are mutating state of held objects
# which is less functional/data oriented.
class Star
  attr_sprite

  def initialize grid
    @grid = grid
    @x = (rand @grid.w) * -1
    @y = (rand @grid.h) * -1
    @w    = 4
    @h    = 4
    @s    = 1 + (4.randomize :ratio)
    @path = 'sprites/tiny-star.png'
  end

  def move
    @x += @s
    @y += @s
    @x = (rand @grid.w) * -1 if @x > @grid.right
    @y = (rand @grid.h) * -1 if @y > @grid.top
  end
end

# calls methods needed for game to run properly
def tick args
  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    args.gtk.console.set_command "reset_with count: 100"
  end

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| Star.new args.grid }
  end

  # update
  args.state.stars.each(&:move)

  # render
  args.outputs.sprites << args.state.stars
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Static Sprites As Classes With Custom Drawing - main.rb

# ./samples/09_performance/06_static_sprites_as_classes_with_custom_drawing/app/main.rb
# Sprites represented as Classes, with a draw_override method, and using the queue ~args.outputs.static_sprites~.
# is the fastest approach. This is comparable to what other game engines set as the default behavior.
# There are tradeoffs for all this speed if the creation of a full blown class, and bypassing
# functional/data-oriented practices.
class Star
  def initialize grid
    @grid = grid
    @x = (rand @grid.w) * -1
    @y = (rand @grid.h) * -1
    @w    = 4
    @h    = 4
    @s    = 1 + (4.randomize :ratio)
    @path = 'sprites/tiny-star.png'
  end

  def move
    @x += @s
    @y += @s
    @x = (rand @grid.w) * -1 if @x > @grid.right
    @y = (rand @grid.h) * -1 if @y > @grid.top
  end

  # if the object that is in args.outputs.sprites (or static_sprites)
  # respond_to? :draw_override, then the method is invoked giving you
  # access to the class used to draw to the canvas.
  def draw_override ffi_draw
    # first move then draw
    move

    # The argument order for ffi.draw_sprite is:
    # x, y, w, h, path
    ffi_draw.draw_sprite @x, @y, @w, @h, @path

    # The argument order for ffi_draw.draw_sprite_2 is (pass in nil for default value):
    # x, y, w, h, path,
    # angle, alpha

    # The argument order for ffi_draw.draw_sprite_3 is:
    # x, y, w, h,
    # path,
    # angle,
    # alpha, red_saturation, green_saturation, blue_saturation
    # flip_horizontally, flip_vertically,
    # tile_x, tile_y, tile_w, tile_h
    # angle_anchor_x, angle_anchor_y,
    # source_x, source_y, source_w, source_h
  end
end

# calls methods needed for game to run properly
def tick args
  # sets console command when sample app initially opens
  if Kernel.global_tick_count == 0
    args.gtk.console.set_command "reset_with count: 100"
  end

  # init
  if args.state.tick_count == 0
    args.state.stars = args.state.star_count.map { |i| Star.new args.grid }
    args.outputs.static_sprites << args.state.stars
  end

  # render framerate
  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.gtk.current_framerate_primitives
end

# resets game, and assigns star count given by user
def reset_with count: count
  $gtk.reset
  $gtk.args.state.star_count = count
end

Performance - Collision Limits - main.rb

# ./samples/09_performance/07_collision_limits/app/main.rb
=begin

 Reminders:
 - find_all: Finds all elements of a collection that meet certain requirements.
   In this sample app, we're finding all bodies that intersect with the center body.

 - args.outputs.solids: An array. The values generate a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - ARRAY#intersect_rect?: Returns true or false depending on if two rectangles intersect.

=end

# This code demonstrates moving objects that loop around once they exceed the scope of the screen,
# which has dimensions of 1280 by 720, and also detects collisions between objects called "bodies".

def body_count num
  $gtk.args.state.other_bodies = num.map { [1280 * rand, 720 * rand, 10, 10] } # other_bodies set using num collection
end

def tick args

  # Center body's values are set using an array
  # Map is used to set values of 2000 other bodies
  # All bodies that intersect with center body are stored in collisions collection
  args.state.center_body  ||= [640 - 100, 360 - 100, 200, 200] # calculations done to place body in center
  args.state.other_bodies ||= 2000.map { [1280 * rand, 720 * rand, 10, 10] } # 2000 bodies given random position on screen

  # finds all bodies that intersect with center body, stores them in collisions
  collisions = args.state.other_bodies.find_all { |b| b.intersect_rect? args.state.center_body }

  args.borders << args.state.center_body # outputs center body as a black border

  # transparency changes based on number of collisions; the more collisions, the redder (more transparent) the box becomes
  args.solids  << [args.state.center_body, 255, 0, 0, collisions.length * 5] # center body is red solid
  args.solids  << args.state.other_bodies # other bodies are output as (black) solids, as well

  args.labels  << [10, 30, args.gtk.current_framerate] # outputs frame rate in bottom left corner

  # Bodies are returned to bottom left corner if positions exceed scope of screen
  args.state.other_bodies.each do |b| # for each body in the other_bodies collection
    b.x += 5 # x and y are both incremented by 5
    b.y += 5
    b.x = 0 if b.x > 1280 # x becomes 0 if star exceeds scope of screen (goes too far right)
    b.y = 0 if b.y > 720 # y becomes 0 if star exceeds scope of screen (goes too far up)
  end
end

# Resets the game.
$gtk.reset

Advanced Debugging - Trace Debugging - main.rb

# ./samples/10_advanced_debugging/01_trace_debugging/app/main.rb
class Game
  attr_gtk

  def method1 num
    method2 num
  end

  def method2 num
    method3 num
  end

  def method3 num
    method4 num
  end

  def method4 num
    if num == 1
      puts "UNLUCKY #{num}."
      state.unlucky_count += 1
      if state.unlucky_count > 3
        raise "NAT 1 finally occurred. Check app/trace.txt for all method invocation history."
      end
    else
      puts "LUCKY #{num}."
    end
  end

  def tick
    state.roll_history ||= []
    state.roll_history << rand(20) + 1
    state.countdown ||= 600
    state.countdown  -= 1
    state.unlucky_count ||= 0
    outputs.labels << [640, 360, "A dice roll of 1 will cause an exception.", 0, 1]
    if state.countdown > 0
      outputs.labels << [640, 340, "Dice roll countdown: #{state.countdown}", 0, 1]
    else
      state.attempts ||= 0
      state.attempts  += 1
      outputs.labels << [640, 340, "ROLLING! #{state.attempts}", 0, 1]
    end
    return if state.countdown > 0
    method1 state.roll_history[-1]
  end
end

$game = Game.new

def tick args
  trace! $game # <------------------- TRACING ENABLED FOR THIS OBJECT
  $game.args = args
  $game.tick
end

Advanced Debugging - Trace Debugging Classes - main.rb

# ./samples/10_advanced_debugging/02_trace_debugging_classes/app/main.rb
class Foobar
  def initialize
    trace! # Trace is added to the constructor.
  end

  def clicky args
    return unless args.inputs.mouse.click
    try_rand rand
  end

  def try_rand num
    return if num < 0.9
    raise "Exception finally occurred. Take a look at logs/trace.txt #{num}."
  end
end

def tick args
  args.labels << [640, 360, "Start clicking. Eventually an exception will be thrown. Then look at logs/trace.txt.", 0, 1]
  args.state.foobar = Foobar.new if args.tick_count
  return unless args.state.foobar
  args.state.foobar.clicky args
end

Advanced Debugging - Unit Tests - exception_raising_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/exception_raising_tests.rb
begin :shared
  class ExceptionalClass
    def initialize exception_to_throw = nil
      raise exception_to_throw if exception_to_throw
    end
  end
end

def test_exception_in_newing_object args, assert
  begin
    ExceptionalClass.new TypeError
    raise "Exception wasn't thrown!"
  rescue Exception => e
    assert.equal! e.class, TypeError, "Exceptions within constructor should be retained."
  end
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - fn_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/fn_tests.rb
def infinity
  1 / 0
end

def neg_infinity
  -1 / 0
end

def nan
  0.0 / 0
end

def test_add args, assert
  assert.equal! (args.fn.add), 0
  assert.equal! (args.fn.+), 0
  assert.equal! (args.fn.+ 1, 2, 3), 6
  assert.equal! (args.fn.+ 0), 0
  assert.equal! (args.fn.+ 0, nil), 0
  assert.equal! (args.fn.+ 0, nan), nil
  assert.equal! (args.fn.+ 0, nil, infinity), nil
  assert.equal! (args.fn.+ [1, 2, 3, [4, 5, 6]]), 21
  assert.equal! (args.fn.+ [nil, [4, 5, 6]]), 15
end

def test_sub args, assert
  neg_infinity = infinity * -1
  assert.equal! (args.fn.+), 0
  assert.equal! (args.fn.- 1, 2, 3), -4
  assert.equal! (args.fn.- 4), -4
  assert.equal! (args.fn.- 4, nan), nil
  assert.equal! (args.fn.- 0, nil), 0
  assert.equal! (args.fn.- 0, nil, infinity), nil
  assert.equal! (args.fn.- [0, 1, 2, 3, [4, 5, 6]]), -21
  assert.equal! (args.fn.- [nil, 0, [4, 5, 6]]), -15
end

def test_div args, assert
  assert.equal! (args.fn.div), 1
  assert.equal! (args.fn./), 1
  assert.equal! (args.fn./ 6, 3), 2
  assert.equal! (args.fn./ 6, infinity), nil
  assert.equal! (args.fn./ 6, nan), nil
  assert.equal! (args.fn./ infinity), nil
  assert.equal! (args.fn./ 0), nil
  assert.equal! (args.fn./ 6, [3]), 2
end

def test_idiv args, assert
  assert.equal! (args.fn.idiv), 1
  assert.equal! (args.fn.idiv 7, 3), 2
  assert.equal! (args.fn.idiv 6, infinity), nil
  assert.equal! (args.fn.idiv 6, nan), nil
  assert.equal! (args.fn.idiv infinity), nil
  assert.equal! (args.fn.idiv 0), nil
  assert.equal! (args.fn.idiv 7, [3]), 2
end

def test_mul args, assert
  assert.equal! (args.fn.mul), 1
  assert.equal! (args.fn.*), 1
  assert.equal! (args.fn.* 7, 3), 21
  assert.equal! (args.fn.* 6, nan), nil
  assert.equal! (args.fn.* 6, infinity), nil
  assert.equal! (args.fn.* infinity), nil
  assert.equal! (args.fn.* 0), 0
  assert.equal! (args.fn.* 7, [3]), 21
end

def test_lt args, assert
  assert.equal! (args.fn.lt 1), 1
  assert.equal! (args.fn.lt), nil
  assert.equal! (args.fn.lt infinity), nil
  assert.equal! (args.fn.lt nan), nil
  assert.equal! (args.fn.lt 10, 9, 8), 8
  assert.equal! (args.fn.< 10, 9, 8), 8
  assert.equal! (args.fn.< [10, 9, [8]]), 8
  assert.equal! (args.fn.< 10, 10), nil
end

def test_lte args, assert
  assert.equal! (args.fn.lte 1), 1
  assert.equal! (args.fn.lte), nil
  assert.equal! (args.fn.lte infinity), nil
  assert.equal! (args.fn.lte nan), nil
  assert.equal! (args.fn.lte 10, 9, 8), 8
  assert.equal! (args.fn.lte 10, 10), 10
  assert.equal! (args.fn.lte  10, 9, [8]), 8
  assert.equal! (args.fn.<=  10, 9, 8), 8
end

def test_gt args, assert
  assert.equal! (args.fn.gt 1), 1
  assert.equal! (args.fn.gt), nil
  assert.equal! (args.fn.gt infinity), nil
  assert.equal! (args.fn.gt nan), nil
  assert.equal! (args.fn.gt 8, 9, 10), 10
  assert.equal! (args.fn.gt [8, 9, [10]]), 10
  assert.equal! (args.fn.gt 10, 10), nil
  assert.equal! (args.fn.gt 10, 10), nil
  assert.equal! (args.fn.gt 10, 9), nil
  assert.equal! (args.fn.>  8, 9, 10), 10
end

def test_gte args, assert
  assert.equal! (args.fn.gte 1), 1
  assert.equal! (args.fn.gte), nil
  assert.equal! (args.fn.gte infinity), nil
  assert.equal! (args.fn.gte nan), nil
  assert.equal! (args.fn.gte 8, 9, 10), 10
  assert.equal! (args.fn.gte 10, 10), 10
  assert.equal! (args.fn.gte 8, 9, [10]), 10
  assert.equal! (args.fn.gte 10, 9), nil
  assert.equal! (args.fn.>=  8, 9, 10), 10
end


def test_acopy args, assert
  orig  = [1, 2, 3]
  clone = args.fn.acopy orig
  assert.equal! clone, [1, 2, 3]
  assert.equal! clone, orig
  assert.not_equal! clone.object_id, orig.object_id
end

def test_aget args, assert
  assert.equal! (args.fn.aget [:a, :b, :c], 1), :b
  assert.equal! (args.fn.aget [:a, :b, :c], nil), nil
  assert.equal! (args.fn.aget nil, 1), nil
end

def test_alength args, assert
  assert.equal! (args.fn.alength [:a, :b, :c]), 3
  assert.equal! (args.fn.alength nil), nil
end

def test_amap args, assert
  inc = lambda { |i| i + 1 }
  ary = [1, 2, 3]
  assert.equal! (args.fn.amap ary, inc), [2, 3, 4]
  assert.equal! (args.fn.amap nil, inc), nil
  assert.equal! (args.fn.amap ary, nil), nil
  assert.equal! (args.fn.amap ary, inc).class, Array
end

def test_and args, assert
  assert.equal! (args.fn.and 1, 2, 3, 4), 4
  assert.equal! (args.fn.and 1, 2, nil, 4), nil
  assert.equal! (args.fn.and), true
end

def test_or args, assert
  assert.equal! (args.fn.or 1, 2, 3, 4), 1
  assert.equal! (args.fn.or 1, 2, nil, 4), 1
  assert.equal! (args.fn.or), nil
  assert.equal! (args.fn.or nil, nil, false, 5, 10), 5
end

def test_eq_eq args, assert
  assert.equal! (args.fn.eq?), true
  assert.equal! (args.fn.eq? 1, 0), false
  assert.equal! (args.fn.eq? 1, 1, 1), true
  assert.equal! (args.fn.== 1, 1, 1), true
  assert.equal! (args.fn.== nil, nil), true
end

def test_apply args, assert
  assert.equal! (args.fn.and [nil, nil, nil]), [nil, nil, nil]
  assert.equal! (args.fn.apply [nil, nil, nil], args.fn.method(:and)), nil
  and_lambda = lambda {|*xs| args.fn.and(*xs)}
  assert.equal! (args.fn.apply [nil, nil, nil], and_lambda), nil
end

def test_areduce args, assert
  assert.equal! (args.fn.areduce [1, 2, 3], 0, lambda { |i, a| i + a }), 6
end

def test_array_hash args, assert
  assert.equal! (args.fn.array_hash :a, 1, :b, 2), { a: 1, b: 2 }
  assert.equal! (args.fn.array_hash), { }
end

Advanced Debugging - Unit Tests - gen_docs.rb

# ./samples/10_advanced_debugging/03_unit_tests/gen_docs.rb
# ./dragonruby mygame --eval samples/99_zz_gtk_unit_tests/gen_docs.rb --no-tick
Kernel.export_docs!

Advanced Debugging - Unit Tests - geometry_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/geometry_tests.rb
begin :shared
  def primitive_representations x, y, w, h
    [
      [x, y, w, h],
      { x: x, y: y, w: w, h: h },
      RectForTest.new(x, y, w, h)
    ]
  end

  class RectForTest
    attr_sprite

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

    def to_s
      "RectForTest: #{[x, y, w, h]}"
    end
  end
end

begin :intersect_rect?
  def test_intersect_rect_point args, assert
    assert.true! [16, 13].intersect_rect?([13, 12, 4, 4]), "point intersects with rect."
  end

  def test_intersect_rect args, assert
    intersecting = primitive_representations(0, 0, 100, 100) +
                   primitive_representations(20, 20, 20, 20)

    intersecting.product(intersecting).each do |rect_one, rect_two|
      assert.true! rect_one.intersect_rect?(rect_two),
                   "intersect_rect? assertion failed for #{rect_one}, #{rect_two} (expected true)."
    end

    not_intersecting = [
      [ 0, 0, 5, 5],
      { x: 10, y: 10, w: 5, h: 5 },
      RectForTest.new(20, 20, 5, 5)
    ]

    not_intersecting.product(not_intersecting)
      .reject { |rect_one, rect_two| rect_one == rect_two }
      .each do |rect_one, rect_two|
      assert.false! rect_one.intersect_rect?(rect_two),
                    "intersect_rect? assertion failed for #{rect_one}, #{rect_two} (expected false)."
    end
  end
end

begin :inside_rect?
  def assert_inside_rect outer: nil, inner: nil, expected: nil, assert: nil
    assert.true! inner.inside_rect?(outer) == expected,
                 "inside_rect? assertion failed for outer: #{outer} inner: #{inner} (expected #{expected})."
  end

  def test_inside_rect args, assert
    outer_rects = primitive_representations(0, 0, 10, 10)
    inner_rects = primitive_representations(1, 1, 5, 5)
    primitive_representations(0, 0, 10, 10).product(primitive_representations(1, 1, 5, 5))
      .each do |outer, inner|
      assert_inside_rect outer: outer, inner: inner,
                         expected: true, assert: assert
    end
  end
end

begin :angle_to
  def test_angle_to args, assert
    origins = primitive_representations(0, 0, 0, 0)
    rights = primitive_representations(1, 0, 0, 0)
    aboves = primitive_representations(0, 1, 0, 0)

    origins.product(aboves).each do |origin, above|
      assert.equal! origin.angle_to(above), 90,
                    "A point directly above should be 90 degrees."

      assert.equal! above.angle_from(origin), 90,
                    "A point coming from above should be 90 degrees."
    end

    origins.product(rights).each do |origin, right|
      assert.equal! origin.angle_to(right) % 360, 0,
                    "A point directly to the right should be 0 degrees."

      assert.equal! right.angle_from(origin) % 360, 0,
                    "A point coming from the right should be 0 degrees."

    end
  end
end

begin :scale_rect
  def test_scale_rect args, assert
    assert.equal! [0, 0, 100, 100].scale_rect(0.5, 0.5),
                  [25.0, 25.0, 50.0, 50.0]

    assert.equal! [0, 0, 100, 100].scale_rect(0.5),
                  [0.0, 0.0, 50.0, 50.0]

    assert.equal! [0, 0, 100, 100].scale_rect_extended(percentage_x: 0.5, percentage_y: 0.5, anchor_x: 0.5, anchor_y: 0.5),
                  [25.0, 25.0, 50.0, 50.0]

    assert.equal! [0, 0, 100, 100].scale_rect_extended(percentage_x: 0.5, percentage_y: 0.5, anchor_x: 0, anchor_y: 0),
                  [0.0, 0.0, 50.0, 50.0]
  end
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - http_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/http_tests.rb
def try_assert_or_schedule args, assert
  if $result[:complete]
    log_info "Request completed! Verifying."
    if $result[:http_response_code] != 200
      log_info "The request yielded a result of #{$result[:http_response_code]} instead of 200."
      exit
    end
    log_info ":try_assert_or_schedule succeeded!"
  else
    args.gtk.schedule_callback Kernel.tick_count + 10 do
      try_assert_or_schedule args, assert
    end
  end
end

def test_http args, assert
  $result = $gtk.http_get 'http://dragonruby.org'
  try_assert_or_schedule args, assert
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - nil_coercion_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/nil_coercion_tests.rb
# numbers
def test_open_entity_add_number args, assert
  assert.nil! args.state.i_value
  args.state.i_value += 5
  assert.equal! args.state.i_value, 5

  assert.nil! args.state.f_value
  args.state.f_value += 5.5
  assert.equal! args.state.f_value, 5.5
end

def test_open_entity_subtract_number args, assert
  assert.nil! args.state.i_value
  args.state.i_value -= 5
  assert.equal! args.state.i_value, -5

  assert.nil! args.state.f_value
  args.state.f_value -= 5.5
  assert.equal! args.state.f_value, -5.5
end

def test_open_entity_multiply_number args, assert
  assert.nil! args.state.i_value
  args.state.i_value *= 5
  assert.equal! args.state.i_value, 0

  assert.nil! args.state.f_value
  args.state.f_value *= 5.5
  assert.equal! args.state.f_value, 0
end

def test_open_entity_divide_number args, assert
  assert.nil! args.state.i_value
  args.state.i_value /= 5
  assert.equal! args.state.i_value, 0

  assert.nil! args.state.f_value
  args.state.f_value /= 5.5
  assert.equal! args.state.f_value, 0
end

# array
def test_open_entity_add_array args, assert
  assert.nil! args.state.values
  args.state.values += [:a, :b, :c]
  assert.equal! args.state.values, [:a, :b, :c]
end

def test_open_entity_subtract_array args, assert
  assert.nil! args.state.values
  args.state.values -= [:a, :b, :c]
  assert.equal! args.state.values, []
end

def test_open_entity_shovel_array args, assert
  assert.nil! args.state.values
  args.state.values << :a
  assert.equal! args.state.values, [:a]
end

def test_open_entity_enumerate args, assert
  assert.nil! args.state.values
  args.state.values = args.state.values.map_with_index { |i| i }
  assert.equal! args.state.values, []

  assert.nil! args.state.values_2
  args.state.values_2 = args.state.values_2.map { |i| i }
  assert.equal! args.state.values_2, []

  assert.nil! args.state.values_3
  args.state.values_3 = args.state.values_3.flat_map { |i| i }
  assert.equal! args.state.values_3, []
end

# hashes
def test_open_entity_indexer args, assert
  GTK::Entity.__reset_id__!
  assert.nil! args.state.values
  args.state.values[:test] = :value
  assert.equal! args.state.values.to_s, { entity_id: 1, entity_name: :values, entity_keys_by_ref: {}, test: :value }.to_s
end

# bug
def test_open_entity_nil_bug args, assert
  GTK::Entity.__reset_id__!
  args.state.foo.a
  args.state.foo.b
  @hello[:foobar]
  assert.nil! args.state.foo.a, "a was not nil."
  # the line below fails
  # assert.nil! args.state.foo.b, "b was not nil."
end

Advanced Debugging - Unit Tests - object_to_primitive_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/object_to_primitive_tests.rb
class PlayerSpriteForTest
end

def test_array_to_sprite args, assert
  array = [[0, 0, 100, 100, "test.png"]].sprites
  puts "No exception was thrown. Sweet!"
end

def test_class_to_sprite args, assert
  array = [PlayerSprite.new].sprites
  assert.true! array.first.is_a?(PlayerSprite)
  puts "No exception was thrown. Sweet!"
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - parsing_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/parsing_tests.rb
def test_parse_json args, assert
  result = args.gtk.parse_json '{ "name": "John Doe", "aliases": ["JD"] }'
  assert.equal! result, { "name"=>"John Doe", "aliases"=>["JD"] }, "Parsing JSON failed."
end

def test_parse_xml args, assert
  result = args.gtk.parse_xml <<-S

  John Doe

S

 expected = {:type=>:element,
             :name=>nil,
             :children=>[{:type=>:element,
                          :name=>"Person",
                          :children=>[{:type=>:element,
                                       :name=>"Name",
                                       :children=>[{:type=>:content,
                                                    :data=>"John Doe"}]}],
                          :attributes=>{"id"=>"100"}}]}

 assert.equal! result, expected, "Parsing xml failed."
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - pretty_format_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/pretty_format_tests.rb
def H opts
  opts
end

def A *opts
  opts
end

def assert_format args, assert, hash, expected
  actual = args.fn.pretty_format hash
  assert.are_equal! actual, expected
end

def test_pretty_print args, assert
  # =============================
  # hash with single value
  # =============================
  input = (H first_name: "John")
  expected = <<-S
{:first_name "John"}
S
  (assert_format args, assert, input, expected)

  # =============================
  # hash with two values
  # =============================
  input = (H first_name: "John", last_name: "Smith")
  expected = <<-S
{:first_name "John"
 :last_name "Smith"}
S

  (assert_format args, assert, input, expected)

  # =============================
  # hash with inner hash
  # =============================
  input = (H first_name: "John",
             last_name: "Smith",
             middle_initial: "I",
             so: (H first_name: "Pocahontas",
                    last_name: "Tsenacommacah"),
             friends: (A (H first_name: "Side", last_name: "Kick"),
                         (H first_name: "Tim", last_name: "Wizard")))
  expected = <<-S
{:first_name "John"
 :last_name "Smith"
 :middle_initial "I"
 :so {:first_name "Pocahontas"
      :last_name "Tsenacommacah"}
 :friends [{:first_name "Side"
            :last_name "Kick"}
           {:first_name "Tim"
            :last_name "Wizard"}]}
S

  (assert_format args, assert, input, expected)

  # =============================
  # array with one value
  # =============================
  input = (A 1)
  expected = <<-S
[1]
S
  (assert_format args, assert, input, expected)

  # =============================
  # array with multiple values
  # =============================
  input = (A 1, 2, 3)
  expected = <<-S
[1
 2
 3]
S
  (assert_format args, assert, input, expected)

  # =============================
  # array with multiple values hashes
  # =============================
  input = (A (H first_name: "Side", last_name: "Kick"),
             (H first_name: "Tim", last_name: "Wizard"))
  expected = <<-S
[{:first_name "Side"
  :last_name "Kick"}
 {:first_name "Tim"
  :last_name "Wizard"}]
S

  (assert_format args, assert, input, expected)
end

def test_nested_nested args, assert
  # =============================
  # nested array in nested hash
  # =============================
  input = (H type: :root,
             text: "Root",
             children: (A (H level: 1,
                             text: "Level 1",
                             children: (A (H level: 2,
                                             text: "Level 2",
                                             children: [])))))

  expected = <<-S
{:type :root
 :text "Root"
 :children [{:level 1
             :text "Level 1"
             :children [{:level 2
                         :text "Level 2"
                         :children []}]}]}

S

  (assert_format args, assert, input, expected)
end

def test_scene args, assert
  script = <<-S
* Scene 1
** Narrator
They say happy endings don't exist.
** Narrator
They say true love is a lie.
S
  input = parse_org args, script
  puts (args.fn.pretty_format input)
end

Advanced Debugging - Unit Tests - require_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/require_tests.rb
def write_src path, src
  $gtk.write_file path, src
end

write_src 'app/unit_testing_game.rb', <<-S
module UnitTesting
  class Game
  end
end
S

write_src 'lib/unit_testing_lib.rb', <<-S
module UnitTesting
  class Lib
  end
end
S

write_src 'app/nested/unit_testing_nested.rb', <<-S
module UnitTesting
  class Nested
  end
end
S

require 'app/unit_testing_game.rb'
require 'app/nested/unit_testing_nested.rb'
require 'lib/unit_testing_lib.rb'

def test_require args, assert
  UnitTesting::Game.new
  UnitTesting::Lib.new
  UnitTesting::Nested.new
  $gtk.exec 'rm ./mygame/app/unit_testing_game.rb'
  $gtk.exec 'rm ./mygame/app/nested/unit_testing_nested.rb'
  $gtk.exec 'rm ./mygame/lib/unit_testing_lib.rb'
  assert.ok!
end

Advanced Debugging - Unit Tests - serialize_deserialize_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/serialize_deserialize_tests.rb
def test_serialize args, assert
  GTK::Entity.__reset_id__!
  args.state.player_one = "test"
  result = args.gtk.serialize_state args.state
  assert.equal! result, "{:entity_id=>3, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>\"test\"}"

  GTK::Entity.__reset_id__!
  args.gtk.write_file 'state.txt', ''
  result = args.gtk.serialize_state 'state.txt', args.state
  assert.equal! result, "{:entity_id=>3, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>\"test\"}"
end

def test_deserialize args, assert
  GTK::Entity.__reset_id__!
  result = args.gtk.deserialize_state '{:entity_id=>3, :tick_count=>-1, :player_one=>"test"}'
  assert.equal! result.player_one, "test"

  GTK::Entity.__reset_id__!
  args.gtk.write_file 'state.txt',  '{:entity_id=>3, :tick_count=>-1, :player_one=>"test"}'
  result = args.gtk.deserialize_state 'state.txt'
  assert.equal! result.player_one, "test"
end

def test_very_large_serialization args, assert
  GTK::Entity.__reset_id__!
  size = 3000
  size.map_with_index do |i|
    args.state.send("k#{i}=".to_sym, i)
  end

  result = args.gtk.serialize_state args.state
  assert.true! (args.gtk.console.log.join.include? "unlikely a string this large will deserialize correctly")
end

def test_strict_entity_serialization args, assert
  GTK::Entity.__reset_id__!
  args.state.player_one = args.state.new_entity(:player, name: "Ryu")
  args.state.player_two = args.state.new_entity_strict(:player_strict, name: "Ken")

  serialized_state = args.gtk.serialize_state args.state
  assert.equal! serialized_state, '{:entity_id=>1, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>{:entity_id=>1, :entity_name=>:player, :entity_keys_by_ref=>{}, :entity_type=>:player, :created_at=>-1, :global_created_at=>-1, :name=>"Ryu"}, :player_two=>{:entity_id=>3, :entity_name=>:player_strict, :entity_type=>:player_strict, :created_at=>-1, :global_created_at_elapsed=>-1, :entity_strict=>true, :entity_keys_by_ref=>{:entity_type=>:entity_name, :global_created_at_elapsed=>:created_at}, :name=>"Ken"}}'

  GTK::Entity.__reset_id__!
  deserialize_state = args.gtk.deserialize_state serialized_state

  assert.equal! args.state.player_one.name, deserialize_state.player_one.name
  assert.true! args.state.player_one.is_a? GTK::OpenEntity

  assert.equal! args.state.player_two.name, deserialize_state.player_two.name
  assert.true! args.state.player_two.is_a? GTK::StrictEntity
end

def test_strict_entity_serialization_with_nil args, assert
  GTK::Entity.__reset_id__!
  args.state.player_one = args.state.new_entity(:player, name: "Ryu")
  args.state.player_two = args.state.new_entity_strict(:player_strict, name: "Ken", blood_type: nil)

  serialized_state = args.gtk.serialize_state args.state
  assert.equal! serialized_state, '{:entity_id=>9, :entity_keys_by_ref=>{}, :tick_count=>-1, :player_one=>{:entity_id=>1, :entity_name=>:player, :entity_keys_by_ref=>{}, :entity_type=>:player, :created_at=>-1, :global_created_at=>-1, :name=>"Ryu"}, :player_two=>{:entity_id=>2, :entity_name=>:player_strict, :entity_type=>:player_strict, :created_at=>-1, :global_created_at_elapsed=>-1, :entity_strict=>true, :entity_keys_by_ref=>{:entity_type=>:entity_name, :global_created_at_elapsed=>:created_at}, :name=>"Ken", :blood_type=>nil}}'

  GTK::Entity.__reset_id__!
  deserialized_state = args.gtk.deserialize_state serialized_state

  assert.equal! args.state.player_one.name, deserialized_state.player_one.name
  assert.true! args.state.player_one.is_a? GTK::OpenEntity

  assert.equal! args.state.player_two.name, deserialized_state.player_two.name
  assert.equal! args.state.player_two.blood_type, deserialized_state.player_two.blood_type
  assert.equal! deserialized_state.player_two.blood_type, nil
  assert.true! args.state.player_two.is_a? GTK::StrictEntity

  deserialized_state.player_two.blood_type = :O
  assert.equal! deserialized_state.player_two.blood_type, :O
end

def test_multiple_strict_entities args, assert
  GTK::Entity.__reset_id__!
  args.state.player = args.state.new_entity_strict(:player_one, name: "Ryu")
  args.state.enemy = args.state.new_entity_strict(:enemy, name: "Bison", other_property: 'extra mean')

  serialized_state = args.gtk.serialize_state args.state

  GTK::Entity.__reset_id__!
  deserialized_state = args.gtk.deserialize_state serialized_state

  assert.equal! deserialized_state.player.name, "Ryu"
  assert.equal! deserialized_state.enemy.other_property, "extra mean"
end

def test_by_reference_state args, assert
  GTK::Entity.__reset_id__!
  args.state.a = { name: "Jane Doe" }
  args.state.b = args.state.a
  assert.equal! args.state.a.object_id, args.state.b.object_id
  serialized_state = args.gtk.serialize_state args.state

  GTK::Entity.__reset_id__!
  deserialized_state = args.gtk.deserialize_state serialized_state
  assert.equal! deserialized_state.a.object_id, deserialized_state.b.object_id
end

def test_by_reference_state_strict_entities args, assert
  GTK::Entity.__reset_id__!
  args.state.a = { name: "Jane Doe" }
  args.state.strict_entity = args.state.new_entity_strict(:couple) do |e|
    e.one = args.state.new_entity_strict(:person, name: "Jane")
    e.two = e.one
  end
  assert.equal! args.state.strict_entity.one, args.state.strict_entity.two
  serialized_state = args.gtk.serialize_state args.state

  GTK::Entity.__reset_id__!
  deserialized_state = args.gtk.deserialize_state serialized_state
  assert.equal! deserialized_state.strict_entity.one, deserialized_state.strict_entity.two
end

Advanced Debugging - Unit Tests - state_serialization_experimental_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/state_serialization_experimental_tests.rb
MAX_CODE_GEN_LENGTH = 50

# NOTE: This is experimental/advanced stuff.
def needs_partitioning? target
  target[:value].to_s.length > MAX_CODE_GEN_LENGTH
end

def partition target
  return [] unless needs_partitioning? target
  if target[:value].is_a? GTK::OpenEntity
    target[:value] = target[:value].hash
  end

  results = []
  idx = 0
  left, right = target[:value].partition do
    idx += 1
    idx.even?
  end
  left, right = Hash[left], Hash[right]
  left = { value: left }
  right = { value: right}
  [left, right]
end

def add_partition target, path, aggregate, final_result
  partitions = partition target
  partitions.each do |part|
    if needs_partitioning? part
      if part[:value].keys.length == 1
        first_key = part[:value].keys[0]
        new_part = { value: part[:value][first_key] }
        path.push first_key
        add_partition new_part, path, aggregate, final_result
        path.pop
      else
        add_partition part, path, aggregate, final_result
      end
    else
      final_result << { value: { __path__: [*path] } }
      final_result << { value: part[:value] }
    end
  end
end

def state_to_string state
  parts_queue = []
  final_queue = []
  add_partition({ value: state.hash },
                [],
                parts_queue,
                final_queue)
  final_queue.reject {|i| i[:value].keys.length == 0}.map do |i|
    i[:value].to_s
  end.join("\n#==================================================#\n")
end

def state_from_string string
  Kernel.eval("$load_data = {}")
  lines = string.split("\n#==================================================#\n")
  lines.each do |l|
    puts "todo: #{l}"
  end

  GTK::OpenEntity.parse_from_hash $load_data
end

def test_save_and_load args, assert
  args.state.item_1.name = "Jane"
  string = state_to_string args.state
  state = state_from_string string
  assert.equal! args.state.item_1.name, state.item_1.name
end

def test_save_and_load_big args, assert
  size = 1000
  size.map_with_index do |i|
    args.state.send("k#{i}=".to_sym, i)
  end

  string = state_to_string args.state
  state = state_from_string string
  size.map_with_index do |i|
    assert.equal! args.state.send("k#{i}".to_sym), state.send("k#{i}".to_sym)
    assert.equal! args.state.send("k#{i}".to_sym), i
    assert.equal! state.send("k#{i}".to_sym), i
  end
end

def test_save_and_load_big_nested args, assert
  args.state.player_one.friend.nested_hash.k0 = 0
  args.state.player_one.friend.nested_hash.k1 = 1
  args.state.player_one.friend.nested_hash.k2 = 2
  args.state.player_one.friend.nested_hash.k3 = 3
  args.state.player_one.friend.nested_hash.k4 = 4
  args.state.player_one.friend.nested_hash.k5 = 5
  args.state.player_one.friend.nested_hash.k6 = 6
  args.state.player_one.friend.nested_hash.k7 = 7
  args.state.player_one.friend.nested_hash.k8 = 8
  args.state.player_one.friend.nested_hash.k9 = 9
  string = state_to_string args.state
  state = state_from_string string
end

$gtk.reset 100
$gtk.log_level = :off

Advanced Debugging - Unit Tests - suggest_autocompletion_tests.rb

# ./samples/10_advanced_debugging/03_unit_tests/suggest_autocompletion_tests.rb
def default_suggest_autocompletion args
  {
    index: 4,
    text: "args.",
    __meta__: {
      other_options: [
        {
          index: Fixnum,
          file: "app/main.rb"
        }
      ]
    }
  }
end

def assert_completion source, *expected
  results = suggest_autocompletion text:  (source.strip.gsub  ":cursor", ""),
                                   index: (source.strip.index ":cursor")

  puts results
end

def test_args_completion args, assert
  $gtk.write_file_root "autocomplete.txt", ($gtk.suggest_autocompletion text: <<-S, index: 128).join("\n")
require 'app/game.rb'

def tick args
  args.gtk.suppress_mailbox = false
  $game ||= Game.new
  $game.args = args
  $game.args.
  $game.tick
end
S

  puts "contents:"
  puts ($gtk.read_file "autocomplete.txt")
end

Http - Retrieve Images - main.rb

# ./samples/11_http/01_retrieve_images/app/main.rb
def tick args
  args.outputs.background_color = [0, 0, 0]

  # Show a warning at the start.
  args.state.warning_debounce ||= 11 * 60
  if args.state.warning_debounce > 0
    args.state.warning_debounce -= 1
    args.outputs.labels << [640, 600, "This app shows random images from the Internet.", 10, 1, 255, 255, 255]
    args.outputs.labels << [640, 500, "Quit in the next few seconds if this is a problem.", 10, 1, 255, 255, 255]
    args.outputs.labels << [640, 350, "#{(args.state.warning_debounce / 60.0).to_i}", 10, 1, 255, 255, 255]
    return
  end

  args.state.download_debounce ||= 0   # start immediately, reset to non zero later.
  args.state.photos ||= []

  # Put a little pause between each download.
  if args.state.download.nil?
    if args.state.download_debounce > 0
      args.state.download_debounce -= 1
    else
      args.state.download = $gtk.http_get 'https://picsum.photos/200/300.jpg'
    end
  end

  if !args.state.download.nil?
    if args.state.download[:complete]
      if args.state.download[:http_response_code] == 200
        fname = "sprites/#{args.state.photos.length}.jpg"
        $gtk.write_file fname, args.state.download[:response_data]
        args.state.photos << [ 100 + rand(1080), 500 - rand(480), fname, rand(80) - 40 ]
      end
      args.state.download = nil
      args.state.download_debounce = (rand(3) + 2) * 60
    end
  end

  # draw any downloaded photos...
  args.state.photos.each { |i|
    args.outputs.primitives << [i[0], i[1], 200, 300, i[2], i[3]].sprite
  }

  # Draw a download progress bar...
  args.outputs.primitives << [0, 0, 1280, 30, 0, 0, 0, 255].solid
  if !args.state.download.nil?
    br = args.state.download[:response_read]
    total = args.state.download[:response_total]
    if total != 0
      pct = br.to_f / total.to_f
      args.outputs.primitives << [0, 0, 1280 * pct, 30, 0, 0, 255, 255].solid
    end
  end
end

Http - Web Server - main.rb

# ./samples/11_http/02_web_server/app/main.rb
def tick args
  args.state.port ||= 3000
  # by default the embedded webserver runs on port 9001 (the port number is over 9000) and is disabled in a production build
  # to enable the http server in a production build, you need to manually start
  # the server up:
  args.gtk.start_server! port: args.state.port, enable_in_prod: true
  args.outputs.background_color = [0, 0, 0]
  args.outputs.labels << [640, 600, "Point your web browser at http://localhost:#{args.state.port}/", 10, 1, 255, 255, 255]

  args.inputs.http_requests.each { |req|
    puts("METHOD: #{req.method}");
    puts("URI: #{req.uri}");
    puts("HEADERS:");
    req.headers.each { |k,v| puts("  #{k}: #{v}") }

    if (req.uri == '/')
      # headers and body can be nil if you don't care about them.
      # If you don't set the Content-Type, it will default to
      #  "text/html; charset=utf-8".
      # Don't set Content-Length; we'll ignore it and calculate it for you
      args.state.reqnum += 1
      req.respond 200, "
This #{req.method} was request number #{args.state.reqnum}!
\n", { 'X-DRGTK-header' => 'Powered by DragonRuby!' }
    else
      req.reject
    end
  }
end

C Extensions - Basics - main.rb

# ./samples/12_c_extensions/01_basics/app/main.rb
$gtk.ffi_misc.gtk_dlopen("ext")
include FFI::CExt

def tick args
  args.outputs.labels  << [640, 500, "mouse.x = #{args.mouse.x.to_i}", 5, 1]
  args.outputs.labels  << [640, 460, "square(mouse.x) = #{square(args.mouse.x.to_i)}", 5, 1]
  args.outputs.labels  << [640, 420, "mouse.y = #{args.mouse.y.to_i}", 5, 1]
  args.outputs.labels  << [640, 380, "square(mouse.y) = #{square(args.mouse.y.to_i)}", 5, 1]
end

C Extensions - Intermediate - main.rb

# ./samples/12_c_extensions/02_intermediate/app/main.rb
$gtk.ffi_misc.gtk_dlopen("ext")
include FFI::RE

def split_words(input)
  words = []
  last = IntPointer.new
  re = re_compile("\\w+")
  first = re_matchp(re, input, last)
  while first != -1
    words << input.slice(first, last.value)
    input = input.slice(last.value + first, input.length)
    first = re_matchp(re, input, last)
  end
  words
end

def tick args
  args.outputs.labels  << [640, 500, split_words("hello, dragonriders!").join(' '), 5, 1]
end

C Extensions - Native Pixel Arrays - main.rb

# ./samples/12_c_extensions/03_native_pixel_arrays/app/main.rb
$gtk.ffi_misc.gtk_dlopen("ext")
include FFI::CExt

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

  update_scanner_texture   # this calls into a C extension!

