# File gtk/sample/misc/cairo-pong.rb, line 116
    def update_ball(ball)
      if ball_hit?(ball)
        if ball.min_x < @x and ball.max_x > min_x # hit our left side
          ball.x -= (ball.max_x - min_x)
          ball.dx = -ball.dx
        elsif ball.max_x > @x and ball.min_x < max_x # hit our right side
          ball.x += (max_x - ball.min_x)
          ball.dx = -ball.dx
        end
      end
    end