dragonruby

DragonRuby Game Toolkit

This skill provides comprehensive guidance for building 2D games with DragonRuby Game Toolkit (DRGTK). Use for game loop implementation, sprite rendering, input handling, collision detection, animation, and scene management.

Quick Reference

Basic Game Structure

def boot args
  args.state = {}
end

def tick args
  # Called 60 times per second
  args.state.player ||= { x: 640, y: 360, w: 50, h: 50, path: 'player.png' }

  # Handle input
  args.state.player.x += 5 if args.inputs.right
  args.state.player.x -= 5 if args.inputs.left

  # Render
  args.outputs.sprites << args.state.player
end

Key Concepts

Concept	Purpose
def tick(args)	Main game loop (60 FPS)
args.outputs	Render sprites, labels, primitives
args.state	Persistent game data storage
args.inputs	Keyboard, mouse, controller input
args.grid	Screen dimensions (1280x720)
Geometry	Collision detection helpers

Coordinate System

• Screen: 1280x720 pixels
• Origin: Bottom-left (0, 0)
• Y-axis: Increases upward

(0, 720) ─────────────── (1280, 720)
    │                        │
    │     1280 × 720         │
    │                        │
(0, 0) ─────────────── (1280, 0)

Rendering Primitives

Use args.outputs.primitives for FIFO (first-in, first-out) render order control.

Sprites (Images)

args.outputs.primitives << {
  x: 100, y: 100, w: 64, h: 64,
  path: 'sprites/player.png',
  angle: 45,
  anchor_x: 0.5, anchor_y: 0.5,
  r: 255, g: 255, b: 255, a: 255,
  flip_horizontally: false
}

Labels (Text)

args.outputs.primitives << {
  x: 640, y: 360,
  text: "Score: #{args.state.score}",
  size_px: 22,
  anchor_x: 0.5, anchor_y: 0.5,
  r: 255, g: 255, b: 255
}

Solids and Borders

# Filled rectangle (use primitive_marker: :solid)
args.outputs.primitives << {
  x: 0, y: 0, w: 100, h: 100,
  r: 255, g: 0, b: 0,
  primitive_marker: :solid
}

# For many rectangles, use path: :solid for better performance
args.outputs.primitives << { x: 0, y: 0, w: 100, h: 100, path: :solid, r: 255, g: 0, b: 0 }

# Outline rectangle
args.outputs.primitives << { x: 0, y: 0, w: 100, h: 100, r: 0, g: 0, b: 0, primitive_marker: :border }