  # New/changed pixel arrays get uploaded to the GPU before we render
  #  anything. At that point, they can be scaled, rotated, and otherwise
  #  used like any other sprite.
  w = 100
  h = 100
  x = (1280 - w) / 2
  y = (720 - h) / 2
  args.outputs.background_color = [64, 0, 128]
  args.outputs.primitives << [x, y, w, h, :scanner, args.state.rotation].sprite
  args.state.rotation += 1

  args.outputs.primitives << args.gtk.current_framerate_primitives
end

Path Finding Algorithms - Breadth First Search - main.rb

# ./samples/13_path_finding_algorithms/01_breadth_first_search/app/main.rb
# A visual demonstration of a breadth first search
# Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# An animation that can respond to user input in real time

# A breadth first search expands in all directions one step at a time
# The frontier is a queue of cells to be expanded from
# The visited hash allows quick lookups of cells that have been expanded from
# The walls hash allows quick lookup of whether a cell is a wall

# The breadth first search starts by adding the red star to the frontier array
# and marking it as visited
# Each step a cell is removed from the front of the frontier array (queue)
# Unless the neighbor is a wall or visited, it is added to the frontier array
# The neighbor is then marked as visited

# The frontier is blue
# Visited cells are light brown
# Walls are camo green
# Even when walls are visited, they will maintain their wall color

# The star can be moved by clicking and dragging
# Walls can be added and removed by clicking and dragging

class BreadthFirstSearch
  attr_gtk

  def initialize(args)
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    args.state.grid.width     = 30
    args.state.grid.height    = 15
    args.state.grid.cell_size = 40

    # Stores which step of the animation is being rendered
    # When the user moves the star or messes with the walls,
    # the breadth first search is recalculated up to this step
    args.state.anim_steps = 0

    # At some step the animation will end,
    # and further steps won't change anything (the whole grid will be explored)
    # This step is roughly the grid's width * height
    # When anim_steps equals max_steps no more calculations will occur
    # and the slider will be at the end
    args.state.max_steps  = args.state.grid.width * args.state.grid.height

    # Whether the animation should play or not
    # If true, every tick moves anim_steps forward one
    # Pressing the stepwise animation buttons will pause the animation
    args.state.play       = true

    # The location of the star and walls of the grid
    # They can be modified to have a different initial grid
    # Walls are stored in a hash for quick look up when doing the search
    args.state.star       = [0, 0]
    args.state.walls      = {
      [3, 3] => true,
      [3, 4] => true,
      [3, 5] => true,
      [3, 6] => true,
      [3, 7] => true,
      [3, 8] => true,
      [3, 9] => true,
      [3, 10] => true,
      [3, 11] => true,
      [4, 3] => true,
      [4, 4] => true,
      [4, 5] => true,
      [4, 6] => true,
      [4, 7] => true,
      [4, 8] => true,
      [4, 9] => true,
      [4, 10] => true,
      [4, 11] => true,

      [13, 0] => true,
      [13, 1] => true,
      [13, 2] => true,
      [13, 3] => true,
      [13, 4] => true,
      [13, 5] => true,
      [13, 6] => true,
      [13, 7] => true,
      [13, 8] => true,
      [13, 9] => true,
      [13, 10] => true,
      [14, 0] => true,
      [14, 1] => true,
      [14, 2] => true,
      [14, 3] => true,
      [14, 4] => true,
      [14, 5] => true,
      [14, 6] => true,
      [14, 7] => true,
      [14, 8] => true,
      [14, 9] => true,
      [14, 10] => true,

      [21, 8] => true,
      [21, 9] => true,
      [21, 10] => true,
      [21, 11] => true,
      [21, 12] => true,
      [21, 13] => true,
      [21, 14] => true,
      [22, 8] => true,
      [22, 9] => true,
      [22, 10] => true,
      [22, 11] => true,
      [22, 12] => true,
      [22, 13] => true,
      [22, 14] => true,
      [23, 8] => true,
      [23, 9] => true,
      [24, 8] => true,
      [24, 9] => true,
      [25, 8] => true,
      [25, 9] => true,
    }

    # Variables that are used by the breadth first search
    # Storing cells that the search has visited, prevents unnecessary steps
    # Expanding the frontier of the search in order makes the search expand
    # from the center outward
    args.state.visited    = {}
    args.state.frontier   = []


    # What the user is currently editing on the grid
    # Possible values are: :none, :slider, :star, :remove_wall, :add_wall

    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    args.state.click_and_drag = :none

    # Store the rects of the buttons that control the animation
    # They are here for user customization
    # Editing these might require recentering the text inside them
    # Those values can be found in the render_button methods
    args.state.buttons.left   = [450, 600, 50, 50]
    args.state.buttons.center = [500, 600, 200, 50]
    args.state.buttons.right  = [700, 600, 50, 50]

    # The variables below are related to the slider
    # They allow the user to customize them
    # They also give a central location for the render and input methods to get
    # information from
    # x & y are the coordinates of the leftmost part of the slider line
    args.state.slider.x = 400
    args.state.slider.y = 675
    # This is the width of the line
    args.state.slider.w = 360
    # This is the offset for the circle
    # Allows the center of the circle to be on the line,
    # as opposed to the upper right corner
    args.state.slider.offset = 20
    # This is the spacing between each of the notches on the slider
    # Notches are places where the circle can rest on the slider line
    # There needs to be a notch for each step before the maximum number of steps
    args.state.slider.spacing = args.state.slider.w.to_f / args.state.max_steps.to_f
  end

  # This method is called every frame/tick
  # Every tick, the current state of the search is rendered on the screen,
  # User input is processed, and
  # The next step in the search is calculated
  def tick
    render
    input
    # If animation is playing, and max steps have not been reached
    # Move the search a step forward
    if state.play && state.anim_steps < state.max_steps
      # Variable that tells the program what step to recalculate up to
      state.anim_steps += 1
      calc
    end
  end

  # Draws everything onto the screen
  def render
    render_buttons
    render_slider

    render_background
    render_visited
    render_frontier
    render_walls
    render_star
  end

  # The methods below subdivide the task of drawing everything to the screen

  # Draws the buttons that control the animation step and state
  def render_buttons
    render_left_button
    render_center_button
    render_right_button
  end

  # Draws the button which steps the search backward
  # Shows the user where to click to move the search backward
  def render_left_button
    # Draws the gray button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.left, gray]
    outputs.borders << [buttons.left, black]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    # If the button size is changed, the label might need to be edited as well
    # to keep the label in the center of the button
    label_x = buttons.left.x + 20
    label_y = buttons.left.y + 35
    outputs.labels  << [label_x, label_y, "<"]
  end

  def render_center_button
    # Draws the gray button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.center, gray]
    outputs.borders << [buttons.center, black]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    # If the button size is changed, the label might need to be edited as well
    # to keep the label in the center of the button
    label_x    = buttons.center.x + 37
    label_y    = buttons.center.y + 35
    label_text = state.play ? "Pause Animation" : "Play Animation"
    outputs.labels << [label_x, label_y, label_text]
  end

  def render_right_button
    # Draws the gray button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.right, gray]
    outputs.borders << [buttons.right, black]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    label_x = buttons.right.x + 20
    label_y = buttons.right.y + 35
    outputs.labels  << [label_x, label_y, ">"]
  end

  # Draws the slider so the user can move it and see the progress of the search
  def render_slider
    # Using primitives hides the line under the white circle of the slider
    # Draws the line
    outputs.primitives << [slider.x, slider.y, slider.x + slider.w, slider.y].line
    # The circle needs to be offset so that the center of the circle
    # overlaps the line instead of the upper right corner of the circle
    # The circle's x value is also moved based on the current seach step
    circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    outputs.primitives << [circle_rect, 'circle-white.png'].sprite
  end

  # Draws what the grid looks like with nothing on it
  def render_background
    render_unvisited
    render_grid_lines
  end

  # Draws a rectangle the size of the entire grid to represent unvisited cells
  def render_unvisited
    outputs.solids << [scale_up([0, 0, grid.width, grid.height]), unvisited_color]
  end

  # Draws grid lines to show the division of the grid into cells
  def render_grid_lines
    for x in 0..grid.width
      outputs.lines << vertical_line(x)
    end

    for y in 0..grid.height
      outputs.lines << horizontal_line(y)
    end
  end

  # Easy way to draw vertical lines given an index
  def vertical_line column
    scale_up([column, 0, column, grid.height])
  end

  # Easy way to draw horizontal lines given an index
  def horizontal_line row
    scale_up([0, row, grid.width, row])
  end

  # Draws the area that is going to be searched from
  # The frontier is the most outward parts of the search
  def render_frontier
    outputs.solids << state.frontier.map do |cell|
      [scale_up([cell.x, cell.y]), frontier_color]
    end
  end

  # Draws the walls
  def render_walls
    outputs.solids << state.walls.map do |wall|
      [scale_up([wall.x, wall.y]), wall_color]
    end
  end

  # Renders cells that have been searched in the appropriate color
  def render_visited
    outputs.solids << state.visited.map do |cell|
      [scale_up([cell.x, cell.y]), visited_color]
    end
  end

  # Renders the star
  def render_star
    outputs.sprites << [scale_up(state.star), 'star.png']
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  def scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone

    # If cell is just an x and y coordinate
    if cell.size == 2
      # Add a width and height of 1
      cell << 1
      cell << 1
    end

    # Scale all the values up
    cell.map! { |value| value * grid.cell_size }

    # Returns the scaled up cell
    cell
  end

  # This method processes user input every tick
  # This method allows the user to use the buttons, slider, and edit the grid
  # There are 2 types of input:
  #   Button Input
  #   Click and Drag Input
  #
  #   Button Input is used for the backward step and forward step buttons
  #   Input is detected by mouse up within the bounds of the rect
  #
  #   Click and Drag Input is used for moving the star, adding walls,
  #   removing walls, and the slider
  #
  #   When the mouse is down on the star, the click_and_drag variable is set to :star
  #   While click_and_drag equals :star, the cursor's position is used to calculate the
  #   appropriate drag behavior
  #
  #   When the mouse goes up click_and_drag is set to :none
  #
  #   A variable has to be used because the star has to continue being edited even
  #   when the cursor is no longer over the star
  #
  #   Similar things occur for the other Click and Drag inputs
  def input
    # Checks whether any of the buttons are being clicked
    input_buttons

    # The detection and processing of click and drag inputs are separate
    # The program has to remember that the user is dragging an object
    # even when the mouse is no longer over that object
    detect_click_and_drag
    process_click_and_drag
  end

  # Detects and Process input for each button
  def input_buttons
    input_left_button
    input_center_button
    input_next_step_button
  end

  # Checks if the previous step button is clicked
  # If it is, it pauses the animation and moves the search one step backward
  def input_left_button
    if left_button_clicked?
      state.play = false
      state.anim_steps -= 1
      recalculate
    end
  end

  # Controls the play/pause button
  # Inverses whether the animation is playing or not when clicked
  def input_center_button
    if center_button_clicked? or inputs.keyboard.key_down.space
      state.play = !state.play
    end
  end

  # Checks if the next step button is clicked
  # If it is, it pauses the animation and moves the search one step forward
  def input_next_step_button
    if right_button_clicked?
      state.play = false
      state.anim_steps += 1
      calc
    end
  end

  # Determines what the user is editing and stores the value
  # Storing the value allows the user to continue the same edit as long as the
  # mouse left click is held
  def detect_click_and_drag
    if inputs.mouse.up
      state.click_and_drag = :none
    elsif star_clicked?
      state.click_and_drag = :star
    elsif wall_clicked?
      state.click_and_drag = :remove_wall
    elsif grid_clicked?
      state.click_and_drag = :add_wall
    elsif slider_clicked?
      state.click_and_drag = :slider
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_click_and_drag
    if state.click_and_drag == :star
      input_star
    elsif state.click_and_drag == :remove_wall
      input_remove_wall
    elsif state.click_and_drag == :add_wall
      input_add_wall
    elsif state.click_and_drag == :slider
      input_slider
    end
  end

  # Moves the star to the grid closest to the mouse
  # Only recalculates the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star
    old_star = state.star.clone
    state.star = cell_closest_to_mouse
    unless old_star == state.star
      recalculate
    end
  end

  # Removes walls that are under the cursor
  def input_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_inside_grid?
      if state.walls.has_key?(cell_closest_to_mouse)
        state.walls.delete(cell_closest_to_mouse)
        recalculate
      end
    end
  end

  # Adds walls at cells under the cursor
  def input_add_wall
    if mouse_inside_grid?
      unless state.walls.has_key?(cell_closest_to_mouse)
        state.walls[cell_closest_to_mouse] = true
        recalculate
      end
    end
  end

  # This method is called when the user is editing the slider
  # It pauses the animation and moves the white circle to the closest integer point
  # on the slider
  # Changes the step of the search to be animated
  def input_slider
    state.play = false
    mouse_x = inputs.mouse.point.x

    # Bounds the mouse_x to the closest x value on the slider line
    mouse_x = slider.x if mouse_x < slider.x
    mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w

    # Sets the current search step to the one represented by the mouse x value
    # The slider's circle moves due to the render_slider method using anim_steps
    state.anim_steps = ((mouse_x - slider.x) / slider.spacing).to_i

    recalculate
  end

  # Whenever the user edits the grid,
  # The search has to be recalculated upto the current step
  # with the current grid as the initial state of the grid
  def recalculate
    # Resets the search
    state.frontier = []
    state.visited = {}

    # Moves the animation forward one step at a time
    state.anim_steps.times { calc }
  end


  # This method moves the search forward one step
  # When the animation is playing it is called every tick
  # And called whenever the current step of the animation needs to be recalculated

  # Moves the search forward one step
  # Parameter called_from_tick is true if it is called from the tick method
  # It is false when the search is being recalculated after user editing the grid
  def calc

    # The setup to the search
    # Runs once when the there is no frontier or visited cells
    if state.frontier.empty? && state.visited.empty?
      state.frontier << state.star
      state.visited[state.star] = true
    end

    # A step in the search
    unless state.frontier.empty?
      # Takes the next frontier cell
      new_frontier = state.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless state.visited.has_key?(neighbor) || state.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited
          state.frontier << neighbor
          state.visited[neighbor] = true
        end
      end
    end
  end


  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1
    neighbors << [cell.x, cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y] unless cell.x == 0

    neighbors
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def cell_closest_to_mouse
    # Closest cell to the mouse
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # These methods detect when the buttons are clicked
  def left_button_clicked?
    inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.left)
  end

  def center_button_clicked?
    inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.center)
  end

  def right_button_clicked?
    inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.right)
  end

  # Signal that the user is going to be moving the slider
  # Is the mouse down on the circle of the slider?
  def slider_clicked?
    circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    inputs.mouse.down && inputs.mouse.point.inside_rect?(circle_rect)
  end

  # Signal that the user is going to be moving the star
  def star_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.star))
  end

  # Signal that the user is going to be removing walls
  def wall_clicked?
    inputs.mouse.down && mouse_inside_a_wall?
  end

  # Signal that the user is going to be adding walls
  def grid_clicked?
    inputs.mouse.down && mouse_inside_grid?
  end

  # Returns whether the mouse is inside of a wall
  # Part of the condition that checks whether the user is removing a wall
  def mouse_inside_a_wall?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(scale_up([wall.x, wall.y]))
    end

    false
  end

  # Returns whether the mouse is inside of a grid
  # Part of the condition that checks whether the user is adding a wall
  def mouse_inside_grid?
    inputs.mouse.point.inside_rect?(scale_up([0, 0, grid.width, grid.height]))
  end


  # These methods provide handy aliases to colors

  # Light brown
  def unvisited_color
    [221, 212, 213]
  end

  # Black
  def grid_line_color
    [255, 255, 255]
  end

  # Dark Brown
  def visited_color
    [204, 191, 179]
  end

  # Blue
  def frontier_color
    [103, 136, 204]
  end

  # Camo Green
  def wall_color
    [134, 134, 120]
  end

  # Button Background
  def gray
    [190, 190, 190]
  end

  # Button Outline
  def black
    [0, 0, 0]
  end

  # These methods make the code more concise
  def grid
    state.grid
  end

  def buttons
    state.buttons
  end

  def slider
    state.slider
  end
end

# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Breadth First Search tick is called
  $breadth_first_search ||= BreadthFirstSearch.new(args)
  $breadth_first_search.args = args
  $breadth_first_search.tick
end


def reset
  $breadth_first_search = nil
end

Path Finding Algorithms - Detailed Breadth First Search - main.rb

# ./samples/13_path_finding_algorithms/02_detailed_breadth_first_search/app/main.rb
# A visual demonstration of a breadth first search
# Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# An animation that can respond to user input in real time

# A breadth first search expands in all directions one step at a time
# The frontier is a queue of cells to be expanded from
# The visited hash allows quick lookups of cells that have been expanded from
# The walls hash allows quick lookup of whether a cell is a wall

# The breadth first search starts by adding the red star to the frontier array
# and marking it as visited
# Each step a cell is removed from the front of the frontier array (queue)
# Unless the neighbor is a wall or visited, it is added to the frontier array
# The neighbor is then marked as visited

# The frontier is blue
# Visited cells are light brown
# Walls are camo green
# Even when walls are visited, they will maintain their wall color

# This search numbers the order in which new cells are explored
# The next cell from where the search will continue is highlighted yellow
# And the cells that will be considered for expansion are in semi-transparent green

# The star can be moved by clicking and dragging
# Walls can be added and removed by clicking and dragging

class DetailedBreadthFirstSearch
  attr_gtk

  def initialize(args)
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    args.state.grid.width     = 9
    args.state.grid.height    = 4
    args.state.grid.cell_size = 90

    # Stores which step of the animation is being rendered
    # When the user moves the star or messes with the walls,
    # the breadth first search is recalculated up to this step
    args.state.anim_steps = 0

    # At some step the animation will end,
    # and further steps won't change anything (the whole grid will be explored)
    # This step is roughly the grid's width * height
    # When anim_steps equals max_steps no more calculations will occur
    # and the slider will be at the end
    args.state.max_steps  = args.state.grid.width * args.state.grid.height

    # The location of the star and walls of the grid
    # They can be modified to have a different initial grid
    # Walls are stored in a hash for quick look up when doing the search
    args.state.star       = [3, 2]
    args.state.walls      = {}

    # Variables that are used by the breadth first search
    # Storing cells that the search has visited, prevents unnecessary steps
    # Expanding the frontier of the search in order makes the search expand
    # from the center outward
    args.state.visited    = {}
    args.state.frontier   = []
    args.state.cell_numbers = []



    # What the user is currently editing on the grid
    # Possible values are: :none, :slider, :star, :remove_wall, :add_wall

    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    args.state.click_and_drag = :none

    # The x, y, w, h values for the buttons
    # Allow easy movement of the buttons location
    # A centralized location to get values to detect input and draw the buttons
    # Editing these values might mean needing to edit the label offsets
    # which can be found in the appropriate render button methods
    args.state.buttons.left  = [450, 600, 160, 50]
    args.state.buttons.right = [610, 600, 160, 50]

    # The variables below are related to the slider
    # They allow the user to customize them
    # They also give a central location for the render and input methods to get
    # information from
    # x & y are the coordinates of the leftmost part of the slider line
    args.state.slider.x = 400
    args.state.slider.y = 675
    # This is the width of the line
    args.state.slider.w = 360
    # This is the offset for the circle
    # Allows the center of the circle to be on the line,
    # as opposed to the upper right corner
    args.state.slider.offset = 20
    # This is the spacing between each of the notches on the slider
    # Notches are places where the circle can rest on the slider line
    # There needs to be a notch for each step before the maximum number of steps
    args.state.slider.spacing = args.state.slider.w.to_f / args.state.max_steps.to_f
  end

  # This method is called every frame/tick
  # Every tick, the current state of the search is rendered on the screen,
  # User input is processed, and
  def tick
    render
    input
  end

  # This method is called from tick and renders everything every tick
  def render
    render_buttons
    render_slider

    render_background
    render_visited
    render_frontier
    render_walls
    render_star

    render_highlights
    render_cell_numbers
  end

  # The methods below subdivide the task of drawing everything to the screen

  # Draws the buttons that move the search backward or forward
  # These buttons are rendered so the user knows where to click to move the search
  def render_buttons
    render_left_button
    render_right_button
  end

  # Renders the button which steps the search backward
  # Shows the user where to click to move the search backward
  def render_left_button
    # Draws the gray button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.left, gray]
    outputs.borders << [buttons.left, black]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    label_x = buttons.left.x + 05
    label_y = buttons.left.y + 35
    outputs.labels  << [label_x, label_y, "< Step backward"]
  end

  # Renders the button which steps the search forward
  # Shows the user where to click to move the search forward
  def render_right_button
    # Draws the gray button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.right, gray]
    outputs.borders << [buttons.right, black]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    label_x = buttons.right.x + 10
    label_y = buttons.right.y + 35
    outputs.labels  << [label_x, label_y, "Step forward >"]
  end

  # Draws the slider so the user can move it and see the progress of the search
  def render_slider
    # Using primitives hides the line under the white circle of the slider
    # Draws the line
    outputs.primitives << [slider.x, slider.y, slider.x + slider.w, slider.y].line
    # The circle needs to be offset so that the center of the circle
    # overlaps the line instead of the upper right corner of the circle
    # The circle's x value is also moved based on the current seach step
    circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    outputs.primitives << [circle_rect, 'circle-white.png'].sprite
  end

  # Draws what the grid looks like with nothing on it
  # Which is a bunch of unvisited cells
  # Drawn first so other things can draw on top of it
  def render_background
    render_unvisited

    # The grid lines make the cells appear separate
    render_grid_lines
  end

  # Draws a rectangle the size of the entire grid to represent unvisited cells
  # Unvisited cells are the default cell
  def render_unvisited
    background = [0, 0, grid.width, grid.height]
    outputs.solids << [scale_up(background), unvisited_color]
  end

  # Draws grid lines to show the division of the grid into cells
  def render_grid_lines
    for x in 0..grid.width
      outputs.lines << [scale_up(vertical_line(x)), grid_line_color]
    end

    for y in 0..grid.height
      outputs.lines << [scale_up(horizontal_line(y)), grid_line_color]
    end
  end

  # Easy way to get a vertical line given an index
  def vertical_line column
    [column, 0, column, grid.height]
  end

  # Easy way to get a horizontal line given an index
  def horizontal_line row
    [0, row, grid.width, row]
  end

  # Draws the area that is going to be searched from
  # The frontier is the most outward parts of the search
  def render_frontier
    state.frontier.each do |cell|
      outputs.solids << [scale_up(cell), frontier_color]
    end
  end

  # Draws the walls
  def render_walls
    state.walls.each_key do |wall|
      outputs.solids << [scale_up(wall), wall_color]
    end
  end

  # Renders cells that have been searched in the appropriate color
  def render_visited
    state.visited.each_key do |cell|
      outputs.solids << [scale_up(cell), visited_color]
    end
  end

  # Renders the star
  def render_star
    outputs.sprites << [scale_up(state.star), 'star.png']
  end

  # Cells have a number rendered in them based on when they were explored
  # This is based off of their index in the cell_numbers array
  # Cells are added to this array the same time they are added to the frontier array
  def render_cell_numbers
    state.cell_numbers.each_with_index do |cell, index|
      # Math that approx centers the number in the cell
      label_x = (cell.x * grid.cell_size) + grid.cell_size / 2 - 5
      label_y = (cell.y * grid.cell_size) + (grid.cell_size / 2) + 5

      outputs.labels << [label_x, label_y, (index + 1).to_s]
    end
  end

  # The next frontier to be expanded is highlighted yellow
  # Its adjacent non-wall neighbors have their border highlighted green
  # This is to show the user how the search expands
  def render_highlights
    return if state.frontier.empty?

    # Highlight the next frontier to be expanded yellow
    next_frontier = state.frontier[0]
    outputs.solids << [scale_up(next_frontier), highlighter_yellow]

    # Neighbors have a semi-transparent green layer over them
    # Unless the neighbor is a wall
    adjacent_neighbors(next_frontier).each do |neighbor|
      unless state.walls.has_key?(neighbor)
        outputs.solids << [scale_up(neighbor), highlighter_green, 70]
      end
    end
  end


  # Cell Size is used when rendering to allow the grid to be scaled up or down
  # Cells in the frontier array and visited hash and walls hash are stored as x & y
  # Scaling up cells and lines when rendering allows omitting of width and height
  def scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone

    # If cell is just an x and y coordinate
    if cell.size == 2
      # Add a width and height of 1
      cell << 1
      cell << 1
    end

    # Scale all the values up
    cell.map! { |value| value * grid.cell_size }

    # Returns the scaled up cell
    cell
  end


  # This method processes user input every tick
  # This method allows the user to use the buttons, slider, and edit the grid
  # There are 2 types of input:
  #   Button Input
  #   Click and Drag Input
  #
  #   Button Input is used for the backward step and forward step buttons
  #   Input is detected by mouse up within the bounds of the rect
  #
  #   Click and Drag Input is used for moving the star, adding walls,
  #   removing walls, and the slider
  #
  #   When the mouse is down on the star, the click_and_drag variable is set to :star
  #   While click_and_drag equals :star, the cursor's position is used to calculate the
  #   appropriate drag behavior
  #
  #   When the mouse goes up click_and_drag is set to :none
  #
  #   A variable has to be used because the star has to continue being edited even
  #   when the cursor is no longer over the star
  #
  #   Similar things occur for the other Click and Drag inputs
  def input
    # Processes inputs for the buttons
    input_buttons

    # Detects which if any click and drag input is occurring
    detect_click_and_drag

    # Does the appropriate click and drag input based on the click_and_drag variable
    process_click_and_drag
  end

  # Detects and Process input for each button
  def input_buttons
    input_left_button
    input_right_button
  end

  # Checks if the previous step button is clicked
  # If it is, it pauses the animation and moves the search one step backward
  def input_left_button
    if left_button_clicked?
      unless state.anim_steps == 0
        state.anim_steps -= 1
        recalculate
      end
    end
  end

  # Checks if the next step button is clicked
  # If it is, it pauses the animation and moves the search one step forward
  def input_right_button
    if right_button_clicked?
      unless state.anim_steps == state.max_steps
        state.anim_steps += 1
        # Although normally recalculate would be called here
        # because the right button only moves the search forward
        # We can just do that
        calc
      end
    end
  end

  # Whenever the user edits the grid,
  # The search has to be recalculated upto the current step

  def recalculate
    # Resets the search
    state.frontier = []
    state.visited = {}
    state.cell_numbers = []

    # Moves the animation forward one step at a time
    state.anim_steps.times { calc }
  end


  # Determines what the user is clicking and planning on dragging
  # Click and drag input is initiated by a click on the appropriate item
  # and ended by mouse up
  # Storing the value allows the user to continue the same edit as long as the
  # mouse left click is held
  def detect_click_and_drag
    if inputs.mouse.up
      state.click_and_drag = :none
    elsif star_clicked?
      state.click_and_drag = :star
    elsif wall_clicked?
      state.click_and_drag = :remove_wall
    elsif grid_clicked?
      state.click_and_drag = :add_wall
    elsif slider_clicked?
      state.click_and_drag = :slider
    end
  end

  # Processes input based on what the user is currently dragging
  def process_click_and_drag
    if state.click_and_drag == :slider
      input_slider
    elsif state.click_and_drag == :star
      input_star
    elsif state.click_and_drag == :remove_wall
      input_remove_wall
    elsif state.click_and_drag == :add_wall
      input_add_wall
    end
  end

  # This method is called when the user is dragging the slider
  # It moves the current animation step to the point represented by the slider
  def input_slider
    mouse_x = inputs.mouse.point.x

    # Bounds the mouse_x to the closest x value on the slider line
    mouse_x = slider.x if mouse_x < slider.x
    mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w

    # Sets the current search step to the one represented by the mouse x value
    # The slider's circle moves due to the render_slider method using anim_steps
    state.anim_steps = ((mouse_x - slider.x) / slider.spacing).to_i

    recalculate
  end

  # Moves the star to the grid closest to the mouse
  # Only recalculates the search if the star changes position
  # Called whenever the user is dragging the star
  def input_star
    old_star = state.star.clone
    state.star = cell_closest_to_mouse
    unless old_star == state.star
      recalculate
    end
  end

  # Removes walls that are under the cursor
  def input_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_inside_grid?
      if state.walls.has_key?(cell_closest_to_mouse)
        state.walls.delete(cell_closest_to_mouse)
        recalculate
      end
    end
  end

  # Adds walls at cells under the cursor
  def input_add_wall
    # Adds a wall to the hash
    # We can use the grid closest to mouse, because the cursor is inside the grid
    if mouse_inside_grid?
      unless state.walls.has_key?(cell_closest_to_mouse)
        state.walls[cell_closest_to_mouse] = true
        recalculate
      end
    end
  end

  # This method moves the search forward one step
  # When the animation is playing it is called every tick
  # And called whenever the current step of the animation needs to be recalculated

  # Moves the search forward one step
  # Parameter called_from_tick is true if it is called from the tick method
  # It is false when the search is being recalculated after user editing the grid
  def calc
    # The setup to the search
    # Runs once when the there is no frontier or visited cells
    if state.frontier.empty? && state.visited.empty?
      state.frontier << state.star
      state.visited[state.star] = true
    end

    # A step in the search
    unless state.frontier.empty?
      # Takes the next frontier cell
      new_frontier = state.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless state.visited.has_key?(neighbor) || state.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited
          state.frontier << neighbor
          state.visited[neighbor] = true

          # Also assign them a frontier number
          state.cell_numbers << neighbor
        end
      end
    end
  end


  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors cell
    neighbors = []

    neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1
    neighbors << [cell.x, cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y] unless cell.x == 0

    neighbors
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the grid closest to the mouse helps with this
  def cell_closest_to_mouse
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    [x, y]
  end


  # These methods detect when the buttons are clicked
  def left_button_clicked?
    (inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.left)) || inputs.keyboard.key_up.left
  end

  def right_button_clicked?
    (inputs.mouse.up && inputs.mouse.point.inside_rect?(buttons.right)) || inputs.keyboard.key_up.right
  end

  # Signal that the user is going to be moving the slider
  def slider_clicked?
    circle_x = (slider.x - slider.offset) + (state.anim_steps * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    inputs.mouse.down && inputs.mouse.point.inside_rect?(circle_rect)
  end

  # Signal that the user is going to be moving the star
  def star_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.star))
  end

  # Signal that the user is going to be removing walls
  def wall_clicked?
    inputs.mouse.down && mouse_inside_a_wall?
  end

  # Signal that the user is going to be adding walls
  def grid_clicked?
    inputs.mouse.down && mouse_inside_grid?
  end

  # Returns whether the mouse is inside of a wall
  # Part of the condition that checks whether the user is removing a wall
  def mouse_inside_a_wall?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(scale_up(wall))
    end

    false
  end

  # Returns whether the mouse is inside of a grid
  # Part of the condition that checks whether the user is adding a wall
  def mouse_inside_grid?
    inputs.mouse.point.inside_rect?(scale_up([0, 0, grid.width, grid.height]))
  end

  # These methods provide handy aliases to colors

  # Light brown
  def unvisited_color
    [221, 212, 213]
  end

  # Black
  def grid_line_color
    [255, 255, 255]
  end

  # Dark Brown
  def visited_color
    [204, 191, 179]
  end

  # Blue
  def frontier_color
    [103, 136, 204]
  end

  # Camo Green
  def wall_color
    [134, 134, 120]
  end

  # Next frontier to be expanded
  def highlighter_yellow
    [214, 231, 125]
  end

  # The neighbors of the next frontier to be expanded
  def highlighter_green
    [65, 191, 127]
  end

  # Button background
  def gray
    [190, 190, 190]
  end

  # Button outline
  def black
    [0, 0, 0]
  end

  # These methods make the code more concise
  def grid
    state.grid
  end

  def buttons
    state.buttons
  end

  def slider
    state.slider
  end
end


def tick args
  # Pressing r resets the program
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  $detailed_breadth_first_search ||= DetailedBreadthFirstSearch.new(args)
  $detailed_breadth_first_search.args = args
  $detailed_breadth_first_search.tick
end


def reset
  $detailed_breadth_first_search = nil
end

Path Finding Algorithms - Breadcrumbs - main.rb

# ./samples/13_path_finding_algorithms/03_breadcrumbs/app/main.rb
class Breadcrumbs
  attr_gtk

  # This method is called every frame/tick
  # Every tick, the current state of the search is rendered on the screen,
  # User input is processed, and
  # The next step in the search is calculated
  def tick
    defaults
    # If the grid has not been searched
    if search.came_from.empty?
      calc
      # Calc Path
    end
    render
    input
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 30
    grid.height    ||= 15
    grid.cell_size ||= 40
    grid.rect      ||= [0, 0, grid.width, grid.height]

    # The location of the star and walls of the grid
    # They can be modified to have a different initial grid
    # Walls are stored in a hash for quick look up when doing the search
    grid.star   ||= [2, 8]
    grid.target ||= [10, 5]
    grid.walls  ||= {
      [3, 3] => true,
      [3, 4] => true,
      [3, 5] => true,
      [3, 6] => true,
      [3, 7] => true,
      [3, 8] => true,
      [3, 9] => true,
      [3, 10] => true,
      [3, 11] => true,
      [4, 3] => true,
      [4, 4] => true,
      [4, 5] => true,
      [4, 6] => true,
      [4, 7] => true,
      [4, 8] => true,
      [4, 9] => true,
      [4, 10] => true,
      [4, 11] => true,
      [13, 0] => true,
      [13, 1] => true,
      [13, 2] => true,
      [13, 3] => true,
      [13, 4] => true,
      [13, 5] => true,
      [13, 6] => true,
      [13, 7] => true,
      [13, 8] => true,
      [13, 9] => true,
      [13, 10] => true,
      [14, 0] => true,
      [14, 1] => true,
      [14, 2] => true,
      [14, 3] => true,
      [14, 4] => true,
      [14, 5] => true,
      [14, 6] => true,
      [14, 7] => true,
      [14, 8] => true,
      [14, 9] => true,
      [14, 10] => true,
      [21, 8] => true,
      [21, 9] => true,
      [21, 10] => true,
      [21, 11] => true,
      [21, 12] => true,
      [21, 13] => true,
      [21, 14] => true,
      [22, 8] => true,
      [22, 9] => true,
      [22, 10] => true,
      [22, 11] => true,
      [22, 12] => true,
      [22, 13] => true,
      [22, 14] => true,
      [23, 8] => true,
      [23, 9] => true,
      [24, 8] => true,
      [24, 9] => true,
      [25, 8] => true,
      [25, 9] => true,
    }

    # Variables that are used by the breadth first search
    # Storing cells that the search has visited, prevents unnecessary steps
    # Expanding the frontier of the search in order makes the search expand
    # from the center outward

    # The cells from which the search is to expand
    search.frontier              ||= []
    # A hash of where each cell was expanded from
    # The key is a cell, and the value is the cell it came from
    search.came_from             ||= {}
    # Cells that are part of the path from the target to the star
    search.path                  ||= {}

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.current_input ||= :none
  end

  def calc
    # Setup the search to start from the star
    search.frontier << grid.star
    search.came_from[grid.star] = nil

    # Until there are no more cells to expand from
    until search.frontier.empty?
      # Takes the next frontier cell
      new_frontier = search.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless search.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited in the first grid
          # Unless the target has been visited
          # Add the neighbor to the frontier and remember which cell it came from
          search.frontier << neighbor
          search.came_from[neighbor] = new_frontier
        end
      end
    end
  end


  # Draws everything onto the screen
  def render
    render_background
    # render_heat_map
    render_walls
    # render_path
    # render_labels
    render_arrows
    render_star
    render_target
    unless grid.walls.has_key?(grid.target)
      render_trail
    end
  end

  def render_trail(current_cell=grid.target)
    return if current_cell == grid.star
    parent_cell = search.came_from[current_cell]
    if current_cell && parent_cell
      outputs.lines << [(current_cell.x + 0.5) * grid.cell_size, (current_cell.y + 0.5) * grid.cell_size,
      (parent_cell.x + 0.5) * grid.cell_size, (parent_cell.y + 0.5) * grid.cell_size, purple]

    end
    render_trail(parent_cell)
  end

  def render_arrows
    search.came_from.each do |child, parent|
      if parent && child
        arrow_cell = [(child.x + parent.x) / 2, (child.y + parent.y) / 2]
        if parent.x > child.x # If the parent cell is to the right of the child cell
          outputs.sprites << [scale_up(arrow_cell), 'arrow.png', 0] # Point the arrow to the right
        elsif parent.x < child.x # If the parent cell is to the right of the child cell
          outputs.sprites << [scale_up(arrow_cell), 'arrow.png', 180] # Point the arrow to the right
        elsif parent.y > child.y # If the parent cell is to the right of the child cell
          outputs.sprites << [scale_up(arrow_cell), 'arrow.png', 90] # Point the arrow to the right
        elsif parent.y < child.y # If the parent cell is to the right of the child cell
          outputs.sprites << [scale_up(arrow_cell), 'arrow.png', 270] # Point the arrow to the right
        end
      end
    end
  end

  # The methods below subdivide the task of drawing everything to the screen

  # Draws what the grid looks like with nothing on it
  def render_background
    render_unvisited
    render_grid_lines
  end

  # Draws both grids
  def render_unvisited
    outputs.solids << [scale_up(grid.rect), unvisited_color]
  end

  # Draws grid lines to show the division of the grid into cells
  def render_grid_lines
    for x in 0..grid.width
      outputs.lines << vertical_line(x)
    end

    for y in 0..grid.height
      outputs.lines << horizontal_line(y)
    end
  end

  # Easy way to draw vertical lines given an index
  def vertical_line column
    scale_up([column, 0, column, grid.height])
  end

  # Easy way to draw horizontal lines given an index
  def horizontal_line row
    scale_up([0, row, grid.width, row])
  end

  # Draws the walls on both grids
  def render_walls
    grid.walls.each_key do |wall|
      outputs.solids << [scale_up(wall), wall_color]
    end
  end

  # Renders the star on both grids
  def render_star
    outputs.sprites << [scale_up(grid.star), 'star.png']
  end

  # Renders the target on both grids
  def render_target
    outputs.sprites << [scale_up(grid.target), 'target.png']
  end

  # Labels the grids
  def render_labels
    outputs.labels << [200, 625, "Without early exit"]
  end

  # Renders the path based off of the search.path hash
  def render_path
    # If the star and target are disconnected there will only be one path
    # The path should not render in that case
    unless search.path.size == 1
      search.path.each_key do | cell |
        # Renders path on both grids
        outputs.solids << [scale_up(cell), path_color]
      end
    end
  end

  # Calculates the path from the target to the star after the search is over
  # Relies on the came_from hash
  # Fills the search.path hash, which is later rendered on screen
  def calc_path
    endpoint = grid.target
    while endpoint
      search.path[endpoint] = true
      endpoint = search.came_from[endpoint]
    end
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  def scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone

    # If cell is just an x and y coordinate
    if cell.size == 2
      # Add a width and height of 1
      cell << 1
      cell << 1
    end

    # Scale all the values up
    cell.map! { |value| value * grid.cell_size }

    # Returns the scaled up cell
    cell
  end

  # This method processes user input every tick
  # Any method with "1" is related to the first grid
  # Any method with "2" is related to the second grid
  def input
    # The program has to remember that the user is dragging an object
    # even when the mouse is no longer over that object
    # So detecting input and processing input is separate
    # detect_input
    # process_input
    if inputs.mouse.up
      state.current_input = :none
    elsif star_clicked?
      state.current_input = :star
    end

    if mouse_inside_grid?
      unless grid.target == cell_closest_to_mouse
        grid.target = cell_closest_to_mouse
      end
      if state.current_input == :star
        unless grid.star == cell_closest_to_mouse
          grid.star = cell_closest_to_mouse
        end
      end
    end
  end

  # Determines what the user is editing and stores the value
  # Storing the value allows the user to continue the same edit as long as the
  # mouse left click is held
  def detect_input
    # When the mouse is up, nothing is being edited
    if inputs.mouse.up
      state.current_input = :none
    # When the star in the no second grid is clicked
    elsif star_clicked?
      state.current_input = :star
    # When the target in the no second grid is clicked
    elsif target_clicked?
      state.current_input = :target
    # When a wall in the first grid is clicked
    elsif wall_clicked?
      state.current_input = :remove_wall
    # When the first grid is clicked
    elsif grid_clicked?
      state.current_input = :add_wall
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_input
    if state.current_input == :star
      input_star
    elsif state.current_input == :target
      input_target
    elsif state.current_input == :remove_wall
      input_remove_wall
    elsif state.current_input == :add_wall
      input_add_wall
    end
  end

  # Moves the star to the cell closest to the mouse in the first grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star
    old_star = grid.star.clone
    grid.star = cell_closest_to_mouse
    unless old_star == grid.star
      reset_search
    end
  end

  # Moves the target to the grid closest to the mouse in the first grid
  # Only reset_searchs the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def input_target
    old_target = grid.target.clone
    grid.target = cell_closest_to_mouse
    unless old_target == grid.target
      reset_search
    end
  end

  # Removes walls in the first grid that are under the cursor
  def input_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_inside_grid?
      if grid.walls.has_key?(cell_closest_to_mouse)
        grid.walls.delete(cell_closest_to_mouse)
        reset_search
      end
    end
  end

  # Adds a wall in the first grid in the cell the mouse is over
  def input_add_wall
    if mouse_inside_grid?
      unless grid.walls.has_key?(cell_closest_to_mouse)
        grid.walls[cell_closest_to_mouse] = true
        reset_search
      end
    end
  end


  # Whenever the user edits the grid,
  # The search has to be reset_searchd upto the current step
  # with the current grid as the initial state of the grid
  def reset_search
    # Reset_Searchs the search
    search.frontier  = []
    search.came_from = {}
    search.path      = {}
  end


  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    # Gets all the valid neighbors into the array
    # From southern neighbor, clockwise
    neighbors << [cell.x, cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y] unless cell.x == 0
    neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1

    # Sorts the neighbors so the rendered path is a zigzag path
    # Cells in a diagonal direction are given priority
    # Comment this line to see the difference
    neighbors = neighbors.sort_by { |neighbor_x, neighbor_y|  proximity_to_star(neighbor_x, neighbor_y) }

    neighbors
  end

  # Finds the vertical and horizontal distance of a cell from the star
  # and returns the larger value
  # This method is used to have a zigzag pattern in the rendered path
  # A cell that is [5, 5] from the star,
  # is explored before over a cell that is [0, 7] away.
  # So, if possible, the search tries to go diagonal (zigzag) first
  def proximity_to_star(x, y)
    distance_x = (grid.star.x - x).abs
    distance_y = (grid.star.y - y).abs

    if distance_x > distance_y
      return distance_x
    else
      return distance_y
    end
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def cell_closest_to_mouse
    # Closest cell to the mouse in the first grid
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # Signal that the user is going to be moving the star from the first grid
  def star_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(grid.star))
  end

  # Signal that the user is going to be moving the target from the first grid
  def target_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(grid.target))
  end

  # Signal that the user is going to be adding walls from the first grid
  def grid_clicked?
    inputs.mouse.down && mouse_inside_grid?
  end

  # Returns whether the mouse is inside of the first grid
  # Part of the condition that checks whether the user is adding a wall
  def mouse_inside_grid?
    inputs.mouse.point.inside_rect?(scale_up(grid.rect))
  end

  # These methods provide handy aliases to colors

  # Light brown
  def unvisited_color
    [221, 212, 213]
    # [255, 255, 255]
  end

  # Camo Green
  def wall_color
    [134, 134, 120]
  end

  # Pastel White
  def path_color
    [231, 230, 228]
  end

  def red
    [255, 0, 0]
  end

  def purple
    [149, 64, 191]
  end

  # Makes code more concise
  def grid
    state.grid
  end

  def search
    state.search
  end
end

# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Breadth First Search tick is called
  $breadcrumbs ||= Breadcrumbs.new(args)
  $breadcrumbs.args = args
  $breadcrumbs.tick
end


def reset
  $breadcrumbs = nil
end

 #  # Representation of how far away visited cells are from the star
 #  # Replaces the render_visited method
 #  # Visually demonstrates the effectiveness of early exit for pathfinding
 #  def render_heat_map
 #    # THIS CODE NEEDS SOME FIXING DUE TO REFACTORING
 #    search.came_from.each_key do | cell |
 #      distance = (grid.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
 #      max_distance = grid.width + grid.height
 #      alpha = 255.to_i * distance.to_i / max_distance.to_i
 #      outputs.solids << [scale_up(visited_cell), red, alpha]
 #      # outputs.solids << [early_exit_scale_up(visited_cell), red, alpha]
 #    end
 #  end

Path Finding Algorithms - Early Exit - main.rb

# ./samples/13_path_finding_algorithms/04_early_exit/app/main.rb
# Comparison of a breadth first search with and without early exit
# Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# Demonstrates the exploration difference caused by early exit
# Also demonstrates how breadth first search is used for path generation

# The left grid is a breadth first search without early exit
# The right grid is a breadth first search with early exit
# The red squares represent how far the search expanded
# The darker the red, the farther the search proceeded
# Comparison of the heat map reveals how much searching can be saved by early exit
# The white path shows path generation via breadth first search
class EarlyExitBreadthFirstSearch
  attr_gtk

  # This method is called every frame/tick
  # Every tick, the current state of the search is rendered on the screen,
  # User input is processed, and
  # The next step in the search is calculated
  def tick
    defaults
    # If the grid has not been searched
    if state.visited.empty?
      # Complete the search
      state.max_steps.times { step }
      # And calculate the path
      calc_path
    end
    render
    input
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 15
    grid.height    ||= 15
    grid.cell_size ||= 40
    grid.rect      ||= [0, 0, grid.width, grid.height]

    # At some step the animation will end,
    # and further steps won't change anything (the whole grid.widthill be explored)
    # This step is roughly the grid's width * height
    # When anim_steps equals max_steps no more calculations will occur
    # and the slider will be at the end
    state.max_steps  ||= args.state.grid.width * args.state.grid.height

    # The location of the star and walls of the grid
    # They can be modified to have a different initial grid
    # Walls are stored in a hash for quick look up when doing the search
    state.star   ||= [2, 8]
    state.target ||= [10, 5]
    state.walls  ||= {}

    # Variables that are used by the breadth first search
    # Storing cells that the search has visited, prevents unnecessary steps
    # Expanding the frontier of the search in order makes the search expand
    # from the center outward

    # Visited cells in the first grid
    state.visited               ||= {}
    # Visited cells in the second grid
    state.early_exit_visited    ||= {}
    # The cells from which the search is to expand
    state.frontier              ||= []
    # A hash of where each cell was expanded from
    # The key is a cell, and the value is the cell it came from
    state.came_from             ||= {}
    # Cells that are part of the path from the target to the star
    state.path                  ||= {}

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.current_input ||= :none
  end

  # Draws everything onto the screen
  def render
    render_background
    render_heat_map
    render_walls
    render_path
    render_star
    render_target
    render_labels
  end

  # The methods below subdivide the task of drawing everything to the screen

  # Draws what the grid looks like with nothing on it
  def render_background
    render_unvisited
    render_grid_lines
  end

  # Draws both grids
  def render_unvisited
    outputs.solids << [scale_up(grid.rect), unvisited_color]
    outputs.solids << [early_exit_scale_up(grid.rect), unvisited_color]
  end

  # Draws grid lines to show the division of the grid into cells
  def render_grid_lines
    for x in 0..grid.width
      outputs.lines << vertical_line(x)
      outputs.lines << early_exit_vertical_line(x)
    end

    for y in 0..grid.height
      outputs.lines << horizontal_line(y)
      outputs.lines << early_exit_horizontal_line(y)
    end
  end

  # Easy way to draw vertical lines given an index
  def vertical_line column
    scale_up([column, 0, column, grid.height])
  end

  # Easy way to draw horizontal lines given an index
  def horizontal_line row
    scale_up([0, row, grid.width, row])
  end

  # Easy way to draw vertical lines given an index
  def early_exit_vertical_line column
    scale_up([column + grid.width + 1, 0, column + grid.width + 1, grid.height])
  end

  # Easy way to draw horizontal lines given an index
  def early_exit_horizontal_line row
    scale_up([grid.width + 1, row, grid.width + grid.width + 1, row])
  end

  # Draws the walls on both grids
  def render_walls
    state.walls.each_key do |wall|
      outputs.solids << [scale_up(wall), wall_color]
      outputs.solids << [early_exit_scale_up(wall), wall_color]
    end
  end

  # Renders the star on both grids
  def render_star
    outputs.sprites << [scale_up(state.star), 'star.png']
    outputs.sprites << [early_exit_scale_up(state.star), 'star.png']
  end

  # Renders the target on both grids
  def render_target
    outputs.sprites << [scale_up(state.target), 'target.png']
    outputs.sprites << [early_exit_scale_up(state.target), 'target.png']
  end

  # Labels the grids
  def render_labels
    outputs.labels << [200, 625, "Without early exit"]
    outputs.labels << [875, 625, "With early exit"]
  end

  # Renders the path based off of the state.path hash
  def render_path
    # If the star and target are disconnected there will only be one path
    # The path should not render in that case
    unless state.path.size == 1
      state.path.each_key do | cell |
        # Renders path on both grids
        outputs.solids << [scale_up(cell), path_color]
        outputs.solids << [early_exit_scale_up(cell), path_color]
      end
    end
  end

  # Calculates the path from the target to the star after the search is over
  # Relies on the came_from hash
  # Fills the state.path hash, which is later rendered on screen
  def calc_path
    endpoint = state.target
    while endpoint
      state.path[endpoint] = true
      endpoint = state.came_from[endpoint]
    end
  end

  # Representation of how far away visited cells are from the star
  # Replaces the render_visited method
  # Visually demonstrates the effectiveness of early exit for pathfinding
  def render_heat_map
    state.visited.each_key do | visited_cell |
      distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
      max_distance = grid.width + grid.height
      alpha = 255.to_i * distance.to_i / max_distance.to_i
      outputs.solids << [scale_up(visited_cell), red, alpha]
      # outputs.solids << [early_exit_scale_up(visited_cell), red, alpha]
    end

    state.early_exit_visited.each_key do | visited_cell |
      distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
      max_distance = grid.width + grid.height
      alpha = 255.to_i * distance.to_i / max_distance.to_i
      outputs.solids << [early_exit_scale_up(visited_cell), red, alpha]
    end
  end

  # Translates the given cell grid.width + 1 to the right and then scales up
  # Used to draw cells for the second grid
  # This method does not work for lines,
  # so separate methods exist for the grid lines
  def early_exit_scale_up(cell)
    cell_clone = cell.clone
    cell_clone.x += grid.width + 1
    scale_up(cell_clone)
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  def scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone

    # If cell is just an x and y coordinate
    if cell.size == 2
      # Add a width and height of 1
      cell << 1
      cell << 1
    end

    # Scale all the values up
    cell.map! { |value| value * grid.cell_size }

    # Returns the scaled up cell
    cell
  end

  # This method processes user input every tick
  # Any method with "1" is related to the first grid
  # Any method with "2" is related to the second grid
  def input
    # The program has to remember that the user is dragging an object
    # even when the mouse is no longer over that object
    # So detecting input and processing input is separate
    detect_input
    process_input
  end

  # Determines what the user is editing and stores the value
  # Storing the value allows the user to continue the same edit as long as the
  # mouse left click is held
  def detect_input
    # When the mouse is up, nothing is being edited
    if inputs.mouse.up
      state.current_input = :none
    # When the star in the no second grid is clicked
    elsif star_clicked?
      state.current_input = :star
    # When the star in the second grid is clicked
    elsif star2_clicked?
      state.current_input = :star2
    # When the target in the no second grid is clicked
    elsif target_clicked?
      state.current_input = :target
    # When the target in the second grid is clicked
    elsif target2_clicked?
      state.current_input = :target2
    # When a wall in the first grid is clicked
    elsif wall_clicked?
      state.current_input = :remove_wall
    # When a wall in the second grid is clicked
    elsif wall2_clicked?
      state.current_input = :remove_wall2
    # When the first grid is clicked
    elsif grid_clicked?
      state.current_input = :add_wall
    # When the second grid is clicked
    elsif grid2_clicked?
      state.current_input = :add_wall2
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_input
    if state.current_input == :star
      input_star
    elsif state.current_input == :star2
      input_star2
    elsif state.current_input == :target
      input_target
    elsif state.current_input == :target2
      input_target2
    elsif state.current_input == :remove_wall
      input_remove_wall
    elsif state.current_input == :remove_wall2
      input_remove_wall2
    elsif state.current_input == :add_wall
      input_add_wall
    elsif state.current_input == :add_wall2
      input_add_wall2
    end
  end

  # Moves the star to the cell closest to the mouse in the first grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star
    old_star = state.star.clone
    state.star = cell_closest_to_mouse
    unless old_star == state.star
      reset_search
    end
  end

  # Moves the star to the cell closest to the mouse in the second grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star2
    old_star = state.star.clone
    state.star = cell_closest_to_mouse2
    unless old_star == state.star
      reset_search
    end
  end

  # Moves the target to the grid closest to the mouse in the first grid
  # Only reset_searchs the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def input_target
    old_target = state.target.clone
    state.target = cell_closest_to_mouse
    unless old_target == state.target
      reset_search
    end
  end

  # Moves the target to the cell closest to the mouse in the second grid
  # Only reset_searchs the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def input_target2
    old_target = state.target.clone
    state.target = cell_closest_to_mouse2
    unless old_target == state.target
      reset_search
    end
  end

  # Removes walls in the first grid that are under the cursor
  def input_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_inside_grid?
      if state.walls.has_key?(cell_closest_to_mouse)
        state.walls.delete(cell_closest_to_mouse)
        reset_search
      end
    end
  end

  # Removes walls in the second grid that are under the cursor
  def input_remove_wall2
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_inside_grid2?
      if state.walls.has_key?(cell_closest_to_mouse2)
        state.walls.delete(cell_closest_to_mouse2)
        reset_search
      end
    end
  end

  # Adds a wall in the first grid in the cell the mouse is over
  def input_add_wall
    if mouse_inside_grid?
      unless state.walls.has_key?(cell_closest_to_mouse)
        state.walls[cell_closest_to_mouse] = true
        reset_search
      end
    end
  end


  # Adds a wall in the second grid in the cell the mouse is over
  def input_add_wall2
    if mouse_inside_grid2?
      unless state.walls.has_key?(cell_closest_to_mouse2)
        state.walls[cell_closest_to_mouse2] = true
        reset_search
      end
    end
  end

  # Whenever the user edits the grid,
  # The search has to be reset_searchd upto the current step
  # with the current grid as the initial state of the grid
  def reset_search
    # Reset_Searchs the search
    state.frontier  = []
    state.visited   = {}
    state.early_exit_visited   = {}
    state.came_from = {}
    state.path      = {}
  end

  # Moves the search forward one step
  def step
    # The setup to the search
    # Runs once when there are no visited cells
    if state.visited.empty?
      state.visited[state.star] = true
      state.early_exit_visited[state.star] = true
      state.frontier << state.star
      state.came_from[state.star] = nil
    end

    # A step in the search
    unless state.frontier.empty?
      # Takes the next frontier cell
      new_frontier = state.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless state.visited.has_key?(neighbor) || state.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited in the first grid
          state.visited[neighbor] = true
          # Unless the target has been visited
          unless state.visited.has_key?(state.target)
            # Mark the neighbor as visited in the second grid as well
            state.early_exit_visited[neighbor] = true
          end

          # Add the neighbor to the frontier and remember which cell it came from
          state.frontier << neighbor
          state.came_from[neighbor] = new_frontier
        end
      end
    end
  end


  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    # Gets all the valid neighbors into the array
    # From southern neighbor, clockwise
    neighbors << [cell.x, cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y] unless cell.x == 0
    neighbors << [cell.x, cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y] unless cell.x == grid.width - 1

    # Sorts the neighbors so the rendered path is a zigzag path
    # Cells in a diagonal direction are given priority
    # Comment this line to see the difference
    neighbors = neighbors.sort_by { |neighbor_x, neighbor_y|  proximity_to_star(neighbor_x, neighbor_y) }

    neighbors
  end

  # Finds the vertical and horizontal distance of a cell from the star
  # and returns the larger value
  # This method is used to have a zigzag pattern in the rendered path
  # A cell that is [5, 5] from the star,
  # is explored before over a cell that is [0, 7] away.
  # So, if possible, the search tries to go diagonal (zigzag) first
  def proximity_to_star(x, y)
    distance_x = (state.star.x - x).abs
    distance_y = (state.star.y - y).abs

    if distance_x > distance_y
      return distance_x
    else
      return distance_y
    end
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def cell_closest_to_mouse
    # Closest cell to the mouse in the first grid
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse in the second grid helps with this
  def cell_closest_to_mouse2
    # Closest cell grid to the mouse in the second
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Translate the cell to the first grid
    x -= grid.width + 1
    # Bound x and y to the first grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # Signal that the user is going to be moving the star from the first grid
  def star_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.star))
  end

  # Signal that the user is going to be moving the star from the second grid
  def star2_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(early_exit_scale_up(state.star))
  end

  # Signal that the user is going to be moving the target from the first grid
  def target_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(scale_up(state.target))
  end

  # Signal that the user is going to be moving the target from the second grid
  def target2_clicked?
    inputs.mouse.down && inputs.mouse.point.inside_rect?(early_exit_scale_up(state.target))
  end

  # Signal that the user is going to be removing walls from the first grid
  def wall_clicked?
    inputs.mouse.down && mouse_inside_wall?
  end

  # Signal that the user is going to be removing walls from the second grid
  def wall2_clicked?
    inputs.mouse.down && mouse_inside_wall2?
  end

  # Signal that the user is going to be adding walls from the first grid
  def grid_clicked?
    inputs.mouse.down && mouse_inside_grid?
  end

  # Signal that the user is going to be adding walls from the second grid
  def grid2_clicked?
    inputs.mouse.down && mouse_inside_grid2?
  end

  # Returns whether the mouse is inside of a wall in the first grid
  # Part of the condition that checks whether the user is removing a wall
  def mouse_inside_wall?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(scale_up(wall))
    end

    false
  end

  # Returns whether the mouse is inside of a wall in the second grid
  # Part of the condition that checks whether the user is removing a wall
  def mouse_inside_wall2?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(early_exit_scale_up(wall))
    end

    false
  end

  # Returns whether the mouse is inside of the first grid
  # Part of the condition that checks whether the user is adding a wall
  def mouse_inside_grid?
    inputs.mouse.point.inside_rect?(scale_up(grid.rect))
  end

  # Returns whether the mouse is inside of the second grid
  # Part of the condition that checks whether the user is adding a wall
  def mouse_inside_grid2?
    inputs.mouse.point.inside_rect?(early_exit_scale_up(grid.rect))
  end

  # These methods provide handy aliases to colors

  # Light brown
  def unvisited_color
    [221, 212, 213]
  end

  # Camo Green
  def wall_color
    [134, 134, 120]
  end

  # Pastel White
  def path_color
    [231, 230, 228]
  end

  def red
    [255, 0, 0]
  end

  # Makes code more concise
  def grid
    state.grid
  end
end

# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Breadth First Search tick is called
  $early_exit_breadth_first_search ||= EarlyExitBreadthFirstSearch.new(args)
  $early_exit_breadth_first_search.args = args
  $early_exit_breadth_first_search.tick
end


def reset
  $early_exit_breadth_first_search = nil
end

Path Finding Algorithms - Dijkstra - main.rb

# ./samples/13_path_finding_algorithms/05_dijkstra/app/main.rb
# Demonstrates how Dijkstra's Algorithm allows movement costs to be considered

# Inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# The first grid is a breadth first search with an early exit.
# It shows a heat map of all the cells that were visited by the search and their relative distance.

