tutorial.rb

require 'rubygems'
require 'gosu'

class Ball
  def initialize(the_window)
    @x = 200
    @vx = 5
    @y = 200
    @w = 20
    @h = 20
    @image = Gosu::Image.new(the_window, "gosuTutorialMedia/ball.png", false)
  end
  def draw
    @image.draw(@x, @y, 1)
  end
  def update
    if @x == the_window.width
      @vx = -5
    end
    if @x == 0
      @vx = 5
    end
    @v = @v + @vx 
  end
end

class GameWindow < Gosu::Window
  attr_reader :width, :height
  def initialize
    @width = 800
    @height = 600
    super @width, @height, false
    self.caption = "Gosu Tutorial Game"
    @ball = Ball.new(self)
  end

  def update
    @ball.update
  end

  def draw
    @ball.draw
  end

end

window = GameWindow.new
window.show