as小球深度和幅度

package
{
import flash.display.Sprite;
import flash.events.Event;

/**
* ...
* @author DefaultUser (Tools -> Custom Arguments...)
*/
public class JumpBall extends Sprite
{
private var jumpDistance:uint = 150; //小球跳动的幅度
private var angle:Number=0; //控制小球运动三角函数变量
private var vr:Number = 0.1; //控制小球运动的速度
private var centerX:Number = 200;
private var centerY:Number = 300;
private var scaleAndalpha:Number = 40; //控制小球深度的缩放及alpha幅度的变量（为体现效果，同时改变alpha值）
private var ball:Ball = new Ball();

public function JumpBall()
{
init();
}

private function init():void
{
addChild(ball);
ball.x = centerX;
ball.y = centerY;
addEventListener(Event.ENTER_FRAME, onEnterFrames);
}

private function onEnterFrames(e:Event):void
{
angle += vr ;
ball.y = centerY - jumpDistance * Math.abs(Math.cos(angle)); //将小球控制成单向运动
ball.alpha=ball.scaleX = ball.scaleY = (60 + scaleAndalpha * Math.abs(Math.cos(angle))) / 100;
}

}
}
//为方便阅读，特将以下代码定义为包外类
import flash.display.Sprite;
class Ball extends Sprite
{
function Ball()
{
graphics.clear();
graphics.beginFill(0xff0000, 1);
graphics.drawCircle(0, 0, 10);
graphics.endFill();
}
}