# The second grid is an implementation of Dijkstra's algorithm.
# Light green cells have 5 times the movement cost of regular cells.
# The heat map will darken based on movement cost.

# Dark green cells are walls, and the search cannot go through them.
class Movement_Costs
  attr_gtk

  # This method is called every frame/tick
  # Every tick, the current state of the search is rendered on the screen,
  # User input is processed, and
  # The next step in the search is calculated
  def tick
    defaults
    render
    input
    calc
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 10
    grid.height    ||= 10
    grid.cell_size ||= 60
    grid.rect      ||= [0, 0, grid.width, grid.height]

    # The location of the star and walls of the grid
    # They can be modified to have a different initial grid
    # Walls are stored in a hash for quick look up when doing the search
    state.star   ||= [1, 5]
    state.target ||= [8, 4]
    state.walls  ||= {[1, 1] => true, [2, 1] => true, [3, 1] => true, [1, 2] => true, [2, 2] => true, [3, 2] => true}
    state.hills  ||= {
      [4, 1] => true,
      [5, 1] => true,
      [4, 2] => true,
      [5, 2] => true,
      [6, 2] => true,
      [4, 3] => true,
      [5, 3] => true,
      [6, 3] => true,
      [3, 4] => true,
      [4, 4] => true,
      [5, 4] => true,
      [6, 4] => true,
      [7, 4] => true,
      [3, 5] => true,
      [4, 5] => true,
      [5, 5] => true,
      [6, 5] => true,
      [7, 5] => true,
      [4, 6] => true,
      [5, 6] => true,
      [6, 6] => true,
      [7, 6] => true,
      [4, 7] => true,
      [5, 7] => true,
      [6, 7] => true,
      [4, 8] => true,
      [5, 8] => true,
    }

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.user_input ||= :none

    # Values that are used for the breadth first search
    # Keeping track of what cells were visited prevents counting cells multiple times
    breadth_first_search.visited    ||= {}
    # The cells from which the breadth first search will expand
    breadth_first_search.frontier   ||= []
    # Keeps track of which cell all cells were searched from
    # Used to recreate the path from the target to the star
    breadth_first_search.came_from  ||= {}

    # Keeps track of the movement cost so far to be at a cell
    # Allows the costs of new cells to be quickly calculated
    # Also doubles as a way to check if cells have already been visited
    dijkstra_search.cost_so_far ||= {}
    # The cells from which the Dijkstra search will expand
    dijkstra_search.frontier    ||= []
    # Keeps track of which cell all cells were searched from
    # Used to recreate the path from the target to the star
    dijkstra_search.came_from   ||= {}
  end

  # Draws everything onto the screen
  def render
    render_background

    render_heat_maps

    render_star
    render_target
    render_hills
    render_walls

    render_paths
  end
  # The methods below subdivide the task of drawing everything to the screen

  # Draws what the grid looks like with nothing on it
  def render_background
    render_unvisited
    render_grid_lines
    render_labels
  end

  # Draws two rectangles the size of the grid in the default cell color
  # Used as part of the background
  def render_unvisited
    outputs.solids << [scale_up(grid.rect), unvisited_color]
    outputs.solids << [move_and_scale_up(grid.rect), unvisited_color]
  end

  # Draws grid lines to show the division of the grid into cells
  def render_grid_lines
    for x in 0..grid.width
      outputs.lines << vertical_line(x)
      outputs.lines << shifted_vertical_line(x)
    end

    for y in 0..grid.height
      outputs.lines << horizontal_line(y)
      outputs.lines << shifted_horizontal_line(y)
    end
  end

  # Easy way to draw vertical lines given an index for the first grid
  def vertical_line column
    scale_up([column, 0, column, grid.height])
  end

  # Easy way to draw horizontal lines given an index for the second grid
  def horizontal_line row
    scale_up([0, row, grid.width, row])
  end

  # Easy way to draw vertical lines given an index for the first grid
  def shifted_vertical_line column
    scale_up([column + grid.width + 1, 0, column + grid.width + 1, grid.height])
  end

  # Easy way to draw horizontal lines given an index for the second grid
  def shifted_horizontal_line row
    scale_up([grid.width + 1, row, grid.width + grid.width + 1, row])
  end

  # Labels the grids
  def render_labels
    outputs.labels << [175, 650, "Number of steps", 3]
    outputs.labels << [925, 650, "Distance", 3]
  end

  def render_paths
    render_breadth_first_search_path
    render_dijkstra_path
  end

  def render_heat_maps
    render_breadth_first_search_heat_map
    render_dijkstra_heat_map
  end

  # Renders the breadth first search on the first grid
  def render_breadth_first_search
  end

  # This heat map shows the cells explored by the breadth first search and how far they are from the star.
  def render_breadth_first_search_heat_map
    # For each cell explored
    breadth_first_search.visited.each_key do | visited_cell |
      # Find its distance from the star
      distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
      max_distance = grid.width + grid.height
      # Get it as a percent of the maximum distance and scale to 255 for use as an alpha value
      alpha = 255.to_i * distance.to_i / max_distance.to_i
      outputs.solids << [scale_up(visited_cell), red, alpha]
    end
  end

  def render_breadth_first_search_path
    # If the search found the target
    if breadth_first_search.visited.has_key?(state.target)
      # Start from the target
      endpoint = state.target
      # And the cell it came from
      next_endpoint = breadth_first_search.came_from[endpoint]
      while endpoint and next_endpoint
        # Draw a path between these two cells
        path = get_path_between(endpoint, next_endpoint)
        outputs.solids << [scale_up(path), path_color]
        # And get the next pair of cells
        endpoint = next_endpoint
        next_endpoint = breadth_first_search.came_from[endpoint]
        # Continue till there are no more cells
      end
    end
  end

  # Renders the Dijkstra search on the second grid
  def render_dijkstra
  end

  def render_dijkstra_heat_map
    dijkstra_search.cost_so_far.each do |visited_cell, cost|
      max_cost = (grid.width + grid.height) #* 5
      alpha = 255.to_i * cost.to_i / max_cost.to_i
      outputs.solids << [move_and_scale_up(visited_cell), red, alpha]
    end
  end

  def render_dijkstra_path
    # If the search found the target
    if dijkstra_search.came_from.has_key?(state.target)
      # Get the target and the cell it came from
      endpoint = state.target
      next_endpoint = dijkstra_search.came_from[endpoint]
      while endpoint and next_endpoint
        # Draw a path between them
        path = get_path_between(endpoint, next_endpoint)
        outputs.solids << [move_and_scale_up(path), path_color]

        # Shift one cell down the path
        endpoint = next_endpoint
        next_endpoint = dijkstra_search.came_from[endpoint]

        # Repeat till the end of the path
      end
    end
  end

  # Renders the star on both grids
  def render_star
    outputs.sprites << [scale_up(state.star), 'star.png']
    outputs.sprites << [move_and_scale_up(state.star), 'star.png']
  end

  # Renders the target on both grids
  def render_target
    outputs.sprites << [scale_up(state.target), 'target.png']
    outputs.sprites << [move_and_scale_up(state.target), 'target.png']
  end

  def render_hills
    state.hills.each_key do |hill|
      outputs.solids << [scale_up(hill), hill_color]
      outputs.solids << [move_and_scale_up(hill), hill_color]
    end
  end

  # Draws the walls on both grids
  def render_walls
    state.walls.each_key do |wall|
      outputs.solids << [scale_up(wall), wall_color]
      outputs.solids << [move_and_scale_up(wall), wall_color]
    end
  end

  def get_path_between(cell_one, cell_two)
    path = nil
    if cell_one.x == cell_two.x
      if cell_one.y < cell_two.y
        path = [cell_one.x + 0.3, cell_one.y + 0.3, 0.4, 1.4]
      else
        path = [cell_two.x + 0.3, cell_two.y + 0.3, 0.4, 1.4]
      end
    else
      if cell_one.x < cell_two.x
        path = [cell_one.x + 0.3, cell_one.y + 0.3, 1.4, 0.4]
      else
        path = [cell_two.x + 0.3, cell_two.y + 0.3, 1.4, 0.4]
      end
    end
    path
  end

  # Representation of how far away visited cells are from the star
  # Replaces the render_visited method
  # Visually demonstrates the effectiveness of early exit for pathfinding
  def render_breadth_first_search_heat_map
    breadth_first_search.visited.each_key do | visited_cell |
      distance = (state.star.x - visited_cell.x).abs + (state.star.y - visited_cell.y).abs
      max_distance = grid.width + grid.height
      alpha = 255.to_i * distance.to_i / max_distance.to_i
      outputs.solids << [scale_up(visited_cell), red, alpha]
    end
  end

  # Translates the given cell grid.width + 1 to the right and then scales up
  # Used to draw cells for the second grid
  # This method does not work for lines,
  # so separate methods exist for the grid lines
  def move_and_scale_up(cell)
    cell_clone = cell.clone
    cell_clone.x += grid.width + 1
    scale_up(cell_clone)
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  def scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone

    # If cell is just an x and y coordinate
    if cell.size == 2
      # Add a width and height of 1
      cell << 1
      cell << 1
    end

    # Scale all the values up
    cell.map! { |value| value * grid.cell_size }

    # Returns the scaled up cell
    cell
  end

  # Handles user input every tick so the grid can be edited
  # Separate input detection and processing is needed
  # For example: Adding walls is started by clicking down on a hill,
  # but the mouse doesn't need to remain over hills to add walls
  def input
    # If the mouse was lifted this tick
    if inputs.mouse.up
      # Set current input to none
      state.user_input = :none
    end

    # If the mouse was clicked this tick
    if inputs.mouse.down
      # Determine what the user is editing and edit the state.user_input variable
      determine_input
    end

    # Process user input based on user_input variable and current mouse position
    process_input
  end

  # Determines what the user is editing and stores the value
  # This method is called the tick the mouse is clicked
  # Storing the value allows the user to continue the same edit as long as the
  # mouse left click is held
  def determine_input
    # If the mouse is over the star in the first grid
    if mouse_over_star?
      # The user is editing the star from the first grid
      state.user_input = :star
    # If the mouse is over the star in the second grid
    elsif mouse_over_star2?
      # The user is editing the star from the second grid
      state.user_input = :star2
    # If the mouse is over the target in the first grid
    elsif mouse_over_target?
      # The user is editing the target from the first grid
      state.user_input = :target
    # If the mouse is over the target in the second grid
    elsif mouse_over_target2?
      # The user is editing the target from the second grid
      state.user_input = :target2
    # If the mouse is over a wall in the first grid
    elsif mouse_over_wall?
      # The user is removing a wall from the first grid
      state.user_input = :remove_wall
    # If the mouse is over a wall in the second grid
    elsif mouse_over_wall2?
      # The user is removing a wall from the second grid
      state.user_input = :remove_wall2
    # If the mouse is over a hill in the first grid
    elsif mouse_over_hill?
      # The user is adding a wall from the first grid
      state.user_input = :add_wall
    # If the mouse is over a hill in the second grid
    elsif mouse_over_hill2?
      # The user is adding a wall from the second grid
      state.user_input = :add_wall2
    # If the mouse is over the first grid
    elsif mouse_over_grid?
      # The user is adding a hill from the first grid
      state.user_input = :add_hill
    # If the mouse is over the second grid
    elsif mouse_over_grid2?
      # The user is adding a hill from the second grid
      state.user_input = :add_hill2
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_input
    if state.user_input == :star
      input_star
    elsif state.user_input == :star2
      input_star2
    elsif state.user_input == :target
      input_target
    elsif state.user_input == :target2
      input_target2
    elsif state.user_input == :remove_wall
      input_remove_wall
    elsif state.user_input == :remove_wall2
      input_remove_wall2
    elsif state.user_input == :add_hill
      input_add_hill
    elsif state.user_input == :add_hill2
      input_add_hill2
    elsif state.user_input == :add_wall
      input_add_wall
    elsif state.user_input == :add_wall2
      input_add_wall2
    end
  end

  # Calculates the two searches
  def calc
    # If the searches have not started
    if breadth_first_search.visited.empty?
      # Calculate the two searches
      calc_breadth_first
      calc_dijkstra
    end
  end


  def calc_breadth_first
    # Sets up the Breadth First Search
    breadth_first_search.visited[state.star]   = true
    breadth_first_search.frontier              << state.star
    breadth_first_search.came_from[state.star] = nil

    until breadth_first_search.frontier.empty?
      return if breadth_first_search.visited.has_key?(state.target)
      # A step in the search
      # Takes the next frontier cell
      new_frontier = breadth_first_search.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do | neighbor |
        # That have not been visited and are not walls
        unless breadth_first_search.visited.has_key?(neighbor) || state.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited in the first grid
          breadth_first_search.visited[neighbor] = true
          breadth_first_search.frontier << neighbor
          # Remember which cell the neighbor came from
          breadth_first_search.came_from[neighbor] = new_frontier
        end
      end
    end
  end

  # Calculates the Dijkstra Search from the beginning to the end

  def calc_dijkstra
    # The initial values for the Dijkstra search
    dijkstra_search.frontier                << [state.star, 0]
    dijkstra_search.came_from[state.star]   = nil
    dijkstra_search.cost_so_far[state.star] = 0

    # Until their are no more cells to be explored
    until dijkstra_search.frontier.empty?
      # Get the next cell to be explored from
      # We get the first element of the array which is the cell. The second element is the priority.
      current = dijkstra_search.frontier.shift[0]

      # Stop the search if we found the target
      return if current == state.target

      # For each of the neighbors
      adjacent_neighbors(current).each do | neighbor |
        # Unless this cell is a wall or has already been explored.
        unless dijkstra_search.came_from.has_key?(neighbor) or state.walls.has_key?(neighbor)
          # Calculate the movement cost of getting to this cell and memo
          new_cost = dijkstra_search.cost_so_far[current] + cost(neighbor)
          dijkstra_search.cost_so_far[neighbor] = new_cost

          # Add this neighbor to the cells too be explored
          dijkstra_search.frontier << [neighbor, new_cost]
          dijkstra_search.came_from[neighbor] = current
        end
      end

      # Sort the frontier so exploration occurs that have a low cost so far.
      # My implementation of a priority queue
      dijkstra_search.frontier = dijkstra_search.frontier.sort_by {|cell, priority| priority}
    end
  end

  def cost(cell)
    if state.hills.has_key?(cell)
      return 5
    else
      return 1
    end
  end




  # Moves the star to the cell closest to the mouse in the first grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star
    old_star = state.star.clone
    unless cell_closest_to_mouse == state.target
      state.star = cell_closest_to_mouse
    end
    unless old_star == state.star
      reset_search
    end
  end

  # Moves the star to the cell closest to the mouse in the second grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def input_star2
    old_star = state.star.clone
    unless cell_closest_to_mouse2 == state.target
      state.star = cell_closest_to_mouse2
    end
    unless old_star == state.star
      reset_search
    end
  end

  # Moves the target to the grid closest to the mouse in the first grid
  # Only reset_searchs the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def input_target
    old_target = state.target.clone
    unless cell_closest_to_mouse == state.star
      state.target = cell_closest_to_mouse
    end
    unless old_target == state.target
      reset_search
    end
  end

  # Moves the target to the cell closest to the mouse in the second grid
  # Only reset_searchs the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def input_target2
    old_target = state.target.clone
    unless cell_closest_to_mouse2 == state.star
      state.target = cell_closest_to_mouse2
    end
    unless old_target == state.target
      reset_search
    end
  end

  # Removes walls in the first grid that are under the cursor
  def input_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_over_grid?
      if state.walls.has_key?(cell_closest_to_mouse) or state.hills.has_key?(cell_closest_to_mouse)
        state.walls.delete(cell_closest_to_mouse)
        state.hills.delete(cell_closest_to_mouse)
        reset_search
      end
    end
  end

  # Removes walls in the second grid that are under the cursor
  def input_remove_wall2
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if mouse_over_grid2?
      if state.walls.has_key?(cell_closest_to_mouse2) or state.hills.has_key?(cell_closest_to_mouse2)
        state.walls.delete(cell_closest_to_mouse2)
        state.hills.delete(cell_closest_to_mouse2)
        reset_search
      end
    end
  end

  # Adds a hill in the first grid in the cell the mouse is over
  def input_add_hill
    if mouse_over_grid?
      unless state.hills.has_key?(cell_closest_to_mouse)
        state.hills[cell_closest_to_mouse] = true
        reset_search
      end
    end
  end


  # Adds a hill in the second grid in the cell the mouse is over
  def input_add_hill2
    if mouse_over_grid2?
      unless state.hills.has_key?(cell_closest_to_mouse2)
        state.hills[cell_closest_to_mouse2] = true
        reset_search
      end
    end
  end

  # Adds a wall in the first grid in the cell the mouse is over
  def input_add_wall
    if mouse_over_grid?
      unless state.walls.has_key?(cell_closest_to_mouse)
        state.hills.delete(cell_closest_to_mouse)
        state.walls[cell_closest_to_mouse] = true
        reset_search
      end
    end
  end

  # Adds a wall in the second grid in the cell the mouse is over
  def input_add_wall2
    if mouse_over_grid2?
      unless state.walls.has_key?(cell_closest_to_mouse2)
        state.hills.delete(cell_closest_to_mouse2)
        state.walls[cell_closest_to_mouse2] = true
        reset_search
      end
    end
  end

  # Whenever the user edits the grid,
  # The search has to be reset_searchd upto the current step
  # with the current grid as the initial state of the grid
  def reset_search
    breadth_first_search.visited    = {}
    breadth_first_search.frontier   = []
    breadth_first_search.came_from  = {}

    dijkstra_search.frontier    = []
    dijkstra_search.came_from   = {}
    dijkstra_search.cost_so_far = {}
  end



  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    # Gets all the valid neighbors into the array
    # From southern neighbor, clockwise
    neighbors << [cell.x    , cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y    ] unless cell.x == 0
    neighbors << [cell.x    , cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y    ] unless cell.x == grid.width - 1

    # Sorts the neighbors so the rendered path is a zigzag path
    # Cells in a diagonal direction are given priority
    # Comment this line to see the difference
    neighbors = neighbors.sort_by { |neighbor_x, neighbor_y|  proximity_to_star(neighbor_x, neighbor_y) }

    neighbors
  end

  # Finds the vertical and horizontal distance of a cell from the star
  # and returns the larger value
  # This method is used to have a zigzag pattern in the rendered path
  # A cell that is [5, 5] from the star,
  # is explored before over a cell that is [0, 7] away.
  # So, if possible, the search tries to go diagonal (zigzag) first
  def proximity_to_star(x, y)
    distance_x = (state.star.x - x).abs
    distance_y = (state.star.y - y).abs

    if distance_x > distance_y
      return distance_x
    else
      return distance_y
    end
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def cell_closest_to_mouse
    # Closest cell to the mouse in the first grid
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse in the second grid helps with this
  def cell_closest_to_mouse2
    # Closest cell grid to the mouse in the second
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Translate the cell to the first grid
    x -= grid.width + 1
    # Bound x and y to the first grid
    x = 0 if x < 0
    y = 0 if y < 0
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # Signal that the user is going to be moving the star from the first grid
  def mouse_over_star?
    inputs.mouse.point.inside_rect?(scale_up(state.star))
  end

  # Signal that the user is going to be moving the star from the second grid
  def mouse_over_star2?
    inputs.mouse.point.inside_rect?(move_and_scale_up(state.star))
  end

  # Signal that the user is going to be moving the target from the first grid
  def mouse_over_target?
    inputs.mouse.point.inside_rect?(scale_up(state.target))
  end

  # Signal that the user is going to be moving the target from the second grid
  def mouse_over_target2?
    inputs.mouse.point.inside_rect?(move_and_scale_up(state.target))
  end

  # Signal that the user is going to be removing walls from the first grid
  def mouse_over_wall?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be removing walls from the second grid
  def mouse_over_wall2?
    state.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(move_and_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be removing hills from the first grid
  def mouse_over_hill?
    state.hills.each_key do | hill |
      return true if inputs.mouse.point.inside_rect?(scale_up(hill))
    end

    false
  end

  # Signal that the user is going to be removing hills from the second grid
  def mouse_over_hill2?
    state.hills.each_key do | hill |
      return true if inputs.mouse.point.inside_rect?(move_and_scale_up(hill))
    end

    false
  end

  # Signal that the user is going to be adding walls from the first grid
  def mouse_over_grid?
    inputs.mouse.point.inside_rect?(scale_up(grid.rect))
  end

  # Signal that the user is going to be adding walls from the second grid
  def mouse_over_grid2?
    inputs.mouse.point.inside_rect?(move_and_scale_up(grid.rect))
  end

  # These methods provide handy aliases to colors

  # Light brown
  def unvisited_color
    [221, 212, 213]
  end

  # Camo Green
  def wall_color
    [134, 134, 120]
  end

  # Pastel White
  def path_color
    [231, 230, 228]
  end

  def red
    [255, 0, 0]
  end

  # A Green
  def hill_color
    [139, 173, 132]
  end

  # Makes code more concise
  def grid
    state.grid
  end

  def breadth_first_search
    state.breadth_first_search
  end

  def dijkstra_search
    state.dijkstra_search
  end
end

# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Dijkstra tick method is called
  $movement_costs ||= Movement_Costs.new(args)
  $movement_costs.args = args
  $movement_costs.tick
end


def reset
  $movement_costs = nil
end

Path Finding Algorithms - Heuristic - main.rb

# ./samples/13_path_finding_algorithms/06_heuristic/app/main.rb
# This program is inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# This time the heuristic search still explored less of the grid, hence finishing faster.
# However, it did not find the shortest path between the star and the target.

# The only difference between this app and Heuristic is the change of the starting position.

class Heuristic_With_Walls
  attr_gtk

  def tick
    defaults
    render
    input
    # If animation is playing, and max steps have not been reached
    # Move the search a step forward
    if state.play && state.current_step < state.max_steps
      # Variable that tells the program what step to recalculate up to
      state.current_step += 1
      move_searches_one_step_forward
    end
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 15
    grid.height    ||= 15
    grid.cell_size ||= 40
    grid.rect      ||= [0, 0, grid.width, grid.height]

    grid.star      ||= [0, 2]
    grid.target    ||= [14, 12]
    grid.walls     ||= {}
    # There are no hills in the Heuristic Search Demo

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.user_input ||= :none

    # These variables allow the breadth first search to take place
    # Came_from is a hash with a key of a cell and a value of the cell that was expanded from to find the key.
    # Used to prevent searching cells that have already been found
    # and to trace a path from the target back to the starting point.
    # Frontier is an array of cells to expand the search from.
    # The search is over when there are no more cells to search from.
    # Path stores the path from the target to the star, once the target has been found
    # It prevents calculating the path every tick.
    bfs.came_from  ||= {}
    bfs.frontier   ||= []
    bfs.path       ||= []

    heuristic.came_from ||= {}
    heuristic.frontier  ||= []
    heuristic.path      ||= []

    # Stores which step of the animation is being rendered
    # When the user moves the star or messes with the walls,
    # the searches are recalculated up to this step

    # Unless the current step has a value
    unless state.current_step
      # Set the current step to 10
      state.current_step = 10
      # And calculate the searches up to step 10
      recalculate_searches
    end

    # At some step the animation will end,
    # and further steps won't change anything (the whole grid will be explored)
    # This step is roughly the grid's width * height
    # When anim_steps equals max_steps no more calculations will occur
    # and the slider will be at the end
    state.max_steps = grid.width * grid.height

    # Whether the animation should play or not
    # If true, every tick moves anim_steps forward one
    # Pressing the stepwise animation buttons will pause the animation
    # An if statement instead of the ||= operator is used for assigning a boolean value.
    # The || operator does not differentiate between nil and false.
    if state.play == nil
      state.play = false
    end

    # Store the rects of the buttons that control the animation
    # They are here for user customization
    # Editing these might require recentering the text inside them
    # Those values can be found in the render_button methods
    buttons.left   = [470, 600, 50, 50]
    buttons.center = [520, 600, 200, 50]
    buttons.right  = [720, 600, 50, 50]

    # The variables below are related to the slider
    # They allow the user to customize them
    # They also give a central location for the render and input methods to get
    # information from
    # x & y are the coordinates of the leftmost part of the slider line
    slider.x = 440
    slider.y = 675
    # This is the width of the line
    slider.w = 360
    # This is the offset for the circle
    # Allows the center of the circle to be on the line,
    # as opposed to the upper right corner
    slider.offset = 20
    # This is the spacing between each of the notches on the slider
    # Notches are places where the circle can rest on the slider line
    # There needs to be a notch for each step before the maximum number of steps
    slider.spacing = slider.w.to_f / state.max_steps.to_f
  end

  # All methods with render draw stuff on the screen
  # UI has buttons, the slider, and labels
  # The search specific rendering occurs in the respective methods
  def render
    render_ui
    render_bfs
    render_heuristic
  end

  def render_ui
    render_buttons
    render_slider
    render_labels
  end

  def render_buttons
    render_left_button
    render_center_button
    render_right_button
  end

  def render_bfs
    render_bfs_grid
    render_bfs_star
    render_bfs_target
    render_bfs_visited
    render_bfs_walls
    render_bfs_frontier
    render_bfs_path
  end

  def render_heuristic
    render_heuristic_grid
    render_heuristic_star
    render_heuristic_target
    render_heuristic_visited
    render_heuristic_walls
    render_heuristic_frontier
    render_heuristic_path
  end

  # This method handles user input every tick
  def input
    # Check and handle button input
    input_buttons

    # If the mouse was lifted this tick
    if inputs.mouse.up
      # Set current input to none
      state.user_input = :none
    end

    # If the mouse was clicked this tick
    if inputs.mouse.down
      # Determine what the user is editing and appropriately edit the state.user_input variable
      determine_input
    end

    # Process user input based on user_input variable and current mouse position
    process_input
  end

  # Determines what the user is editing
  # This method is called when the mouse is clicked down
  def determine_input
    if mouse_over_slider?
      state.user_input = :slider
    # If the mouse is over the star in the first grid
    elsif bfs_mouse_over_star?
      # The user is editing the star from the first grid
      state.user_input = :bfs_star
    # If the mouse is over the star in the second grid
    elsif heuristic_mouse_over_star?
      # The user is editing the star from the second grid
      state.user_input = :heuristic_star
    # If the mouse is over the target in the first grid
    elsif bfs_mouse_over_target?
      # The user is editing the target from the first grid
      state.user_input = :bfs_target
    # If the mouse is over the target in the second grid
    elsif heuristic_mouse_over_target?
      # The user is editing the target from the second grid
      state.user_input = :heuristic_target
    # If the mouse is over a wall in the first grid
    elsif bfs_mouse_over_wall?
      # The user is removing a wall from the first grid
      state.user_input = :bfs_remove_wall
    # If the mouse is over a wall in the second grid
    elsif heuristic_mouse_over_wall?
      # The user is removing a wall from the second grid
      state.user_input = :heuristic_remove_wall
    # If the mouse is over the first grid
    elsif bfs_mouse_over_grid?
      # The user is adding a wall from the first grid
      state.user_input = :bfs_add_wall
    # If the mouse is over the second grid
    elsif heuristic_mouse_over_grid?
      # The user is adding a wall from the second grid
      state.user_input = :heuristic_add_wall
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_input
    if state.user_input == :slider
      process_input_slider
    elsif state.user_input == :bfs_star
      process_input_bfs_star
    elsif state.user_input == :heuristic_star
      process_input_heuristic_star
    elsif state.user_input == :bfs_target
      process_input_bfs_target
    elsif state.user_input == :heuristic_target
      process_input_heuristic_target
    elsif state.user_input == :bfs_remove_wall
      process_input_bfs_remove_wall
    elsif state.user_input == :heuristic_remove_wall
      process_input_heuristic_remove_wall
    elsif state.user_input == :bfs_add_wall
      process_input_bfs_add_wall
    elsif state.user_input == :heuristic_add_wall
      process_input_heuristic_add_wall
    end
  end

  def render_slider
    # Using primitives hides the line under the white circle of the slider
    # Draws the line
    outputs.primitives << [slider.x, slider.y, slider.x + slider.w, slider.y].line
    # The circle needs to be offset so that the center of the circle
    # overlaps the line instead of the upper right corner of the circle
    # The circle's x value is also moved based on the current seach step
    circle_x = (slider.x - slider.offset) + (state.current_step * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    outputs.primitives << [circle_rect, 'circle-white.png'].sprite
  end

  def render_labels
    outputs.labels << [205, 625, "Breadth First Search"]
    outputs.labels << [820, 625, "Heuristic Best-First Search"]
  end

  def render_left_button
    # Draws the button_color button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.left, button_color]
    outputs.borders << [buttons.left]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    # If the button size is changed, the label might need to be edited as well
    # to keep the label in the center of the button
    label_x = buttons.left.x + 20
    label_y = buttons.left.y + 35
    outputs.labels  << [label_x, label_y, "<"]
  end

  def render_center_button
    # Draws the button_color button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.center, button_color]
    outputs.borders << [buttons.center]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    # If the button size is changed, the label might need to be edited as well
    # to keep the label in the center of the button
    label_x    = buttons.center.x + 37
    label_y    = buttons.center.y + 35
    label_text = state.play ? "Pause Animation" : "Play Animation"
    outputs.labels << [label_x, label_y, label_text]
  end

  def render_right_button
    # Draws the button_color button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.right, button_color]
    outputs.borders << [buttons.right]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    label_x = buttons.right.x + 20
    label_y = buttons.right.y + 35
    outputs.labels  << [label_x, label_y, ">"]
  end

  def render_bfs_grid
    # A large rect the size of the grid
    outputs.solids << [bfs_scale_up(grid.rect), default_color]

    # The vertical grid lines
    for x in 0..grid.width
      outputs.lines << bfs_vertical_line(x)
    end

    # The horizontal grid lines
    for y in 0..grid.height
      outputs.lines << bfs_horizontal_line(y)
    end
  end

  def render_heuristic_grid
    # A large rect the size of the grid
    outputs.solids << [heuristic_scale_up(grid.rect), default_color]

    # The vertical grid lines
    for x in 0..grid.width
      outputs.lines << heuristic_vertical_line(x)
    end

    # The horizontal grid lines
    for y in 0..grid.height
      outputs.lines << heuristic_horizontal_line(y)
    end
  end

  # Returns a vertical line for a column of the first grid
  def bfs_vertical_line column
    bfs_scale_up([column, 0, column, grid.height])
  end

  # Returns a horizontal line for a column of the first grid
  def bfs_horizontal_line row
    bfs_scale_up([0, row, grid.width, row])
  end

  # Returns a vertical line for a column of the second grid
  def heuristic_vertical_line column
    bfs_scale_up([column + grid.width + 1, 0, column + grid.width + 1, grid.height])
  end

  # Returns a horizontal line for a column of the second grid
  def heuristic_horizontal_line row
    bfs_scale_up([grid.width + 1, row, grid.width + grid.width + 1, row])
  end

  # Renders the star on the first grid
  def render_bfs_star
    outputs.sprites << [bfs_scale_up(grid.star), 'star.png']
  end

  # Renders the star on the second grid
  def render_heuristic_star
    outputs.sprites << [heuristic_scale_up(grid.star), 'star.png']
  end

  # Renders the target on the first grid
  def render_bfs_target
    outputs.sprites << [bfs_scale_up(grid.target), 'target.png']
  end

  # Renders the target on the second grid
  def render_heuristic_target
    outputs.sprites << [heuristic_scale_up(grid.target), 'target.png']
  end

  # Renders the walls on the first grid
  def render_bfs_walls
    grid.walls.each_key do | wall |
      outputs.solids << [bfs_scale_up(wall), wall_color]
    end
  end

  # Renders the walls on the second grid
  def render_heuristic_walls
    grid.walls.each_key do | wall |
      outputs.solids << [heuristic_scale_up(wall), wall_color]
    end
  end

  # Renders the visited cells on the first grid
  def render_bfs_visited
    bfs.came_from.each_key do | visited_cell |
      outputs.solids << [bfs_scale_up(visited_cell), visited_color]
    end
  end

  # Renders the visited cells on the second grid
  def render_heuristic_visited
    heuristic.came_from.each_key do | visited_cell |
      outputs.solids << [heuristic_scale_up(visited_cell), visited_color]
    end
  end

  # Renders the frontier cells on the first grid
  def render_bfs_frontier
    bfs.frontier.each do | frontier_cell |
      outputs.solids << [bfs_scale_up(frontier_cell), frontier_color, 200]
    end
  end

  # Renders the frontier cells on the second grid
  def render_heuristic_frontier
    heuristic.frontier.each do | frontier_cell |
      outputs.solids << [heuristic_scale_up(frontier_cell), frontier_color, 200]
    end
  end

  # Renders the path found by the breadth first search on the first grid
  def render_bfs_path
    bfs.path.each do | path |
      outputs.solids << [bfs_scale_up(path), path_color]
    end
  end

  # Renders the path found by the heuristic search on the second grid
  def render_heuristic_path
    heuristic.path.each do | path |
      outputs.solids << [heuristic_scale_up(path), path_color]
    end
  end

  # Returns the rect for the path between two cells based on their relative positions
  def get_path_between(cell_one, cell_two)
    path = nil

    # If cell one is above cell two
    if cell_one.x == cell_two.x and cell_one.y > cell_two.y
      # Path starts from the center of cell two and moves upward to the center of cell one
      path = [cell_two.x + 0.3, cell_two.y + 0.3, 0.4, 1.4]
    # If cell one is below cell two
    elsif cell_one.x == cell_two.x and cell_one.y < cell_two.y
      # Path starts from the center of cell one and moves upward to the center of cell two
      path = [cell_one.x + 0.3, cell_one.y + 0.3, 0.4, 1.4]
    # If cell one is to the left of cell two
    elsif cell_one.x > cell_two.x and cell_one.y == cell_two.y
      # Path starts from the center of cell two and moves rightward to the center of cell one
      path = [cell_two.x + 0.3, cell_two.y + 0.3, 1.4, 0.4]
    # If cell one is to the right of cell two
    elsif cell_one.x < cell_two.x and cell_one.y == cell_two.y
      # Path starts from the center of cell one and moves rightward to the center of cell two
      path = [cell_one.x + 0.3, cell_one.y + 0.3, 1.4, 0.4]
    end

    path
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  # This method scales up cells for the first grid
  def bfs_scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone

    # If cell is just an x and y coordinate
    if cell.size == 2
      # Add a width and height of 1
      cell << 1
      cell << 1
    end

    # Scale all the values up
    cell.map! { |value| value * grid.cell_size }

    # Returns the scaled up cell
    cell
  end

  # Translates the given cell grid.width + 1 to the right and then scales up
  # Used to draw cells for the second grid
  # This method does not work for lines,
  # so separate methods exist for the grid lines
  def heuristic_scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone
    # Translates the cell to the second grid equivalent
    cell.x += grid.width + 1
    # Proceeds as if scaling up for the first grid
    bfs_scale_up(cell)
  end

  # Checks and handles input for the buttons
  # Called when the mouse is lifted
  def input_buttons
    input_left_button
    input_center_button
    input_right_button
  end

  # Checks if the previous step button is clicked
  # If it is, it pauses the animation and moves the search one step backward
  def input_left_button
    if left_button_clicked?
      state.play = false
      state.current_step -= 1
      recalculate_searches
    end
  end

  # Controls the play/pause button
  # Inverses whether the animation is playing or not when clicked
  def input_center_button
    if center_button_clicked? || inputs.keyboard.key_down.space
      state.play = !state.play
    end
  end

  # Checks if the next step button is clicked
  # If it is, it pauses the animation and moves the search one step forward
  def input_right_button
    if right_button_clicked?
      state.play = false
      state.current_step += 1
      move_searches_one_step_forward
    end
  end

  # These methods detect when the buttons are clicked
  def left_button_clicked?
    inputs.mouse.point.inside_rect?(buttons.left) && inputs.mouse.up
  end

  def center_button_clicked?
    inputs.mouse.point.inside_rect?(buttons.center) && inputs.mouse.up
  end

  def right_button_clicked?
    inputs.mouse.point.inside_rect?(buttons.right) && inputs.mouse.up
  end


  # Signal that the user is going to be moving the slider
  # Is the mouse over the circle of the slider?
  def mouse_over_slider?
    circle_x = (slider.x - slider.offset) + (state.current_step * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    inputs.mouse.point.inside_rect?(circle_rect)
  end

  # Signal that the user is going to be moving the star from the first grid
  def bfs_mouse_over_star?
    inputs.mouse.point.inside_rect?(bfs_scale_up(grid.star))
  end

  # Signal that the user is going to be moving the star from the second grid
  def heuristic_mouse_over_star?
    inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.star))
  end

  # Signal that the user is going to be moving the target from the first grid
  def bfs_mouse_over_target?
    inputs.mouse.point.inside_rect?(bfs_scale_up(grid.target))
  end

  # Signal that the user is going to be moving the target from the second grid
  def heuristic_mouse_over_target?
    inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.target))
  end

  # Signal that the user is going to be removing walls from the first grid
  def bfs_mouse_over_wall?
    grid.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(bfs_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be removing walls from the second grid
  def heuristic_mouse_over_wall?
    grid.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(heuristic_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be adding walls from the first grid
  def bfs_mouse_over_grid?
    inputs.mouse.point.inside_rect?(bfs_scale_up(grid.rect))
  end

  # Signal that the user is going to be adding walls from the second grid
  def heuristic_mouse_over_grid?
    inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.rect))
  end

  # This method is called when the user is editing the slider
  # It pauses the animation and moves the white circle to the closest integer point
  # on the slider
  # Changes the step of the search to be animated
  def process_input_slider
    state.play = false
    mouse_x = inputs.mouse.point.x

    # Bounds the mouse_x to the closest x value on the slider line
    mouse_x = slider.x if mouse_x < slider.x
    mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w

    # Sets the current search step to the one represented by the mouse x value
    # The slider's circle moves due to the render_slider method using anim_steps
    state.current_step = ((mouse_x - slider.x) / slider.spacing).to_i

    recalculate_searches
  end

  # Moves the star to the cell closest to the mouse in the first grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def process_input_bfs_star
    old_star = grid.star.clone
    unless bfs_cell_closest_to_mouse == grid.target
      grid.star = bfs_cell_closest_to_mouse
    end
    unless old_star == grid.star
      recalculate_searches
    end
  end

  # Moves the star to the cell closest to the mouse in the second grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def process_input_heuristic_star
    old_star = grid.star.clone
    unless heuristic_cell_closest_to_mouse == grid.target
      grid.star = heuristic_cell_closest_to_mouse
    end
    unless old_star == grid.star
      recalculate_searches
    end
  end

  # Moves the target to the grid closest to the mouse in the first grid
  # Only recalculate_searchess the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def process_input_bfs_target
    old_target = grid.target.clone
    unless bfs_cell_closest_to_mouse == grid.star
      grid.target = bfs_cell_closest_to_mouse
    end
    unless old_target == grid.target
      recalculate_searches
    end
  end

  # Moves the target to the cell closest to the mouse in the second grid
  # Only recalculate_searchess the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def process_input_heuristic_target
    old_target = grid.target.clone
    unless heuristic_cell_closest_to_mouse == grid.star
      grid.target = heuristic_cell_closest_to_mouse
    end
    unless old_target == grid.target
      recalculate_searches
    end
  end

  # Removes walls in the first grid that are under the cursor
  def process_input_bfs_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if bfs_mouse_over_grid?
      if grid.walls.has_key?(bfs_cell_closest_to_mouse)
        grid.walls.delete(bfs_cell_closest_to_mouse)
        recalculate_searches
      end
    end
  end

  # Removes walls in the second grid that are under the cursor
  def process_input_heuristic_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if heuristic_mouse_over_grid?
      if grid.walls.has_key?(heuristic_cell_closest_to_mouse)
        grid.walls.delete(heuristic_cell_closest_to_mouse)
        recalculate_searches
      end
    end
  end
  # Adds a wall in the first grid in the cell the mouse is over
  def process_input_bfs_add_wall
    if bfs_mouse_over_grid?
      unless grid.walls.has_key?(bfs_cell_closest_to_mouse)
        grid.walls[bfs_cell_closest_to_mouse] = true
        recalculate_searches
      end
    end
  end

  # Adds a wall in the second grid in the cell the mouse is over
  def process_input_heuristic_add_wall
    if heuristic_mouse_over_grid?
      unless grid.walls.has_key?(heuristic_cell_closest_to_mouse)
        grid.walls[heuristic_cell_closest_to_mouse] = true
        recalculate_searches
      end
    end
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def bfs_cell_closest_to_mouse
    # Closest cell to the mouse in the first grid
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse in the second grid helps with this
  def heuristic_cell_closest_to_mouse
    # Closest cell grid to the mouse in the second
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Translate the cell to the first grid
    x -= grid.width + 1
    # Bound x and y to the first grid
    x = 0 if x < 0
    y = 0 if y < 0
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  def recalculate_searches
    # Reset the searches
    bfs.came_from    = {}
    bfs.frontier     = []
    bfs.path         = []
    heuristic.came_from = {}
    heuristic.frontier  = []
    heuristic.path      = []

    # Move the searches forward to the current step
    state.current_step.times { move_searches_one_step_forward }
  end

  def move_searches_one_step_forward
    bfs_one_step_forward
    heuristic_one_step_forward
  end

  def bfs_one_step_forward
    return if bfs.came_from.has_key?(grid.target)

    # Only runs at the beginning of the search as setup.
    if bfs.came_from.empty?
      bfs.frontier << grid.star
      bfs.came_from[grid.star] = nil
    end

    # A step in the search
    unless bfs.frontier.empty?
      # Takes the next frontier cell
      new_frontier = bfs.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless bfs.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited
          bfs.frontier << neighbor
          bfs.came_from[neighbor] = new_frontier
        end
      end
    end

    # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
    # Comment this line and let a path generate to see the difference
    bfs.frontier = bfs.frontier.sort_by {| cell | proximity_to_star(cell) }

    # If the search found the target
    if bfs.came_from.has_key?(grid.target)
      # Calculate the path between the target and star
      bfs_calc_path
    end
  end

  # Calculates the path between the target and star for the breadth first search
  # Only called when the breadth first search finds the target
  def bfs_calc_path
    # Start from the target
    endpoint = grid.target
    # And the cell it came from
    next_endpoint = bfs.came_from[endpoint]
    while endpoint and next_endpoint
      # Draw a path between these two cells and store it
      path = get_path_between(endpoint, next_endpoint)
      bfs.path << path
      # And get the next pair of cells
      endpoint = next_endpoint
      next_endpoint = bfs.came_from[endpoint]
      # Continue till there are no more cells
    end
  end

  # Moves the heuristic search forward one step
  # Can be called from tick while the animation is playing
  # Can also be called when recalculating the searches after the user edited the grid
  def heuristic_one_step_forward
    # Stop the search if the target has been found
    return if heuristic.came_from.has_key?(grid.target)

    # If the search has not begun
    if heuristic.came_from.empty?
      # Setup the search to begin from the star
      heuristic.frontier << grid.star
      heuristic.came_from[grid.star] = nil
    end

    # One step in the heuristic search

    # Unless there are no more cells to explore from
    unless heuristic.frontier.empty?
      # Get the next cell to explore from
      new_frontier = heuristic.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless heuristic.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited
          heuristic.frontier << neighbor
          heuristic.came_from[neighbor] = new_frontier
        end
      end
    end

    # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
    heuristic.frontier = heuristic.frontier.sort_by {| cell | proximity_to_star(cell) }
    # Sort the frontier so cells that are close to the target are then prioritized
    heuristic.frontier = heuristic.frontier.sort_by {| cell | heuristic_heuristic(cell)  }

