package
  {
          import flash.display.Sprite;
          import flash.events.Event;
          import flash.display.StageScaleMode;
          import flash.display.StageAlign;
  
          public class @ax-animation-ch10-AngleBounceOpt extends Sprite
          {
                  private var ball:animation_ch10_Ball;
                  private var line:Sprite;
                  private var gravity:Number = 0.3;
                  private var bounce:Number = -0.6;
                  
                  public function @ax-animation-ch10-AngleBounceOpt()
                  {
                          init();
                  }
                  
                  private function init():void
                  {
                          stage.scaleMode = StageScaleMode.NO_SCALE;
                          stage.align = StageAlign.TOP_LEFT;
                          ball = new animation_ch10_Ball();
                          addChild(ball);
                          ball.x = 100;
                          ball.y = 100;
                          
                          line = new Sprite();
                          line.graphics.lineStyle(1);
                          line.graphics.lineTo(300, 0);
                          addChild(line);
                          line.x = 50;
                          line.y = 200;
                          line.rotation = 30;
                          
                          addEventListener(Event.ENTER_FRAME, onEnterFrame);
                  }
                  
                  private function onEnterFrame(event:Event):void
                  {
                          // normal motion code
                          ball.vy += gravity;
                          ball.x += ball.vx;
                          ball.y += ball.vy;
                          
                          // get angle, sine and cosine
                          var angle:Number = line.rotation * Math.PI / 180;
                          var cos:Number = Math.cos(angle);
                          var sin:Number = Math.sin(angle);
                          
                          // get position of ball, relative to line
                          var x1:Number = ball.x - line.x;
                          var y1:Number = ball.y - line.y;
                          
                          // rotate coordinates
                          var y2:Number = cos * y1 - sin * x1;
                          
                          // perform bounce with rotated values
                          if(y2 > -ball.height / 2)
                          {
                                  // rotate coordinates
                                  var x2:Number = cos * x1 + sin * y1;
                                  
                                  // rotate velocity
                                  var vx1:Number = cos * ball.vx + sin * ball.vy;
                                  var vy1:Number = cos * ball.vy - sin * ball.vx;
                          
                                  y2 = -ball.height / 2;
                                  vy1 *= bounce;
                                  
                                  // 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;
                          }
                  }
          }
  }