rotate everything back;


      x1 = cos * x2 - sin * y2;
      y1 = cos * y2 + sin * x2;
      ball.vx = cos * vx1 - sin * vy1;
      ball.vy = cos * vy1 + sin * vx1;
      ball.x = line.x + x1;
      ball.y = line.y + y1;
     }
    }
   }
  }