    # If the search found the target
    if heuristic.came_from.has_key?(grid.target)
      # Calculate the path between the target and star
      heuristic_calc_path
    end
  end

  # Returns one-dimensional absolute distance between cell and target
  # Returns a number to compare distances between cells and the target
  def heuristic_heuristic(cell)
    (grid.target.x - cell.x).abs + (grid.target.y - cell.y).abs
  end

  # Calculates the path between the target and star for the heuristic search
  # Only called when the heuristic search finds the target
  def heuristic_calc_path
    # Start from the target
    endpoint = grid.target
    # And the cell it came from
    next_endpoint = heuristic.came_from[endpoint]
    while endpoint and next_endpoint
      # Draw a path between these two cells and store it
      path = get_path_between(endpoint, next_endpoint)
      heuristic.path << path
      # And get the next pair of cells
      endpoint = next_endpoint
      next_endpoint = heuristic.came_from[endpoint]
      # Continue till there are no more cells
    end
  end

  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    # Gets all the valid neighbors into the array
    # From southern neighbor, clockwise
    neighbors << [cell.x    , cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y    ] unless cell.x == 0
    neighbors << [cell.x    , cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y    ] unless cell.x == grid.width - 1

    neighbors
  end

  # Finds the vertical and horizontal distance of a cell from the star
  # and returns the larger value
  # This method is used to have a zigzag pattern in the rendered path
  # A cell that is [5, 5] from the star,
  # is explored before over a cell that is [0, 7] away.
  # So, if possible, the search tries to go diagonal (zigzag) first
  def proximity_to_star(cell)
    distance_x = (grid.star.x - cell.x).abs
    distance_y = (grid.star.y - cell.y).abs

    if distance_x > distance_y
      return distance_x
    else
      return distance_y
    end
  end

  # Methods that allow code to be more concise. Subdivides args.state, which is where all variables are stored.
  def grid
    state.grid
  end

  def buttons
    state.buttons
  end

  def slider
    state.slider
  end

  def bfs
    state.bfs
  end

  def heuristic
    state.heuristic
  end

  # Descriptive aliases for colors
  def default_color
    [221, 212, 213] # Light Brown
  end

  def wall_color
    [134, 134, 120] # Camo Green
  end

  def visited_color
    [204, 191, 179] # Dark Brown
  end

  def frontier_color
    [103, 136, 204] # Blue
  end

  def path_color
    [231, 230, 228] # Pastel White
  end

  def button_color
    [190, 190, 190] # Gray
  end
end
# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Breadth First Search tick is called
  $heuristic_with_walls ||= Heuristic_With_Walls.new(args)
  $heuristic_with_walls.args = args
  $heuristic_with_walls.tick
end


def reset
  $heuristic_with_walls = nil
end

Path Finding Algorithms - Heuristic With Walls - main.rb

# ./samples/13_path_finding_algorithms/07_heuristic_with_walls/app/main.rb
# This program is inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html
# The effectiveness of the Heuristic search algorithm is shown through this demonstration.
# Notice that both searches find the shortest path
# The heuristic search, however, explores less of the grid, and is therefore faster.
# The heuristic search prioritizes searching cells that are closer to the target.
# Make sure to look at the Heuristic with walls program to see some of the downsides of the heuristic algorithm.

class Heuristic
  attr_gtk

  def tick
    defaults
    render
    input
    # If animation is playing, and max steps have not been reached
    # Move the search a step forward
    if state.play && state.current_step < state.max_steps
      # Variable that tells the program what step to recalculate up to
      state.current_step += 1
      move_searches_one_step_forward
    end
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 15
    grid.height    ||= 15
    grid.cell_size ||= 40
    grid.rect      ||= [0, 0, grid.width, grid.height]

    grid.star      ||= [0, 2]
    grid.target    ||= [14, 12]
    grid.walls     ||= {
      [2, 2] => true,
      [3, 2] => true,
      [4, 2] => true,
      [5, 2] => true,
      [6, 2] => true,
      [7, 2] => true,
      [8, 2] => true,
      [9, 2] => true,
      [10, 2] => true,
      [11, 2] => true,
      [12, 2] => true,
      [12, 3] => true,
      [12, 4] => true,
      [12, 5] => true,
      [12, 6] => true,
      [12, 7] => true,
      [12, 8] => true,
      [12, 9] => true,
      [12, 10] => true,
      [12, 11] => true,
      [12, 12] => true,
      [2, 12] => true,
      [3, 12] => true,
      [4, 12] => true,
      [5, 12] => true,
      [6, 12] => true,
      [7, 12] => true,
      [8, 12] => true,
      [9, 12] => true,
      [10, 12] => true,
      [11, 12] => true,
      [12, 12] => true
    }
    # There are no hills in the Heuristic Search Demo

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.user_input ||= :none

    # These variables allow the breadth first search to take place
    # Came_from is a hash with a key of a cell and a value of the cell that was expanded from to find the key.
    # Used to prevent searching cells that have already been found
    # and to trace a path from the target back to the starting point.
    # Frontier is an array of cells to expand the search from.
    # The search is over when there are no more cells to search from.
    # Path stores the path from the target to the star, once the target has been found
    # It prevents calculating the path every tick.
    bfs.came_from  ||= {}
    bfs.frontier   ||= []
    bfs.path       ||= []

    heuristic.came_from ||= {}
    heuristic.frontier  ||= []
    heuristic.path      ||= []

    # Stores which step of the animation is being rendered
    # When the user moves the star or messes with the walls,
    # the searches are recalculated up to this step

    # Unless the current step has a value
    unless state.current_step
      # Set the current step to 10
      state.current_step = 10
      # And calculate the searches up to step 10
      recalculate_searches
    end

    # At some step the animation will end,
    # and further steps won't change anything (the whole grid will be explored)
    # This step is roughly the grid's width * height
    # When anim_steps equals max_steps no more calculations will occur
    # and the slider will be at the end
    state.max_steps = grid.width * grid.height

    # Whether the animation should play or not
    # If true, every tick moves anim_steps forward one
    # Pressing the stepwise animation buttons will pause the animation
    # An if statement instead of the ||= operator is used for assigning a boolean value.
    # The || operator does not differentiate between nil and false.
    if state.play == nil
      state.play = false
    end

    # Store the rects of the buttons that control the animation
    # They are here for user customization
    # Editing these might require recentering the text inside them
    # Those values can be found in the render_button methods
    buttons.left   = [470, 600, 50, 50]
    buttons.center = [520, 600, 200, 50]
    buttons.right  = [720, 600, 50, 50]

    # The variables below are related to the slider
    # They allow the user to customize them
    # They also give a central location for the render and input methods to get
    # information from
    # x & y are the coordinates of the leftmost part of the slider line
    slider.x = 440
    slider.y = 675
    # This is the width of the line
    slider.w = 360
    # This is the offset for the circle
    # Allows the center of the circle to be on the line,
    # as opposed to the upper right corner
    slider.offset = 20
    # This is the spacing between each of the notches on the slider
    # Notches are places where the circle can rest on the slider line
    # There needs to be a notch for each step before the maximum number of steps
    slider.spacing = slider.w.to_f / state.max_steps.to_f
  end

  # All methods with render draw stuff on the screen
  # UI has buttons, the slider, and labels
  # The search specific rendering occurs in the respective methods
  def render
    render_ui
    render_bfs
    render_heuristic
  end

  def render_ui
    render_buttons
    render_slider
    render_labels
  end

  def render_buttons
    render_left_button
    render_center_button
    render_right_button
  end

  def render_bfs
    render_bfs_grid
    render_bfs_star
    render_bfs_target
    render_bfs_visited
    render_bfs_walls
    render_bfs_frontier
    render_bfs_path
  end

  def render_heuristic
    render_heuristic_grid
    render_heuristic_star
    render_heuristic_target
    render_heuristic_visited
    render_heuristic_walls
    render_heuristic_frontier
    render_heuristic_path
  end

  # This method handles user input every tick
  def input
    # Check and handle button input
    input_buttons

    # If the mouse was lifted this tick
    if inputs.mouse.up
      # Set current input to none
      state.user_input = :none
    end

    # If the mouse was clicked this tick
    if inputs.mouse.down
      # Determine what the user is editing and appropriately edit the state.user_input variable
      determine_input
    end

    # Process user input based on user_input variable and current mouse position
    process_input
  end

  # Determines what the user is editing
  # This method is called when the mouse is clicked down
  def determine_input
    if mouse_over_slider?
      state.user_input = :slider
    # If the mouse is over the star in the first grid
    elsif bfs_mouse_over_star?
      # The user is editing the star from the first grid
      state.user_input = :bfs_star
    # If the mouse is over the star in the second grid
    elsif heuristic_mouse_over_star?
      # The user is editing the star from the second grid
      state.user_input = :heuristic_star
    # If the mouse is over the target in the first grid
    elsif bfs_mouse_over_target?
      # The user is editing the target from the first grid
      state.user_input = :bfs_target
    # If the mouse is over the target in the second grid
    elsif heuristic_mouse_over_target?
      # The user is editing the target from the second grid
      state.user_input = :heuristic_target
    # If the mouse is over a wall in the first grid
    elsif bfs_mouse_over_wall?
      # The user is removing a wall from the first grid
      state.user_input = :bfs_remove_wall
    # If the mouse is over a wall in the second grid
    elsif heuristic_mouse_over_wall?
      # The user is removing a wall from the second grid
      state.user_input = :heuristic_remove_wall
    # If the mouse is over the first grid
    elsif bfs_mouse_over_grid?
      # The user is adding a wall from the first grid
      state.user_input = :bfs_add_wall
    # If the mouse is over the second grid
    elsif heuristic_mouse_over_grid?
      # The user is adding a wall from the second grid
      state.user_input = :heuristic_add_wall
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_input
    if state.user_input == :slider
      process_input_slider
    elsif state.user_input == :bfs_star
      process_input_bfs_star
    elsif state.user_input == :heuristic_star
      process_input_heuristic_star
    elsif state.user_input == :bfs_target
      process_input_bfs_target
    elsif state.user_input == :heuristic_target
      process_input_heuristic_target
    elsif state.user_input == :bfs_remove_wall
      process_input_bfs_remove_wall
    elsif state.user_input == :heuristic_remove_wall
      process_input_heuristic_remove_wall
    elsif state.user_input == :bfs_add_wall
      process_input_bfs_add_wall
    elsif state.user_input == :heuristic_add_wall
      process_input_heuristic_add_wall
    end
  end

  def render_slider
    # Using primitives hides the line under the white circle of the slider
    # Draws the line
    outputs.primitives << [slider.x, slider.y, slider.x + slider.w, slider.y].line
    # The circle needs to be offset so that the center of the circle
    # overlaps the line instead of the upper right corner of the circle
    # The circle's x value is also moved based on the current seach step
    circle_x = (slider.x - slider.offset) + (state.current_step * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    outputs.primitives << [circle_rect, 'circle-white.png'].sprite
  end

  def render_labels
    outputs.labels << [205, 625, "Breadth First Search"]
    outputs.labels << [820, 625, "Heuristic Best-First Search"]
  end

  def render_left_button
    # Draws the button_color button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.left, button_color]
    outputs.borders << [buttons.left]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    # If the button size is changed, the label might need to be edited as well
    # to keep the label in the center of the button
    label_x = buttons.left.x + 20
    label_y = buttons.left.y + 35
    outputs.labels  << [label_x, label_y, "<"]
  end

  def render_center_button
    # Draws the button_color button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.center, button_color]
    outputs.borders << [buttons.center]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    # If the button size is changed, the label might need to be edited as well
    # to keep the label in the center of the button
    label_x    = buttons.center.x + 37
    label_y    = buttons.center.y + 35
    label_text = state.play ? "Pause Animation" : "Play Animation"
    outputs.labels << [label_x, label_y, label_text]
  end

  def render_right_button
    # Draws the button_color button, and a black border
    # The border separates the buttons visually
    outputs.solids  << [buttons.right, button_color]
    outputs.borders << [buttons.right]

    # Renders an explanatory label in the center of the button
    # Explains to the user what the button does
    label_x = buttons.right.x + 20
    label_y = buttons.right.y + 35
    outputs.labels  << [label_x, label_y, ">"]
  end

  def render_bfs_grid
    # A large rect the size of the grid
    outputs.solids << [bfs_scale_up(grid.rect), default_color]

    # The vertical grid lines
    for x in 0..grid.width
      outputs.lines << bfs_vertical_line(x)
    end

    # The horizontal grid lines
    for y in 0..grid.height
      outputs.lines << bfs_horizontal_line(y)
    end
  end

  def render_heuristic_grid
    # A large rect the size of the grid
    outputs.solids << [heuristic_scale_up(grid.rect), default_color]

    # The vertical grid lines
    for x in 0..grid.width
      outputs.lines << heuristic_vertical_line(x)
    end

    # The horizontal grid lines
    for y in 0..grid.height
      outputs.lines << heuristic_horizontal_line(y)
    end
  end

  # Returns a vertical line for a column of the first grid
  def bfs_vertical_line column
    bfs_scale_up([column, 0, column, grid.height])
  end

  # Returns a horizontal line for a column of the first grid
  def bfs_horizontal_line row
    bfs_scale_up([0, row, grid.width, row])
  end

  # Returns a vertical line for a column of the second grid
  def heuristic_vertical_line column
    bfs_scale_up([column + grid.width + 1, 0, column + grid.width + 1, grid.height])
  end

  # Returns a horizontal line for a column of the second grid
  def heuristic_horizontal_line row
    bfs_scale_up([grid.width + 1, row, grid.width + grid.width + 1, row])
  end

  # Renders the star on the first grid
  def render_bfs_star
    outputs.sprites << [bfs_scale_up(grid.star), 'star.png']
  end

  # Renders the star on the second grid
  def render_heuristic_star
    outputs.sprites << [heuristic_scale_up(grid.star), 'star.png']
  end

  # Renders the target on the first grid
  def render_bfs_target
    outputs.sprites << [bfs_scale_up(grid.target), 'target.png']
  end

  # Renders the target on the second grid
  def render_heuristic_target
    outputs.sprites << [heuristic_scale_up(grid.target), 'target.png']
  end

  # Renders the walls on the first grid
  def render_bfs_walls
    grid.walls.each_key do | wall |
      outputs.solids << [bfs_scale_up(wall), wall_color]
    end
  end

  # Renders the walls on the second grid
  def render_heuristic_walls
    grid.walls.each_key do | wall |
      outputs.solids << [heuristic_scale_up(wall), wall_color]
    end
  end

  # Renders the visited cells on the first grid
  def render_bfs_visited
    bfs.came_from.each_key do | visited_cell |
      outputs.solids << [bfs_scale_up(visited_cell), visited_color]
    end
  end

  # Renders the visited cells on the second grid
  def render_heuristic_visited
    heuristic.came_from.each_key do | visited_cell |
      outputs.solids << [heuristic_scale_up(visited_cell), visited_color]
    end
  end

  # Renders the frontier cells on the first grid
  def render_bfs_frontier
    bfs.frontier.each do | frontier_cell |
      outputs.solids << [bfs_scale_up(frontier_cell), frontier_color, 200]
    end
  end

  # Renders the frontier cells on the second grid
  def render_heuristic_frontier
    heuristic.frontier.each do | frontier_cell |
      outputs.solids << [heuristic_scale_up(frontier_cell), frontier_color, 200]
    end
  end

  # Renders the path found by the breadth first search on the first grid
  def render_bfs_path
    bfs.path.each do | path |
      outputs.solids << [bfs_scale_up(path), path_color]
    end
  end

  # Renders the path found by the heuristic search on the second grid
  def render_heuristic_path
    heuristic.path.each do | path |
      outputs.solids << [heuristic_scale_up(path), path_color]
    end
  end

  # Returns the rect for the path between two cells based on their relative positions
  def get_path_between(cell_one, cell_two)
    path = []

    # If cell one is above cell two
    if cell_one.x == cell_two.x and cell_one.y > cell_two.y
      # Path starts from the center of cell two and moves upward to the center of cell one
      path = [cell_two.x + 0.3, cell_two.y + 0.3, 0.4, 1.4]
    # If cell one is below cell two
    elsif cell_one.x == cell_two.x and cell_one.y < cell_two.y
      # Path starts from the center of cell one and moves upward to the center of cell two
      path = [cell_one.x + 0.3, cell_one.y + 0.3, 0.4, 1.4]
    # If cell one is to the left of cell two
    elsif cell_one.x > cell_two.x and cell_one.y == cell_two.y
      # Path starts from the center of cell two and moves rightward to the center of cell one
      path = [cell_two.x + 0.3, cell_two.y + 0.3, 1.4, 0.4]
    # If cell one is to the right of cell two
    elsif cell_one.x < cell_two.x and cell_one.y == cell_two.y
      # Path starts from the center of cell one and moves rightward to the center of cell two
      path = [cell_one.x + 0.3, cell_one.y + 0.3, 1.4, 0.4]
    end

    path
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  # This method scales up cells for the first grid
  def bfs_scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone

    # If cell is just an x and y coordinate
    if cell.size == 2
      # Add a width and height of 1
      cell << 1
      cell << 1
    end

    # Scale all the values up
    cell.map! { |value| value * grid.cell_size }

    # Returns the scaled up cell
    cell
  end

  # Translates the given cell grid.width + 1 to the right and then scales up
  # Used to draw cells for the second grid
  # This method does not work for lines,
  # so separate methods exist for the grid lines
  def heuristic_scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone
    # Translates the cell to the second grid equivalent
    cell.x += grid.width + 1
    # Proceeds as if scaling up for the first grid
    bfs_scale_up(cell)
  end

  # Checks and handles input for the buttons
  # Called when the mouse is lifted
  def input_buttons
    input_left_button
    input_center_button
    input_right_button
  end

  # Checks if the previous step button is clicked
  # If it is, it pauses the animation and moves the search one step backward
  def input_left_button
    if left_button_clicked?
      state.play = false
      state.current_step -= 1
      recalculate_searches
    end
  end

  # Controls the play/pause button
  # Inverses whether the animation is playing or not when clicked
  def input_center_button
    if center_button_clicked? || inputs.keyboard.key_down.space
      state.play = !state.play
    end
  end

  # Checks if the next step button is clicked
  # If it is, it pauses the animation and moves the search one step forward
  def input_right_button
    if right_button_clicked?
      state.play = false
      state.current_step += 1
      move_searches_one_step_forward
    end
  end

  # These methods detect when the buttons are clicked
  def left_button_clicked?
    inputs.mouse.point.inside_rect?(buttons.left) && inputs.mouse.up
  end

  def center_button_clicked?
    inputs.mouse.point.inside_rect?(buttons.center) && inputs.mouse.up
  end

  def right_button_clicked?
    inputs.mouse.point.inside_rect?(buttons.right) && inputs.mouse.up
  end


  # Signal that the user is going to be moving the slider
  # Is the mouse over the circle of the slider?
  def mouse_over_slider?
    circle_x = (slider.x - slider.offset) + (state.current_step * slider.spacing)
    circle_y = (slider.y - slider.offset)
    circle_rect = [circle_x, circle_y, 37, 37]
    inputs.mouse.point.inside_rect?(circle_rect)
  end

  # Signal that the user is going to be moving the star from the first grid
  def bfs_mouse_over_star?
    inputs.mouse.point.inside_rect?(bfs_scale_up(grid.star))
  end

  # Signal that the user is going to be moving the star from the second grid
  def heuristic_mouse_over_star?
    inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.star))
  end

  # Signal that the user is going to be moving the target from the first grid
  def bfs_mouse_over_target?
    inputs.mouse.point.inside_rect?(bfs_scale_up(grid.target))
  end

  # Signal that the user is going to be moving the target from the second grid
  def heuristic_mouse_over_target?
    inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.target))
  end

  # Signal that the user is going to be removing walls from the first grid
  def bfs_mouse_over_wall?
    grid.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(bfs_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be removing walls from the second grid
  def heuristic_mouse_over_wall?
    grid.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(heuristic_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be adding walls from the first grid
  def bfs_mouse_over_grid?
    inputs.mouse.point.inside_rect?(bfs_scale_up(grid.rect))
  end

  # Signal that the user is going to be adding walls from the second grid
  def heuristic_mouse_over_grid?
    inputs.mouse.point.inside_rect?(heuristic_scale_up(grid.rect))
  end

  # This method is called when the user is editing the slider
  # It pauses the animation and moves the white circle to the closest integer point
  # on the slider
  # Changes the step of the search to be animated
  def process_input_slider
    state.play = false
    mouse_x = inputs.mouse.point.x

    # Bounds the mouse_x to the closest x value on the slider line
    mouse_x = slider.x if mouse_x < slider.x
    mouse_x = slider.x + slider.w if mouse_x > slider.x + slider.w

    # Sets the current search step to the one represented by the mouse x value
    # The slider's circle moves due to the render_slider method using anim_steps
    state.current_step = ((mouse_x - slider.x) / slider.spacing).to_i

    recalculate_searches
  end

  # Moves the star to the cell closest to the mouse in the first grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def process_input_bfs_star
    old_star = grid.star.clone
    unless bfs_cell_closest_to_mouse == grid.target
      grid.star = bfs_cell_closest_to_mouse
    end
    unless old_star == grid.star
      recalculate_searches
    end
  end

  # Moves the star to the cell closest to the mouse in the second grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def process_input_heuristic_star
    old_star = grid.star.clone
    unless heuristic_cell_closest_to_mouse == grid.target
      grid.star = heuristic_cell_closest_to_mouse
    end
    unless old_star == grid.star
      recalculate_searches
    end
  end

  # Moves the target to the grid closest to the mouse in the first grid
  # Only recalculate_searchess the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def process_input_bfs_target
    old_target = grid.target.clone
    unless bfs_cell_closest_to_mouse == grid.star
      grid.target = bfs_cell_closest_to_mouse
    end
    unless old_target == grid.target
      recalculate_searches
    end
  end

  # Moves the target to the cell closest to the mouse in the second grid
  # Only recalculate_searchess the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def process_input_heuristic_target
    old_target = grid.target.clone
    unless heuristic_cell_closest_to_mouse == grid.star
      grid.target = heuristic_cell_closest_to_mouse
    end
    unless old_target == grid.target
      recalculate_searches
    end
  end

  # Removes walls in the first grid that are under the cursor
  def process_input_bfs_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if bfs_mouse_over_grid?
      if grid.walls.has_key?(bfs_cell_closest_to_mouse)
        grid.walls.delete(bfs_cell_closest_to_mouse)
        recalculate_searches
      end
    end
  end

  # Removes walls in the second grid that are under the cursor
  def process_input_heuristic_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if heuristic_mouse_over_grid?
      if grid.walls.has_key?(heuristic_cell_closest_to_mouse)
        grid.walls.delete(heuristic_cell_closest_to_mouse)
        recalculate_searches
      end
    end
  end
  # Adds a wall in the first grid in the cell the mouse is over
  def process_input_bfs_add_wall
    if bfs_mouse_over_grid?
      unless grid.walls.has_key?(bfs_cell_closest_to_mouse)
        grid.walls[bfs_cell_closest_to_mouse] = true
        recalculate_searches
      end
    end
  end

  # Adds a wall in the second grid in the cell the mouse is over
  def process_input_heuristic_add_wall
    if heuristic_mouse_over_grid?
      unless grid.walls.has_key?(heuristic_cell_closest_to_mouse)
        grid.walls[heuristic_cell_closest_to_mouse] = true
        recalculate_searches
      end
    end
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def bfs_cell_closest_to_mouse
    # Closest cell to the mouse in the first grid
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse in the second grid helps with this
  def heuristic_cell_closest_to_mouse
    # Closest cell grid to the mouse in the second
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Translate the cell to the first grid
    x -= grid.width + 1
    # Bound x and y to the first grid
    x = 0 if x < 0
    y = 0 if y < 0
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  def recalculate_searches
    # Reset the searches
    bfs.came_from    = {}
    bfs.frontier     = []
    bfs.path         = []
    heuristic.came_from = {}
    heuristic.frontier  = []
    heuristic.path      = []

    # Move the searches forward to the current step
    state.current_step.times { move_searches_one_step_forward }
  end

  def move_searches_one_step_forward
    bfs_one_step_forward
    heuristic_one_step_forward
  end

  def bfs_one_step_forward
    return if bfs.came_from.has_key?(grid.target)

    # Only runs at the beginning of the search as setup.
    if bfs.came_from.empty?
      bfs.frontier << grid.star
      bfs.came_from[grid.star] = nil
    end

    # A step in the search
    unless bfs.frontier.empty?
      # Takes the next frontier cell
      new_frontier = bfs.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless bfs.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited
          bfs.frontier << neighbor
          bfs.came_from[neighbor] = new_frontier
        end
      end
    end

    # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
    # Comment this line and let a path generate to see the difference
    bfs.frontier = bfs.frontier.sort_by {| cell | proximity_to_star(cell) }

    # If the search found the target
    if bfs.came_from.has_key?(grid.target)
      # Calculate the path between the target and star
      bfs_calc_path
    end
  end

  # Calculates the path between the target and star for the breadth first search
  # Only called when the breadth first search finds the target
  def bfs_calc_path
    # Start from the target
    endpoint = grid.target
    # And the cell it came from
    next_endpoint = bfs.came_from[endpoint]
    while endpoint and next_endpoint
      # Draw a path between these two cells and store it
      path = get_path_between(endpoint, next_endpoint)
      bfs.path << path
      # And get the next pair of cells
      endpoint = next_endpoint
      next_endpoint = bfs.came_from[endpoint]
      # Continue till there are no more cells
    end
  end

  # Moves the heuristic search forward one step
  # Can be called from tick while the animation is playing
  # Can also be called when recalculating the searches after the user edited the grid
  def heuristic_one_step_forward
    # Stop the search if the target has been found
    return if heuristic.came_from.has_key?(grid.target)

    # If the search has not begun
    if heuristic.came_from.empty?
      # Setup the search to begin from the star
      heuristic.frontier << grid.star
      heuristic.came_from[grid.star] = nil
    end

    # One step in the heuristic search

    # Unless there are no more cells to explore from
    unless heuristic.frontier.empty?
      # Get the next cell to explore from
      new_frontier = heuristic.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do |neighbor|
        # That have not been visited and are not walls
        unless heuristic.came_from.has_key?(neighbor) || grid.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited
          heuristic.frontier << neighbor
          heuristic.came_from[neighbor] = new_frontier
        end
      end
    end

    # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
    heuristic.frontier = heuristic.frontier.sort_by {| cell | proximity_to_star(cell) }
    # Sort the frontier so cells that are close to the target are then prioritized
    heuristic.frontier = heuristic.frontier.sort_by {| cell | heuristic_heuristic(cell)  }

    # If the search found the target
    if heuristic.came_from.has_key?(grid.target)
      # Calculate the path between the target and star
      heuristic_calc_path
    end
  end

  # Returns one-dimensional absolute distance between cell and target
  # Returns a number to compare distances between cells and the target
  def heuristic_heuristic(cell)
    (grid.target.x - cell.x).abs + (grid.target.y - cell.y).abs
  end

  # Calculates the path between the target and star for the heuristic search
  # Only called when the heuristic search finds the target
  def heuristic_calc_path
    # Start from the target
    endpoint = grid.target
    # And the cell it came from
    next_endpoint = heuristic.came_from[endpoint]
    while endpoint and next_endpoint
      # Draw a path between these two cells and store it
      path = get_path_between(endpoint, next_endpoint)
      heuristic.path << path
      # And get the next pair of cells
      endpoint = next_endpoint
      next_endpoint = heuristic.came_from[endpoint]
      # Continue till there are no more cells
    end
  end

  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    # Gets all the valid neighbors into the array
    # From southern neighbor, clockwise
    neighbors << [cell.x    , cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y    ] unless cell.x == 0
    neighbors << [cell.x    , cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y    ] unless cell.x == grid.width - 1

    neighbors
  end

  # Finds the vertical and horizontal distance of a cell from the star
  # and returns the larger value
  # This method is used to have a zigzag pattern in the rendered path
  # A cell that is [5, 5] from the star,
  # is explored before over a cell that is [0, 7] away.
  # So, if possible, the search tries to go diagonal (zigzag) first
  def proximity_to_star(cell)
    distance_x = (grid.star.x - cell.x).abs
    distance_y = (grid.star.y - cell.y).abs

    if distance_x > distance_y
      return distance_x
    else
      return distance_y
    end
  end

  # Methods that allow code to be more concise. Subdivides args.state, which is where all variables are stored.
  def grid
    state.grid
  end

  def buttons
    state.buttons
  end

  def slider
    state.slider
  end

  def bfs
    state.bfs
  end

  def heuristic
    state.heuristic
  end

  # Descriptive aliases for colors
  def default_color
    [221, 212, 213] # Light Brown
  end

  def wall_color
    [134, 134, 120] # Camo Green
  end

  def visited_color
    [204, 191, 179] # Dark Brown
  end

  def frontier_color
    [103, 136, 204] # Blue
  end

  def path_color
    [231, 230, 228] # Pastel White
  end

  def button_color
    [190, 190, 190] # Gray
  end
end
# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Breadth First Search tick is called
  $heuristic ||= Heuristic.new(args)
  $heuristic.args = args
  $heuristic.tick
end


def reset
  $heuristic = nil
end

Path Finding Algorithms - A Star - main.rb

# ./samples/13_path_finding_algorithms/08_a_star/app/main.rb
# This program is inspired by https://www.redblobgames.com/pathfinding/a-star/introduction.html

# The A* Search works by incorporating both the distance from the starting point
# and the distance from the target in its heurisitic.

# It tends to find the correct (shortest) path even when the Greedy Best-First Search does not,
# and it explores less of the grid, and is therefore faster, than Dijkstra's Search.

class A_Star_Algorithm
  attr_gtk

  def tick
    defaults
    render
    input

    if dijkstra.came_from.empty?
      calc_searches
    end
  end

  def defaults
    # Variables to edit the size and appearance of the grid
    # Freely customizable to user's liking
    grid.width     ||= 15
    grid.height    ||= 15
    grid.cell_size ||= 27
    grid.rect      ||= [0, 0, grid.width, grid.height]

    grid.star      ||= [0, 2]
    grid.target    ||= [11, 13]
    grid.walls     ||= {
      [2, 2] => true,
      [3, 2] => true,
      [4, 2] => true,
      [5, 2] => true,
      [6, 2] => true,
      [7, 2] => true,
      [8, 2] => true,
      [9, 2] => true,
      [10, 2] => true,
      [11, 2] => true,
      [12, 2] => true,
      [12, 3] => true,
      [12, 4] => true,
      [12, 5] => true,
      [12, 6] => true,
      [12, 7] => true,
      [12, 8] => true,
      [12, 9] => true,
      [12, 10] => true,
      [12, 11] => true,
      [12, 12] => true,
      [5, 12] => true,
      [6, 12] => true,
      [7, 12] => true,
      [8, 12] => true,
      [9, 12] => true,
      [10, 12] => true,
      [11, 12] => true,
      [12, 12] => true
    }

    # What the user is currently editing on the grid
    # We store this value, because we want to remember the value even when
    # the user's cursor is no longer over what they're interacting with, but
    # they are still clicking down on the mouse.
    state.user_input ||= :none

    # These variables allow the breadth first search to take place
    # Came_from is a hash with a key of a cell and a value of the cell that was expanded from to find the key.
    # Used to prevent searching cells that have already been found
    # and to trace a path from the target back to the starting point.
    # Frontier is an array of cells to expand the search from.
    # The search is over when there are no more cells to search from.
    # Path stores the path from the target to the star, once the target has been found
    # It prevents calculating the path every tick.
    dijkstra.came_from   ||= {}
    dijkstra.cost_so_far ||= {}
    dijkstra.frontier    ||= []
    dijkstra.path        ||= []

    greedy.came_from ||= {}
    greedy.frontier  ||= []
    greedy.path      ||= []

    a_star.frontier  ||= []
    a_star.came_from ||= {}
    a_star.path      ||= []
  end

  # All methods with render draw stuff on the screen
  # UI has buttons, the slider, and labels
  # The search specific rendering occurs in the respective methods
  def render
    render_labels
    render_dijkstra
    render_greedy
    render_a_star
  end

  def render_labels
    outputs.labels << [150, 450, "Dijkstra's"]
    outputs.labels << [550, 450, "Greedy Best-First"]
    outputs.labels << [1025, 450, "A* Search"]
  end

  def render_dijkstra
    render_dijkstra_grid
    render_dijkstra_star
    render_dijkstra_target
    render_dijkstra_visited
    render_dijkstra_walls
    render_dijkstra_path
  end

  def render_greedy
    render_greedy_grid
    render_greedy_star
    render_greedy_target
    render_greedy_visited
    render_greedy_walls
    render_greedy_path
  end

  def render_a_star
    render_a_star_grid
    render_a_star_star
    render_a_star_target
    render_a_star_visited
    render_a_star_walls
    render_a_star_path
  end

  # This method handles user input every tick
  def input
    # If the mouse was lifted this tick
    if inputs.mouse.up
      # Set current input to none
      state.user_input = :none
    end

    # If the mouse was clicked this tick
    if inputs.mouse.down
      # Determine what the user is editing and appropriately edit the state.user_input variable
      determine_input
    end

    # Process user input based on user_input variable and current mouse position
    process_input
  end

  # Determines what the user is editing
  # This method is called when the mouse is clicked down
  def determine_input
    # If the mouse is over the star in the first grid
    if dijkstra_mouse_over_star?
      # The user is editing the star from the first grid
      state.user_input = :dijkstra_star
    # If the mouse is over the star in the second grid
    elsif greedy_mouse_over_star?
      # The user is editing the star from the second grid
      state.user_input = :greedy_star
    # If the mouse is over the star in the third grid
    elsif a_star_mouse_over_star?
      # The user is editing the star from the third grid
      state.user_input = :a_star_star
    # If the mouse is over the target in the first grid
    elsif dijkstra_mouse_over_target?
      # The user is editing the target from the first grid
      state.user_input = :dijkstra_target
    # If the mouse is over the target in the second grid
    elsif greedy_mouse_over_target?
      # The user is editing the target from the second grid
      state.user_input = :greedy_target
    # If the mouse is over the target in the third grid
    elsif a_star_mouse_over_target?
      # The user is editing the target from the third grid
      state.user_input = :a_star_target
    # If the mouse is over a wall in the first grid
    elsif dijkstra_mouse_over_wall?
      # The user is removing a wall from the first grid
      state.user_input = :dijkstra_remove_wall
    # If the mouse is over a wall in the second grid
    elsif greedy_mouse_over_wall?
      # The user is removing a wall from the second grid
      state.user_input = :greedy_remove_wall
    # If the mouse is over a wall in the third grid
    elsif a_star_mouse_over_wall?
      # The user is removing a wall from the third grid
      state.user_input = :a_star_remove_wall
    # If the mouse is over the first grid
    elsif dijkstra_mouse_over_grid?
      # The user is adding a wall from the first grid
      state.user_input = :dijkstra_add_wall
    # If the mouse is over the second grid
    elsif greedy_mouse_over_grid?
      # The user is adding a wall from the second grid
      state.user_input = :greedy_add_wall
    # If the mouse is over the third grid
    elsif a_star_mouse_over_grid?
      # The user is adding a wall from the third grid
      state.user_input = :a_star_add_wall
    end
  end

  # Processes click and drag based on what the user is currently dragging
  def process_input
    if state.user_input == :dijkstra_star
      process_input_dijkstra_star
    elsif state.user_input == :greedy_star
      process_input_greedy_star
    elsif state.user_input == :a_star_star
      process_input_a_star_star
    elsif state.user_input == :dijkstra_target
      process_input_dijkstra_target
    elsif state.user_input == :greedy_target
      process_input_greedy_target
    elsif state.user_input == :a_star_target
      process_input_a_star_target
    elsif state.user_input == :dijkstra_remove_wall
      process_input_dijkstra_remove_wall
    elsif state.user_input == :greedy_remove_wall
      process_input_greedy_remove_wall
    elsif state.user_input == :a_star_remove_wall
      process_input_a_star_remove_wall
    elsif state.user_input == :dijkstra_add_wall
      process_input_dijkstra_add_wall
    elsif state.user_input == :greedy_add_wall
      process_input_greedy_add_wall
    elsif state.user_input == :a_star_add_wall
      process_input_a_star_add_wall
    end
  end

  def render_dijkstra_grid
    # A large rect the size of the grid
    outputs.solids << [dijkstra_scale_up(grid.rect), default_color]

    # The vertical grid lines
    for x in 0..grid.width
      outputs.lines << dijkstra_vertical_line(x)
    end

    # The horizontal grid lines
    for y in 0..grid.height
      outputs.lines << dijkstra_horizontal_line(y)
    end
  end

  def render_greedy_grid
    # A large rect the size of the grid
    outputs.solids << [greedy_scale_up(grid.rect), default_color]

    # The vertical grid lines
    for x in 0..grid.width
      outputs.lines << greedy_vertical_line(x)
    end

    # The horizontal grid lines
    for y in 0..grid.height
      outputs.lines << greedy_horizontal_line(y)
    end
  end

  def render_a_star_grid
    # A large rect the size of the grid
    outputs.solids << [a_star_scale_up(grid.rect), default_color]

    # The vertical grid lines
    for x in 0..grid.width
      outputs.lines << a_star_vertical_line(x)
    end

    # The horizontal grid lines
    for y in 0..grid.height
      outputs.lines << a_star_horizontal_line(y)
    end
  end

  # Returns a vertical line for a column of the first grid
  def dijkstra_vertical_line column
    dijkstra_scale_up([column, 0, column, grid.height])
  end

  # Returns a horizontal line for a column of the first grid
  def dijkstra_horizontal_line row
    dijkstra_scale_up([0, row, grid.width, row])
  end

  # Returns a vertical line for a column of the second grid
  def greedy_vertical_line column
    dijkstra_scale_up([column + grid.width + 1, 0, column + grid.width + 1, grid.height])
  end

  # Returns a horizontal line for a column of the second grid
  def greedy_horizontal_line row
    dijkstra_scale_up([grid.width + 1, row, grid.width + grid.width + 1, row])
  end

  # Returns a vertical line for a column of the third grid
  def a_star_vertical_line column
    dijkstra_scale_up([column + (grid.width * 2) + 2, 0, column + (grid.width * 2) + 2, grid.height])
  end

  # Returns a horizontal line for a column of the third grid
  def a_star_horizontal_line row
    dijkstra_scale_up([(grid.width * 2) + 2, row, (grid.width * 2) + grid.width + 2, row])
  end

  # Renders the star on the first grid
  def render_dijkstra_star
    outputs.sprites << [dijkstra_scale_up(grid.star), 'star.png']
  end

  # Renders the star on the second grid
  def render_greedy_star
    outputs.sprites << [greedy_scale_up(grid.star), 'star.png']
  end

  # Renders the star on the third grid
  def render_a_star_star
    outputs.sprites << [a_star_scale_up(grid.star), 'star.png']
  end

  # Renders the target on the first grid
  def render_dijkstra_target
    outputs.sprites << [dijkstra_scale_up(grid.target), 'target.png']
  end

  # Renders the target on the second grid
  def render_greedy_target
    outputs.sprites << [greedy_scale_up(grid.target), 'target.png']
  end

  # Renders the target on the third grid
  def render_a_star_target
    outputs.sprites << [a_star_scale_up(grid.target), 'target.png']
  end

  # Renders the walls on the first grid
  def render_dijkstra_walls
    grid.walls.each_key do | wall |
      outputs.solids << [dijkstra_scale_up(wall), wall_color]
    end
  end

  # Renders the walls on the second grid
  def render_greedy_walls
    grid.walls.each_key do | wall |
      outputs.solids << [greedy_scale_up(wall), wall_color]
    end
  end

  # Renders the walls on the third grid
  def render_a_star_walls
    grid.walls.each_key do | wall |
      outputs.solids << [a_star_scale_up(wall), wall_color]
    end
  end

  # Renders the visited cells on the first grid
  def render_dijkstra_visited
    dijkstra.came_from.each_key do | visited_cell |
      outputs.solids << [dijkstra_scale_up(visited_cell), visited_color]
    end
  end

  # Renders the visited cells on the second grid
  def render_greedy_visited
    greedy.came_from.each_key do | visited_cell |
      outputs.solids << [greedy_scale_up(visited_cell), visited_color]
    end
  end

  # Renders the visited cells on the third grid
  def render_a_star_visited
    a_star.came_from.each_key do | visited_cell |
      outputs.solids << [a_star_scale_up(visited_cell), visited_color]
    end
  end

  # Renders the path found by the breadth first search on the first grid
  def render_dijkstra_path
    dijkstra.path.each do | path |
      outputs.solids << [dijkstra_scale_up(path), path_color]
    end
  end

  # Renders the path found by the greedy search on the second grid
  def render_greedy_path
    greedy.path.each do | path |
      outputs.solids << [greedy_scale_up(path), path_color]
    end
  end

  # Renders the path found by the a_star search on the third grid
  def render_a_star_path
    a_star.path.each do | path |
      outputs.solids << [a_star_scale_up(path), path_color]
    end
  end

  # Returns the rect for the path between two cells based on their relative positions
  def get_path_between(cell_one, cell_two)
    path = []

    # If cell one is above cell two
    if cell_one.x == cell_two.x and cell_one.y > cell_two.y
      # Path starts from the center of cell two and moves upward to the center of cell one
      path = [cell_two.x + 0.3, cell_two.y + 0.3, 0.4, 1.4]
    # If cell one is below cell two
    elsif cell_one.x == cell_two.x and cell_one.y < cell_two.y
      # Path starts from the center of cell one and moves upward to the center of cell two
      path = [cell_one.x + 0.3, cell_one.y + 0.3, 0.4, 1.4]
    # If cell one is to the left of cell two
    elsif cell_one.x > cell_two.x and cell_one.y == cell_two.y
      # Path starts from the center of cell two and moves rightward to the center of cell one
      path = [cell_two.x + 0.3, cell_two.y + 0.3, 1.4, 0.4]
    # If cell one is to the right of cell two
    elsif cell_one.x < cell_two.x and cell_one.y == cell_two.y
      # Path starts from the center of cell one and moves rightward to the center of cell two
      path = [cell_one.x + 0.3, cell_one.y + 0.3, 1.4, 0.4]
    end

    path
  end

  # In code, the cells are represented as 1x1 rectangles
  # When drawn, the cells are larger than 1x1 rectangles
  # This method is used to scale up cells, and lines
  # Objects are scaled up according to the grid.cell_size variable
  # This allows for easy customization of the visual scale of the grid
  # This method scales up cells for the first grid
  def dijkstra_scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone

    # If cell is just an x and y coordinate
    if cell.size == 2
      # Add a width and height of 1
      cell << 1
      cell << 1
    end

    # Scale all the values up
    cell.map! { |value| value * grid.cell_size }

    # Returns the scaled up cell
    cell
  end

  # Translates the given cell grid.width + 1 to the right and then scales up
  # Used to draw cells for the second grid
  # This method does not work for lines,
  # so separate methods exist for the grid lines
  def greedy_scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone
    # Translates the cell to the second grid equivalent
    cell.x += grid.width + 1
    # Proceeds as if scaling up for the first grid
    dijkstra_scale_up(cell)
  end

  # Translates the given cell (grid.width + 1) * 2 to the right and then scales up
  # Used to draw cells for the third grid
  # This method does not work for lines,
  # so separate methods exist for the grid lines
  def a_star_scale_up(cell)
    # Prevents the original value of cell from being edited
    cell = cell.clone
    # Translates the cell to the second grid equivalent
    cell.x += grid.width + 1
    # Translates the cell to the third grid equivalent
    cell.x += grid.width + 1
    # Proceeds as if scaling up for the first grid
    dijkstra_scale_up(cell)
  end

  # Signal that the user is going to be moving the star from the first grid
  def dijkstra_mouse_over_star?
    inputs.mouse.point.inside_rect?(dijkstra_scale_up(grid.star))
  end

  # Signal that the user is going to be moving the star from the second grid
  def greedy_mouse_over_star?
    inputs.mouse.point.inside_rect?(greedy_scale_up(grid.star))
  end

  # Signal that the user is going to be moving the star from the third grid
  def a_star_mouse_over_star?
    inputs.mouse.point.inside_rect?(a_star_scale_up(grid.star))
  end

  # Signal that the user is going to be moving the target from the first grid
  def dijkstra_mouse_over_target?
    inputs.mouse.point.inside_rect?(dijkstra_scale_up(grid.target))
  end

  # Signal that the user is going to be moving the target from the second grid
  def greedy_mouse_over_target?
    inputs.mouse.point.inside_rect?(greedy_scale_up(grid.target))
  end

  # Signal that the user is going to be moving the target from the third grid
  def a_star_mouse_over_target?
    inputs.mouse.point.inside_rect?(a_star_scale_up(grid.target))
  end

  # Signal that the user is going to be removing walls from the first grid
  def dijkstra_mouse_over_wall?
    grid.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(dijkstra_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be removing walls from the second grid
  def greedy_mouse_over_wall?
    grid.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(greedy_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be removing walls from the third grid
  def a_star_mouse_over_wall?
    grid.walls.each_key do | wall |
      return true if inputs.mouse.point.inside_rect?(a_star_scale_up(wall))
    end

    false
  end

  # Signal that the user is going to be adding walls from the first grid
  def dijkstra_mouse_over_grid?
    inputs.mouse.point.inside_rect?(dijkstra_scale_up(grid.rect))
  end

  # Signal that the user is going to be adding walls from the second grid
  def greedy_mouse_over_grid?
    inputs.mouse.point.inside_rect?(greedy_scale_up(grid.rect))
  end

  # Signal that the user is going to be adding walls from the third grid
  def a_star_mouse_over_grid?
    inputs.mouse.point.inside_rect?(a_star_scale_up(grid.rect))
  end

  # Moves the star to the cell closest to the mouse in the first grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def process_input_dijkstra_star
    old_star = grid.star.clone
    unless dijkstra_cell_closest_to_mouse == grid.target
      grid.star = dijkstra_cell_closest_to_mouse
    end
    unless old_star == grid.star
      reset_searches
    end
  end

  # Moves the star to the cell closest to the mouse in the second grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def process_input_greedy_star
    old_star = grid.star.clone
    unless greedy_cell_closest_to_mouse == grid.target
      grid.star = greedy_cell_closest_to_mouse
    end
    unless old_star == grid.star
      reset_searches
    end
  end

  # Moves the star to the cell closest to the mouse in the third grid
  # Only resets the search if the star changes position
  # Called whenever the user is editing the star (puts mouse down on star)
  def process_input_a_star_star
    old_star = grid.star.clone
    unless a_star_cell_closest_to_mouse == grid.target
      grid.star = a_star_cell_closest_to_mouse
    end
    unless old_star == grid.star
      reset_searches
    end
  end

  # Moves the target to the grid closest to the mouse in the first grid
  # Only reset_searchess the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def process_input_dijkstra_target
    old_target = grid.target.clone
    unless dijkstra_cell_closest_to_mouse == grid.star
      grid.target = dijkstra_cell_closest_to_mouse
    end
    unless old_target == grid.target
      reset_searches
    end
  end

  # Moves the target to the cell closest to the mouse in the second grid
  # Only reset_searchess the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def process_input_greedy_target
    old_target = grid.target.clone
    unless greedy_cell_closest_to_mouse == grid.star
      grid.target = greedy_cell_closest_to_mouse
    end
    unless old_target == grid.target
      reset_searches
    end
  end

  # Moves the target to the cell closest to the mouse in the third grid
  # Only reset_searchess the search if the target changes position
  # Called whenever the user is editing the target (puts mouse down on target)
  def process_input_a_star_target
    old_target = grid.target.clone
    unless a_star_cell_closest_to_mouse == grid.star
      grid.target = a_star_cell_closest_to_mouse
    end
    unless old_target == grid.target
      reset_searches
    end
  end

  # Removes walls in the first grid that are under the cursor
  def process_input_dijkstra_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if dijkstra_mouse_over_grid?
      if grid.walls.has_key?(dijkstra_cell_closest_to_mouse)
        grid.walls.delete(dijkstra_cell_closest_to_mouse)
        reset_searches
      end
    end
  end

  # Removes walls in the second grid that are under the cursor
  def process_input_greedy_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if greedy_mouse_over_grid?
      if grid.walls.has_key?(greedy_cell_closest_to_mouse)
        grid.walls.delete(greedy_cell_closest_to_mouse)
        reset_searches
      end
    end
  end

