gistfile1.rb

#!/usr/bin/env ruby

require 'gosu'

module GoUp
  def self.update(obj, window)
    obj.move(0, -1)
  end
end

module GoDown
  def self.update(obj, window)
    obj.move(0, 1)
  end
end

class GameWindow < Gosu::Window
  def initialize
    super 640, 480, false
    self.caption = "Gosu tutorial game"

    @dots = []
    @dots << Dot.new(self, GoUp)
    @dots << Dot.new(self, GoDown)
    @dots.each do |dot|
      i = @dots.index(dot) + 1
      dot.warp(i * 160, i * 120)
    end
  end

  def update
    @dots.each do |dot|
      dot.update(self)
    end
    
    #if button_down? Gosu::KbLeft or button_down? Gosu::GpLeft then
      #@dot.move(-1)
    #end
    #if button_down? Gosu::KbRight or button_down? Gosu::GpRight then
      #@dot.move(1)
    #end
    #if button_down? Gosu::KbUp or button_down? Gosu::GpButton0 then
      #@dot.move(0, -1)
    #end
    #if button_down? Gosu::KbDown or button_down? Gosu::GpButton1 then
      #@dot.move(0, 1)
    #end
  end

  def draw
    @dots.each {|dot| dot.draw }
  end

  def button_down(id)
    if id == Gosu::KbEscape
      close
    end
  end
end

class Dot
  def initialize(window, solver)
    @image = Gosu::Image.new(window, "anchor.png", false)
    @solver = solver
    @x = @y = 0.0
  end

  def warp(x, y)
    @x, @y = x, y
  end

  def move(offsetX = 0, offsetY = 0)
    @x += offsetX
    @y += offsetY
    @x %= 640
    @y %= 480
  end

  def update(window)
    @solver.update(self, window)
  end

  def draw
    @image.draw_rot(@x, @y, 1, 0)
  end
end

GameWindow.new.show