Pong Clone - Ruby, Shoes, Hackety Hack!

Pong_Forever.rb

# Pong Forever! (Pong Clone)
# Let the critiquing begin!

# Set element attributes
screen_width = 640
screen_height = 480
paddle_height = 80
paddle_width = 10
ball_diameter = 20
ball_speed = 2
paddle_speed = 2

# Create canvas and make resizable
Shoes.app :width => screen_width, :height => screen_height, :resizable => true do
  background black

  # Center ball and paddles vertically
  ball_center = (self.height / 2) - (ball_diameter / 2)
  paddle_center = (self.height / 2) - (paddle_height / 2)

  # Create ball and paddles
  @ball = oval(0,ball_center,20, :fill => white)
  @left_paddle = rect(0,paddle_center,paddle_width,paddle_height, :fill => green)
  @right_paddle = rect(self.width-paddle_width,paddle_center,paddle_width, paddle_height, :fill => green)
  
  # Start with paddles in stopped position
  @moving = 0

  # Set x and y ball speed
  y_dir = x_dir = ball_speed

  # Animate at 200 fps
  @anim = animate 200 do |i|
    # Set top and bottom boundaries, reverse y direction on hit
    if @ball.top >= (self.height - @ball.height) or @ball.top < 0
      y_dir *= -1
    end

    # If ball hits left or right boundary, stop animation remove ball and paddles
    if @ball.left >= (self.width - @ball.width) or @ball.left < 0
      @anim.toggle
      @ball.remove
      @left_paddle.remove
      @right_paddle.remove
      # Ask to play again. If yes, recreate ball and paddles and restart animation. If no, close.
      if confirm("Play again?")
        @ball = oval(0,ball_height,20, :fill => white)
        @left_paddle = rect(0,screen_height / 2,paddle_width,paddle_height, :fill => green)
        @right_paddle = rect(self.width-paddle_width,screen_height / 2, paddle_width,paddle_height, :fill => green)
        @moving = 0
        @anim.toggle
      else
        close()
      end
    end

    # If ball hits left or right paddle within vertical bounaries, reverse x direction. (this one is ugly)
    if @ball.left <= (@left_paddle.left + @left_paddle.width) && x_dir < 0 && 
      @ball.top + @ball.height > @left_paddle.top &&
      @ball.top < @left_paddle.top + @left_paddle.height ||
      @ball.left + @ball.width >= @right_paddle.left && 
      @ball.top + @ball.height > @right_paddle.top && 
      @ball.top < @right_paddle.top + @right_paddle.height
      x_dir *= -1
    end

    # Move ball and paddles
    @ball.move(@ball.left + x_dir, @ball.top + y_dir)
    @left_paddle.move @left_paddle.left, @left_paddle.top + @moving
    @right_paddle.move @right_paddle.left, @right_paddle.top + @moving

    # Stop paddles if they reach the top or bottom boundary
    if @left_paddle.top <= 0 || @left_paddle.top + @left_paddle.height >= self.height
      @moving = 0
    end

  end

  # Set paddle direction based on up or down key
  keypress do |key|
    if key == :up
      @moving = paddle_speed * -1
    elsif key == :down
      @moving = paddle_speed
    end
  end

end