  # Removes walls in the third grid that are under the cursor
  def process_input_a_star_remove_wall
    # The mouse needs to be inside the grid, because we only want to remove walls
    # the cursor is directly over
    # Recalculations should only occur when a wall is actually deleted
    if a_star_mouse_over_grid?
      if grid.walls.has_key?(a_star_cell_closest_to_mouse)
        grid.walls.delete(a_star_cell_closest_to_mouse)
        reset_searches
      end
    end
  end

  # Adds a wall in the first grid in the cell the mouse is over
  def process_input_dijkstra_add_wall
    if dijkstra_mouse_over_grid?
      unless grid.walls.has_key?(dijkstra_cell_closest_to_mouse)
        grid.walls[dijkstra_cell_closest_to_mouse] = true
        reset_searches
      end
    end
  end

  # Adds a wall in the second grid in the cell the mouse is over
  def process_input_greedy_add_wall
    if greedy_mouse_over_grid?
      unless grid.walls.has_key?(greedy_cell_closest_to_mouse)
        grid.walls[greedy_cell_closest_to_mouse] = true
        reset_searches
      end
    end
  end

  # Adds a wall in the third grid in the cell the mouse is over
  def process_input_a_star_add_wall
    if a_star_mouse_over_grid?
      unless grid.walls.has_key?(a_star_cell_closest_to_mouse)
        grid.walls[a_star_cell_closest_to_mouse] = true
        reset_searches
      end
    end
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse helps with this
  def dijkstra_cell_closest_to_mouse
    # Closest cell to the mouse in the first grid
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Bound x and y to the grid
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse in the second grid helps with this
  def greedy_cell_closest_to_mouse
    # Closest cell grid to the mouse in the second
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Translate the cell to the first grid
    x -= grid.width + 1
    # Bound x and y to the first grid
    x = 0 if x < 0
    y = 0 if y < 0
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  # When the user grabs the star and puts their cursor to the far right
  # and moves up and down, the star is supposed to move along the grid as well
  # Finding the cell closest to the mouse in the third grid helps with this
  def a_star_cell_closest_to_mouse
    # Closest cell grid to the mouse in the second
    x = (inputs.mouse.point.x / grid.cell_size).to_i
    y = (inputs.mouse.point.y / grid.cell_size).to_i
    # Translate the cell to the first grid
    x -= (grid.width + 1) * 2
    # Bound x and y to the first grid
    x = 0 if x < 0
    y = 0 if y < 0
    x = grid.width - 1 if x > grid.width - 1
    y = grid.height - 1 if y > grid.height - 1
    # Return closest cell
    [x, y]
  end

  def reset_searches
    # Reset the searches
    dijkstra.came_from      = {}
    dijkstra.cost_so_far    = {}
    dijkstra.frontier       = []
    dijkstra.path           = []

    greedy.came_from = {}
    greedy.frontier  = []
    greedy.path      = []
    a_star.came_from = {}
    a_star.frontier  = []
    a_star.path      = []
  end

  def calc_searches
    calc_dijkstra
    calc_greedy
    calc_a_star
    # Move the searches forward to the current step
    # state.current_step.times { move_searches_one_step_forward }
  end

  def calc_dijkstra
    # Sets up the search to begin from the star
    dijkstra.frontier << grid.star
    dijkstra.came_from[grid.star] = nil
    dijkstra.cost_so_far[grid.star] = 0

    # Until the target is found or there are no more cells to explore from
    until dijkstra.came_from.has_key?(grid.target) or dijkstra.frontier.empty?
      # Take the next frontier cell. The first element is the cell, the second is the priority.
      new_frontier = dijkstra.frontier.shift#[0]
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do | neighbor |
        # That have not been visited and are not walls
        unless dijkstra.came_from.has_key?(neighbor) or grid.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited
          dijkstra.frontier << neighbor
          dijkstra.came_from[neighbor] = new_frontier
          dijkstra.cost_so_far[neighbor] = dijkstra.cost_so_far[new_frontier] + 1
        end
      end

      # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
      # Comment this line and let a path generate to see the difference
      dijkstra.frontier = dijkstra.frontier.sort_by {| cell | proximity_to_star(cell) }
      dijkstra.frontier = dijkstra.frontier.sort_by {| cell | dijkstra.cost_so_far[cell] }
    end


    # If the search found the target
    if dijkstra.came_from.has_key?(grid.target)
      # Calculate the path between the target and star
      dijkstra_calc_path
    end
  end

  def calc_greedy
    # Sets up the search to begin from the star
    greedy.frontier << grid.star
    greedy.came_from[grid.star] = nil

    # Until the target is found or there are no more cells to explore from
    until greedy.came_from.has_key?(grid.target) or greedy.frontier.empty?
      # Take the next frontier cell
      new_frontier = greedy.frontier.shift
      # For each of its neighbors
      adjacent_neighbors(new_frontier).each do | neighbor |
        # That have not been visited and are not walls
        unless greedy.came_from.has_key?(neighbor) or grid.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited
          greedy.frontier << neighbor
          greedy.came_from[neighbor] = new_frontier
        end
      end
      # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
      # Comment this line and let a path generate to see the difference
      greedy.frontier = greedy.frontier.sort_by {| cell | proximity_to_star(cell) }
      # Sort the frontier so cells that are close to the target are then prioritized
      greedy.frontier = greedy.frontier.sort_by {| cell | greedy_heuristic(cell)  }
    end


    # If the search found the target
    if greedy.came_from.has_key?(grid.target)
      # Calculate the path between the target and star
      greedy_calc_path
    end
  end

  def calc_a_star
    # Setup the search to start from the star
    a_star.came_from[grid.star] = nil
    a_star.cost_so_far[grid.star] = 0
    a_star.frontier << grid.star

    # Until there are no more cells to explore from or the search has found the target
    until a_star.frontier.empty? or a_star.came_from.has_key?(grid.target)
      # Get the next cell to expand from
      current_frontier = a_star.frontier.shift

      # For each of that cells neighbors
      adjacent_neighbors(current_frontier).each do | neighbor |
        # That have not been visited and are not walls
        unless a_star.came_from.has_key?(neighbor) or grid.walls.has_key?(neighbor)
          # Add them to the frontier and mark them as visited
          a_star.frontier << neighbor
          a_star.came_from[neighbor] = current_frontier
          a_star.cost_so_far[neighbor] = a_star.cost_so_far[current_frontier] + 1
        end
      end

      # Sort the frontier so that cells that are in a zigzag pattern are prioritized over those in an line
      # Comment this line and let a path generate to see the difference
      a_star.frontier = a_star.frontier.sort_by {| cell | proximity_to_star(cell) }
      a_star.frontier = a_star.frontier.sort_by {| cell | a_star.cost_so_far[cell] + greedy_heuristic(cell) }
    end

    # If the search found the target
    if a_star.came_from.has_key?(grid.target)
      # Calculate the path between the target and star
      a_star_calc_path
    end
  end

  # Calculates the path between the target and star for the breadth first search
  # Only called when the breadth first search finds the target
  def dijkstra_calc_path
    # Start from the target
    endpoint = grid.target
    # And the cell it came from
    next_endpoint = dijkstra.came_from[endpoint]
    while endpoint and next_endpoint
      # Draw a path between these two cells and store it
      path = get_path_between(endpoint, next_endpoint)
      dijkstra.path << path
      # And get the next pair of cells
      endpoint = next_endpoint
      next_endpoint = dijkstra.came_from[endpoint]
      # Continue till there are no more cells
    end
  end

  # Returns one-dimensional absolute distance between cell and target
  # Returns a number to compare distances between cells and the target
  def greedy_heuristic(cell)
    (grid.target.x - cell.x).abs + (grid.target.y - cell.y).abs
  end

  # Calculates the path between the target and star for the greedy search
  # Only called when the greedy search finds the target
  def greedy_calc_path
    # Start from the target
    endpoint = grid.target
    # And the cell it came from
    next_endpoint = greedy.came_from[endpoint]
    while endpoint and next_endpoint
      # Draw a path between these two cells and store it
      path = get_path_between(endpoint, next_endpoint)
      greedy.path << path
      # And get the next pair of cells
      endpoint = next_endpoint
      next_endpoint = greedy.came_from[endpoint]
      # Continue till there are no more cells
    end
  end

  # Calculates the path between the target and star for the a_star search
  # Only called when the a_star search finds the target
  def a_star_calc_path
    # Start from the target
    endpoint = grid.target
    # And the cell it came from
    next_endpoint = a_star.came_from[endpoint]

    while endpoint and next_endpoint
      # Draw a path between these two cells and store it
      path = get_path_between(endpoint, next_endpoint)
      a_star.path << path
      # And get the next pair of cells
      endpoint = next_endpoint
      next_endpoint = a_star.came_from[endpoint]
      # Continue till there are no more cells
    end
  end

  # Returns a list of adjacent cells
  # Used to determine what the next cells to be added to the frontier are
  def adjacent_neighbors(cell)
    neighbors = []

    # Gets all the valid neighbors into the array
    # From southern neighbor, clockwise
    neighbors << [cell.x    , cell.y - 1] unless cell.y == 0
    neighbors << [cell.x - 1, cell.y    ] unless cell.x == 0
    neighbors << [cell.x    , cell.y + 1] unless cell.y == grid.height - 1
    neighbors << [cell.x + 1, cell.y    ] unless cell.x == grid.width - 1

    neighbors
  end

  # Finds the vertical and horizontal distance of a cell from the star
  # and returns the larger value
  # This method is used to have a zigzag pattern in the rendered path
  # A cell that is [5, 5] from the star,
  # is explored before over a cell that is [0, 7] away.
  # So, if possible, the search tries to go diagonal (zigzag) first
  def proximity_to_star(cell)
    distance_x = (grid.star.x - cell.x).abs
    distance_y = (grid.star.y - cell.y).abs

    if distance_x > distance_y
      return distance_x
    else
      return distance_y
    end
  end

  # Methods that allow code to be more concise. Subdivides args.state, which is where all variables are stored.
  def grid
    state.grid
  end

  def dijkstra
    state.dijkstra
  end

  def greedy
    state.greedy
  end

  def a_star
    state.a_star
  end

  # Descriptive aliases for colors
  def default_color
    [221, 212, 213] # Light Brown
  end

  def wall_color
    [134, 134, 120] # Camo Green
  end

  def visited_color
    [204, 191, 179] # Dark Brown
  end

  def path_color
    [231, 230, 228] # Pastel White
  end

  def button_color
    [190, 190, 190] # Gray
  end
end


# Method that is called by DragonRuby periodically
# Used for updating animations and calculations
def tick args

  # Pressing r will reset the application
  if args.inputs.keyboard.key_down.r
    args.gtk.reset
    reset
    return
  end

  # Every tick, new args are passed, and the Breadth First Search tick is called
  $a_star_algorithm ||= A_Star_Algorithm.new(args)
  $a_star_algorithm.args = args
  $a_star_algorithm.tick
end


def reset
  $a_star_algorithm = nil
end

Path Finding Algorithms - Tower Defense - main.rb

# ./samples/13_path_finding_algorithms/09_tower_defense/app/main.rb
# An example of some major components in a tower defence game
# The pathing of the tanks is determined by A* algorithm -- try editing the walls

# The turrets shoot bullets at the closest tank. The bullets are heat-seeking

def tick args
  $gtk.reset if args.inputs.keyboard.key_down.r
  defaults args
  render args
  calc args
end

def defaults args
  args.outputs.background_color = wall_color
  args.state.grid_size = 5
  args.state.tile_size = 50
  args.state.grid_start ||= [0, 0]
  args.state.grid_goal  ||= [4, 4]

  # Try editing these walls to see the path change!
  args.state.walls ||= {
    [0, 4] => true,
    [1, 3] => true,
    [3, 1] => true,
    # [4, 0] => true,
  }

  args.state.a_star.frontier ||= []
  args.state.a_star.came_from ||= {}
  args.state.a_star.path ||= []

  args.state.tanks ||= []
  args.state.tank_spawn_period ||= 60
  args.state.tank_sprite_path ||= 'sprites/circle/white.png'
  args.state.tank_speed ||= 1

  args.state.turret_shoot_period = 10
  # Turrets can be entered as [x, y] but are immediately mapped to hashes
  # Walls are also added where the turrets are to prevent tanks from pathing over them
  args.state.turrets ||= [
    [2, 2]
  ].each { |turret| args.state.walls[turret] = true}.map do |x, y|
    {
      x: x * args.state.tile_size,
      y: y * args.state.tile_size,
      w: args.state.tile_size,
      h: args.state.tile_size,
      path: 'sprites/circle/gray.png',
      range: 100
    }
  end

  args.state.bullet_size ||= 25
  args.state.bullets ||= []
  args.state.bullet_path ||= 'sprites/circle/orange.png'
  #
end

def render args
  render_grid args
  render_a_star args
  args.outputs.sprites << args.state.tanks
  args.outputs.sprites << args.state.turrets
  args.outputs.sprites << args.state.bullets
end

def render_grid args
  # Draw a square the size and color of the grid
  args.outputs.solids << [
    0,
    0,
    args.state.grid_size * args.state.tile_size,
    args.state.grid_size * args.state.tile_size,
    grid_color
  ]

  # Draw lines across the grid to show tiles
  (args.state.grid_size + 1).times do | value |
    render_horizontal_line(args, value)
    render_vertical_line(args, value)
  end

  # Render special tiles
  render_tile(args, args.state.grid_start, start_color)
  render_tile(args, args.state.grid_goal, goal_color)
  args.state.walls.keys.each { |wall| render_tile(args, wall, wall_color) }
end

def render_vertical_line args, x
  args.outputs.lines << [
    x * args.state.tile_size,
    0,
    x * args.state.tile_size,
    args.state.tile_size * args.state.grid_size,
  ]
end

def render_horizontal_line args, y
  args.outputs.lines << [
    0,
    y * args.state.tile_size,
    args.state.tile_size * args.state.grid_size,
    y * args.state.tile_size,
  ]
end

def render_tile args, tile, color
  args.outputs.solids << [
    tile.x * args.state.tile_size,
    tile.y * args.state.tile_size,
    args.state.tile_size,
    args.state.tile_size,
    color
  ]
end

def calc args
  calc_a_star args
  calc_tanks args
  calc_turrets args
  calc_bullets args
end

def calc_a_star args
  # Only does this one time
  return unless args.state.a_star.path.empty?

  # Start the search from the grid start
  args.state.a_star.frontier << args.state.grid_start
  args.state.a_star.came_from[args.state.grid_start] = nil

  # Until a path to the goal has been found or there are no more tiles to explore
  until (args.state.a_star.came_from.has_key?(args.state.grid_goal)|| args.state.a_star.frontier.empty?)
    # For the first tile in the frontier
    tile_to_expand_from = args.state.a_star.frontier.shift
    # Add each of its neighbors to the frontier
    neighbors(args, tile_to_expand_from).each do | tile |
      args.state.a_star.frontier << tile
      args.state.a_star.came_from[tile] = tile_to_expand_from
    end
  end

  # Stop calculating a path if the goal was never reached
  return unless args.state.a_star.came_from.has_key? args.state.grid_goal

  # Fill path by tracing back from the goal
  current_cell = args.state.grid_goal
  while current_cell
    args.state.a_star.path.unshift current_cell
    current_cell = args.state.a_star.came_from[current_cell]
  end

  puts "The path has been calculated"
  puts args.state.a_star.path
end

def calc_tanks args
  spawn_tank args
  move_tanks args
end

def move_tanks args
  # Remove tanks that have reached the end of their path
  args.state.tanks.reject! { |tank| tank[:a_star].empty? }

  # Tanks have an array that has each tile it has to go to in order from a* path
  args.state.tanks.each do | tank |
    destination = tank[:a_star][0]
    # Move the tank towards the destination
    tank[:x] += copy_sign(args.state.tank_speed, ((destination.x * args.state.tile_size) - tank[:x]))
    tank[:y] += copy_sign(args.state.tank_speed, ((destination.y * args.state.tile_size) - tank[:y]))
    # If the tank has reached its destination
    if (destination.x * args.state.tile_size) == tank[:x] and
        (destination.y * args.state.tile_size) == tank[:y]
      # Set the destination to the next point in the path
      tank[:a_star].shift
    end
  end
end

def calc_turrets args
  return unless args.state.tick_count.mod_zero? args.state.turret_shoot_period
  args.state.turrets.each do | turret |
    # Finds the closest tank
    target = nil
    shortest_distance = turret[:range] + 1
    args.state.tanks.each do | tank |
      distance = distance_between(turret[:x], turret[:y], tank[:x], tank[:y])
      if distance < shortest_distance
        target = tank
        shortest_distance = distance
      end
    end
    # If there is a tank in range, fires a bullet
    if target
      args.state.bullets << {
        x: turret[:x],
        y: turret[:y],
        w: args.state.bullet_size,
        h: args.state.bullet_size,
        path: args.state.bullet_path,
        # Note that this makes it heat-seeking, because target is passed by reference
        # Could do target.clone to make the bullet go to where the tank initially was
        target: target
      }
    end
  end
end

def calc_bullets args
  # Bullets aim for the center of their targets
  args.state.bullets.each { |bullet| move bullet, center_of(bullet[:target])}
  args.state.bullets.reject! { |b| b.intersect_rect? b[:target] }
end

def center_of object
  object = object.clone
  object[:x] += 0.5
  object[:y] += 0.5
  object
end

def render_a_star args
  args.state.a_star.path.map do |tile|
    # Map each x, y coordinate to the center of the tile and scale up
    [(tile.x + 0.5) * args.state.tile_size, (tile.y + 0.5) * args.state.tile_size]
  end.inject do | point_a,  point_b |
    # Render the line between each point
    args.outputs.lines << [point_a.x, point_a.y, point_b.x, point_b.y, a_star_color]
    point_b
  end
end

# Moves object to target at speed
def move object, target, speed = 1
  if target.is_a? Hash
    object[:x] += copy_sign(speed, target[:x] - object[:x])
    object[:y] += copy_sign(speed, target[:y] - object[:y])
  else
    object[:x] += copy_sign(speed, target.x - object[:x])
    object[:y] += copy_sign(speed, target.y - object[:y])
  end
end
#
#
def distance_between a_x, a_y, b_x, b_y
  (((b_x - a_x) ** 2) + ((b_y - a_y) ** 2)) ** 0.5
end

def copy_sign value, sign
  return 0 if sign == 0
  return value if sign > 0
  -value
end
#
def spawn_tank args
  return unless args.state.tick_count.mod_zero? args.state.tank_spawn_period
  args.state.tanks << {
    x: args.state.grid_start.x,
    y: args.state.grid_start.y,
    w: args.state.tile_size,
    h: args.state.tile_size,
    path: args.state.tank_sprite_path,
    a_star: args.state.a_star.path.clone
  }
end

def neighbors args, tile
  [[tile.x, tile.y - 1],
   [tile.x, tile.y + 1],
   [tile.x + 1, tile.y],
   [tile.x - 1, tile.y]].reject do | neighbor |
    args.state.a_star.came_from.has_key?(neighbor) or
      tile_out_of_bounds?(args, neighbor) or
      args.state.walls.has_key? neighbor
  end
end

def tile_out_of_bounds? args, tile
  tile.x < 0 or tile.y < 0 or tile.x >= args.state.grid_size or tile.y >= args.state.grid_size
end

def grid_color
  [133, 226, 144]
end

def start_color
  [226, 144, 133]
end

def goal_color
  [226, 133, 144]
end

def wall_color
  [133, 144, 226]
end

def a_star_color
  [0, 0, 255]
end

3d - 3d Cube - main.rb

# ./samples/99_genre_3d/01_3d_cube/app/main.rb
STARTX             = 0.0
STARTY             = 0.0
ENDY               = 20.0
ENDX               = 20.0
SPINPOINT          = 10
SPINDURATION       = 400
POINTSIZE          = 8
BOXDEPTH           = 40
YAW                = 1
DISTANCE           = 10

def tick args
  args.outputs.background_color = [0, 0, 0]
  a = Math.sin(args.state.tick_count / SPINDURATION) * Math.tan(args.state.tick_count / SPINDURATION)
  s = Math.sin(a)
  c = Math.cos(a)
  x = STARTX
  y = STARTY
  offset_x = (1280 - (ENDX - STARTX)) / 2
  offset_y =  (360 - (ENDY - STARTY)) / 2

  srand(1)
  while y < ENDY do
    while x < ENDX do
      if (y == STARTY ||
          y == (ENDY / 0.5) * 2 ||
          y == (ENDY / 0.5) * 2 + 0.5 ||
          y == ENDY - 0.5 ||
          x == STARTX ||
          x == ENDX - 0.5)
        z = rand(BOXDEPTH)
        z *= Math.sin(a / 2)
        x -= SPINPOINT
        u = (x * c) - (z * s)
        v = (x * s) + (z * c)
        k = DISTANCE.fdiv(100) + (v / 500 * YAW)
        u = u / k
        v = y / k
        w = POINTSIZE / 10 / k
        args.outputs.sprites << { x: offset_x + u - w, y: offset_y + v - w, w: w, h: w, path: 'sprites/square-blue.png'}
        x += SPINPOINT
      end
      x += 0.5
    end
    y += 0.5
    x = STARTX
  end
end

$gtk.reset

3d - Wireframe - main.rb

# ./samples/99_genre_3d/02_wireframe/app/main.rb
def tick args
  args.state.model   ||= Object3D.new('data/shuttle.off')
  args.state.mtx     ||= rotate3D(0, 0, 0)
  args.state.inv_mtx ||= rotate3D(0, 0, 0)
  delta_mtx          = rotate3D(args.inputs.up_down * 0.01, input_roll(args) * 0.01, args.inputs.left_right * 0.01)
  args.outputs.lines << args.state.model.edges
  args.state.model.fast_3x3_transform! args.state.inv_mtx
  args.state.inv_mtx = mtx_mul(delta_mtx.transpose, args.state.inv_mtx)
  args.state.mtx     = mtx_mul(args.state.mtx, delta_mtx)
  args.state.model.fast_3x3_transform! args.state.mtx
  args.outputs.background_color = [0, 0, 0]
  args.outputs.debug << args.gtk.framerate_diagnostics_primitives
end

def input_roll args
  roll = 0
  roll += 1 if args.inputs.keyboard.e
  roll -= 1 if args.inputs.keyboard.q
  roll
end

def rotate3D(theta_x = 0.1, theta_y = 0.1, theta_z = 0.1)
  c_x, s_x = Math.cos(theta_x), Math.sin(theta_x)
  c_y, s_y = Math.cos(theta_y), Math.sin(theta_y)
  c_z, s_z = Math.cos(theta_z), Math.sin(theta_z)
  rot_x    = [[1, 0, 0], [0, c_x, -s_x], [0, s_x, c_x]]
  rot_y    = [[c_y, 0, s_y], [0, 1, 0], [-s_y, 0, c_y]]
  rot_z    = [[c_z, -s_z, 0], [s_z, c_z, 0], [0, 0, 1]]
  mtx_mul(mtx_mul(rot_x, rot_y), rot_z)
end

def mtx_mul(a, b)
  is = (0...a.length)
  js = (0...b[0].length)
  ks = (0...b.length)
  is.map do |i|
    js.map do |j|
      ks.map do |k|
        a[i][k] * b[k][j]
      end.reduce(&:plus)
    end
  end
end

class Object3D
  attr_reader :vert_count, :face_count, :edge_count, :verts, :faces, :edges

  def initialize(path)
    @vert_count = 0
    @face_count = 0
    @edge_count = 0
    @verts      = []
    @faces      = []
    @edges      = []
    _init_from_file path
  end

  def _init_from_file path
    file_lines = $gtk.read_file(path).split("\n")
                     .reject { |line| line.start_with?('#') || line.split(' ').length == 0 } # Strip out simple comments and blank lines
                     .map { |line| line.split('#')[0] } # Strip out end of line comments
                     .map { |line| line.split(' ') } # Tokenize by splitting on whitespace
    raise "OFF file did not start with OFF." if file_lines.shift != ["OFF"] # OFF meshes are supposed to begin with "OFF" as the first line.
    raise " line malformed" if file_lines[0].length != 3 # The second line needs to have 3 numbers. Raise an error if it doesn't.
    @vert_count, @face_count, @edge_count = file_lines.shift&.map(&:to_i) # Update the counts
    # Only the vertex and face counts need to be accurate. Raise an error if they are inaccurate.
    raise "Incorrect number of vertices and/or faces (Parsed VFE header: #{@vert_count} #{@face_count} #{@edge_count})" if file_lines.length != @vert_count + @face_count
    # Grab all the lines describing vertices.
    vert_lines = file_lines[0, @vert_count]
    # Grab all the lines describing faces.
    face_lines = file_lines[@vert_count, @face_count]
    # Create all the vertices
    @verts = vert_lines.map_with_index { |line, id| Vertex.new(line, id) }
    # Create all the faces
    @faces = face_lines.map { |line| Face.new(line, @verts) }
    # Create all the edges
    @edges = @faces.flat_map(&:edges).uniq do |edge|
      sorted = edge.sorted
      [sorted.point_a, sorted.point_b]
    end
  end

  def fast_3x3_transform! mtx
    @verts.each { |vert| vert.fast_3x3_transform! mtx }
  end
end

class Face

  attr_reader :verts, :edges

  def initialize(data, verts)
    vert_count = data[0].to_i
    vert_ids   = data[1, vert_count].map(&:to_i)
    @verts     = vert_ids.map { |i| verts[i] }
    @edges     = []
    (0...vert_count).each { |i| @edges[i] = Edge.new(verts[vert_ids[i - 1]], verts[vert_ids[i]]) }
    @edges.rotate! 1
  end
end

class Edge
  attr_reader :point_a, :point_b

  def initialize(point_a, point_b)
    @point_a = point_a
    @point_b = point_b
  end

  def sorted
    @point_a.id < @point_b.id ? self : Edge.new(@point_b, @point_a)
  end

  def draw_override ffi
    ffi.draw_line(@point_a.render_x, @point_a.render_y, @point_b.render_x, @point_b.render_y, 255, 0, 0, 128)
    ffi.draw_line(@point_a.render_x+1, @point_a.render_y, @point_b.render_x+1, @point_b.render_y, 255, 0, 0, 128)
    ffi.draw_line(@point_a.render_x, @point_a.render_y+1, @point_b.render_x, @point_b.render_y+1, 255, 0, 0, 128)
    ffi.draw_line(@point_a.render_x+1, @point_a.render_y+1, @point_b.render_x+1, @point_b.render_y+1, 255, 0, 0, 128)
  end

  def primitive_marker
    :line
  end
end

class Vertex
  attr_accessor :x, :y, :z, :id

  def initialize(data, id)
    @x  = data[0].to_f
    @y  = data[1].to_f
    @z  = data[2].to_f
    @id = id
  end

  def fast_3x3_transform! mtx
    _x, _y, _z = @x, @y, @z
    @x         = mtx[0][0] * _x + mtx[0][1] * _y + mtx[0][2] * _z
    @y         = mtx[1][0] * _x + mtx[1][1] * _y + mtx[1][2] * _z
    @z         = mtx[2][0] * _x + mtx[2][1] * _y + mtx[2][2] * _z
  end

  def render_x
    @x * (10 / (5 - @y)) * 170 + 640
  end

  def render_y
    @z * (10 / (5 - @y)) * 170 + 360
  end
end

3d - Wireframe - Data - what-is-this.txt

# ./samples/99_genre_3d/02_wireframe/data/what-is-this.txt
https://en.wikipedia.org/wiki/OFF_(file_format)

Arcade - Bullet Hell - main.rb

# ./samples/99_genre_arcade/bullet_hell/app/main.rb
def tick args
  args.state.base_columns   ||= 10.times.map { |n| 50 * n + 1280 / 2 - 5 * 50 + 5 }
  args.state.base_rows      ||= 5.times.map { |n| 50 * n + 720 - 5 * 50 }
  args.state.offset_columns = 10.times.map { |n| (n - 4.5) * Math.sin(Kernel.tick_count.to_radians) * 12 }
  args.state.offset_rows    = 5.map { 0 }
  args.state.columns        = 10.times.map { |i| args.state.base_columns[i] + args.state.offset_columns[i] }
  args.state.rows           = 5.times.map { |i| args.state.base_rows[i] + args.state.offset_rows[i] }
  args.state.explosions     ||= []
  args.state.enemies        ||= []
  args.state.score          ||= 0
  args.state.wave           ||= 0
  if args.state.enemies.empty?
    args.state.wave      += 1
    args.state.wave_root = Math.sqrt(args.state.wave)
    args.state.enemies   = make_enemies
  end
  args.state.player         ||= {x: 620, y: 80, w: 40, h: 40, path: 'sprites/circle-gray.png', angle: 90, cooldown: 0, alive: true}
  args.state.enemy_bullets  ||= []
  args.state.player_bullets ||= []
  args.state.lives          ||= 3
  args.state.missed_shots   ||= 0
  args.state.fired_shots    ||= 0

  update_explosions args
  update_enemy_positions args

  if args.inputs.left && args.state.player[:x] > (300 + 5)
    args.state.player[:x] -= 5
  end
  if args.inputs.right && args.state.player[:x] < (1280 - args.state.player[:w] - 300 - 5)
    args.state.player[:x] += 5
  end

  args.state.enemy_bullets.each do |bullet|
    bullet[:x] += bullet[:dx]
    bullet[:y] += bullet[:dy]
  end
  args.state.player_bullets.each do |bullet|
    bullet[:x] += bullet[:dx]
    bullet[:y] += bullet[:dy]
  end

  args.state.enemy_bullets  = args.state.enemy_bullets.find_all { |bullet| bullet[:y].between?(-16, 736) }
  args.state.player_bullets = args.state.player_bullets.find_all do |bullet|
    if bullet[:y].between?(-16, 736)
      true
    else
      args.state.missed_shots += 1
      false
    end
  end

  args.state.enemies = args.state.enemies.reject do |enemy|
    if args.state.player[:alive] && 1500 > (args.state.player[:x] - enemy[:x]) ** 2 + (args.state.player[:y] - enemy[:y]) ** 2
      args.state.explosions << {x: enemy[:x] + 4, y: enemy[:y] + 4, w: 32, h: 32, path: 'sprites/explosion-0.png', age: 0}
      args.state.explosions << {x: args.state.player[:x] + 4, y: args.state.player[:y] + 4, w: 32, h: 32, path: 'sprites/explosion-0.png', age: 0}
      args.state.player[:alive] = false
      true
    else
      false
    end
  end
  args.state.enemy_bullets.each do |bullet|
    if args.state.player[:alive] && 400 > (args.state.player[:x] - bullet[:x] + 12) ** 2 + (args.state.player[:y] - bullet[:y] + 12) ** 2
      args.state.explosions << {x: args.state.player[:x] + 4, y: args.state.player[:y] + 4, w: 32, h: 32, path: 'sprites/explosion-0.png', age: 0}
      args.state.player[:alive] = false
      bullet[:despawn]          = true
    end
  end
  args.state.enemies = args.state.enemies.reject do |enemy|
    args.state.player_bullets.any? do |bullet|
      if 400 > (enemy[:x] - bullet[:x] + 12) ** 2 + (enemy[:y] - bullet[:y] + 12) ** 2
        args.state.explosions << {x: enemy[:x] + 4, y: enemy[:y] + 4, w: 32, h: 32, path: 'sprites/explosion-0.png', age: 0}
        bullet[:despawn] = true
        args.state.score += 1000 * args.state.wave
        true
      else
        false
      end
    end
  end

  args.state.player_bullets = args.state.player_bullets.reject { |bullet| bullet[:despawn] }
  args.state.enemy_bullets  = args.state.enemy_bullets.reject { |bullet| bullet[:despawn] }

  args.state.player[:cooldown] -= 1
  if args.inputs.keyboard.key_held.space && args.state.player[:cooldown] <= 0 && args.state.player[:alive]
    args.state.player_bullets << {x: args.state.player[:x] + 12, y: args.state.player[:y] + 28, w: 16, h: 16, path: 'sprites/star.png', dx: 0, dy: 8}.sprite
    args.state.fired_shots       += 1
    args.state.player[:cooldown] = 10 + 20 / args.state.wave
  end
  args.state.enemies.each do |enemy|
    if Math.rand < 0.0005 + 0.0005 * args.state.wave && args.state.player[:alive] && enemy[:move_state] == :normal
      args.state.enemy_bullets << {x: enemy[:x] + 12, y: enemy[:y] - 8, w: 16, h: 16, path: 'sprites/star.png', dx: 0, dy: -3 - args.state.wave_root}.sprite
    end
  end

  args.outputs.background_color = [0, 0, 0]
  args.outputs.primitives << args.state.enemies.map do |enemy|
    [enemy[:x], enemy[:y], 40, 40, enemy[:path], -90].sprite
  end
  args.outputs.primitives << args.state.player if args.state.player[:alive]
  args.outputs.primitives << args.state.explosions
  args.outputs.primitives << args.state.player_bullets
  args.outputs.primitives << args.state.enemy_bullets
  accuracy = args.state.fired_shots.zero? ? 1 : (args.state.fired_shots - args.state.missed_shots) / args.state.fired_shots
  args.outputs.primitives << [
    [0, 0, 300, 720, 96, 0, 0].solid,
    [1280 - 300, 0, 300, 720, 96, 0, 0].solid,
    [1280 - 290, 60, "Wave     #{args.state.wave}", 255, 255, 255].label,
    [1280 - 290, 40, "Accuracy #{(accuracy * 100).floor}%", 255, 255, 255].label,
    [1280 - 290, 20, "Score    #{(args.state.score * accuracy).floor}", 255, 255, 255].label,
  ]
  args.outputs.primitives << args.state.lives.times.map do |n|
    [1280 - 290 + 50 * n, 80, 40, 40, 'sprites/circle-gray.png', 90].sprite
  end
  #args.outputs.debug << args.gtk.framerate_diagnostics_primitives

  if (!args.state.player[:alive]) && args.state.enemy_bullets.empty? && args.state.explosions.empty? && args.state.enemies.all? { |enemy| enemy[:move_state] == :normal }
    args.state.player[:alive] = true
    args.state.player[:x]     = 624
    args.state.player[:y]     = 80
    args.state.lives          -= 1
    if args.state.lives == -1
      args.state.clear!
    end
  end
end

def make_enemies
  enemies = []
  enemies += 10.times.map { |n| {x: Math.rand * 1280 * 2 - 640, y: Math.rand * 720 * 2 + 720, row: 0, col: n, path: 'sprites/circle-orange.png', move_state: :retreat} }
  enemies += 10.times.map { |n| {x: Math.rand * 1280 * 2 - 640, y: Math.rand * 720 * 2 + 720, row: 1, col: n, path: 'sprites/circle-orange.png', move_state: :retreat} }
  enemies += 8.times.map { |n| {x: Math.rand * 1280 * 2 - 640, y: Math.rand * 720 * 2 + 720, row: 2, col: n + 1, path: 'sprites/circle-blue.png', move_state: :retreat} }
  enemies += 8.times.map { |n| {x: Math.rand * 1280 * 2 - 640, y: Math.rand * 720 * 2 + 720, row: 3, col: n + 1, path: 'sprites/circle-blue.png', move_state: :retreat} }
  enemies += 4.times.map { |n| {x: Math.rand * 1280 * 2 - 640, y: Math.rand * 720 * 2 + 720, row: 4, col: n + 3, path: 'sprites/circle-green.png', move_state: :retreat} }
  enemies
end

def update_explosions args
  args.state.explosions.each do |explosion|
    explosion[:age]  += 0.5
    explosion[:path] = "sprites/explosion-#{explosion[:age].floor}.png"
  end
  args.state.explosions = args.state.explosions.reject { |explosion| explosion[:age] >= 7 }
end

def update_enemy_positions args
  args.state.enemies.each do |enemy|
    if enemy[:move_state] == :normal
      enemy[:x]          = args.state.columns[enemy[:col]]
      enemy[:y]          = args.state.rows[enemy[:row]]
      enemy[:move_state] = :dive if Math.rand < 0.0002 + 0.00005 * args.state.wave && args.state.player[:alive]
    elsif enemy[:move_state] == :dive
      enemy[:target_x] ||= args.state.player[:x]
      enemy[:target_y] ||= args.state.player[:y]
      dx               = enemy[:target_x] - enemy[:x]
      dy               = enemy[:target_y] - enemy[:y]
      vel              = Math.sqrt(dx * dx + dy * dy)
      speed_limit      = 2 + args.state.wave_root
      if vel > speed_limit
        dx /= vel / speed_limit
        dy /= vel / speed_limit
      end
      if vel < 1 || !args.state.player[:alive]
        enemy[:move_state] = :retreat
      end
      enemy[:x] += dx
      enemy[:y] += dy
    elsif enemy[:move_state] == :retreat
      enemy[:target_x] = args.state.columns[enemy[:col]]
      enemy[:target_y] = args.state.rows[enemy[:row]]
      dx               = enemy[:target_x] - enemy[:x]
      dy               = enemy[:target_y] - enemy[:y]
      vel              = Math.sqrt(dx * dx + dy * dy)
      speed_limit      = 2 + args.state.wave_root
      if vel > speed_limit
        dx /= vel / speed_limit
        dy /= vel / speed_limit
      elsif vel < 1
        enemy[:move_state] = :normal
        enemy[:target_x]   = nil
        enemy[:target_y]   = nil
      end
      enemy[:x] += dx
      enemy[:y] += dy
    end
  end
end

Arcade - Dueling Starships - main.rb

# ./samples/99_genre_arcade/dueling_starships/app/main.rb
class DuelingSpaceships
  attr_accessor :state, :inputs, :outputs, :grid

  def tick
    defaults
    render
    calc
    input
  end

  def defaults
    outputs.background_color = [0, 0, 0]
    state.ship_blue       ||= new_blue_ship
    state.ship_red        ||= new_red_ship
    state.flames          ||= []
    state.bullets         ||= []
    state.ship_blue_score ||= 0
    state.ship_red_score  ||= 0
    state.stars           ||= 100.map do
      [rand.add(2).to_square(grid.w_half.randomize(:sign, :ratio),
                             grid.h_half.randomize(:sign, :ratio)),
       128 + 128.randomize(:ratio), 255, 255]
    end
  end

  def default_ship x, y, angle, sprite_path, bullet_sprite_path, color
    state.new_entity(:ship,
                    { x: x,
                      y: y,
                      dy: 0,
                      dx: 0,
                      damage: 0,
                      dead: false,
                      angle: angle,
                      max_alpha: 255,
                      sprite_path: sprite_path,
                      bullet_sprite_path: bullet_sprite_path,
                      color: color })
  end

  def new_red_ship
    default_ship(400, 250.randomize(:sign, :ratio),
                 180, 'sprites/ship_red.png', 'sprites/red_bullet.png',
                 [255, 90, 90])
  end

  def new_blue_ship
    default_ship(-400, 250.randomize(:sign, :ratio),
                 0, 'sprites/ship_blue.png', 'sprites/blue_bullet.png',
                 [110, 140, 255])
  end

  def render
    render_instructions
    render_score
    render_universe
    render_flames
    render_ships
    render_bullets
  end

  def render_ships
    update_ship_outputs(state.ship_blue)
    update_ship_outputs(state.ship_red)
    outputs.sprites << [state.ship_blue.sprite, state.ship_red.sprite]
    outputs.labels  << [state.ship_blue.label, state.ship_red.label]
  end

  def render_instructions
    return if state.ship_blue.dx  > 0  || state.ship_blue.dy > 0  ||
              state.ship_red.dx   > 0  || state.ship_red.dy  > 0  ||
              state.flames.length > 0

    outputs.labels << [grid.left.shift_right(30),
                       grid.bottom.shift_up(30),
                       "Two gamepads needed to play. R1 to accelerate. Left and right on D-PAD to turn ship. Hold A to shoot. Press B to drop mines.",
                       0, 0, 255, 255, 255]
  end

  def calc
    calc_thrusts
    calc_ships
    calc_bullets
    calc_winner
  end

  def input
    input_accelerate
    input_turn
    input_bullets_and_mines
  end

  def render_score
    outputs.labels << [grid.left.shift_right(80),
                       grid.top.shift_down(40),
                       state.ship_blue_score, 30, 1, state.ship_blue.color]

    outputs.labels << [grid.right.shift_left(80),
                       grid.top.shift_down(40),
                       state.ship_red_score,  30, 1, state.ship_red.color]
  end

  def render_universe
    return if outputs.static_solids.any?
    outputs.static_solids << grid.rect
    outputs.static_solids << state.stars
  end

  def apply_round_finished_alpha entity
    return entity unless state.round_finished_debounce
    entity.a *= state.round_finished_debounce.percentage_of(2.seconds)
    return entity
  end

  def update_ship_outputs ship, sprite_size = 66
    ship.sprite =
      apply_round_finished_alpha [sprite_size.to_square(ship.x, ship.y),
                                  ship.sprite_path,
                                  ship.angle,
                                  ship.dead ? 0 : 255 * ship.created_at.ease(2.seconds)].sprite
    ship.label =
      apply_round_finished_alpha [ship.x,
                                  ship.y + 100,
                                  "." * 5.minus(ship.damage).greater(0), 20, 1, ship.color, 255].label
  end

  def render_flames sprite_size = 6
    outputs.sprites << state.flames.map do |p|
      apply_round_finished_alpha [sprite_size.to_square(p.x, p.y),
                                  'sprites/flame.png', 0,
                                  p.max_alpha * p.created_at.ease(p.lifetime, :flip)].sprite
    end
  end

  def render_bullets sprite_size = 10
    outputs.sprites << state.bullets.map do |b|
      apply_round_finished_alpha [b.sprite_size.to_square(b.x, b.y),
                                  b.owner.bullet_sprite_path,
                                  0, b.max_alpha].sprite
    end
  end

  def wrap_location! location
    location.x = grid.left    if location.x > grid.right
    location.x = grid.right   if location.x < grid.left
    location.y = grid.top     if location.y < grid.bottom
    location.y = grid.bottom  if location.y > grid.top
    location
  end

  def calc_thrusts
    state.flames =
      state.flames
        .reject(&:old?)
        .map do |p|
          p.speed *= 0.9
          p.y += p.angle.vector_y(p.speed)
          p.x += p.angle.vector_x(p.speed)
          wrap_location! p
      end
  end

  def all_ships
    [state.ship_blue, state.ship_red]
  end

  def alive_ships
    all_ships.reject { |s| s.dead }
  end

  def calc_bullet bullet
    bullet.y += bullet.angle.vector_y(bullet.speed)
    bullet.x += bullet.angle.vector_x(bullet.speed)
    wrap_location! bullet
    explode_bullet! bullet if bullet.old?
    return if bullet.exploded
    return if state.round_finished
    alive_ships.each do |s|
      if s != bullet.owner &&
         s.sprite.intersect_rect?(bullet.sprite_size.to_square(bullet.x, bullet.y))
        explode_bullet! bullet, 10, 5, 30
        s.damage += 1
      end
    end
  end

  def calc_bullets
    state.bullets.each    { |b| calc_bullet b }
    state.bullets.reject! { |b| b.exploded }
  end

  def create_explosion! type, entity, flame_count, max_speed, lifetime, max_alpha = 255
    flame_count.times do
      state.flames << state.new_entity(type,
                                     { angle: 360.randomize(:ratio),
                                       speed: max_speed.randomize(:ratio),
                                       lifetime: lifetime,
                                       x: entity.x,
                                       y: entity.y,
                                       max_alpha: max_alpha })
    end
  end

  def explode_bullet! bullet, flame_override = 5, max_speed = 5, lifetime = 10
    bullet.exploded = true
    create_explosion! :bullet_explosion,
                      bullet,
                      flame_override,
                      max_speed,
                      lifetime,
                      bullet.max_alpha
  end

  def calc_ship ship
    ship.x += ship.dx
    ship.y += ship.dy
    wrap_location! ship
  end

  def calc_ships
    all_ships.each { |s| calc_ship s }
    return if all_ships.any? { |s| s.dead }
    return if state.round_finished
    return unless state.ship_blue.sprite.intersect_rect?(state.ship_red.sprite)
    state.ship_blue.damage = 5
    state.ship_red.damage  = 5
  end

  def create_thruster_flames! ship
    state.flames << state.new_entity(:ship_thruster,
                                   { angle: ship.angle + 180 + 60.randomize(:sign, :ratio),
                                     speed: 5.randomize(:ratio),
                                     max_alpha: 255 * ship.created_at_elapsed.percentage_of(2.seconds),
                                     lifetime: 30,
                                     x: ship.x - ship.angle.vector_x(40) + 5.randomize(:sign, :ratio),
                                     y: ship.y - ship.angle.vector_y(40) + 5.randomize(:sign, :ratio) })
  end

  def input_accelerate_ship should_move_ship, ship
    return if ship.dead

    should_move_ship &&= (ship.dx + ship.dy).abs < 5

    if should_move_ship
      create_thruster_flames! ship
      ship.dx += ship.angle.vector_x 0.050
      ship.dy += ship.angle.vector_y 0.050
    else
      ship.dx *= 0.99
      ship.dy *= 0.99
    end
  end

  def input_accelerate
    input_accelerate_ship inputs.controller_one.key_held.r1 || inputs.keyboard.up, state.ship_blue
    input_accelerate_ship inputs.controller_two.key_held.r1, state.ship_red
  end

  def input_turn_ship direction, ship
    ship.angle -= 3 * direction
  end

  def input_turn
    input_turn_ship inputs.controller_one.left_right + inputs.keyboard.left_right, state.ship_blue
    input_turn_ship inputs.controller_two.left_right, state.ship_red
  end

  def input_bullet create_bullet, ship
    return unless create_bullet
    return if ship.dead

    state.bullets << state.new_entity(:ship_bullet,
                                    { owner: ship,
                                      angle: ship.angle,
                                      max_alpha: 255 * ship.created_at_elapsed.percentage_of(2.seconds),
                                      speed: 5 + ship.dx.mult(ship.angle.vector_x) + ship.dy.mult(ship.angle.vector_y),
                                      lifetime: 120,
                                      sprite_size: 10,
                                      x: ship.x + ship.angle.vector_x * 32,
                                      y: ship.y + ship.angle.vector_y * 32 })
  end

  def input_mine create_mine, ship
    return unless create_mine
    return if ship.dead

    state.bullets << state.new_entity(:ship_bullet,
                                    { owner: ship,
                                      angle: 360.randomize(:sign, :ratio),
                                      max_alpha: 255 * ship.created_at_elapsed.percentage_of(2.seconds),
                                      speed: 0.02,
                                      sprite_size: 10,
                                      lifetime: 600,
                                      x: ship.x + ship.angle.vector_x * -50,
                                      y: ship.y + ship.angle.vector_y * -50 })
  end

  def input_bullets_and_mines
    return if state.bullets.length > 100

    [
      [inputs.controller_one.key_held.a || inputs.keyboard.key_held.space,
       inputs.controller_one.key_down.b || inputs.keyboard.key_down.down,
       state.ship_blue],
      [inputs.controller_two.key_held.a, inputs.controller_two.key_down.b, state.ship_red]
    ].each do |a_held, b_down, ship|
      input_bullet(a_held && state.tick_count.mod_zero?(10).or(a_held == 0), ship)
      input_mine(b_down, ship)
    end
  end

  def calc_kill_ships
    alive_ships.find_all { |s| s.damage >= 5 }.each do |s|
      s.dead = true
      create_explosion! :ship_explosion, s, 20, 20, 30, s.max_alpha
    end
  end

  def calc_score
    return if state.round_finished
    return if alive_ships.length > 1

    if alive_ships.first == state.ship_red
      state.ship_red_score += 1
    elsif alive_ships.first == state.ship_blue
      state.ship_blue_score += 1
    end

    state.round_finished = true
  end

  def calc_reset_ships
    return unless state.round_finished
    state.round_finished_debounce ||= 2.seconds
    state.round_finished_debounce -= 1
    return if state.round_finished_debounce > 0
    start_new_round!
  end

  def start_new_round!
    state.ship_blue = new_blue_ship
    state.ship_red  = new_red_ship
    state.round_finished = false
    state.round_finished_debounce = nil
    state.flames.clear
    state.bullets.clear
  end

  def calc_winner
    calc_kill_ships
    calc_score
    calc_reset_ships
  end
end

