simple-conveyor

app.rb

class Game
  attr_gtk # attr_gtk class macro

  SPRITES = {
    conveyor_belt: {
      source_x: 0,
      source_w: 16,
      source_h: 16,
      source_y: 0,
      animations: {
        frames: 16,
        frame_length: 60 * 6,
        repeat: true,
      },
      angle: 270,
      path: "sprites/conveyor-1.png"
    }
  }

  def initialize(args)
    @tick_count = 0
    @animations = {} # Basic map of running animations, keyed off an object_id.
    @entities = []
    @conveyors = []

    conveyor_size = 64

    16.times do |i|
      @conveyors << {
        x: 100 + conveyor_size * i,
        y: Grid.h / 2,
        w: conveyor_size,
        h: conveyor_size,
        **SPRITES[:conveyor_belt],
        primitive_marker: :sprite,
      }
    end
  end

  # Pass a tick count so we can sync them all if we add one.
  def animation_for_conveyor_belt(conveyor_belt)
    sprite = SPRITES[:conveyor_belt]
    animations = sprite.animations
    frame_index = Numeric.frame_index(
      count: animations.frames,
      hold_for: animations.frame_length / 60,
      repeat: animations.repeat,
      repeat_index: animations.repeat_index || 0,
      tick_count_override: @tick_count
    )

    {
      **conveyor_belt,
      **sprite,
      source_x: frame_index * sprite.source_w, # only source_w increments.
    }
  end

  def tick
    defaults
    calc
    render
    @tick_count += 1
  end

  def defaults
  end

  def calc
    if @tick_count % 120 == 0
      @entities << {
        x: @conveyors[0].x ,
        y: @conveyors[0].y + 16,
        w: 32,
        h: 32,
        path: "sprites/circle/red.png"
      }
    end

    # For obvious reasons, doing a many-to-many collision is really bad. But this is just an example.
    @entities.each do |spr|
      if Geometry.find_intersect_rect(spr, @conveyors)
        spr.x += (100 / 60)
      end
    end
  end

  def render
    @conveyors.each { |spr| spr.merge!(animation_for_conveyor_belt(spr)) }
    outputs.primitives
      .concat(@conveyors)
      .concat(@entities) # always render entities on top
  end
end

def boot(args)
  args.state = {}
end

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

$game = nil

^ Sprite used

Video:

2026-04-20_22-04-09.remuxed.mp4