package
  {
          import flash.display.Sprite;
          import flash.events.Event;
          import flash.events.MouseEvent;
          
          public class @ax-animation-ch08-MultiSpring extends Sprite
          {
                  private var ball:animation_ch08_Ball;
                  private var handles:Array;
                  private var spring:Number = 0.1;
                  private var friction:Number = 0.8;
                  private var numHandles:Number = 3;
                  
                  public function @ax-animation-ch08-MultiSpring()
                  {
                          init();
                  }
                  
                  private function init():void
                  {
                          ball = new animation_ch08_Ball(20);
                          addChild(ball);
                          
                          handles = new Array();
                          for(var i:uint = 0; i < numHandles; i++)
                          {
                                  var handle:animation_ch08_Ball = new animation_ch08_Ball(10, 0x0000ff);
                                  handle.x = Math.random() * stage.stageWidth;
                                  handle.y = Math.random() * stage.stageHeight;
                                  handle.addEventListener(MouseEvent.MOUSE_DOWN, onPress);
                                  addChild(handle);
                                  handles.push(handle);
                          }
                          
                          addEventListener(Event.ENTER_FRAME, onEnterFrame);
                          addEventListener(MouseEvent.MOUSE_UP, onRelease);
                  }
                  
                  private function onEnterFrame(event:Event):void
                  {
                          for(var i:uint = 0; i < numHandles; i++)
                          {
                                  var handle:animation_ch08_Ball = handles[i] as animation_ch08_Ball;
                                  var dx:Number = handle.x - ball.x;
                                  var dy:Number = handle.y - ball.y;
                                  ball.vx += dx * spring;
                                  ball.vy += dy * spring;
                          }
                          
                          ball.vx *= friction;
                          ball.vy *= friction;
                          ball.x += ball.vx;
                          ball.y += ball.vy;
                          
                          graphics.clear();
                          graphics.lineStyle(1);
                          for(i = 0; i < numHandles; i++)
                          {
                                  graphics.moveTo(ball.x, ball.y);
                                  graphics.lineTo(handles[i].x, handles[i].y);
                          }
                  }
                  
                  private function onPress(event:MouseEvent):void
                  {
                          event.target.startDrag();
                  }
                  
                  private function onRelease(event:MouseEvent):void
                  {
                          event.target.stopDrag();
                  }
          }
  }