$dueling_spaceship = DuelingSpaceships.new

def tick args
  args.grid.origin_center!
  $dueling_spaceship.inputs  = args.inputs
  $dueling_spaceship.outputs = args.outputs
  $dueling_spaceship.state    = args.state
  $dueling_spaceship.grid    = args.grid
  $dueling_spaceship.tick
end

arcade/flappy dragon/credits.txt

# ./samples/99_genre_arcade/flappy_dragon/CREDITS.txt
code: Amir Rajan, https://twitter.com/amirrajan
graphics and audio: Nick Culbertson, https://twitter.com/MobyPixel

arcade/flappy dragon/main.rb

# ./samples/99_genre_arcade/flappy_dragon/app/main.rb
class FlappyDragon
  attr_accessor :grid, :inputs, :state, :outputs

  def tick
    defaults
    render
    calc
    process_inputs
  end

  def defaults
    state.flap_power              = 11
    state.gravity                 = 0.9
    state.ceiling                 = 600
    state.ceiling_flap_power      = 6
    state.wall_countdown_length   = 100
    state.wall_gap_size           = 100
    state.wall_countdown        ||= 0
    state.hi_score              ||= 0
    state.score                 ||= 0
    state.walls                 ||= []
    state.x                     ||= 50
    state.y                     ||= 500
    state.dy                    ||= 0
    state.scene                 ||= :menu
    state.scene_at              ||= 0
    state.difficulty            ||= :normal
    state.new_difficulty        ||= :normal
    state.countdown             ||= 4.seconds
    state.flash_at              ||= 0
  end

  def render
    outputs.sounds << "sounds/flappy-song.ogg" if state.tick_count == 1
    render_score
    render_menu
    render_game
  end

  def render_score
    outputs.primitives << [10, 710, "HI SCORE: #{state.hi_score}", large_white_typeset].label
    outputs.primitives << [10, 680, "SCORE: #{state.score}", large_white_typeset].label
    outputs.primitives << [10, 650, "DIFFICULTY: #{state.difficulty.upcase}", large_white_typeset].label
  end

  def render_menu
    return unless state.scene == :menu
    render_overlay

    outputs.labels << [640, 700, "Flappy Dragon", 50, 1, 255, 255, 255]
    outputs.labels << [640, 500, "Instructions: Press Spacebar to flap. Don't die.", 4, 1, 255, 255, 255]
    outputs.labels << [430, 430, "[Tab]    Change difficulty", 4, 0, 255, 255, 255]
    outputs.labels << [430, 400, "[Enter]  Start at New Difficulty ", 4, 0, 255, 255, 255]
    outputs.labels << [430, 370, "[Escape] Cancel/Resume ", 4, 0, 255, 255, 255]
    outputs.labels << [640, 300, "(mouse, touch, and game controllers work, too!) ", 4, 1, 255, 255, 255]
    outputs.labels << [640, 200, "Difficulty: #{state.new_difficulty.capitalize}", 4, 1, 255, 255, 255]

    outputs.labels << [10, 100, "Code:   @amirrajan",     255, 255, 255]
    outputs.labels << [10,  80, "Art:    @mobypixel",     255, 255, 255]
    outputs.labels << [10,  60, "Music:  @mobypixel",     255, 255, 255]
    outputs.labels << [10,  40, "Engine: DragonRuby GTK", 255, 255, 255]
  end

  def render_overlay
    outputs.primitives << [grid.rect.scale_rect(1.1, 0, 0), 0, 0, 0, 230].solid
  end

  def render_game
    render_game_over
    render_background
    render_walls
    render_dragon
    render_flash
  end

  def render_game_over
    return unless state.scene == :game
    outputs.labels << [638, 358, score_text, 20, 1]
    outputs.labels << [635, 360, score_text, 20, 1, 255, 255, 255]
    outputs.labels << [638, 428, countdown_text, 20, 1]
    outputs.labels << [635, 430, countdown_text, 20, 1, 255, 255, 255]
  end

  def render_background
    outputs.sprites << [0, 0, 1280, 720, 'sprites/background.png']

    scroll_point_at   = state.tick_count
    scroll_point_at   = state.scene_at if state.scene == :menu
    scroll_point_at   = state.death_at if state.countdown > 0
    scroll_point_at ||= 0

    outputs.sprites << scrolling_background(scroll_point_at, 'sprites/parallax_back.png',   0.25)
    outputs.sprites << scrolling_background(scroll_point_at, 'sprites/parallax_middle.png', 0.50)
    outputs.sprites << scrolling_background(scroll_point_at, 'sprites/parallax_front.png',  1.00, -80)
  end

  def render_walls
    state.walls.each do |w|
      w.sprites = [
        [w.x, w.bottom_height - 720, 100, 720, 'sprites/wall.png', 180],
        [w.x, w.top_y,               100, 720, 'sprites/wallbottom.png', 0]
      ]
    end
    outputs.sprites << state.walls.map(&:sprites)
  end

  def render_dragon
    state.show_death = true if state.countdown == 3.seconds

    render_debug_hitbox false

    if state.show_death == false || !state.death_at
      animation_index = state.flapped_at.frame_index 6, 2, false if state.flapped_at
      sprite_name = "sprites/dragon_fly#{animation_index.or(0) + 1}.png"
      state.dragon_sprite = [state.x, state.y, 100, 80, sprite_name, state.dy * 1.2]
    else
      sprite_name = "sprites/dragon_die.png"
      state.dragon_sprite = [state.x, state.y, 100, 80, sprite_name, state.dy * 1.2]
      sprite_changed_elapsed    = state.death_at.elapsed_time - 1.seconds
      state.dragon_sprite.angle += (sprite_changed_elapsed ** 1.3) * state.death_fall_direction * -1
      state.dragon_sprite.x     += (sprite_changed_elapsed ** 1.2) * state.death_fall_direction
      state.dragon_sprite.y     += (sprite_changed_elapsed * 14 - sprite_changed_elapsed ** 1.6)
    end

    outputs.sprites << state.dragon_sprite
  end

  def render_debug_hitbox show
    return unless show
    outputs.borders << [dragon_collision_box.rect, 255, 0, 0] if state.dragon_sprite
    outputs.borders << state.walls.flat_map do |w|
       w.sprites.map { |s| [s.rect, 255, 0, 0] }
    end
  end

  def render_flash
    return unless state.flash_at

    outputs.primitives << [grid.rect,
                           white,
                           255 * state.flash_at.ease(20, :flip)].solid

    state.flash_at = 0 if state.flash_at.elapsed_time > 20
  end

  def calc
    return unless state.scene == :game
    reset_game if state.countdown == 1
    state.countdown -= 1 and return if state.countdown > 0
    calc_walls
    calc_flap
    calc_game_over
  end

  def calc_walls
    state.walls.each { |w| w.x -= 8 }

    walls_count_before_removal = state.walls.length

    state.walls.reject! { |w| w.x < -100 }

    state.score += 1 if state.walls.count < walls_count_before_removal

    state.wall_countdown -= 1 and return if state.wall_countdown > 0

    state.walls << state.new_entity(:wall) do |w|
      w.x             = grid.right
      w.opening       = grid.top
                            .randomize(:ratio)
                            .greater(200)
                            .lesser(520)
      w.bottom_height = w.opening - state.wall_gap_size
      w.top_y         = w.opening + state.wall_gap_size
    end

    state.wall_countdown = state.wall_countdown_length
  end

  def calc_flap
    state.y += state.dy
    state.dy = state.dy.lesser state.flap_power
    state.dy -= state.gravity
    return if state.y < state.ceiling
    state.y  = state.ceiling
    state.dy = state.dy.lesser state.ceiling_flap_power
  end

  def calc_game_over
    return unless game_over?

    state.death_at = state.tick_count
    state.death_from = state.walls.first
    state.death_fall_direction = -1
    state.death_fall_direction =  1 if state.x > state.death_from.x
    outputs.sounds << "sounds/hit-sound.wav"
    begin_countdown
  end

  def process_inputs
    process_inputs_menu
    process_inputs_game
  end

  def process_inputs_menu
    return unless state.scene == :menu

    changediff = inputs.keyboard.key_down.tab || inputs.controller_one.key_down.select
    if inputs.mouse.click
      p = inputs.mouse.click.point
      if (p.y >= 165) && (p.y < 200) && (p.x >= 500) && (p.x < 800)
        changediff = true
      end
    end

    if changediff
      case state.new_difficulty
      when :easy
        state.new_difficulty = :normal
      when :normal
        state.new_difficulty = :hard
      when :hard
        state.new_difficulty = :flappy
      when :flappy
        state.new_difficulty = :easy
      end
    end

    if inputs.keyboard.key_down.enter || inputs.controller_one.key_down.start || inputs.controller_one.key_down.a
      state.difficulty = state.new_difficulty
      change_to_scene :game
      reset_game false
      state.hi_score = 0
      begin_countdown
    end

    if inputs.keyboard.key_down.escape || (inputs.mouse.click && !changediff) || inputs.controller_one.key_down.b
      state.new_difficulty = state.difficulty
      change_to_scene :game
    end
  end

  def process_inputs_game
    return unless state.scene == :game

    clicked_menu = false
    if inputs.mouse.click
      p = inputs.mouse.click.point
      clicked_menu = (p.y >= 620) && (p.x < 275)
    end

    if clicked_menu || inputs.keyboard.key_down.escape || inputs.keyboard.key_down.enter || inputs.controller_one.key_down.start
      change_to_scene :menu
    elsif (inputs.mouse.down || inputs.mouse.click || inputs.keyboard.key_down.space || inputs.controller_one.key_down.a) && state.countdown == 0
      state.dy = 0
      state.dy += state.flap_power
      state.flapped_at = state.tick_count
      outputs.sounds << "sounds/fly-sound.wav"
    end
  end

  def scrolling_background at, path, rate, y = 0
    [
      [   0 - at.*(rate) % 1440, y, 1440, 720, path],
      [1440 - at.*(rate) % 1440, y, 1440, 720, path]
    ]
  end

  def white
    [255, 255, 255]
  end

  def large_white_typeset
    [5, 0, 255, 255, 255]
  end

  def at_beginning?
    state.walls.count == 0
  end

  def dragon_collision_box
    state.dragon_sprite
        .scale_rect(1.0 - collision_forgiveness, 0.5, 0.5)
        .rect_shift_right(10)
        .rect_shift_up(state.dy * 2)
  end

  def game_over?
    return true if state.y <= 0.-(500 * collision_forgiveness) && !at_beginning?

    state.walls
        .flat_map { |w| w.sprites }
        .any? do |s|
          s.intersect_rect?(dragon_collision_box)
        end
  end

  def collision_forgiveness
    case state.difficulty
    when :easy
      0.9
    when :normal
      0.7
    when :hard
      0.5
    when :flappy
      0.3
    else
      0.9
    end
  end

  def countdown_text
    state.countdown ||= -1
    return ""          if state.countdown == 0
    return "GO!"       if state.countdown.idiv(60) == 0
    return "GAME OVER" if state.death_at
    return "READY?"
  end

  def begin_countdown
    state.countdown = 4.seconds
  end

  def score_text
    return ""                        unless state.countdown > 1.seconds
    return ""                        unless state.death_at
    return "SCORE: 0 (LOL)"          if state.score == 0
    return "HI SCORE: #{state.score}" if state.score == state.hi_score
    return "SCORE: #{state.score}"
  end

  def reset_game set_flash = true
    state.flash_at = state.tick_count if set_flash
    state.walls = []
    state.y = 500
    state.dy = 0
    state.hi_score = state.hi_score.greater(state.score)
    state.score = 0
    state.wall_countdown = state.wall_countdown_length.fdiv(2)
    state.show_death = false
    state.death_at = nil
  end

  def change_to_scene scene
    state.scene = scene
    state.scene_at = state.tick_count
    inputs.keyboard.clear
    inputs.controller_one.clear
  end
end

$flappy_dragon = FlappyDragon.new

def tick args
  $flappy_dragon.grid = args.grid
  $flappy_dragon.inputs = args.inputs
  $flappy_dragon.state = args.state
  $flappy_dragon.outputs = args.outputs
  $flappy_dragon.tick
end

Arcade - Pong - main.rb

# ./samples/99_genre_arcade/pong/app/main.rb
def tick args
  defaults args
  render args
  calc args
  input args
end

def defaults args
  args.state.ball.debounce       ||= 3 * 60
  args.state.ball.size           ||= 10
  args.state.ball.size_half      ||= args.state.ball.size / 2
  args.state.ball.x              ||= 640
  args.state.ball.y              ||= 360
  args.state.ball.dx             ||= 5.randomize(:sign)
  args.state.ball.dy             ||= 5.randomize(:sign)
  args.state.left_paddle.y       ||= 360
  args.state.right_paddle.y      ||= 360
  args.state.paddle.h            ||= 120
  args.state.paddle.w            ||= 10
  args.state.left_paddle.score   ||= 0
  args.state.right_paddle.score  ||= 0
end

def render args
  render_center_line args
  render_scores args
  render_countdown args
  render_ball args
  render_paddles args
  render_instructions args
end

begin :render_methods
  def render_center_line args
    args.outputs.lines  << [640, 0, 640, 720]
  end

  def render_scores args
    args.outputs.labels << [
      [320, 650, args.state.left_paddle.score, 10, 1],
      [960, 650, args.state.right_paddle.score, 10, 1]
    ]
  end

  def render_countdown args
    return unless args.state.ball.debounce > 0
    args.outputs.labels << [640, 360, "%.2f" % args.state.ball.debounce.fdiv(60), 10, 1]
  end

  def render_ball args
    args.outputs.solids << solid_ball(args)
  end

  def render_paddles args
    args.outputs.solids << solid_left_paddle(args)
    args.outputs.solids << solid_right_paddle(args)
  end

  def render_instructions args
    args.outputs.labels << [320, 30, "W and S keys to move left paddle.",  0, 1]
    args.outputs.labels << [920, 30, "O and L keys to move right paddle.", 0, 1]
  end
end

def calc args
  args.state.ball.debounce -= 1 and return if args.state.ball.debounce > 0
  calc_move_ball args
  calc_collision_with_left_paddle args
  calc_collision_with_right_paddle args
  calc_collision_with_walls args
end

begin :calc_methods
  def calc_move_ball args
    args.state.ball.x += args.state.ball.dx
    args.state.ball.y += args.state.ball.dy
  end

  def calc_collision_with_left_paddle args
    if solid_left_paddle(args).intersect_rect? solid_ball(args)
      args.state.ball.dx *= -1
    elsif args.state.ball.x < 0
      args.state.right_paddle.score += 1
      calc_reset_round args
    end
  end

  def calc_collision_with_right_paddle args
    if solid_right_paddle(args).intersect_rect? solid_ball(args)
      args.state.ball.dx *= -1
    elsif args.state.ball.x > 1280
      args.state.left_paddle.score += 1
      calc_reset_round args
    end
  end

  def calc_collision_with_walls args
    if args.state.ball.y + args.state.ball.size_half > 720
      args.state.ball.y = 720 - args.state.ball.size_half
      args.state.ball.dy *= -1
    elsif args.state.ball.y - args.state.ball.size_half < 0
      args.state.ball.y = args.state.ball.size_half
      args.state.ball.dy *= -1
    end
  end

  def calc_reset_round args
    args.state.ball.x = 640
    args.state.ball.y = 360
    args.state.ball.dx = 5.randomize(:sign)
    args.state.ball.dy = 5.randomize(:sign)
    args.state.ball.debounce = 3 * 60
  end
end

def input args
  input_left_paddle args
  input_right_paddle args
end

begin :input_methods
  def input_left_paddle args
    if args.inputs.controller_one.key_down.down  || args.inputs.keyboard.key_down.s
      args.state.left_paddle.y -= 40
    elsif args.inputs.controller_one.key_down.up || args.inputs.keyboard.key_down.w
      args.state.left_paddle.y += 40
    end
  end

  def input_right_paddle args
    if args.inputs.controller_two.key_down.down  || args.inputs.keyboard.key_down.l
      args.state.right_paddle.y -= 40
    elsif args.inputs.controller_two.key_down.up || args.inputs.keyboard.key_down.o
      args.state.right_paddle.y += 40
    end
  end
end

begin :assets
  def solid_ball args
    centered_rect args.state.ball.x, args.state.ball.y, args.state.ball.size, args.state.ball.size
  end

  def solid_left_paddle args
    centered_rect_vertically 0, args.state.left_paddle.y, args.state.paddle.w, args.state.paddle.h
  end

  def solid_right_paddle args
    centered_rect_vertically 1280 - args.state.paddle.w, args.state.right_paddle.y, args.state.paddle.w, args.state.paddle.h
  end

  def centered_rect x, y, w, h
    [x - w / 2, y - h / 2, w, h]
  end

  def centered_rect_vertically x, y, w, h
    [x, y - h / 2, w, h]
  end
end

Arcade - Snakemoji - main.rb

# ./samples/99_genre_arcade/snakemoji/app/main.rb
# coding: utf-8
################################
#  So I was working on a snake game while
#  learning DragonRuby, and at some point I had a thought
#  what if I use "😀" as a function name, surely it wont work right...?
#  RIGHT....?
#  BUT IT DID, IT WORKED
#  it all went downhill from then
#  Created by Anton K. (ai Doge)
#  https://gist.github.com/scorp200
#############LICENSE############
#  Feel free to use this anywhere and however you want
#  You can sell this to EA for $1,000,000 if you want, its completely free.
#  Just rememeber you are helping this... thing... to spread...
#  ALSO! I am not liable for any mental, physical or financial damage caused.
#############LICENSE############


class Array
  #Helper function
  def move! vector
    self.x += vector.x
    self.y += vector.y
    return self
  end

  #Helper function to draw snake body
  def draw! 🎮, 📺, color
    translate 📺.solids, 🎮.⛓, [self.x * 🎮.⚖️ + 🎮.🛶 / 2, self.y * 🎮.⚖️ + 🎮.🛶 / 2, 🎮.⚖️ - 🎮.🛶, 🎮.⚖️ - 🎮.🛶, color]
  end

  #This is where it all started, I was trying to find  good way to multiply a map by a number, * is already used so is **
  #I kept trying different combinations of symbols, when suddenly...
  def 😀 value
    self.map {|d| d * value}
  end
end

#Draw stuff with an offset
def translate output_collection, ⛓, what
  what.x += ⛓.x
  what.y += ⛓.y
  output_collection << what
end

BLUE = [33, 150, 243]
RED = [244, 67, 54]
GOLD = [255, 193, 7]
LAST = 0

def tick args
  defaults args.state
  render args.state, args.outputs
  input args.state, args.inputs
  update args.state
end

def update 🎮
  #Update every 10 frames
  if 🎮.tick_count.mod_zero? 10
    #Add new snake body piece at head's location
    🎮.🐍 << [*🎮.🤖]
    #Assign Next Direction to Direction
    🎮.🚗 = *🎮.🚦

    #Trim the snake a bit if its longer than current size
    if 🎮.🐍.length > 🎮.🛒
      🎮.🐍 = 🎮.🐍[-🎮.🛒..-1]
    end

    #Move the head in the Direction
    🎮.🤖.move! 🎮.🚗

    #If Head is outside the playing field, or inside snake's body restart game
    if 🎮.🤖.x < 0 || 🎮.🤖.x >= 🎮.🗺.x || 🎮.🤖.y < 0 || 🎮.🤖.y >= 🎮.🗺.y || 🎮.🚗 != [0, 0] && 🎮.🐍.any? {|s| s == 🎮.🤖}
      LAST = 🎮.💰
      🎮.as_hash.clear
      return
    end

    #If head lands on food add size and score
    if 🎮.🤖 == 🎮.🍎
      🎮.🛒 += 1
      🎮.💰 += (🎮.🛒 * 0.8).floor.to_i + 5
      spawn_🍎 🎮
      puts 🎮.🍎
    end
  end

  #Every second remove 1 point
  if 🎮.💰 > 0 && 🎮.tick_count.mod_zero?(60)
    🎮.💰 -= 1
  end
end

def spawn_🍎 🎮
  #Food
  🎮.🍎 ||= [*🎮.🤖]
  #Randomly spawns food inside the playing field, keep doing this if the food keeps landing on the snake's body
  while 🎮.🐍.any? {|s| s == 🎮.🍎} || 🎮.🍎 == 🎮.🤖 do
    🎮.🍎 = [rand(🎮.🗺.x), rand(🎮.🗺.y)]
  end
end

def render 🎮, 📺
  #Paint the background black
  📺.solids << [0, 0, 1280, 720, 0, 0, 0, 255]
  #Draw a border for the playing field
  translate 📺.borders, 🎮.⛓, [0, 0, 🎮.🗺.x * 🎮.⚖️, 🎮.🗺.y * 🎮.⚖️, 255, 255, 255]

  #Draw the snake's body
  🎮.🐍.map do |🐍| 🐍.draw! 🎮, 📺, BLUE end
  #Draw the head
  🎮.🤖.draw! 🎮, 📺, BLUE
  #Draw the food
  🎮.🍎.draw! 🎮, 📺, RED

  #Draw current score
  translate 📺.labels, 🎮.⛓, [5, 715, "Score: #{🎮.💰}", GOLD]
  #Draw your last score, if any
  translate 📺.labels, 🎮.⛓, [[*🎮.🤖.😀(🎮.⚖️)].move!([0, 🎮.⚖️ * 2]), "Your Last score is #{LAST}", 0, 1, GOLD] unless LAST == 0 || 🎮.🚗 != [0, 0]
  #Draw starting message, only if Direction is 0
  translate 📺.labels, 🎮.⛓, [🎮.🤖.😀(🎮.⚖️), "Press any Arrow key to start", 0, 1, GOLD] unless 🎮.🚗 != [0, 0]
end

def input 🎮, 🕹
  #Left and Right keyboard input, only change if X direction is 0
  if 🕹.keyboard.key_held.left && 🎮.🚗.x == 0
    🎮.🚦 = [-1, 0]
  elsif 🕹.keyboard.key_held.right && 🎮.🚗.x == 0
    🎮.🚦 = [1, 0]
  end

  #Up and Down keyboard input, only change if Y direction is 0
  if 🕹.keyboard.key_held.up && 🎮.🚗.y == 0
    🎮.🚦 = [0, 1]
  elsif 🕹.keyboard.key_held.down && 🎮.🚗.y == 0
    🎮.🚦 = [0, -1]
  end
end

def defaults 🎮
  #Playing field size
  🎮.🗺 ||= [20, 20]
  #Scale for drawing, screen height / Field height
  🎮.⚖️ ||= 720 / 🎮.🗺.y
  #Offset, offset all rendering to the center of the screen
  🎮.⛓ ||= [(1280 - 720).fdiv(2), 0]
  #Padding, make the snake body slightly smaller than the scale
  🎮.🛶 ||= (🎮.⚖️ * 0.2).to_i
  #Snake Size
  🎮.🛒 ||= 3
  #Snake head, the only part we are actually controlling
  🎮.🤖 ||= [🎮.🗺.x / 2, 🎮.🗺.y / 2]
  #Snake body map, follows the head
  🎮.🐍 ||= []
  #Direction the head moves to
  🎮.🚗 ||= [0, 0]
  #Next_Direction, during input check only change this variable and then when game updates asign this to Direction
  🎮.🚦 ||= [*🎮.🚗]
  #Your score
  🎮.💰 ||= 0
  #Spawns Food randomly
  spawn_🍎(🎮) unless 🎮.🍎?
end

Arcade - Solar System - main.rb

# ./samples/99_genre_arcade/solar_system/app/main.rb
# Focused tutorial video: https://s3.amazonaws.com/s3.dragonruby.org/dragonruby-nddnug-workshop.mp4
# Workshop/Presentation which provides motivation for creating a game engine: https://www.youtube.com/watch?v=S3CFce1arC8

def defaults args
  args.outputs.background_color = [0, 0, 0]
  args.state.x ||= 640
  args.state.y ||= 360
  args.state.stars ||= 100.map do
    [1280 * rand, 720 * rand, rand.fdiv(10), 255 * rand, 255 * rand, 255 * rand]
  end

  args.state.sun ||= args.state.new_entity(:sun) do |s|
    s.s = 100
    s.path = 'sprites/sun.png'
  end

  args.state.planets = [
    [:mercury,   65,  5,          88],
    [:venus,    100, 10,         225],
    [:earth,    120, 10,         365],
    [:mars,     140,  8,         687],
    [:jupiter,  280, 30, 365 *  11.8],
    [:saturn,   350, 20, 365 *  29.5],
    [:uranus,   400, 15, 365 *    84],
    [:neptune,  440, 15, 365 * 164.8],
    [:pluto,    480,  5, 365 * 247.8],
  ].map do |name, distance, size, year_in_days|
    args.state.new_entity(name) do |p|
      p.path = "sprites/#{name}.png"
      p.distance = distance * 0.7
      p.s = size * 0.7
      p.year_in_days = year_in_days
    end
  end

  args.state.ship ||= args.state.new_entity(:ship) do |s|
    s.x = 1280 * rand
    s.y = 720 * rand
    s.angle = 0
  end
end

def to_sprite args, entity
  x = 0
  y = 0

  if entity.year_in_days
    day = args.state.tick_count
    day_in_year = day % entity.year_in_days
    entity.random_start_day ||= day_in_year * rand
    percentage_of_year = day_in_year.fdiv(entity.year_in_days)
    angle = 365 * percentage_of_year
    x = angle.vector_x(entity.distance)
    y = angle.vector_y(entity.distance)
  end

  [640 + x - entity.s.half, 360 + y - entity.s.half, entity.s, entity.s, entity.path]
end

def render args
  args.outputs.solids << [0, 0, 1280, 720]

  args.outputs.sprites << args.state.stars.map do |x, y, _, r, g, b|
    [x, y, 10, 10, 'sprites/star.png', 0, 100, r, g, b]
  end

  args.outputs.sprites << to_sprite(args, args.state.sun)
  args.outputs.sprites << args.state.planets.map { |p| to_sprite args, p }
  args.outputs.sprites << [args.state.ship.x, args.state.ship.y, 20, 20, 'sprites/ship.png', args.state.ship.angle]
end

def calc args
  args.state.stars = args.state.stars.map do |x, y, speed, r, g, b|
    x += speed
    y += speed
    x = 0 if x > 1280
    y = 0 if y > 720
    [x, y, speed, r, g, b]
  end

  if args.state.tick_count == 0
    args.outputs.sounds << 'sounds/bg.ogg'
  end
end

def process_inputs args
  if args.inputs.keyboard.left || args.inputs.controller_one.key_held.left
    args.state.ship.angle += 1
  elsif args.inputs.keyboard.right || args.inputs.controller_one.key_held.right
    args.state.ship.angle -= 1
  end

  if args.inputs.keyboard.up || args.inputs.controller_one.key_held.a
    args.state.ship.x += args.state.ship.angle.x_vector
    args.state.ship.y += args.state.ship.angle.y_vector
  end
end

def tick args
  defaults args
  render args
  calc args
  process_inputs args
end

def r
  $gtk.reset
end

Arcade - Sound Golf - main.rb

# ./samples/99_genre_arcade/sound_golf/app/main.rb
=begin

 APIs Listing that haven't been encountered in previous sample apps:

 - sample: Chooses random element from array.
   In this sample app, the target note is set by taking a sample from the collection
   of available notes.

 Reminders:
 - args.grid.(left|right|top|bottom): Pixel value for the boundaries of the virtual
   720 p screen (Dragon Ruby Game Toolkits's virtual resolution is always 1280x720).

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   For example, if we want to create a new button, we would declare it as a new entity and
   then define its properties.

 - String interpolation: Uses #{} syntax; everything between the #{ and the } is evaluated
   as Ruby code, and the placeholder is replaced with its corresponding value or result.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - find_all: Finds all elements from a collection that meet a certain requirements (and excludes the ones that don't).

 - first: Returns the first element of an array.

 - inside_rect: Returns true or false depending on if the point is inside the rect.

 - to_sym: Returns symbol corresponding to string. Will create a symbol if it does
   not already exist.

=end

# This sample app allows users to test their musical skills by matching the piano sound that plays in each
# level to the correct note.

# Runs all the methods necessary for the game to function properly.
def tick args
  defaults args
  render args
  calc args
  input_mouse args
  tick_instructions args, "Sample app shows how to play sounds. args.outputs.sounds << \"path_to_wav.wav\""
end

# Sets default values and creates empty collections
# Initialization happens in the first frame only
def defaults args
  args.state.notes ||= []
  args.state.click_feedbacks ||= []
  args.state.current_level ||= 1
  args.state.times_wrong ||= 0 # when game starts, user hasn't guessed wrong yet
end

# Uses a label to display current level, and shows the score
# Creates a button to play the sample note, and displays the available notes that could be a potential match
def render args

  # grid.w_half positions the label in the horizontal center of the screen.
  args.outputs.labels << [args.grid.w_half, args.grid.top.shift_down(40), "Hole #{args.state.current_level} of 9", 0, 1, 0, 0, 0]

  render_score args # shows score on screen

  args.state.play_again_button ||= { x: 560, y: args.grid.h * 3 / 4 - 40, w: 160, h: 60, label: 'again' } # array definition, text/title
  args.state.play_note_button ||= { x: 560, y: args.grid.h * 3 / 4 - 40, w: 160, h: 60, label: 'play' }

  if args.state.game_over # if game is over, a "play again" button is shown
    # Calculations ensure that Play Again label is displayed in center of border
    # Remove calculations from y parameters and see what happens to border and label placement
    args.outputs.labels <<  [args.grid.w_half, args.grid.h * 3 / 4, "Play Again", 0, 1, 0, 0, 0] # outputs label
    args.outputs.borders << args.state.play_again_button # outputs border
  else # otherwise, if game is not over
    # Calculations ensure that label appears in center of border
    args.outputs.labels <<  [args.grid.w_half, args.grid.h * 3 / 4, "Play Note ##{args.state.current_level}", 0, 1, 0, 0, 0] # outputs label
    args.outputs.borders << args.state.play_note_button # outputs border
  end

  return if args.state.game_over # return if game is over

  args.outputs.labels <<   [args.grid.w_half, 400, "I think the note is a(n)...",  0, 1, 0, 0, 0] # outputs label

  # Shows all of the available notes that can be potential matches.
  available_notes.each_with_index do |note, i|
    args.state.notes[i] ||= piano_button(args, note, i + 1) # calls piano_button method on each note (creates label and border)
    args.outputs.labels <<   args.state.notes[i].label # outputs note on screen with a label and a border
    args.outputs.borders <<  args.state.notes[i].border
  end

  # Shows whether or not the user is correct by filling the screen with either red or green
  args.outputs.solids << args.state.click_feedbacks.map { |c| c.solid }
end

# Shows the score (number of times the user guesses wrong) onto the screen using labels.
def render_score args
  if args.state.times_wrong == 0 # if the user has guessed wrong zero times, the score is par
    args.outputs.labels << [args.grid.w_half, args.grid.top.shift_down(80), "Score: PAR", 0, 1, 0, 0, 0]
  else # otherwise, number of times the user has guessed wrong is shown
    args.outputs.labels << [args.grid.w_half, args.grid.top.shift_down(80), "Score: +#{args.state.times_wrong}", 0, 1, 0, 0, 0] # shows score using string interpolation
  end
end

# Sets the target note for the level and performs calculations on click_feedbacks.
def calc args
  args.state.target_note ||= available_notes.sample # chooses a note from available_notes collection as target note
  args.state.click_feedbacks.each    { |c| c.solid[-1] -= 5 } # remove this line and solid color will remain on screen indefinitely
  # comment this line out and the solid color will keep flashing on screen instead of being removed from click_feedbacks collection
  args.state.click_feedbacks.reject! { |c| c.solid[-1] <= 0 }
end

# Uses input from the user to play the target note, as well as the other notes that could be a potential match.
def input_mouse args
  return unless args.inputs.mouse.click # return unless the mouse is clicked

  # finds button that was clicked by user
  button_clicked = args.outputs.borders.find_all do |b| # go through borders collection to find all borders that meet requirements
    args.inputs.mouse.click.point.inside_rect? b # find button border that mouse was clicked inside of
  end.find_all { |b| b.is_a? Hash }.first # reject, return first element

  return unless button_clicked # return unless button_clicked as a value (a button was clicked)

  queue_click_feedback args, # calls queue_click_feedback method on the button that was clicked
                       button_clicked.x,
                       button_clicked.y,
                       button_clicked.w,
                       button_clicked.h,
                       150, 100, 200 # sets color of button to shade of purple

  if button_clicked[:label] == 'play' # if "play note" button is pressed
    args.outputs.sounds << "sounds/#{args.state.target_note}.wav" # sound of target note is output
  elsif button_clicked[:label] == 'again' # if "play game again" button is pressed
    args.state.target_note = nil # no target note
    args.state.current_level = 1 # starts at level 1 again
    args.state.times_wrong = 0 # starts off with 0 wrong guesses
    args.state.game_over = false # the game is not over (because it has just been restarted)
  else # otherwise if neither of those buttons were pressed
    args.outputs.sounds << "sounds/#{button_clicked[:label]}.wav" # sound of clicked note is played
    if button_clicked[:label] == args.state.target_note # if clicked note is target note
      args.state.target_note = nil # target note is emptied

      if args.state.current_level < 9 # if game hasn't reached level 9
        args.state.current_level += 1 # game goes to next level
      else # otherwise, if game has reached level 9
        args.state.game_over = true # the game is over
      end

      queue_click_feedback args, 0, 0, args.grid.w, args.grid.h, 100, 200, 100 # green shown if user guesses correctly
    else # otherwise, if clicked note is not target note
      args.state.times_wrong += 1 # increments times user guessed wrong
      queue_click_feedback args, 0, 0, args.grid.w, args.grid.h, 200, 100, 100 # red shown is user guesses wrong
    end
  end
end

# Creates a collection of all of the available notes as symbols
def available_notes
  [:C3, :D3, :E3, :F3, :G3, :A3, :B3, :C4]
end

# Creates buttons for each note, and sets a label (the note's name) and border for each note's button.
def piano_button args, note, position
  args.state.new_entity(:button) do |b| # declares button as new entity
    b.label  =  [460 + 40.mult(position), args.grid.h * 0.4, "#{note}", 0, 1, 0, 0, 0] # label definition
    b.border =  { x: 460 + 40.mult(position) - 20, y: args.grid.h * 0.4 - 32, w: 40, h: 40, label: note } # border definition, text/title; 20 subtracted so label is in center of border
  end
end

# Color of click feedback changes depending on what button was clicked, and whether the guess is right or wrong
# If a button is clicked, the inside of button is purple (see input_mouse method)
# If correct note is clicked, screen turns green
# If incorrect note is clicked, screen turns red (again, see input_mouse method)
def queue_click_feedback args, x, y, w, h, *color
  args.state.click_feedbacks << args.state.new_entity(:click_feedback) do |c| # declares feedback as new entity
    c.solid =  [x, y, w, h, *color, 255] # sets color
  end
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Arcade - Twinstick - main.rb

# ./samples/99_genre_arcade/twinstick/app/main.rb
def tick args
  args.state.player         ||= {x: 600, y: 320, w: 80, h: 80, path: 'sprites/circle-white.png', vx: 0, vy: 0, health: 10, cooldown: 0, score: 0}
  args.state.enemies        ||= []
  args.state.player_bullets ||= []
  args.state.tick_count     ||= -1
  args.state.tick_count     += 1
  spawn_enemies args
  kill_enemies args
  move_enemies args
  move_bullets args
  move_player args
  fire_player args
  args.state.player[:r] = args.state.player[:g] = args.state.player[:b] = (args.state.player[:health] * 25.5).clamp(0, 255)
  label_color           = args.state.player[:health] <= 5 ? 255 : 0
  args.outputs.labels << [
      {
          x: args.state.player.x + 40, y: args.state.player.y + 60, alignment_enum: 1, text: "#{args.state.player[:health]} HP",
          r: label_color, g: label_color, b: label_color
      }, {
          x: args.state.player.x + 40, y: args.state.player.y + 40, alignment_enum: 1, text: "#{args.state.player[:score]} PTS",
          r: label_color, g: label_color, b: label_color, size_enum: 2 - args.state.player[:score].to_s.length,
      }
  ]
  args.outputs.sprites << [args.state.player, args.state.enemies, args.state.player_bullets]
  args.state.clear! if args.state.player[:health] < 0 # Reset the game if the player's health drops below zero
end

def spawn_enemies args
  # Spawn enemies more frequently as the player's score increases.
  if rand < (100+args.state.player[:score])/(10000 + args.state.player[:score]) || args.state.tick_count.zero?
    theta = rand * Math::PI * 2
    args.state.enemies << {
        x: 600 + Math.cos(theta) * 800, y: 320 + Math.sin(theta) * 800, w: 80, h: 80, path: 'sprites/circle-white.png',
        r: (256 * rand).floor, g: (256 * rand).floor, b: (256 * rand).floor
    }
  end
end

def kill_enemies args
  args.state.enemies.reject! do |enemy|
    # Check if enemy and player are within 80 pixels of each other (i.e. overlapping)
    if 6400 > (enemy.x - args.state.player.x) ** 2 + (enemy.y - args.state.player.y) ** 2
      # Enemy is touching player. Kill enemy, and reduce player HP by 1.
      args.state.player[:health] -= 1
    else
      args.state.player_bullets.any? do |bullet|
        # Check if enemy and bullet are within 50 pixels of each other (i.e. overlapping)
        if 2500 > (enemy.x - bullet.x + 30) ** 2 + (enemy.y - bullet.y + 30) ** 2
          # Increase player health by one for each enemy killed by a bullet after the first enemy, up to a maximum of 10 HP
          args.state.player[:health] += 1 if args.state.player[:health] < 10 && bullet[:kills] > 0
          # Keep track of how many enemies have been killed by this particular bullet
          bullet[:kills]             += 1
          # Earn more points by killing multiple enemies with one shot.
          args.state.player[:score]  += bullet[:kills]
        end
      end
    end
  end
end

def move_enemies args
  args.state.enemies.each do |enemy|
    # Get the angle from the enemy to the player
    theta   = Math.atan2(enemy.y - args.state.player.y, enemy.x - args.state.player.x)
    # Convert the angle to a vector pointing at the player
    dx, dy  = theta.to_degrees.vector 5
    # Move the enemy towards thr player
    enemy.x -= dx
    enemy.y -= dy
  end
end

def move_bullets args
  args.state.player_bullets.each do |bullet|
    # Move the bullets according to the bullet's velocity
    bullet.x += bullet[:vx]
    bullet.y += bullet[:vy]
  end
  args.state.player_bullets.reject! do |bullet|
    # Despawn bullets that are outside the screen area
    bullet.x < -20 || bullet.y < -20 || bullet.x > 1300 || bullet.y > 740
  end
end

def move_player args
  # Get the currently held direction.
  dx, dy                 = move_directional_vector args
  # Take the weighted average of the old velocities and the desired velocities.
  # Since move_directional_vector returns values between -1 and 1,
  #   and we want to limit the speed to 7.5, we multiply dx and dy by 7.5*0.1 to get 0.75
  args.state.player[:vx] = args.state.player[:vx] * 0.9 + dx * 0.75
  args.state.player[:vy] = args.state.player[:vy] * 0.9 + dy * 0.75
  # Move the player
  args.state.player.x    += args.state.player[:vx]
  args.state.player.y    += args.state.player[:vy]
  # If the player is about to go out of bounds, put them back in bounds.
  args.state.player.x    = args.state.player.x.clamp(0, 1201)
  args.state.player.y    = args.state.player.y.clamp(0, 640)
end


def fire_player args
  # Reduce the firing cooldown each tick
  args.state.player[:cooldown] -= 1
  # If the player is allowed to fire
  if args.state.player[:cooldown] <= 0
    dx, dy = shoot_directional_vector args # Get the bullet velocity
    return if dx == 0 && dy == 0 # If the velocity is zero, the player doesn't want to fire. Therefore, we just return early.
    # Add a new bullet to the list of player bullets.
    args.state.player_bullets << {
        x:     args.state.player.x + 30 + 40 * dx,
        y:     args.state.player.y + 30 + 40 * dy,
        w:     20, h: 20,
        path:  'sprites/circle-white.png',
        r:     0, g: 0, b: 0,
        vx:    10 * dx + args.state.player[:vx] / 7.5, vy: 10 * dy + args.state.player[:vy] / 7.5, # Factor in a bit of the player's velocity
        kills: 0
    }
    args.state.player[:cooldown] = 30 # Reset the cooldown
  end
end

# Custom function for getting a directional vector just for movement using WASD
def move_directional_vector args
  dx = 0
  dx += 1 if args.inputs.keyboard.d
  dx -= 1 if args.inputs.keyboard.a
  dy = 0
  dy += 1 if args.inputs.keyboard.w
  dy -= 1 if args.inputs.keyboard.s
  if dx != 0 && dy != 0
    dx *= 0.7071
    dy *= 0.7071
  end
  [dx, dy]
end

# Custom function for getting a directional vector just for shooting using the arrow keys
def shoot_directional_vector args
  dx = 0
  dx += 1 if args.inputs.keyboard.key_down.right || args.inputs.keyboard.key_held.right
  dx -= 1 if args.inputs.keyboard.key_down.left || args.inputs.keyboard.key_held.left
  dy = 0
  dy += 1 if args.inputs.keyboard.key_down.up || args.inputs.keyboard.key_held.up
  dy -= 1 if args.inputs.keyboard.key_down.down || args.inputs.keyboard.key_held.down
  if dx != 0 && dy != 0
    dx *= 0.7071
    dy *= 0.7071
  end
  [dx, dy]
end

Crafting - Craft Game Starting Point - main.rb

# ./samples/99_genre_crafting/craft_game_starting_point/app/main.rb
# ==================================================
# A NOTE TO JAM CRAFT PARTICIPANTS:
# The comments and code in here are just as small piece of DragonRuby's capabilities.
# Be sure to check out the rest of the sample apps. Start with README.txt and go from there!
# ==================================================

# def tick args is the entry point into your game. This function is called at
# a fixed update time of 60hz (60 fps).
def tick args
  # The defaults function intitializes the game.
  defaults args

  # After the game is initialized, render it.
  render args

  # After rendering the player should be able to respond to input.
  input args

  # After responding to input, the game performs any additional calculations.
  calc args
end

def defaults args
  # hide the mouse cursor for this game, we are going to render our own cursor
  if args.state.tick_count == 0
    args.gtk.hide_cursor
  end

  args.state.click_ripples ||= []

  # everything is on a 1280x720 virtual canvas, so you can
  # hardcode locations

  # define the borders for where the inventory is located
  # args.state is a data structure that accepts any arbitrary parameters
  # so you can create an object graph without having to create any classes.

  # Bottom left is 0, 0. Top right is 1280, 720.
  # The inventory area is at the top of the screen
  # the number 80 is the size of all the sprites, so that is what is being
  # used to decide the with and height
  args.state.sprite_size = 80

  args.state.inventory_border.w  = args.state.sprite_size * 10
  args.state.inventory_border.h  = args.state.sprite_size * 3
  args.state.inventory_border.x  = 10
  args.state.inventory_border.y  = 710 - args.state.inventory_border.h

  # define the borders for where the crafting area is located
  # the crafting area is below the inventory area
  # the number 80 is the size of all the sprites, so that is what is being
  # used to decide the with and height
  args.state.craft_border.x =  10
  args.state.craft_border.y = 220
  args.state.craft_border.w = args.state.sprite_size * 3
  args.state.craft_border.h = args.state.sprite_size * 3

  # define the area where results are located
  # the crafting result is to the right of the craft area
  args.state.result_border.x =  10 + args.state.sprite_size * 3 + args.state.sprite_size
  args.state.result_border.y = 220 + args.state.sprite_size
  args.state.result_border.w = args.state.sprite_size
  args.state.result_border.h = args.state.sprite_size

  # initialize items for the first time if they are nil
  # you start with 15 wood, 1 chest, and 5 plank
  # Ruby has built in syntax for dictionaries (they look a lot like json objects).
  # Ruby also has a special type called a Symbol denoted with a : followed by a word.
  # Symbols are nice because they remove the need for magic strings.
  if !args.state.items
    args.state.items = [
      {
        id: :wood, # :wood is a Symbol, this is better than using "wood" for the id
        quantity: 15,
        path: 'sprites/wood.png',
        location: :inventory,
        ordinal_x: 0, ordinal_y: 0
      },
      {
        id: :chest,
        quantity: 1,
        path: 'sprites/chest.png',
        location: :inventory,
        ordinal_x: 1, ordinal_y: 0
      },
      {
        id: :plank,
        quantity: 5,
        path: 'sprites/plank.png',
        location: :inventory,
        ordinal_x: 2, ordinal_y: 0
      },
    ]

    # after initializing the oridinal positions, derive the pixel
    # locations assuming that the width and height are 80
    args.state.items.each { |item| set_inventory_position args, item }
  end

  # define all the oridinal positions of the inventory slots
  if !args.state.inventory_area
    args.state.inventory_area = [
      { ordinal_x: 0,  ordinal_y: 0 },
      { ordinal_x: 1,  ordinal_y: 0 },
      { ordinal_x: 2,  ordinal_y: 0 },
      { ordinal_x: 3,  ordinal_y: 0 },
      { ordinal_x: 4,  ordinal_y: 0 },
      { ordinal_x: 5,  ordinal_y: 0 },
      { ordinal_x: 6,  ordinal_y: 0 },
      { ordinal_x: 7,  ordinal_y: 0 },
      { ordinal_x: 8,  ordinal_y: 0 },
      { ordinal_x: 9,  ordinal_y: 0 },
      { ordinal_x: 0,  ordinal_y: 1 },
      { ordinal_x: 1,  ordinal_y: 1 },
      { ordinal_x: 2,  ordinal_y: 1 },
      { ordinal_x: 3,  ordinal_y: 1 },
      { ordinal_x: 4,  ordinal_y: 1 },
      { ordinal_x: 5,  ordinal_y: 1 },
      { ordinal_x: 6,  ordinal_y: 1 },
      { ordinal_x: 7,  ordinal_y: 1 },
      { ordinal_x: 8,  ordinal_y: 1 },
      { ordinal_x: 9,  ordinal_y: 1 },
      { ordinal_x: 0,  ordinal_y: 2 },
      { ordinal_x: 1,  ordinal_y: 2 },
      { ordinal_x: 2,  ordinal_y: 2 },
      { ordinal_x: 3,  ordinal_y: 2 },
      { ordinal_x: 4,  ordinal_y: 2 },
      { ordinal_x: 5,  ordinal_y: 2 },
      { ordinal_x: 6,  ordinal_y: 2 },
      { ordinal_x: 7,  ordinal_y: 2 },
      { ordinal_x: 8,  ordinal_y: 2 },
      { ordinal_x: 9,  ordinal_y: 2 },
    ]

    # after initializing the oridinal positions, derive the pixel
    # locations assuming that the width and height are 80
    args.state.inventory_area.each { |i| set_inventory_position args, i }

    # if you want to see the result you can use the Ruby function called "puts".
    # Uncomment this line to see the value.
    # puts args.state.inventory_area

    # You can see all things written via puts in DragonRuby's Console, or under logs/log.txt.
    # To bring up DragonRuby's Console, press the ~ key within the game.
  end

  # define all the oridinal positions of the craft slots
  if !args.state.craft_area
    args.state.craft_area = [
      { ordinal_x: 0, ordinal_y: 0 },
      { ordinal_x: 0, ordinal_y: 1 },
      { ordinal_x: 0, ordinal_y: 2 },
      { ordinal_x: 1, ordinal_y: 0 },
      { ordinal_x: 1, ordinal_y: 1 },
      { ordinal_x: 1, ordinal_y: 2 },
      { ordinal_x: 2, ordinal_y: 0 },
      { ordinal_x: 2, ordinal_y: 1 },
      { ordinal_x: 2, ordinal_y: 2 },
    ]

    # after initializing the oridinal positions, derive the pixel
    # locations assuming that the width and height are 80
    args.state.craft_area.each { |c| set_craft_position args, c }
  end
end


def render args
  # for the results area, create a sprite that show its boundaries
  args.outputs.primitives << { x: args.state.result_border.x,
                               y: args.state.result_border.y,
                               w: args.state.result_border.w,
                               h: args.state.result_border.h,
                               path: 'sprites/border-black.png' }

  # for each inventory spot, create a sprite
  # args.outputs.primitives is how DragonRuby performs a render.
  # Adding a single hash or multiple hashes to this array will tell
  # DragonRuby to render those primitives on that frame.

