// rotate coordinates
      var y2:Number = cos * y1 - sin * x1;
      
      // rotate velocity
      var vy1:Number = cos * ball.vy - sin * ball.vx;
      
      // perform bounce with rotated values
      if(y2 > -ball.height / 2 && y2 < vy1)
      {
       // rotate coordinates
       var x2:Number = cos * x1 + sin * y1;
       
       // rotate velocity
       var vx1:Number = cos * ball.vx + sin * ball.vy;
      
       y2 = -ball.height / 2;
       vy1 *= bounce;