  # The .map function on Array is used instead of any kind of looping.
  # .map returns a new object for every object within an Array.
  args.outputs.primitives << args.state.inventory_area.map do |a|
    { x: a.x, y: a.y, w: a.w, h: a.h, path: 'sprites/border-black.png' }
  end

  # for each craft spot, create a sprite
  args.outputs.primitives << args.state.craft_area.map do |a|
    { x: a.x, y: a.y, w: a.w, h: a.h, path: 'sprites/border-black.png' }
  end

  # after the borders have been rendered, render the
  # items within those slots (and allow for highlighting)
  # if an item isn't currently being held
  allow_inventory_highlighting = !args.state.held_item

  # go through each item and render them
  # use Array's find_all method to remove any items that are currently being held
  args.state.items.find_all { |item| item[:location] != :held }.map do |item|
    # if an item is currently being held, don't render it in it's spot within the
    # inventory or craft area (this is handled via the find_all method).

    # the item_prefab returns a hash containing all the visual components of an item.
    # the main sprite, the black background, the quantity text, and a hover indication
    # if the mouse is currently hovering over the item.
    args.outputs.primitives << item_prefab(args, item, allow_inventory_highlighting, args.inputs.mouse)
  end

  # The last thing we want to render is the item currently being held.
  args.outputs.primitives << item_prefab(args, args.state.held_item, allow_inventory_highlighting, args.inputs.mouse)

  args.outputs.primitives << args.state.click_ripples

  # render a mouse cursor since we have the OS cursor hidden
  args.outputs.primitives << { x: args.inputs.mouse.x - 5, y: args.inputs.mouse.y - 5, w: 10, h: 10, path: 'sprites/circle-gray.png', a: 128 }
end

# Alrighty! This is where all the fun happens
def input args
  # if the mouse is clicked and not item is currently being held
  # args.state.held_item is nil when the game starts.
  # If the player clicks, the property args.inputs.mouse.click will
  # be a non nil value, we don't want to process any of the code here
  # if the mouse hasn't been clicked
  return if !args.inputs.mouse.click

  # if a click occurred, add a ripple to the ripple queue
  args.state.click_ripples << { x: args.inputs.mouse.x - 5, y: args.inputs.mouse.y - 5, w: 10, h: 10, path: 'sprites/circle-gray.png', a: 128 }

  # if the mouse has been clicked, and no item is currently held...
  if !args.state.held_item
    # see if any of the items intersect the pointer using the inside_rect? method
    # the find method will either return the first object that returns true
    # for the match clause, or it'll return nil if nothing matches the match clause
    found = args.state.items.find do |item|
      # for each item in args.state.items, run the following boolean check
      args.inputs.mouse.click.point.inside_rect?(item)
    end

    # if an item intersects the mouse pointer, then set the item's location to :held and
    # set args.state.held_item to the item for later reference
    if found
      args.state.held_item = found
      found[:location] = :held
    end

  # if the mouse is clicked and an item is currently beign held....
  elsif args.state.held_item
    # determine if a slot within the craft area was clicked
    craft_area = args.state.craft_area.find { |a| args.inputs.mouse.click.point.inside_rect? a }

    # also determine if a slot within the inventory area was clicked
    inventory_area = args.state.inventory_area.find { |a| args.inputs.mouse.click.point.inside_rect? a }

    # if the click was within a craft area
    if craft_area
      # check to see if an item is already there and ignore the click if an item is found
      # item_at_craft_slot is a helper method that returns an item or nil for a given oridinal
      # position
      item_already_there = item_at_craft_slot args, craft_area[:ordinal_x], craft_area[:ordinal_y]

      # if an item *doesn't* exist in the craft area
      if !item_already_there
        # if the quantity they are currently holding is greater than 1
        if args.state.held_item[:quantity] > 1
          # remove one item (creating a seperate item of the same type), and place it
          # at the oridinal position and location of the craft area
          # the .merge method on Hash creates a new Hash, but updates any values
          # passed as arguments to merge
          new_item = args.state.held_item.merge(quantity: 1,
                                                location: :craft,
                                                ordinal_x: craft_area[:ordinal_x],
                                                ordinal_y: craft_area[:ordinal_y])

          # after the item is crated, place it into the args.state.items collection
          args.state.items << new_item

          # then subtract one from the held item
          args.state.held_item[:quantity] -= 1

        # if the craft area is available and there is only one item being held
        elsif args.state.held_item[:quantity] == 1
          # instead of creating any new items just set the location of the held item
          # to the oridinal position of the craft area, and then nil out the
          # held item state so that a new item can be picked up
          args.state.held_item[:location] = :craft
          args.state.held_item[:ordinal_x] = craft_area[:ordinal_x]
          args.state.held_item[:ordinal_y] = craft_area[:ordinal_y]
          args.state.held_item = nil
        end
      end

    # if the selected area is an inventory area (as opposed to within the craft area)
    elsif inventory_area

      # check to see if there is already an item in that inventory slot
      # the item_at_inventory_slot helper method returns an item or nil
      item_already_there = item_at_inventory_slot args, inventory_area[:ordinal_x], inventory_area[:ordinal_y]

      # if there is already an item there, and the item types/id match
      if item_already_there && item_already_there[:id] == args.state.held_item[:id]
        # then merge the item quantities
        held_quantity = args.state.held_item[:quantity]
        item_already_there[:quantity] += held_quantity

        # remove the item being held from the items collection (since it's quantity is now 0)
        args.state.items.reject! { |i| i[:location] == :held }

        # nil out the held_item so a new item can be picked up
        args.state.held_item = nil

      # if there currently isn't an item there, then put the held item in the slot
      elsif !item_already_there
        args.state.held_item[:location] = :inventory
        args.state.held_item[:ordinal_x] = inventory_area[:ordinal_x]
        args.state.held_item[:ordinal_y] = inventory_area[:ordinal_y]

        # nil out the held_item so a new item can be picked up
        args.state.held_item = nil
      end
    end
  end
end

# the calc method is executed after input
def calc args
  # make sure that the real position of the inventory
  # items are updated every frame to ensure that they
  # are placed correctly given their location and oridinal positions
  # instead of using .map, here we use .each (since we are not returning a new item and just updating the items in place)
  args.state.items.each do |item|
    # based on the location of the item, invoke the correct pixel conversion method
    if item[:location] == :inventory
      set_inventory_position args, item
    elsif item[:location] == :craft
      set_craft_position args, item
    elsif item[:location] == :held
      # if the item is held, center the item around the mouse pointer
      args.state.held_item.x = args.inputs.mouse.x - args.state.held_item.w.half
      args.state.held_item.y = args.inputs.mouse.y - args.state.held_item.h.half
    end
  end

  # for each hash/sprite in the click ripples queue,
  # expand its size by 20 percent and decrease its alpha
  # by 10.
  args.state.click_ripples.each do |ripple|
    delta_w = ripple.w * 1.2 - ripple.w
    delta_h = ripple.h * 1.2 - ripple.h
    ripple.x -= delta_w.half
    ripple.y -= delta_h.half
    ripple.w += delta_w
    ripple.h += delta_h
    ripple.a -= 10
  end

  # remove any items from the collection where the alpha value is less than equal to
  # zero using the reject! method (reject with an exclamation point at the end changes the
  # array value in place, while reject without the exclamation point returns a new array).
  args.state.click_ripples.reject! { |ripple| ripple.a <= 0 }
end

# helper function for finding an item at a craft slot
def item_at_craft_slot args, ordinal_x, ordinal_y
  args.state.items.find { |i| i[:location] == :craft && i[:ordinal_x] == ordinal_x && i[:ordinal_y] == ordinal_y }
end

# helper function for finding an item at an inventory slot
def item_at_inventory_slot args, ordinal_x, ordinal_y
  args.state.items.find { |i| i[:location] == :inventory && i[:ordinal_x] == ordinal_x && i[:ordinal_y] == ordinal_y }
end

# helper function that creates a visual representation of an item
def item_prefab args, item, should_highlight, mouse
  return nil unless item

  overlay = nil

  x = item.x
  y = item.y
  w = item.w
  h = item.h

  if should_highlight && mouse.point.inside_rect?(item)
    overlay = { x: x, y: y, w: w, h: h, path: "sprites/square-blue.png", a: 130, }
  end

  [
    # sprites are hashes with a path property, this is the main sprite
    { x: x,      y: y, w: args.state.sprite_size, h: args.state.sprite_size, path: item[:path], },

    # this represents the black area in the bottom right corner of the main sprite so that the
    # quantity is visible
    { x: x + 55, y: y, w: 25, h: 25, path: "sprites/square-black.png", }, # sprites are hashes with a path property

    # labels are hashes with a text property
    { x: x + 56, y: y + 22, text: "#{item[:quantity]}", r: 255, g: 255, b: 255, },

    # this is the mouse overlay, if the overlay isn't applicable, then this value will be nil (nil values will not be rendered)
    overlay
  ]
end

# helper function for deriving the position of an item within inventory
def set_inventory_position args, item
  item.x = args.state.inventory_border.x + item[:ordinal_x] * 80
  item.y = (args.state.inventory_border.y + args.state.inventory_border.h - 80) - item[:ordinal_y] * 80
  item.w = 80
  item.h = 80
end

# helper function for deriving the position of an item within the craft area
def set_craft_position args, item
  item.x = args.state.craft_border.x + item[:ordinal_x] * 80
  item.y = (args.state.craft_border.y + args.state.inventory_border.h - 80) - item[:ordinal_y] * 80
  item.w = 80
  item.h = 80
end

# Any lines outside of a function will be executed when the file is reloaded.
# So every time you save main.rb, the game will be reset.
# Comment out the line below if you don't want this to happen.
$gtk.reset

Dev Tools - Add Buttons To Console - main.rb

# ./samples/99_genre_dev_tools/add_buttons_to_console/app/main.rb
# You can customize the buttons that show up in the Console.
class GTK::Console::Menu
  # STEP 1: Override the custom_buttons function.
  def custom_buttons
    [
      (button id: :yay,
              # row for button
              row: 3,
              # column for button
              col: 10,
              # text
              text: "I AM CUSTOM",
              # when clicked call the custom_button_clicked function
              method: :custom_button_clicked),

      (button id: :yay,
              # row for button
              row: 3,
              # column for button
              col: 9,
              # text
              text: "CUSTOM ALSO",
              # when clicked call the custom_button_also_clicked function
              method: :custom_button_also_clicked)
    ]
  end

  # STEP 2: Define the function that should be called.
  def custom_button_clicked
    log "* INFO: I AM CUSTOM was clicked!"
  end

  def custom_button_also_clicked
    log "* INFO: Custom Button Clicked at #{Kernel.global_tick_count}!"

    all_buttons_as_string = $gtk.console.menu.buttons.map do |b|
      <<-S.strip
** id: #{b[:id]}
:PROPERTIES:
:id:     :#{b[:id]}
:method: :#{b[:method]}
:text:   #{b[:text]}
:END:
S
    end.join("\n")

    log <<-S
* INFO: Here are all the buttons:
#{all_buttons_as_string}
S
  end
end

def tick args
  args.outputs.labels << [args.grid.center.x, args.grid.center.y,
                          "Open the DragonRuby Console to see the custom menu items.",
                          0, 1]
end

Dev Tools - Animation Creator Starting Point - main.rb

# ./samples/99_genre_dev_tools/animation_creator_starting_point/app/main.rb
class OneBitLowrezPaint
  attr_gtk

  def tick
    outputs.background_color = [0, 0, 0]
    defaults
    render_instructions
    render_canvas
    render_buttons_frame_selection
    render_animation_frame_thumbnails
    render_animation
    input_mouse_click
    input_keyboard
    calc_auto_export
    calc_buttons_frame_selection
    calc_animation_frames
    process_queue_create_sprite
    process_queue_reset_sprite
    process_queue_update_rt_animation_frame
  end

  def defaults
    state.animation_frames_per_second = 12
    queues.create_sprite ||= []
    queues.reset_sprite ||= []
    queues.update_rt_animation_frame ||= []

    if !state.animation_frames
      state.animation_frames ||= []
      add_animation_frame_to_end
    end

    state.last_mouse_down ||= 0
    state.last_mouse_up   ||= 0

    state.buttons_frame_selection.left = 10
    state.buttons_frame_selection.top  = grid.top - 10
    state.buttons_frame_selection.size = 20

    defaults_canvas_sprite

    state.edit_mode ||= :drawing
  end

  def defaults_canvas_sprite
    rt_canvas.size   = 16
    rt_canvas.zoom   = 30
    rt_canvas.width  = rt_canvas.size * rt_canvas.zoom
    rt_canvas.height = rt_canvas.size * rt_canvas.zoom
    rt_canvas.sprite = { x: 0,
                         y: 0,
                         w: rt_canvas.width,
                         h: rt_canvas.height,
                         path: :rt_canvas }.center_inside_rect(x: 0, y: 0, w: 640, h: 720)

    return unless state.tick_count == 1

    outputs[:rt_canvas].width      = rt_canvas.width
    outputs[:rt_canvas].height     = rt_canvas.height
    outputs[:rt_canvas].sprites   << (rt_canvas.size + 1).map_with_index do |x|
      (rt_canvas.size + 1).map_with_index do |y|
        path = 'sprites/square-white.png'
        path = 'sprites/square-blue.png' if x == 7 || x == 8
        { x: x * rt_canvas.zoom,
          y: y * rt_canvas.zoom,
          w: rt_canvas.zoom,
          h: rt_canvas.zoom,
          path: path,
          a: 50 }
      end
    end
  end

  def render_instructions
    instructions = [
      "* Hotkeys:",
      "- d: hold to erase, release to draw.",
      "- a: add frame.",
      "- c: copy frame.",
      "- v: paste frame.",
      "- x: delete frame.",
      "- b: go to previous frame.",
      "- f: go to next frame.",
      "- w: save to ./canvas directory.",
      "- l: load from ./canvas."
    ]

    instructions.each.with_index do |l, i|
      outputs.labels << { x: 840, y: 500 - (i * 20), text: "#{l}",
                          r: 180, g: 180, b: 180, size_enum: 0 }
    end
  end

  def render_canvas
    return if state.tick_count.zero?
    outputs.sprites << rt_canvas.sprite
  end

  def render_buttons_frame_selection
    args.outputs.primitives << state.buttons_frame_selection.items.map_with_index do |b, i|
      label = { x: b.x + state.buttons_frame_selection.size.half,
                y: b.y,
                text: "#{i + 1}", r: 180, g: 180, b: 180,
                size_enum: -4, alignment_enum: 1 }.label

      selection_border = b.merge(r: 40, g: 40, b: 40).border

      if i == state.animation_frames_selected_index
        selection_border = b.merge(r: 40, g: 230, b: 200).border
      end

      [selection_border, label]
    end
  end

  def render_animation_frame_thumbnails
    return if state.tick_count.zero?

    outputs[:current_animation_frame].width   = rt_canvas.size
    outputs[:current_animation_frame].height  = rt_canvas.size
    outputs[:current_animation_frame].solids <<  selected_animation_frame[:pixels].map_with_index do |f, i|
      { x: f.x,
        y: f.y,
        w: 1,
        h: 1, r: 255, g: 255, b: 255 }
    end

    outputs.sprites << rt_canvas.sprite.merge(path: :current_animation_frame)

    state.animation_frames.map_with_index do |animation_frame, animation_frame_index|
      outputs.sprites << state.buttons_frame_selection[:items][animation_frame_index][:inner_rect]
                              .merge(path: animation_frame[:rt_name])
    end
  end

  def render_animation
    sprite_index = 0.frame_index count: state.animation_frames.length,
                                 hold_for: 60 / state.animation_frames_per_second,
                                 repeat: true

    args.outputs.sprites << { x: 700 - 8,
                              y: 120,
                              w: 16,
                              h: 16,
                              path: (sprite_path sprite_index) }

    args.outputs.sprites << { x: 700 - 16,
                              y: 230,
                              w: 32,
                              h: 32,
                              path: (sprite_path sprite_index) }

    args.outputs.sprites << { x: 700 - 32,
                              y: 360,
                              w: 64,
                              h: 64,
                              path: (sprite_path sprite_index) }

    args.outputs.sprites << { x: 700 - 64,
                              y: 520,
                              w: 128,
                              h: 128,
                              path: (sprite_path sprite_index) }
  end

  def input_mouse_click
    if inputs.mouse.up
      state.last_mouse_up = state.tick_count
    elsif inputs.mouse.moved && user_is_editing?
      edit_current_animation_frame inputs.mouse.point
    end

    return unless inputs.mouse.click

    clicked_frame_button = state.buttons_frame_selection.items.find do |b|
      inputs.mouse.point.inside_rect? b
    end

    if (clicked_frame_button)
      state.animation_frames_selected_index = clicked_frame_button[:index]
    end

    if (inputs.mouse.point.inside_rect? rt_canvas.sprite)
      state.last_mouse_down = state.tick_count
      edit_current_animation_frame inputs.mouse.point
    end
  end

  def input_keyboard
    # w to save
    if inputs.keyboard.key_down.w
      t = Time.now
      state.save_description = "Time: #{t} (#{t.to_i})"
      gtk.serialize_state 'canvas/state.txt', state
      gtk.serialize_state "tmp/canvas_backups/#{t.to_i}/state.txt", state
      animation_frames.each_with_index do |animation_frame, i|
        queues.update_rt_animation_frame << { index: i,
                                              at: state.tick_count + i,
                                              queue_sprite_creation: true }
        queues.create_sprite << { index: i,
                                  at: state.tick_count + animation_frames.length + i,
                                  path_override: "tmp/canvas_backups/#{t.to_i}/sprite-#{i}.png" }
      end
      gtk.notify! "Canvas saved."
    end

    # l to load
    if inputs.keyboard.key_down.l
      args.state = gtk.deserialize_state 'canvas/state.txt'
      animation_frames.each_with_index do |a, i|
        queues.update_rt_animation_frame << { index: i,
                                              at: state.tick_count + i,
                                              queue_sprite_creation: true }
      end
      gtk.notify! "Canvas loaded."
    end

    # d to go into delete mode, release to paint
    if inputs.keyboard.key_held.d
      state.edit_mode = :erasing
      gtk.notify! "Erasing." if inputs.keyboard.key_held.d == (state.tick_count - 1)
    elsif inputs.keyboard.key_up.d
      state.edit_mode = :drawing
      gtk.notify! "Drawing."
    end

    # a to add a frame to the end
    if inputs.keyboard.key_down.a
      queues.create_sprite << { index: state.animation_frames_selected_index,
                                at: state.tick_count }
      queues.create_sprite << { index: state.animation_frames_selected_index + 1,
                                at: state.tick_count }
      add_animation_frame_to_end
      gtk.notify! "Frame added to end."
    end

    # c or t to copy
    if (inputs.keyboard.key_down.c || inputs.keyboard.key_down.t)
      state.clipboard = [selected_animation_frame[:pixels]].flatten
      gtk.notify! "Current frame copied."
    end

    # v or q to paste
    if (inputs.keyboard.key_down.v || inputs.keyboard.key_down.q) && state.clipboard
      selected_animation_frame[:pixels] = [state.clipboard].flatten
      queues.update_rt_animation_frame << { index: state.animation_frames_selected_index,
                                            at: state.tick_count,
                                            queue_sprite_creation: true }
      gtk.notify! "Pasted."
    end

    # f to go forward/next frame
    if (inputs.keyboard.key_down.f)
      if (state.animation_frames_selected_index == (state.animation_frames.length - 1))
        state.animation_frames_selected_index = 0
      else
        state.animation_frames_selected_index += 1
      end
      gtk.notify! "Next frame."
    end

    # b to go back/previous frame
    if (inputs.keyboard.key_down.b)
      if (state.animation_frames_selected_index == 0)
        state.animation_frames_selected_index = state.animation_frames.length - 1
      else
        state.animation_frames_selected_index -= 1
      end
      gtk.notify! "Previous frame."
    end

    # x to delete frame
    if (inputs.keyboard.key_down.x) && animation_frames.length > 1
      state.clipboard = selected_animation_frame[:pixels]
      state.animation_frames = animation_frames.find_all { |v| v[:index] != state.animation_frames_selected_index }
      if state.animation_frames_selected_index >= state.animation_frames.length
        state.animation_frames_selected_index = state.animation_frames.length - 1
      end
      gtk.notify! "Frame deleted."
    end
  end

  def calc_auto_export
    return if user_is_editing?
    return if state.last_mouse_up.elapsed_time != 30
    # auto export current animation frame if there is no editing for 30 ticks
    queues.create_sprite << { index: state.animation_frames_selected_index,
                              at: state.tick_count }
  end

  def calc_buttons_frame_selection
    state.buttons_frame_selection.items = animation_frames.length.map_with_index do |i|
      { x: state.buttons_frame_selection.left + i * state.buttons_frame_selection.size,
        y: state.buttons_frame_selection.top - state.buttons_frame_selection.size,
        inner_rect: {
          x: (state.buttons_frame_selection.left + 2) + i * state.buttons_frame_selection.size,
          y: (state.buttons_frame_selection.top - state.buttons_frame_selection.size + 2),
          w: 16,
          h: 16,
        },
        w: state.buttons_frame_selection.size,
        h: state.buttons_frame_selection.size,
        index: i }
    end
  end

  def calc_animation_frames
    animation_frames.each_with_index do |animation_frame, i|
      animation_frame[:index] = i
      animation_frame[:rt_name] = "animation_frame_#{i}"
    end
  end

  def process_queue_create_sprite
    sprites_to_create = queues.create_sprite
                              .find_all { |h| h[:at].elapsed? }

    queues.create_sprite = queues.create_sprite - sprites_to_create

    sprites_to_create.each do |h|
      export_animation_frame h[:index], h[:path_override]
    end
  end

  def process_queue_reset_sprite
    sprites_to_reset = queues.reset_sprite
                             .find_all { |h| h[:at].elapsed? }

    queues.reset_sprite -= sprites_to_reset

    sprites_to_reset.each { |h| gtk.reset_sprite (sprite_path h[:index]) }
  end

  def process_queue_update_rt_animation_frame
    animation_frames_to_update = queues.update_rt_animation_frame
                                       .find_all { |h| h[:at].elapsed? }

    queues.update_rt_animation_frame -= animation_frames_to_update

    animation_frames_to_update.each do |h|
      update_animation_frame_render_target animation_frames[h[:index]]

      if h[:queue_sprite_creation]
        queues.create_sprite << { index: h[:index],
                                  at: state.tick_count + 1 }
      end
    end
  end

  def update_animation_frame_render_target animation_frame
    return if !animation_frame

    outputs[animation_frame[:rt_name]].width   = state.rt_canvas.size
    outputs[animation_frame[:rt_name]].height  = state.rt_canvas.size
    outputs[animation_frame[:rt_name]].solids << animation_frame[:pixels].map do |f|
      { x: f.x,
        y: f.y,
        w: 1,
        h: 1, r: 255, g: 255, b: 255 }
    end
  end

  def animation_frames
    state.animation_frames
  end

  def add_animation_frame_to_end
    animation_frames << {
      index: animation_frames.length,
      pixels: [],
      rt_name: "animation_frame_#{animation_frames.length}"
    }

    state.animation_frames_selected_index = (animation_frames.length - 1)
    queues.update_rt_animation_frame << { index: state.animation_frames_selected_index,
                                          at: state.tick_count,
                                          queue_sprite_creation: true }
  end

  def sprite_path i
    "canvas/sprite-#{i}.png"
  end

  def export_animation_frame i, path_override = nil
    return if !state.animation_frames[i]

    outputs.screenshots << state.buttons_frame_selection
                                .items[i][:inner_rect]
                                .merge(path: path_override || (sprite_path i))

    outputs.screenshots << state.buttons_frame_selection
                                .items[i][:inner_rect]
                                .merge(path: "tmp/sprite_backups/#{Time.now.to_i}-sprite-#{i}.png")

    queues.reset_sprite << { index: i, at: state.tick_count }
  end

  def selected_animation_frame
    state.animation_frames[state.animation_frames_selected_index]
  end

  def edit_current_animation_frame point
    draw_area_point = (to_draw_area point)
    if state.edit_mode == :drawing && (!selected_animation_frame[:pixels].include? draw_area_point)
      selected_animation_frame[:pixels] << draw_area_point
      queues.update_rt_animation_frame << { index: state.animation_frames_selected_index,
                                            at: state.tick_count,
                                            queue_sprite_creation: !user_is_editing? }
    elsif state.edit_mode == :erasing && (selected_animation_frame[:pixels].include? draw_area_point)
      selected_animation_frame[:pixels] = selected_animation_frame[:pixels].reject { |p| p == draw_area_point }
      queues.update_rt_animation_frame << { index: state.animation_frames_selected_index,
                                            at: state.tick_count,
                                            queue_sprite_creation: !user_is_editing? }
    end
  end

  def user_is_editing?
    state.last_mouse_down > state.last_mouse_up
  end

  def to_draw_area point
    x, y = point
    x -= rt_canvas.sprite.x
    y -= rt_canvas.sprite.y
    { x: x.idiv(rt_canvas.zoom),
      y: y.idiv(rt_canvas.zoom) }
  end

  def rt_canvas
    state.rt_canvas ||= state.new_entity(:rt_canvas)
  end

  def queues
    state.queues ||= state.new_entity(:queues)
  end
end

$game = OneBitLowrezPaint.new

def tick args
  $game.args = args
  $game.tick
end

# $gtk.reset

Dev Tools - Tile Editor Starting Point - main.rb

# ./samples/99_genre_dev_tools/tile_editor_starting_point/app/main.rb
=begin

 APIs listing that haven't been encountered in previous sample apps:

 - to_s: Returns a string representation of an object.
   For example, if we had
   500.to_s
   the string "500" would be returned.
   Similar to to_i, which returns an integer representation of an object.

 - Ceil: Returns an integer number greater than or equal to the original
   with no decimal.

 Reminders:

 - ARRAY#inside_rect?: Returns true or false depending on if the point is inside a rect.

 - args.outputs.labels: An array. The values generate a label.
   The parameters are [X, Y, TEXT, SIZE, ALIGNMENT, RED, GREEN, BLUE, ALPHA, FONT STYLE]
   For more information about labels, go to mygame/documentation/02-labels.md.

 - args.outputs.sprites: An array. The values generate a sprite.
   The parameters are [X, Y, WIDTH, HEIGHT, IMAGE PATH]
   For more information about sprites, go to mygame/documentation/05-sprites.md.

 - args.outputs.solids: An array. The values generate a solid.
   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
   For more information about solids, go to mygame/documentation/03-solids-and-borders.md.

 - args.outputs.lines: An array. The values generate a line.
   The parameters are [X1, Y1, X2, Y2, RED, GREEN, BLUE]
   For more information about lines, go to mygame/documentation/04-lines.md.

 - args.state.new_entity: Used when we want to create a new object, like a sprite or button.
   In this sample app, new_entity is used to create a new button that clears the grid.
   (Remember, you can use state to define ANY property and it will be retained across frames.)

=end

# This sample app shows an empty grid that the user can paint in. There are different image tiles that
# the user can use to fill the grid, and the "Clear" button can be pressed to clear the grid boxes.

class TileEditor
  attr_accessor :inputs, :state, :outputs, :grid, :args

  # Runs all the methods necessary for the game to function properly.
  def tick
    defaults
    render
    check_click
    draw_buttons
  end

  # Sets default values
  # Initialization only happens in the first frame
  # NOTE: The values of some of these variables may seem confusingly large at first.
  # The gridSize is 1600 but it seems a lot smaller on the screen, for example.
  # But keep in mind that by using the "W", "A", "S", and "D" keys, you can
  # move the grid's view in all four directions for more grid spaces.
  def defaults
    state.tileCords      ||= []
    state.tileQuantity   ||= 6
    state.tileSize       ||= 50
    state.tileSelected   ||= 1
    state.tempX          ||= 50
    state.tempY          ||= 500
    state.speed          ||= 4
    state.centerX        ||= 4000
    state.centerY        ||= 4000
    state.originalCenter ||= [state.centerX, state.centerY]
    state.gridSize       ||= 1600
    state.lineQuantity   ||= 50
    state.increment      ||= state.gridSize / state.lineQuantity
    state.gridX          ||= []
    state.gridY          ||= []
    state.filled_squares ||= []
    state.grid_border    ||= [390, 140, 500, 500]

    get_grid unless state.tempX == 0 # calls get_grid in the first frame only
    determineTileCords unless state.tempX == 0 # calls determineTileCords in first frame
    state.tempX = 0 # sets tempX to 0; the two methods aren't called again
  end

  # Calculates the placement of lines or separators in the grid
  def get_grid
    curr_x = state.centerX - (state.gridSize / 2) # starts at left of grid
    deltaX = state.gridSize / state.lineQuantity # finds distance to place vertical lines evenly through width of grid
    (state.lineQuantity + 2).times do
      state.gridX << curr_x # adds curr_x to gridX collection
      curr_x += deltaX # increment curr_x by the distance between vertical lines
    end

    curr_y = state.centerY - (state.gridSize / 2) # starts at bottom of grid
    deltaY = state.gridSize / state.lineQuantity # finds distance to place horizontal lines evenly through height of grid
    (state.lineQuantity + 2).times do
      state.gridY << curr_y # adds curr_y to gridY collection
      curr_y += deltaY # increments curr_y to distance between horizontal lines
    end
  end

  # Determines coordinate positions of patterned tiles (on the left side of the grid)
  def determineTileCords
    state.tempCounter ||= 1 # initializes tempCounter to 1
    state.tileQuantity.times do # there are 6 different kinds of tiles
      state.tileCords += [[state.tempX, state.tempY, state.tempCounter]] # adds tile definition to collection
      state.tempX += 75 # increments tempX to put horizontal space between the patterned tiles
      state.tempCounter += 1 # increments tempCounter
      if state.tempX > 200 # if tempX exceeds 200 pixels
        state.tempX = 50 # a new row of patterned tiles begins
        state.tempY -= 75 # the new row is 75 pixels lower than the previous row
      end
    end
  end

  # Outputs objects (grid, tiles, etc) onto the screen
  def render
    outputs.sprites << state.tileCords.map do # outputs tileCords collection using images in sprites folder
      |x, y, order|
      [x, y, state.tileSize, state.tileSize, 'sprites/image' + order.to_s + ".png"]
    end
    outputs.solids << [0, 0, 1280, 720, 255, 255, 255] # outputs white background
    add_grid # outputs grid
    print_title # outputs title and current tile pattern
  end

  # Creates a grid by outputting vertical and horizontal grid lines onto the screen.
  # Outputs sprites for the filled_squares collection onto the screen.
  def add_grid

    # Outputs the grid's border.
    outputs.borders << state.grid_border
    temp = 0

    # Before looking at the code that outputs the vertical and horizontal lines in the
    # grid, take note of the fact that:
    # grid_border[1] refers to the border's bottom line (running horizontally),
    # grid_border[2] refers to the border's top line (running (horizontally),
    # grid_border[0] refers to the border's left line (running vertically),
    # and grid_border[3] refers to the border's right line (running vertically).

    #           [2]
    #       ----------
    #       |        |
    # [0]   |        | [3]
    #       |        |
    #       ----------
    #           [1]

    # Calculates the positions and outputs the x grid lines in the color gray.
    state.gridX.map do # perform an action on all elements of the gridX collection
      |x|
      temp += 1 # increment temp

      # if x's value is greater than (or equal to) the x value of the border's left side
      # and less than (or equal to) the x value of the border's right side
      if x >= state.centerX - (state.grid_border[2] / 2) && x <= state.centerX + (state.grid_border[2] / 2)
        delta = state.centerX - 640
        # vertical lines have the same starting and ending x positions
        # starting y and ending y positions lead from the bottom of the border to the top of the border
        outputs.lines << [x - delta, state.grid_border[1], x - delta, state.grid_border[1] + state.grid_border[2], 150, 150, 150] # sets definition of vertical line and outputs it
      end
    end
    temp = 0

    # Calculates the positions and outputs the y grid lines in the color gray.
    state.gridY.map do # perform an action on all elements of the gridY collection
      |y|
      temp += 1 # increment temp

      # if y's value is greater than (or equal to) the y value of the border's bottom side
      # and less than (or equal to) the y value of the border's top side
      if y >= state.centerY - (state.grid_border[3] / 2) && y <= state.centerY + (state.grid_border[3] / 2)
        delta = state.centerY - 393
        # horizontal lines have the same starting and ending y positions
        # starting x and ending x positions lead from the left side of the border to the right side of the border
        outputs.lines << [state.grid_border[0], y - delta, state.grid_border[0] + state.grid_border[3], y - delta, 150, 150, 150] # sets definition of horizontal line and outputs it
      end
    end

    # Sets values and outputs sprites for the filled_squares collection.
    state.filled_squares.map do # perform an action on every element of the filled_squares collection
      |x, y, w, h, sprite|
        # if x's value is greater than (or equal to) the x value of 17 pixels to the left of the border's left side
        # and less than (or equal to) the x value of the border's right side
        # and y's value is greater than (or equal to) the y value of the border's bottom side
        # and less than (or equal to) the y value of 25 pixels above the border's top side
        # NOTE: The allowance of 17 pixels and 25 pixels is due to the fact that a grid box may be slightly cut off or
        # not entirely visible in the grid's view (until it is moved using "W", "A", "S", "D")
        if x >= state.centerX - (state.grid_border[2] / 2) - 17 && x <= state.centerX + (state.grid_border[2] / 2) &&
           y >= state.centerY - (state.grid_border[3] / 2) && y <= state.centerY + (state.grid_border[3] / 2) + 25
          # calculations done to place sprites in grid spaces that are meant to filled in
          # mess around with the x and y values and see how the sprite placement changes
          outputs.sprites << [x - state.centerX + 630, y - state.centerY + 360, w, h, sprite]
        end
      end

      # outputs a white solid along the left side of the grid (change the color and you'll be able to see it against the white background)
      # state.increment subtracted in x parameter because solid's position is denoted by bottom left corner
      # state.increment subtracted in y parameter to avoid covering the title label
      outputs.primitives << [state.grid_border[0] - state.increment,
                             state.grid_border[1] - state.increment, state.increment, state.grid_border[3] + (state.increment * 2),
                             255, 255, 255].solid

      # outputs a white solid along the right side of the grid
      # state.increment subtracted from y parameter to avoid covering title label
      outputs.primitives << [state.grid_border[0] + state.grid_border[2],
                             state.grid_border[1] - state.increment, state.increment, state.grid_border[3] + (state.increment * 2),
                             255, 255, 255].solid

      # outputs a white solid along the bottom of the grid
      # state.increment subtracted from y parameter to avoid covering last row of grid boxes
      outputs.primitives << [state.grid_border[0] - state.increment, state.grid_border[1] - state.increment,
                             state.grid_border[2] + (2 * state.increment), state.increment, 255, 255, 255].solid

      # outputs a white solid along the top of the grid
      outputs.primitives << [state.grid_border[0] - state.increment, state.grid_border[1] + state.grid_border[3],
                             state.grid_border[2] + (2 * state.increment), state.increment, 255, 255, 255].solid

  end

  # Outputs title and current tile pattern
  def print_title
    outputs.labels << [640, 700, 'Mouse to Place Tile, WASD to Move Around', 7, 1] # title label
    outputs.lines << horizontal_separator(660, 0, 1280) # outputs horizontal separator
    outputs.labels << [1050, 500, 'Current:', 3, 1] # outputs Current label
    outputs.sprites << [1110, 474, state.tileSize / 2, state.tileSize / 2, 'sprites/image' + state.tileSelected.to_s + ".png"] # outputs sprite of current tile pattern using images in sprites folder; output is half the size of a tile
  end

  # Sets the starting position, ending position, and color for the horizontal separator.
  def horizontal_separator y, x, x2
    [x, y, x2, y, 150, 150, 150] # definition of separator; horizontal line means same starting/ending y
  end

  # Checks if the mouse is being clicked or dragged
  def check_click
    if inputs.keyboard.key_down.r # if the "r" key is pressed down
      $dragon.reset
    end

    if inputs.mouse.down #is mouse up or down?
      state.mouse_held = true
      if inputs.mouse.position.x < state.grid_border[0] # if mouse's x position is inside the grid's borders
        state.tileCords.map do # perform action on all elements of tileCords collection
          |x, y, order|
          # if mouse's x position is greater than (or equal to) the starting x position of a tile
          # and the mouse's x position is also less than (or equal to) the ending x position of that tile,
          # and the mouse's y position is greater than (or equal to) the starting y position of that tile,
          # and the mouse's y position is also less than (or equal to) the ending y position of that tile,
          # (BASICALLY, IF THE MOUSE'S POSITION IS WITHIN THE STARTING AND ENDING POSITIONS OF A TILE)
          if inputs.mouse.position.x >= x && inputs.mouse.position.x <= x + state.tileSize &&
             inputs.mouse.position.y >= y && inputs.mouse.position.y <= y + state.tileSize
            state.tileSelected = order # that tile is selected
          end
        end
      end
    elsif inputs.mouse.up # otherwise, if the mouse is in the "up" state
      state.mouse_held = false # mouse is not held down or dragged
      state.mouse_dragging = false
    end

    if state.mouse_held &&    # mouse needs to be down
       !inputs.mouse.click &&     # must not be first click
       ((inputs.mouse.previous_click.point.x - inputs.mouse.position.x).abs > 15 ||
        (inputs.mouse.previous_click.point.y - inputs.mouse.position.y).abs > 15) # Need to move 15 pixels before "drag"
      state.mouse_dragging = true
    end

    # if mouse is clicked inside grid's border, search_lines method is called with click input type
    if ((inputs.mouse.click) && (inputs.mouse.click.point.inside_rect? state.grid_border))
      search_lines(inputs.mouse.click.point, :click)

    # if mouse is dragged inside grid's border, search_lines method is called with drag input type
    elsif ((state.mouse_dragging) && (inputs.mouse.position.inside_rect? state.grid_border))
      search_lines(inputs.mouse.position, :drag)
    end

    # Changes grid's position on screen by moving it up, down, left, or right.

    # centerX is incremented by speed if the "d" key is pressed and if that sum is less than
    # the original left side of the center plus half the grid, minus half the top border of grid.
    # MOVES GRID RIGHT (increasing x)
    state.centerX += state.speed if inputs.keyboard.key_held.d &&
                                    (state.centerX + state.speed) < state.originalCenter[0] + (state.gridSize / 2) - (state.grid_border[2] / 2)
    # centerX is decremented by speed if the "a" key is pressed and if that difference is greater than
    # the original left side of the center minus half the grid, plus half the top border of grid.
    # MOVES GRID LEFT (decreasing x)
    state.centerX -= state.speed if inputs.keyboard.key_held.a &&
                                    (state.centerX - state.speed) > state.originalCenter[0] - (state.gridSize / 2) + (state.grid_border[2] / 2)
    # centerY is incremented by speed if the "w" key is pressed and if that sum is less than
    # the original bottom of the center plus half the grid, minus half the right border of grid.
    # MOVES GRID UP (increasing y)
    state.centerY += state.speed if inputs.keyboard.key_held.w &&
                                    (state.centerY + state.speed) < state.originalCenter[1] + (state.gridSize / 2) - (state.grid_border[3] / 2)
    # centerY is decremented by speed if the "s" key is pressed and if the difference is greater than
    # the original bottom of the center minus half the grid, plus half the right border of grid.
    # MOVES GRID DOWN (decreasing y)
    state.centerY -= state.speed if inputs.keyboard.key_held.s &&
                                    (state.centerY - state.speed) > state.originalCenter[1] - (state.gridSize / 2) + (state.grid_border[3] / 2)
  end

  # Performs calculations on the gridX and gridY collections, and sets values.
  # Sets the definition of a grid box, including the image that it is filled with.
  def search_lines (point, input_type)
    point.x += state.centerX - 630 # increments x and y
    point.y += state.centerY - 360
    findX = 0
    findY = 0
    increment = state.gridSize / state.lineQuantity # divides grid by number of separators

    state.gridX.map do # perform an action on every element of collection
      |x|
      # findX increments x by 10 if point.x is less than that sum and findX is currently 0
      findX = x + 10 if point.x < (x + 10) && findX == 0
    end

    state.gridY.map do
      |y|
      # findY is set to y if point.y is less than that value and findY is currently 0
      findY = y if point.y < (y) && findY == 0
    end
    # position of a box is denoted by bottom left corner, which is why the increment is being subtracted
    grid_box = [findX - (increment.ceil), findY - (increment.ceil), increment.ceil, increment.ceil,
                "sprites/image" + state.tileSelected.to_s + ".png"] # sets sprite definition

    if input_type == :click # if user clicks their mouse
      if state.filled_squares.include? grid_box # if grid box is already filled in
        state.filled_squares.delete grid_box # box is cleared and removed from filled_squares
      else
        state.filled_squares << grid_box # otherwise, box is filled in and added to filled_squares
      end
    elsif input_type == :drag # if user drags mouse
      unless state.filled_squares.include? grid_box # unless grid box dragged over is already filled in
        state.filled_squares << grid_box # box is filled in and added to filled_squares
      end
    end
  end

  # Creates a "Clear" button using labels and borders.
  def draw_buttons
    x, y, w, h = 390, 50, 240, 50
    state.clear_button        ||= state.new_entity(:button_with_fade)

    # x and y positions are set to display "Clear" label in center of the button
    # Try changing first two parameters to simply x, y and see what happens to the text placement
    state.clear_button.label  ||= [x + w.half, y + h.half + 10, "Clear", 0, 1]
    state.clear_button.border ||= [x, y, w, h] # definition of button's border

    # If the mouse is clicked inside the borders of the clear button
    if inputs.mouse.click && inputs.mouse.click.point.inside_rect?(state.clear_button.border)
      state.clear_button.clicked_at = inputs.mouse.click.created_at # value is frame of mouse click
      state.filled_squares.clear # filled squares collection is emptied (squares are cleared)
      inputs.mouse.previous_click = nil # no previous click
    end

    outputs.labels << state.clear_button.label # outputs clear button
    outputs.borders << state.clear_button.border

    # When the clear button is clicked, the color of the button changes
    # and the transparency changes, as well. If you change the time from
    # 0.25.seconds to 1.25.seconds or more, the change will last longer.
    if state.clear_button.clicked_at
      outputs.solids << [x, y, w, h, 0, 180, 80, 255 * state.clear_button.clicked_at.ease(0.25.seconds, :flip)]
    end
  end
end

$tile_editor = TileEditor.new

def tick args
  $tile_editor.inputs = args.inputs
  $tile_editor.grid = args.grid
  $tile_editor.args = args
  $tile_editor.outputs = args.outputs
  $tile_editor.state = args.state
  $tile_editor.tick
  tick_instructions args, "Roll your own tile editor. CLICK to select a sprite. CLICK in grid to place sprite. WASD to move around."
end

def tick_instructions args, text, y = 715
  return if args.state.key_event_occurred
  if args.inputs.mouse.click ||
     args.inputs.keyboard.directional_vector ||
     args.inputs.keyboard.key_down.enter ||
     args.inputs.keyboard.key_down.escape
    args.state.key_event_occurred = true
  end

  args.outputs.debug << [0, y - 50, 1280, 60].solid
  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
end

Dungeon Crawl - Classics Jam - main.rb

# ./samples/99_genre_dungeon_crawl/classics_jam/app/main.rb
class Game
  attr_gtk

  def tick
    defaults
    render
    input
    calc
  end

  def defaults
    player.x              ||= 640
    player.y              ||= 360
    player.w              ||= 16
    player.h              ||= 16
    player.attacked_at    ||= -1
    player.angle          ||= 0
    player.future_player  ||= future_player_position 0, 0
    player.projectiles    ||= []
    player.damage         ||= 0
    state.level           ||= create_level level_one_template
  end

  def render
    outputs.sprites << level.walls.map do |w|
      w.merge(path: 'sprites/square/gray.png')
    end

    outputs.sprites << level.spawn_locations.map do |s|
      s.merge(path: 'sprites/square/blue.png')
    end

    outputs.sprites << player.projectiles.map do |p|
      p.merge(path: 'sprites/square/blue.png')
    end

    outputs.sprites << level.enemies.map do |e|
      e.merge(path: 'sprites/square/red.png')
    end

    outputs.sprites << player.merge(path: 'sprites/circle/green.png', angle: player.angle)

    outputs.labels << { x: 30, y: 30.from_top, text: "damage: #{player.damage || 0}" }
  end

  def input
    player.angle = inputs.directional_angle || player.angle
    if inputs.controller_one.key_down.a || inputs.keyboard.key_down.space
      player.attacked_at = state.tick_count
    end
  end

  def calc
    calc_player
    calc_projectiles
    calc_enemies
    calc_spawn_locations
  end

  def calc_player
    if player.attacked_at == state.tick_count
      player.projectiles << { at: state.tick_count,
                              x: player.x,
                              y: player.y,
                              angle: player.angle,
                              w: 4,
                              h: 4 }.center_inside_rect(player)
    end

    if player.attacked_at.elapsed_time > 5
      future_player = future_player_position inputs.left_right * 2, inputs.up_down * 2
      future_player_collision = future_collision player, future_player, level.walls
      player.x = future_player_collision.x if !future_player_collision.dx_collision
      player.y = future_player_collision.y if !future_player_collision.dy_collision
    end
  end

  def calc_projectile_collisions entities
    entities.each do |e|
      e.damage ||= 0
      player.projectiles.each do |p|
        if !p.collided && (p.intersect_rect? e)
          p.collided = true
          e.damage  += 1
        end
      end
    end
  end

  def calc_projectiles
    player.projectiles.map! do |p|
      dx, dy = p.angle.vector 10
      p.merge(x: p.x + dx, y: p.y + dy)
    end

    calc_projectile_collisions level.walls + level.enemies + level.spawn_locations
    player.projectiles.reject! { |p| p.at.elapsed_time > 10000 }
    player.projectiles.reject! { |p| p.collided }
    level.enemies.reject! { |e| e.damage > e.hp }
    level.spawn_locations.reject! { |s| s.damage > s.hp }
  end

  def calc_enemies
    level.enemies.map! do |e|
      dx =  0
      dx =  1 if e.x < player.x
      dx = -1 if e.x > player.x
      dy =  0
      dy =  1 if e.y < player.y
      dy = -1 if e.y > player.y
      future_e           = future_entity_position dx, dy, e
      future_e_collision = future_collision e, future_e, level.enemies + level.walls
      e.next_x = e.x
      e.next_y = e.y
      e.next_x = future_e_collision.x if !future_e_collision.dx_collision
      e.next_y = future_e_collision.y if !future_e_collision.dy_collision
      e
    end

    level.enemies.map! do |e|
      e.x = e.next_x
      e.y = e.next_y
      e
    end

    level.enemies.each do |e|
      player.damage += 1 if e.intersect_rect? player
    end
  end

  def calc_spawn_locations
    level.spawn_locations.map! do |s|
      s.merge(countdown: s.countdown - 1)
    end
    level.spawn_locations
         .find_all { |s| s.countdown.neg? }
         .each do |s|
      s.countdown = s.rate
      s.merge(countdown: s.rate)
      new_enemy = create_enemy s
      if !(level.enemies.find { |e| e.intersect_rect? new_enemy })
        level.enemies << new_enemy
      end
    end
  end

  def create_enemy spawn_location
    to_cell(spawn_location.ordinal_x, spawn_location.ordinal_y).merge hp: 2
  end

  def create_level level_template
    {
      walls:           level_template.walls.map { |w| to_cell(w.ordinal_x, w.ordinal_y).merge(w) },
      enemies:         [],
      spawn_locations: level_template.spawn_locations.map { |s| to_cell(s.ordinal_x, s.ordinal_y).merge(s) }
    }
  end

  def level_one_template
    {
      walls:           [{ ordinal_x: 25, ordinal_y: 20},
                        { ordinal_x: 25, ordinal_y: 21},
                        { ordinal_x: 25, ordinal_y: 22},
                        { ordinal_x: 25, ordinal_y: 23}],
      spawn_locations: [{ ordinal_x: 10, ordinal_y: 10, rate: 120, countdown: 0, hp: 5 }]
    }
  end

  def player
    state.player ||= {}
  end

  def level
    state.level  ||= {}
  end

  def future_collision entity, future_entity, others
    dx_collision = others.find { |o| o != entity && (o.intersect_rect? future_entity.dx) }
    dy_collision = others.find { |o| o != entity && (o.intersect_rect? future_entity.dy) }

    {
      dx_collision: dx_collision,
      x: future_entity.dx.x,
      dy_collision: dy_collision,
      y: future_entity.dy.y
    }
  end

  def future_entity_position dx, dy, entity
    {
      dx:   entity.merge(x: entity.x + dx),
      dy:   entity.merge(y: entity.y + dy),
      both: entity.merge(x: entity.x + dx, y: entity.y + dy)
    }
  end

  def future_player_position  dx, dy
    future_entity_position dx, dy, player
  end

  def to_cell ordinal_x, ordinal_y
    { x: ordinal_x * 16, y: ordinal_y * 16, w: 16, h: 16 }
  end
end

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

$gtk.reset
$game = nil

Lowrez - Nokia 3310 - main.rb

# ./samples/99_genre_lowrez/nokia_3310/app/main.rb
require 'app/nokia.rb'

def tick args
  # =======================================================================
  # ==== HELLO WORLD ======================================================
  # =======================================================================
  # Steps to get started:
  # 1. ~def tick args~ is the entry point for your game.
  # 2. There are quite a few code samples below, remove the "##"
  #    before each line and save the file to see the changes.
  # 3. 0,  0 is in bottom left and 83, 47 is in top right corner.
  # 4. Be sure to come to the discord channel if you need
  #    more help: [[http://discord.dragonruby.org]].

  # Commenting and uncommenting code:
  # - Add a "#" infront of lines to comment out code
  # - Remove the "#" infront of lines to comment out code

  # Invoke the hello_world subroutine/method
  hello_world args # <---- add a "#" to the beginning of the line to stop running this subroutine/method.

  # =======================================================================
  # ==== HOW TO RENDER A LABEL ============================================
  # =======================================================================

  # Uncomment the line below to invoke the how_to_render_a_label subroutine/method.
  # Note: The method is defined in this file with the signature ~def how_to_render_a_label args~
  #       Scroll down to the method to see the details.

  # Remove the "#" at the beginning of the line below
  # how_to_render_a_label args # <---- remove the "#" at the beginning of this line to run the method


  # =======================================================================
  # ==== HOW TO RENDER A FILLED SQUARE (SOLID) ============================
  # =======================================================================
  # Remove the "#" at the beginning of the line below
  # how_to_render_solids args


  # =======================================================================
  # ==== HOW TO RENDER AN UNFILLED SQUARE (BORDER) ========================
  # =======================================================================
  # Remove the "#" at the beginning of the line below
  # how_to_render_borders args


  # =======================================================================
  # ==== HOW TO RENDER A LINE =============================================
  # =======================================================================
  # Remove the "#" at the beginning of the line below
  # how_to_render_lines args


  # =======================================================================
  # == HOW TO RENDER A SPRITE =============================================
  # =======================================================================
  # Remove the "#" at the beginning of the line below
  # how_to_render_sprites args


  # =======================================================================
  # ==== HOW TO MOVE A SPRITE BASED OFF OF USER INPUT =====================
  # =======================================================================
  # Remove the "#" at the beginning of the line below
  # how_to_move_a_sprite args


  # =======================================================================
  # ==== HOW TO ANIMATE A SPRITE (SEPERATE PNGS) ==========================
  # =======================================================================
  # Remove the "#" at the beginning of the line below
  # how_to_animate_a_sprite args


  # =======================================================================
  # ==== HOW TO ANIMATE A SPRITE (SPRITE SHEET) ===========================
  # =======================================================================
  # Remove the "#" at the beginning of the line below
  # how_to_animate_a_sprite_sheet args


  # =======================================================================
  # ==== HOW TO DETERMINE COLLISION =============================================
  # =======================================================================
  # Remove the "#" at the beginning of the line below
  # how_to_determine_collision args


  # =======================================================================
  # ==== HOW TO CREATE BUTTONS ==================================================
  # =======================================================================
  # Remove the "#" at the beginning of the line below
  # how_to_create_buttons args

  # ==== The line below renders a debug grid, mouse information, and current tick
  # render_debug args
end

# =======================================================================
# ==== HELLO WORLD ======================================================
# =======================================================================
def hello_world args
  args.nokia.solids  << { x: 0, y: 64, w: 10, h: 10, r: 255 }

  args.nokia.labels  << {
    x: 42,
    y: 46,
    text: "nokia 3310 jam 3",
    size_enum: NOKIA_FONT_SM,
    alignment_enum: 1,
    r: 0,
    g: 0,
    b: 0,
    a: 255,
    font: NOKIA_FONT_PATH
  }

  args.nokia.sprites << {
    x: 42 - 10,
    y: 26 - 10,
    w: 20,
    h: 20,
    path: 'sprites/monochrome-ship.png',
    a: 255,
    angle: args.state.tick_count % 360
  }
end

# =======================================================================
# ==== HOW TO RENDER A LABEL ============================================
# =======================================================================
def how_to_render_a_label args
  # NOTE: Text is aligned from the TOP LEFT corner

  # Render an EXTRA LARGE/XL label (remove the "#" in front of each line below)
  args.nokia.labels << { x: 0, y: 46, text: "Hello World",
                         size_enum: NOKIA_FONT_XL,
                         r: 0, g: 0, b: 0, a: 255,
                         font: NOKIA_FONT_PATH }

  # Render a LARGE/LG label (remove the "#" in front of each line below)
  args.nokia.labels << { x: 0, y: 29, text: "Hello World",
                          size_enum: NOKIA_FONT_LG,
                          r: 0, g: 0, b: 0, a: 255,
                          font: NOKIA_FONT_PATH }

  # Render a MEDIUM/MD label (remove the "#" in front of each line below)
  args.nokia.labels << { x: 0, y: 16, text: "Hello World",
                          size_enum: NOKIA_FONT_MD,
                          r: 0, g: 0, b: 0, a: 255,
                          font: NOKIA_FONT_PATH }

  # Render a SMALL/SM label (remove the "#" in front of each line below)
  args.nokia.labels << { x: 0, y: 7, text: "Hello World",
                          size_enum: NOKIA_FONT_SM,
                          r: 0, g: 0, b: 0, a: 255,
                          font: NOKIA_FONT_PATH }

  # You are provided args.nokia.default_label which returns a Hash that you
  # can ~merge~ properties with
  # Example 1
  args.nokia.labels << args.nokia
                            .default_label
                            .merge(text: "Default")

  # Example 2
  args.nokia.labels << args.nokia
                            .default_label
                            .merge(x: 31,
                                   text: "Default")
end

# =============================================================================
# ==== HOW TO RENDER FILLED SQUARES (SOLIDS) ==================================
# =============================================================================
def how_to_render_solids args
  # Render a square at 0, 0 with a width and height of 1
  args.nokia.solids << { x: 0, y: 0, w: 1, h: 1 }

  # Render a square at 1, 1 with a width and height of 2
  args.nokia.solids << { x: 1, y: 1, w: 2, h: 2 }

  # Render a square at 3, 3 with a width and height of 3
  args.nokia.solids << { x: 3, y: 3, w: 3, h: 3 }

  # Render a square at 6, 6 with a width and height of 4
  args.nokia.solids << { x: 6, y: 6, w: 4, h: 4 }
end

# =============================================================================
# ==== HOW TO RENDER UNFILLED SQUARES (BORDERS) ===============================
# =============================================================================
def how_to_render_borders args
  # Render a square at 0, 0 with a width and height of 3
  args.nokia.borders << { x: 0, y: 0, w: 3, h: 3, a: 255 }

  # Render a square at 3, 3 with a width and height of 3
  args.nokia.borders << { x: 3, y: 3, w: 4, h: 4, a: 255 }

  # Render a square at 5, 5 with a width and height of 4
  args.nokia.borders << { x: 7, y: 7, w: 5, h: 5, a: 255 }
end

# =============================================================================
# ==== HOW TO RENDER A LINE ===================================================
# =============================================================================
def how_to_render_lines args
  # Render a horizontal line at the bottom
  args.nokia.lines << { x: 0, y: 0, x2: 83, y2:  0 }

  # Render a vertical line at the left
  args.nokia.lines << { x: 0, y: 0, x2:  0, y2: 47 }

  # Render a diagonal line starting from the bottom left and going to the top right
  args.nokia.lines << { x: 0, y: 0, x2: 83, y2: 47 }
end

# =============================================================================
# == HOW TO RENDER A SPRITE ===================================================
# =============================================================================
def how_to_render_sprites args
  # Loop 10 times and create 10 sprites in 10 positions
  # Render a sprite at the bottom left with a width and height of 5 and a path of 'sprites/monochrome-ship.png'
  10.times do |i|
    args.nokia.sprites << {
      x: i * 8.4,
      y: i * 4.8,
      w: 5,
      h: 5,
      path: 'sprites/monochrome-ship.png'
    }
  end

  # Given an array of positions create sprites
  positions = [
    { x: 20, y: 32 },
    { x: 45, y: 15 },
    { x: 72, y: 23 },
  ]

  positions.each do |position|
    # use Ruby's ~Hash#merge~ function to create a sprite
    args.nokia.sprites << position.merge(path: 'sprites/monochrome-ship.png',
                                          w: 5,
                                          h: 5)
  end
end

# =============================================================================
# ==== HOW TO ANIMATE A SPRITE (SEPERATE PNGS) ==========================
# =============================================================================
def how_to_animate_a_sprite args
  # STEP 1: Define when you want the animation to start. The animation in this case will start in 3 seconds
  start_animation_on_tick = 180

  # STEP 2: Get the frame_index given the start tick.
  sprite_index = start_animation_on_tick.frame_index count: 7,     # how many sprites?
                                                     hold_for: 8,  # how long to hold each sprite?
                                                     repeat: true  # should it repeat?

  # STEP 3: frame_index will return nil if the frame hasn't arrived yet
  if sprite_index
    # if the sprite_index is populated, use it to determine the sprite path and render it
    sprite_path  = "sprites/explosion-#{sprite_index}.png"
    args.nokia.sprites << { x: 42 - 16,
                             y: 47 - 32,
                             w: 32,
                             h: 32,
                             path: sprite_path }
  else
    # if the sprite_index is nil, render a countdown instead
    countdown_in_seconds = ((start_animation_on_tick - args.state.tick_count) / 60).round(1)

    args.nokia.labels  << args.nokia
                               .default_label
                               .merge(x: 0,
                                      y: 18,
                                      text: "Count Down: #{countdown_in_seconds.to_sf}",
                                      alignment_enum: 0)
  end

  # render the current tick and the resolved sprite index
  args.nokia.labels  << args.nokia
                               .default_label
                               .merge(x: 0,
                                      y: 11,
                                      text: "Tick: #{args.state.tick_count}")
  args.nokia.labels  << args.nokia
                               .default_label
                               .merge(x: 0,
                                      y: 5,
                                      text: "sprite_index: #{sprite_index}")
end

# =============================================================================
# ==== HOW TO ANIMATE A SPRITE (SPRITE SHEET) =================================
# =============================================================================
def how_to_animate_a_sprite_sheet args
  # STEP 1: Define when you want the animation to start. The animation in this case will start in 3 seconds
  start_animation_on_tick = 180

  # STEP 2: Get the frame_index given the start tick.
  sprite_index = start_animation_on_tick.frame_index count: 7,     # how many sprites?
                                                     hold_for: 8,  # how long to hold each sprite?
                                                     repeat: true  # should it repeat?

  # STEP 3: frame_index will return nil if the frame hasn't arrived yet
  if sprite_index
    # if the sprite_index is populated, use it to determine the source rectangle and render it
    args.nokia.sprites << {
      x: 42 - 16,
      y: 47 - 32,
      w: 32,
      h: 32,
      path:  "sprites/explosion-sheet.png",
      source_x: 32 * sprite_index,
      source_y: 0,
      source_w: 32,
      source_h: 32
    }
  else
    # if the sprite_index is nil, render a countdown instead
    countdown_in_seconds = ((start_animation_on_tick - args.state.tick_count) / 60).round(1)

    args.nokia.labels  << args.nokia
                               .default_label
                               .merge(x: 0,
                                      y: 18,
                                      text: "Count Down: #{countdown_in_seconds.to_sf}",
                                      alignment_enum: 0)
  end

  # render the current tick and the resolved sprite index
  args.nokia.labels  << args.nokia
                               .default_label
                               .merge(x: 0,
                                      y: 11,
                                      text: "tick: #{args.state.tick_count}")
  args.nokia.labels  << args.nokia
                               .default_label
                               .merge(x: 0,
                                      y: 5,
                                      text: "sprite_index: #{sprite_index}")
end

# =============================================================================
# ==== HOW TO STORE STATE, ACCEPT INPUT, AND RENDER SPRITE BASED OFF OF STATE =
# =============================================================================
def how_to_move_a_sprite args
  args.nokia.labels << args.nokia
                            .default_label
                            .merge(x: 42,
                                   y: 46, text: "Use Arrow Keys",
                                   alignment_enum: 1)

  args.nokia.labels << args.nokia
                            .default_label
                            .merge(x: 42,
                                   y: 41, text: "Or WASD",
                                   alignment_enum: 1)

  args.nokia.labels << args.nokia
                            .default_label
                            .merge(x: 42,
                                   y: 36, text: "Or Click",
                                   alignment_enum: 1)

  # set the initial values for x and y using ||= ("or equal operator")
  args.state.ship.x ||= 0
  args.state.ship.y ||= 0

  # if a mouse click occurs, update the ship's x and y to be the location of the click
  if args.nokia.mouse_click
    args.state.ship.x = args.nokia.mouse_click.x
    args.state.ship.y = args.nokia.mouse_click.y
  end

  # if a or left arrow is pressed/held, decrement the ships x position
  if args.nokia.keyboard.left
    args.state.ship.x -= 1
  end

  # if d or right arrow is pressed/held, increment the ships x position
  if args.nokia.keyboard.right
    args.state.ship.x += 1
  end

  # if s or down arrow is pressed/held, decrement the ships y position
  if args.nokia.keyboard.down
    args.state.ship.y -= 1
  end

  # if w or up arrow is pressed/held, increment the ships y position
  if args.nokia.keyboard.up
    args.state.ship.y += 1
  end

  # render the sprite to the screen using the position stored in args.state.ship
  args.nokia.sprites << {
    x: args.state.ship.x,
    y: args.state.ship.y,
    w: 5,
    h: 5,
    path: 'sprites/monochrome-ship.png',
    # parameters beyond this point are optional
    angle: 0, # Note: rotation angle is denoted in degrees NOT radians
    r: 255,
    g: 255,
    b: 255,
    a: 255
  }
end

# =======================================================================
# ==== HOW TO DETERMINE COLLISION =======================================
# =======================================================================
def how_to_determine_collision args
  # Render the instructions
  args.nokia.labels << args.nokia
                            .default_label
                            .merge(x: 42,
                                   y: 46, text: "Click Anywhere",
                                   alignment_enum: 1)

  # if a mouse click occurs:
  # - set ship_one if it isn't set
  # - set ship_two if it isn't set
  # - otherwise reset ship one and ship two
  if args.nokia.mouse_click
    # is ship_one set?
    if !args.state.ship_one
      args.state.ship_one = { x: args.nokia.mouse_click.x - 5,
                              y: args.nokia.mouse_click.y - 5,
                              w: 10,
                              h: 10 }
    # is ship_one set?
    elsif !args.state.ship_two
      args.state.ship_two = { x: args.nokia.mouse_click.x - 5,
                              y: args.nokia.mouse_click.y - 5,
                              w: 10,
                              h: 10 }
    # should we reset?
    else
      args.state.ship_one = nil
      args.state.ship_two = nil
    end
  end

  # render ship one if it's set
  if args.state.ship_one
    # use Ruby's .merge method which is available on ~Hash~ to set the sprite and alpha
    # render ship one
    args.nokia.sprites << args.state.ship_one.merge(path: 'sprites/monochrome-ship.png')
  end

  if args.state.ship_two
    # use Ruby's .merge method which is available on ~Hash~ to set the sprite and alpha
    # render ship two
    args.nokia.sprites << args.state.ship_two.merge(path: 'sprites/monochrome-ship.png')
  end

  # if both ship one and ship two are set, then determine collision
  if args.state.ship_one && args.state.ship_two
    # collision is determined using the intersect_rect? method
    if args.state.ship_one.intersect_rect? args.state.ship_two
      # if collision occurred, render the words collision!
      args.nokia.labels << args.nokia
                            .default_label
                            .merge(x: 42,
                                   y: 5,
                                   text: "Collision!",
                                   alignment_enum: 1)
    else
      # if collision occurred, render the words no collision.
      args.nokia.labels << args.nokia
                            .default_label
                            .merge(x: 42,
                                   y: 5,
                                   text: "No Collision.",
                                   alignment_enum: 1)
    end
  else
    # if both ship one and ship two aren't set, then render --
      args.nokia.labels << args.nokia
                            .default_label
                            .merge(x: 42,
                                   y: 6,
                                   text: "--",
                                   alignment_enum: 1)
  end
end

# =============================================================================
# ==== HOW TO CREATE BUTTONS ==================================================
# =============================================================================
def how_to_create_buttons args
  # Define a button style
  args.state.button_style = { w: 82, h: 10, }

  # Render instructions
  args.state.button_message ||= "Press a Button!"
  args.nokia.labels << args.nokia
                            .default_label
                            .merge(x: 42,
                                   y: 82,
                                   text: args.state.button_message,
                                   alignment_enum: 1)


  # Creates button one using a border and a label
  args.state.button_one_border = args.state.button_style.merge( x: 1, y: 32)
  args.nokia.borders << args.state.button_one_border
  args.nokia.labels  << args.nokia
                             .default_label
                             .merge(x: args.state.button_one_border.x + 2,
                                    y: args.state.button_one_border.y + NOKIA_FONT_SM_HEIGHT + 2,
                                    text: "Button One")

  # Creates button two using a border and a label
  args.state.button_two_border = args.state.button_style.merge( x: 1, y: 20)

  args.nokia.borders << args.state.button_two_border
  args.nokia.labels << args.nokia
                            .default_label
                            .merge(x: args.state.button_two_border.x + 2,
                                   y: args.state.button_two_border.y + NOKIA_FONT_SM_HEIGHT + 2,
                                   text: "Button Two")

  # Initialize the state variable that tracks which button was clicked to "" (empty stringI
  args.state.last_button_clicked ||= "--"

  # If a click occurs, check to see if either button one, or button two was clicked
  # using the inside_rect? method of the mouse
  # set args.state.last_button_clicked accordingly
  if args.nokia.mouse_click
    if args.nokia.mouse_click.inside_rect? args.state.button_one_border
      args.state.last_button_clicked = "One Clicked!"
    elsif args.nokia.mouse_click.inside_rect? args.state.button_two_border
      args.state.last_button_clicked = "Two Clicked!"
    else
      args.state.last_button_clicked = "--"
    end
  end

  # Render the current value of args.state.last_button_clicked
  args.nokia.labels << args.nokia
                             .default_label
                             .merge(x: 42,
                                    y: 5,
                                    text: args.state.last_button_clicked,
                                    alignment_enum: 1)
end

def render_debug args
  if !args.state.grid_rendered
    (NOKIA_HEIGHT + 1).map_with_index do |i|
      args.outputs.static_debug << {
        x:  NOKIA_X_OFFSET,
        y:  NOKIA_Y_OFFSET + (i * NOKIA_ZOOM),
        x2: NOKIA_X_OFFSET + NOKIA_ZOOMED_WIDTH,
        y2: NOKIA_Y_OFFSET + (i * NOKIA_ZOOM),
        r: 128,
        g: 128,
        b: 128,
        a: 80
      }.line
    end

    (NOKIA_WIDTH + 1).map_with_index do |i|
      args.outputs.static_debug << {
        x:  NOKIA_X_OFFSET + (i * NOKIA_ZOOM),
        y:  NOKIA_Y_OFFSET,
        x2: NOKIA_X_OFFSET + (i * NOKIA_ZOOM),
        y2: NOKIA_Y_OFFSET + NOKIA_ZOOMED_HEIGHT,
        r: 128,
        g: 128,
        b: 128,
        a: 80
      }.line
    end
  end

  args.state.grid_rendered = true

  args.state.last_click ||= 0
  args.state.last_up    ||= 0
  args.state.last_click   = args.state.tick_count if args.nokia.mouse_down # you can also use args.nokia.click
  args.state.last_up      = args.state.tick_count if args.nokia.mouse_up
  args.state.label_style  = { size_enum: -1.5 }

  args.state.watch_list = [
    "args.state.tick_count is:      #{args.state.tick_count}",
    "args.nokia.mouse_position is:  #{args.nokia.mouse_position.x}, #{args.nokia.mouse_position.y}",
    "args.nokia.mouse_down tick:    #{args.state.last_click || "never"}",
    "args.nokia.mouse_up tick:      #{args.state.last_up || "false"}",
  ]

  args.outputs.debug << args.state
                            .watch_list
                            .map_with_index do |text, i|
    {
      x: 5,
      y: 720 - (i * 18),
      text: text,
      size_enum: -1.5,
      r: 255, g: 255, b: 255
    }.label
  end

  args.outputs.debug << {
    x: 640,
    y:  25,
    text: "INFO: dev mode is currently enabled. Comment out the invocation of ~render_debug~ within the ~tick~ method to hide the debug layer.",
    size_enum: -0.5,
    alignment_enum: 1,
    r: 255, g: 255, b: 255
  }.label
end

def snake_demo args

end

$gtk.reset

Lowrez - Nokia 3310 - nokia.rb

# ./samples/99_genre_lowrez/nokia_3310/app/nokia.rb
# Emulation of a 64x64 canvas. Don't change this file unless you know what you're doing :-)
# Head over to main.rb and study the code there.

NOKIA_WIDTH           = 84
NOKIA_HEIGHT          = 48
NOKIA_ZOOM            = 12
NOKIA_ZOOMED_WIDTH    = NOKIA_WIDTH  * NOKIA_ZOOM
NOKIA_ZOOMED_HEIGHT   = NOKIA_HEIGHT * NOKIA_ZOOM
NOKIA_X_OFFSET        = (1280 - NOKIA_ZOOMED_WIDTH).half
NOKIA_Y_OFFSET        = ( 720 - NOKIA_ZOOMED_HEIGHT).half

NOKIA_FONT_XL         = -1
NOKIA_FONT_XL_HEIGHT  = 20

NOKIA_FONT_LG         = -3.5
NOKIA_FONT_LG_HEIGHT  = 15

NOKIA_FONT_MD         = -6
NOKIA_FONT_MD_HEIGHT  = 10

NOKIA_FONT_SM         = -8.5
NOKIA_FONT_SM_HEIGHT  = 5

NOKIA_FONT_PATH       = 'fonts/lowrez.ttf'


class NokiaOutputs
  attr_accessor :width, :height

  def initialize args
    @args = args
  end

  def outputs_nokia
    return @args.outputs if @args.state.tick_count <= 0
    return @args.outputs[:nokia]
  end

  def solids
    outputs_nokia.solids
  end

  def borders
    outputs_nokia.borders
  end

  def sprites
    outputs_nokia.sprites
  end

  def labels
    outputs_nokia.labels
  end

  def default_label
    {
      x: 0,
      y: 63,
      text: "",
      size_enum: NOKIA_FONT_SM,
      alignment_enum: 0,
      r: 0,
      g: 0,
      b: 0,
      a: 255,
      font: NOKIA_FONT_PATH
    }
  end

  def lines
    outputs_nokia.lines
  end

  def primitives
    outputs_nokia.primitives
  end

  def click
    return nil unless @args.inputs.mouse.click
    mouse
  end

  def mouse_click
    click
  end

  def mouse_down
    @args.inputs.mouse.down
  end

  def mouse_up
    @args.inputs.mouse.up
  end

  def mouse
    [
      ((@args.inputs.mouse.x - NOKIA_X_OFFSET).idiv(NOKIA_ZOOM)),
      ((@args.inputs.mouse.y - NOKIA_Y_OFFSET).idiv(NOKIA_ZOOM))
    ]
  end

  def mouse_position
    mouse
  end

  def keyboard
    @args.inputs.keyboard
  end
end

class GTK::Args
  def init_nokia
    return if @nokia
    @nokia = NokiaOutputs.new self
  end

  def nokia
    @nokia
  end
end

module GTK
  class Runtime
    alias_method :__original_tick_core__, :tick_core unless Runtime.instance_methods.include?(:__original_tick_core__)

    def tick_core
      @args.init_nokia

      __original_tick_core__

      return if @args.state.tick_count <= 0

      @args.render_target(:nokia)
           .labels
           .each do |l|
        l.y  += 1
        if (l.a || 255) > 128
          l.r = 67
          l.g = 82
          l.b = 61
          l.a = 255
        else
          l.a = 0
        end
      end

      @args.render_target(:nokia)
           .sprites
           .each do |s|
        if (s.a || 255) > 128
          s.a = 255
        else
          s.a = 0
        end
      end

      @args.render_target(:nokia)
           .solids
           .each do |s|
        if (s.a || 255) > 128
          s.r = 67
          s.g = 82
          s.b = 61
          s.a = 255
        else
          s.a = 0
        end
      end

      @args.render_target(:nokia)
           .borders
           .each do |s|
        if (s.a || 255) > 128
          s.r = 67
          s.g = 82
          s.b = 61
          s.a = 255
        else
          s.a = 0
        end
      end

      @args.render_target(:nokia)
           .lines
           .each do |l|
        l.y  += 1
        l.y2 += 1
        l.y2 += 1 if l.y1 != l.y2
        l.x2 += 1 if l.x1 != l.x2

        if (l.a || 255) > 128
          l.r = 67
          l.g = 82
          l.b = 61
          l.a = 255
        else
          l.a = 0
        end
      end

      @args.outputs.borders << {
        x: NOKIA_X_OFFSET      - 1,
        y: NOKIA_Y_OFFSET      - 1,
        w: NOKIA_ZOOMED_WIDTH  + 2,
        h: NOKIA_ZOOMED_HEIGHT + 2,
        r: 128, g: 128, b: 128
      }


      @args.outputs.background_color = [199, 240, 216]

      @args.outputs.solids << [0, 0, NOKIA_X_OFFSET, 720]
      @args.outputs.solids << [0, 0, 1280, NOKIA_Y_OFFSET]
      @args.outputs.solids << [NOKIA_X_OFFSET + NOKIA_ZOOMED_WIDTH, 0, NOKIA_X_OFFSET, 720]
      @args.outputs.solids << [0, NOKIA_Y_OFFSET.from_top, 1280, NOKIA_Y_OFFSET]

      @args.outputs
           .sprites << { x: NOKIA_X_OFFSET,
                         y: NOKIA_Y_OFFSET,
                         w: NOKIA_ZOOMED_WIDTH,
                         h: NOKIA_ZOOMED_HEIGHT,
                         source_x: 0,
                         source_y: 0,
                         source_w: NOKIA_WIDTH,
                         source_h: NOKIA_HEIGHT,
                         path: :nokia }

      if [email protected]_rendered
        (NOKIA_HEIGHT + 1).map_with_index do |i|
          @args.outputs.static_lines << {
            x:  NOKIA_X_OFFSET,
            y:  NOKIA_Y_OFFSET + (i * NOKIA_ZOOM),
            x2: NOKIA_X_OFFSET + NOKIA_ZOOMED_WIDTH,
            y2: NOKIA_Y_OFFSET + (i * NOKIA_ZOOM),
            r: 199,
            g: 240,
            b: 216,
            a: 100
          }.line
        end

        (NOKIA_WIDTH + 1).map_with_index do |i|
          @args.outputs.static_lines << {
            x:  NOKIA_X_OFFSET + (i * NOKIA_ZOOM),
            y:  NOKIA_Y_OFFSET,
            x2: NOKIA_X_OFFSET + (i * NOKIA_ZOOM),
            y2: NOKIA_Y_OFFSET + NOKIA_ZOOMED_HEIGHT,
            r: 199,
            g: 240,
            b: 216,
            a: 100
          }.line
        end

        @args.state.overlay_rendered = true
      end
    end
  end
end

Lowrez - Resolution 64x64 - lowrez.rb

# ./samples/99_genre_lowrez/resolution_64x64/app/lowrez.rb
# Emulation of a 64x64 canvas. Don't change this file unless you know what you're doing :-)
# Head over to main.rb and study the code there.

LOWREZ_SIZE            = 64
LOWREZ_ZOOM            = 10
LOWREZ_ZOOMED_SIZE     = LOWREZ_SIZE * LOWREZ_ZOOM
LOWREZ_X_OFFSET        = (1280 - LOWREZ_ZOOMED_SIZE).half
LOWREZ_Y_OFFSET        = ( 720 - LOWREZ_ZOOMED_SIZE).half

LOWREZ_FONT_XL         = -1
LOWREZ_FONT_XL_HEIGHT  = 20

LOWREZ_FONT_LG         = -3.5
LOWREZ_FONT_LG_HEIGHT  = 15

LOWREZ_FONT_MD         = -6
LOWREZ_FONT_MD_HEIGHT  = 10

LOWREZ_FONT_SM         = -8.5
LOWREZ_FONT_SM_HEIGHT  = 5

LOWREZ_FONT_PATH       = 'fonts/lowrez.ttf'


class LowrezOutputs
  attr_accessor :width, :height

  def initialize args
    @args = args
    @background_color ||= [0, 0, 0]
    @args.outputs.background_color = @background_color
  end

  def background_color
    @background_color ||= [0, 0, 0]
  end

  def background_color= opts
    @background_color = opts
    @args.outputs.background_color = @background_color

    outputs_lowrez.solids << [0, 0, LOWREZ_SIZE, LOWREZ_SIZE, @background_color]
  end

  def outputs_lowrez
    return @args.outputs if @args.state.tick_count <= 0
    return @args.outputs[:lowrez]
  end

  def solids
    outputs_lowrez.solids
  end

  def borders
    outputs_lowrez.borders
  end

  def sprites
    outputs_lowrez.sprites
  end

  def labels
    outputs_lowrez.labels
  end

  def default_label
    {
      x: 0,
      y: 63,
      text: "",
      size_enum: LOWREZ_FONT_SM,
      alignment_enum: 0,
      r: 0,
      g: 0,
      b: 0,
      a: 255,
      font: LOWREZ_FONT_PATH
    }
  end

  def lines
    outputs_lowrez.lines
  end

  def primitives
    outputs_lowrez.primitives
  end

  def click
    return nil unless @args.inputs.mouse.click
    mouse
  end

  def mouse_click
    click
  end

  def mouse_down
    @args.inputs.mouse.down
  end

  def mouse_up
    @args.inputs.mouse.up
  end

  def mouse
    [
      ((@args.inputs.mouse.x - LOWREZ_X_OFFSET).idiv(LOWREZ_ZOOM)),
      ((@args.inputs.mouse.y - LOWREZ_Y_OFFSET).idiv(LOWREZ_ZOOM))
    ]
  end

  def mouse_position
    mouse
  end

  def keyboard
    @args.inputs.keyboard
  end
end

class GTK::Args
  def init_lowrez
    return if @lowrez
    @lowrez = LowrezOutputs.new self
  end

  def lowrez
    @lowrez
  end
end

module GTK
  class Runtime
    alias_method :__original_tick_core__, :tick_core unless Runtime.instance_methods.include?(:__original_tick_core__)

    def tick_core
      @args.init_lowrez
      __original_tick_core__

      return if @args.state.tick_count <= 0

      @args.render_target(:lowrez)
           .labels
           .each do |l|
        l.y  += 1
      end

      @args.render_target(:lowrez)
           .lines
           .each do |l|
        l.y  += 1
        l.y2 += 1
        l.y2 += 1 if l.y1 != l.y2
        l.x2 += 1 if l.x1 != l.x2
      end

      @args.outputs
           .sprites << { x: 320,
                         y: 40,
                         w: 640,
                         h: 640,
                         source_x: 0,
                         source_y: 0,
                         source_w: 64,
                         source_h: 64,
                         path: :lowrez }
    end
  end
end

Lowrez - Resolution 64x64 - main.rb

# ./samples/99_genre_lowrez/resolution_64x64/app/main.rb
require 'app/lowrez.rb'

def tick args
  # How to set the background color
  args.lowrez.background_color = [255, 255, 255]

  # ==== HELLO WORLD ======================================================
  # Steps to get started:
  # 1. ~def tick args~ is the entry point for your game.
  # 2. There are quite a few code samples below, remove the "##"
  #    before each line and save the file to see the changes.
  # 3. 0,  0 is in bottom left and 63, 63 is in top right corner.
  # 4. Be sure to come to the discord channel if you need
  #    more help: [[http://discord.dragonruby.org]].

  # Commenting and uncommenting code:
  # - Add a "#" infront of lines to comment out code
  # - Remove the "#" infront of lines to comment out code

  # Invoke the hello_world subroutine/method
  hello_world args # <---- add a "#" to the beginning of the line to stop running this subroutine/method.
  # =======================================================================


  # ==== HOW TO RENDER A LABEL ============================================
  # Uncomment the line below to invoke the how_to_render_a_label subroutine/method.
  # Note: The method is defined in this file with the signature ~def how_to_render_a_label args~
  #       Scroll down to the method to see the details.

  # Remove the "#" at the beginning of the line below
  # how_to_render_a_label args # <---- remove the "#" at the begging of this line to run the method
  # =======================================================================


  # ==== HOW TO RENDER A FILLED SQUARE (SOLID) ============================
  # Remove the "#" at the beginning of the line below
  # how_to_render_solids args
  # =======================================================================


  # ==== HOW TO RENDER AN UNFILLED SQUARE (BORDER) ========================
  # Remove the "#" at the beginning of the line below
  # how_to_render_borders args
  # =======================================================================


  # ==== HOW TO RENDER A LINE =============================================
  # Remove the "#" at the beginning of the line below
  # how_to_render_lines args
  # =======================================================================


  # == HOW TO RENDER A SPRITE =============================================
  # Remove the "#" at the beginning of the line below
  # how_to_render_sprites args
  # =======================================================================


  # ==== HOW TO MOVE A SPRITE BASED OFF OF USER INPUT =====================
  # Remove the "#" at the beginning of the line below
  # how_to_move_a_sprite args
  # =======================================================================


  # ==== HOW TO ANIMATE A SPRITE (SEPERATE PNGS) ==========================
  # Remove the "#" at the beginning of the line below
  # how_to_animate_a_sprite args
  # =======================================================================


  # ==== HOW TO ANIMATE A SPRITE (SPRITE SHEET) ===========================
  # Remove the "#" at the beginning of the line below
  # how_to_animate_a_sprite_sheet args
  # =======================================================================


  # ==== HOW TO DETERMINE COLLISION =============================================
  # Remove the "#" at the beginning of the line below
  # how_to_determine_collision args
  # =======================================================================


  # ==== HOW TO CREATE BUTTONS ==================================================
  # Remove the "#" at the beginning of the line below
  # how_to_create_buttons args
  # =======================================================================


  # ==== The line below renders a debug grid, mouse information, and current tick
  render_debug args
end

def hello_world args
  args.lowrez.solids  << { x: 0, y: 64, w: 10, h: 10, r: 255 }

  args.lowrez.labels  << {
    x: 32,
    y: 63,
    text: "lowrezjam 2020",
    size_enum: LOWREZ_FONT_SM,
    alignment_enum: 1,
    r: 0,
    g: 0,
    b: 0,
    a: 255,
    font: LOWREZ_FONT_PATH
  }

  args.lowrez.sprites << {
    x: 32 - 10,
    y: 32 - 10,
    w: 20,
    h: 20,
    path: 'sprites/lowrez-ship-blue.png',
    a: args.state.tick_count % 255,
    angle: args.state.tick_count % 360
  }
end


# =======================================================================
# ==== HOW TO RENDER A LABEL ============================================
# =======================================================================
def how_to_render_a_label args
  # NOTE: Text is aligned from the TOP LEFT corner

  # Render an EXTRA LARGE/XL label (remove the "#" in front of each line below)
  args.lowrez.labels << { x: 0, y: 57, text: "Hello World",
                         size_enum: LOWREZ_FONT_XL,
                         r: 0, g: 0, b: 0, a: 255,
                         font: LOWREZ_FONT_PATH }

  # Render a LARGE/LG label (remove the "#" in front of each line below)
  args.lowrez.labels << { x: 0, y: 36, text: "Hello World",
                          size_enum: LOWREZ_FONT_LG,
                          r: 0, g: 0, b: 0, a: 255,
                          font: LOWREZ_FONT_PATH }

  # Render a MEDIUM/MD label (remove the "#" in front of each line below)
  args.lowrez.labels << { x: 0, y: 20, text: "Hello World",
                          size_enum: LOWREZ_FONT_MD,
                          r: 0, g: 0, b: 0, a: 255,
                          font: LOWREZ_FONT_PATH }

  # Render a SMALL/SM label (remove the "#" in front of each line below)
  args.lowrez.labels << { x: 0, y: 9, text: "Hello World",
                          size_enum: LOWREZ_FONT_SM,
                          r: 0, g: 0, b: 0, a: 255,
                          font: LOWREZ_FONT_PATH }

  # You are provided args.lowrez.default_label which returns a Hash that you
  # can ~merge~ properties with
  # Example 1
  args.lowrez.labels << args.lowrez
                            .default_label
                            .merge(text: "Default")

  # Example 2
  args.lowrez.labels << args.lowrez
                            .default_label
                            .merge(x: 31,
                                   text: "Default",
                                   r: 128,
                                   g: 128,
                                   b: 128)
end

## # =============================================================================
## # ==== HOW TO RENDER FILLED SQUARES (SOLIDS) ==================================
## # =============================================================================
def how_to_render_solids args
  # Render a red square at 0, 0 with a width and height of 1
  args.lowrez.solids << { x: 0, y: 0, w: 1, h: 1, r: 255, g: 0, b: 0, a: 255 }

  # Render a red square at 1, 1 with a width and height of 2
  args.lowrez.solids << { x: 1, y: 1, w: 2, h: 2, r: 255, g: 0, b: 0, a: 255 }

  # Render a red square at 3, 3 with a width and height of 3
  args.lowrez.solids << { x: 3, y: 3, w: 3, h: 3, r: 255, g: 0, b: 0 }

  # Render a red square at 6, 6 with a width and height of 4
  args.lowrez.solids << { x: 6, y: 6, w: 4, h: 4, r: 255, g: 0, b: 0 }
end

## # =============================================================================
## # ==== HOW TO RENDER UNFILLED SQUARES (BORDERS) ===============================
## # =============================================================================
def how_to_render_borders args
  # Render a red square at 0, 0 with a width and height of 3
  args.lowrez.borders << { x: 0, y: 0, w: 3, h: 3, r: 255, g: 0, b: 0, a: 255 }

  # Render a red square at 3, 3 with a width and height of 3
  args.lowrez.borders << { x: 3, y: 3, w: 4, h: 4, r: 255, g: 0, b: 0, a: 255 }

  # Render a red square at 5, 5 with a width and height of 4
  args.lowrez.borders << { x: 7, y: 7, w: 5, h: 5, r: 255, g: 0, b: 0, a: 255 }
end

## # =============================================================================
## # ==== HOW TO RENDER A LINE ===================================================
## # =============================================================================
def how_to_render_lines args
  # Render a horizontal line at the bottom
  args.lowrez.lines << { x: 0, y: 0, x2: 63, y2:  0, r: 255 }

  # Render a vertical line at the left
  args.lowrez.lines << { x: 0, y: 0, x2:  0, y2: 63, r: 255 }

  # Render a diagonal line starting from the bottom left and going to the top right
  args.lowrez.lines << { x: 0, y: 0, x2: 63, y2: 63, r: 255 }
end

## # =============================================================================
## # == HOW TO RENDER A SPRITE ===================================================
## # =============================================================================
def how_to_render_sprites args
  # Loop 10 times and create 10 sprites in 10 positions
  # Render a sprite at the bottom left with a width and height of 5 and a path of 'sprites/lowrez-ship-blue.png'
  10.times do |i|
    args.lowrez.sprites << {
      x: i * 5,
      y: i * 5,
      w: 5,
      h: 5,
      path: 'sprites/lowrez-ship-blue.png'
    }
  end

  # Given an array of positions create sprites
  positions = [
    { x: 10, y: 42 },
    { x: 15, y: 45 },
    { x: 22, y: 33 },
  ]

  positions.each do |position|
    # use Ruby's ~Hash#merge~ function to create a sprite
    args.lowrez.sprites << position.merge(path: 'sprites/lowrez-ship-red.png',
                                          w: 5,
                                          h: 5)
  end
end

## # =============================================================================
## # ==== HOW TO ANIMATE A SPRITE (SEPERATE PNGS) ==========================
## # =============================================================================
def how_to_animate_a_sprite args
  # STEP 1: Define when you want the animation to start. The animation in this case will start in 3 seconds
  start_animation_on_tick = 180

  # STEP 2: Get the frame_index given the start tick.
  sprite_index = start_animation_on_tick.frame_index count: 7,     # how many sprites?
                                                     hold_for: 4,  # how long to hold each sprite?
                                                     repeat: true  # should it repeat?

  # STEP 3: frame_index will return nil if the frame hasn't arrived yet
  if sprite_index
    # if the sprite_index is populated, use it to determine the sprite path and render it
    sprite_path  = "sprites/explosion-#{sprite_index}.png"
    args.lowrez.sprites << { x: 0, y: 0, w: 64, h: 64, path: sprite_path }
  else
    # if the sprite_index is nil, render a countdown instead
    countdown_in_seconds = ((start_animation_on_tick - args.state.tick_count) / 60).round(1)

    args.lowrez.labels  << args.lowrez
                               .default_label
                               .merge(x: 32,
                                      y: 32,
                                      text: "Count Down: #{countdown_in_seconds}",
                                      alignment_enum: 1)
  end

  # render the current tick and the resolved sprite index
  args.lowrez.labels  << args.lowrez
                               .default_label
                               .merge(x: 0,
                                      y: 11,
                                      text: "Tick: #{args.state.tick_count}")
  args.lowrez.labels  << args.lowrez
                               .default_label
                               .merge(x: 0,
                                      y: 5,
                                      text: "sprite_index: #{sprite_index}")
end

## # =============================================================================
## # ==== HOW TO ANIMATE A SPRITE (SPRITE SHEET) =================================
## # =============================================================================
def how_to_animate_a_sprite_sheet args
  # STEP 1: Define when you want the animation to start. The animation in this case will start in 3 seconds
  start_animation_on_tick = 180

  # STEP 2: Get the frame_index given the start tick.
  sprite_index = start_animation_on_tick.frame_index count: 7,     # how many sprites?
                                                     hold_for: 4,  # how long to hold each sprite?
                                                     repeat: true  # should it repeat?

  # STEP 3: frame_index will return nil if the frame hasn't arrived yet
  if sprite_index
    # if the sprite_index is populated, use it to determine the source rectangle and render it
    args.lowrez.sprites << {
      x: 0,
      y: 0,
      w: 64,
      h: 64,
      path:  "sprites/explosion-sheet.png",
      source_x: 32 * sprite_index,
      source_y: 0,
      source_w: 32,
      source_h: 32
    }
  else
    # if the sprite_index is nil, render a countdown instead
    countdown_in_seconds = ((start_animation_on_tick - args.state.tick_count) / 60).round(1)

    args.lowrez.labels  << args.lowrez
                               .default_label
                               .merge(x: 32,
                                      y: 32,
                                      text: "Count Down: #{countdown_in_seconds}",
                                      alignment_enum: 1)
  end

  # render the current tick and the resolved sprite index
  args.lowrez.labels  << args.lowrez
                               .default_label
                               .merge(x: 0,
                                      y: 11,
                                      text: "tick: #{args.state.tick_count}")
  args.lowrez.labels  << args.lowrez
                               .default_label
                               .merge(x: 0,
                                      y: 5,
                                      text: "sprite_index: #{sprite_index}")
end

## # =============================================================================
## # ==== HOW TO STORE STATE, ACCEPT INPUT, AND RENDER SPRITE BASED OFF OF STATE =
## # =============================================================================
def how_to_move_a_sprite args
  args.lowrez.labels << args.lowrez
                            .default_label
                            .merge(x: 32,
                                   y: 62, text: "Use Arrow Keys",
                                   alignment_enum: 1)

  args.lowrez.labels << args.lowrez
                            .default_label
                            .merge(x: 32,
                                   y: 56, text: "Use WASD",
                                   alignment_enum: 1)

  args.lowrez.labels << args.lowrez
                            .default_label
                            .merge(x: 32,
                                   y: 50, text: "Or Click",
                                   alignment_enum: 1)

  # set the initial values for x and y using ||= ("or equal operator")
  args.state.ship.x ||= 0
  args.state.ship.y ||= 0

  # if a mouse click occurs, update the ship's x and y to be the location of the click
  if args.lowrez.mouse_click
    args.state.ship.x = args.lowrez.mouse_click.x
    args.state.ship.y = args.lowrez.mouse_click.y
  end

  # if a or left arrow is pressed/held, decrement the ships x position
  if args.lowrez.keyboard.left
    args.state.ship.x -= 1
  end

  # if d or right arrow is pressed/held, increment the ships x position
  if args.lowrez.keyboard.right
    args.state.ship.x += 1
  end

  # if s or down arrow is pressed/held, decrement the ships y position
  if args.lowrez.keyboard.down
    args.state.ship.y -= 1
  end

  # if w or up arrow is pressed/held, increment the ships y position
  if args.lowrez.keyboard.up
    args.state.ship.y += 1
  end

  # render the sprite to the screen using the position stored in args.state.ship
  args.lowrez.sprites << {
    x: args.state.ship.x,
    y: args.state.ship.y,
    w: 5,
    h: 5,
    path: 'sprites/lowrez-ship-blue.png',
    # parameters beyond this point are optional
    angle: 0, # Note: rotation angle is denoted in degrees NOT radians
    r: 255,
    g: 255,
    b: 255,
    a: 255
  }
end

# =======================================================================
# ==== HOW TO DETERMINE COLLISION =======================================
# =======================================================================
def how_to_determine_collision args
  # Render the instructions
  args.lowrez.labels << args.lowrez
                            .default_label
                            .merge(x: 32,
                                   y: 62, text: "Click Anywhere",
                                   alignment_enum: 1)

  # if a mouse click occurs:
  # - set ship_one if it isn't set
  # - set ship_two if it isn't set
  # - otherwise reset ship one and ship two
  if args.lowrez.mouse_click
    # is ship_one set?
    if !args.state.ship_one
      args.state.ship_one = { x: args.lowrez.mouse_click.x - 10,
                              y: args.lowrez.mouse_click.y - 10,
                              w: 20,
                              h: 20 }
    # is ship_one set?
    elsif !args.state.ship_two
      args.state.ship_two = { x: args.lowrez.mouse_click.x - 10,
                              y: args.lowrez.mouse_click.y - 10,
                              w: 20,
                              h: 20 }
    # should we reset?
    else
      args.state.ship_one = nil
      args.state.ship_two = nil
    end
  end

  # render ship one if it's set
  if args.state.ship_one
    # use Ruby's .merge method which is available on ~Hash~ to set the sprite and alpha
    # render ship one
    args.lowrez.sprites << args.state.ship_one.merge(path: 'sprites/lowrez-ship-blue.png', a: 100)
  end

  if args.state.ship_two
    # use Ruby's .merge method which is available on ~Hash~ to set the sprite and alpha
    # render ship two
    args.lowrez.sprites << args.state.ship_two.merge(path: 'sprites/lowrez-ship-red.png', a: 100)
  end

  # if both ship one and ship two are set, then determine collision
  if args.state.ship_one && args.state.ship_two
    # collision is determined using the intersect_rect? method
    if args.state.ship_one.intersect_rect? args.state.ship_two
      # if collision occurred, render the words collision!
      args.lowrez.labels << args.lowrez
                            .default_label
                            .merge(x: 31,
                                   y: 5,
                                   text: "Collision!",
                                   alignment_enum: 1)
    else
      # if collision occurred, render the words no collision.
      args.lowrez.labels << args.lowrez
                            .default_label
                            .merge(x: 31,
                                   y: 5,
                                   text: "No Collision.",
                                   alignment_enum: 1)
    end
  else
    # if both ship one and ship two aren't set, then render --
      args.lowrez.labels << args.lowrez
                            .default_label
                            .merge(x: 31,
                                   y: 6,
                                   text: "--",
                                   alignment_enum: 1)
  end
end

## # =============================================================================
## # ==== HOW TO CREATE BUTTONS ==================================================
## # =============================================================================
def how_to_create_buttons args
  # Define a button style
  args.state.button_style = { w: 62, h: 10, r: 80, g: 80, b: 80 }
  args.state.label_style  = { r: 80, g: 80, b: 80 }

  # Render instructions
  args.state.button_message ||= "Press a Button!"
  args.lowrez.labels << args.lowrez
                            .default_label
                            .merge(args.state.label_style)
                            .merge(x: 32,
                                   y: 62,
                                   text: args.state.button_message,
                                   alignment_enum: 1)


  # Creates button one using a border and a label
  args.state.button_one_border = args.state.button_st