[LayaAir 1.0]请问这是原因？

package {

	

	

	import laya.display.Graphics;

	import laya.display.Sprite;

	import laya.events.Event;

	import laya.maths.Point;

	import laya.utils.Browser;

	import laya.webgl.WebGL;

	import laya.wx.mini.MiniAdpter;



	public class LayaSample {

		

		public var sprite:Sprite = new Sprite();

		public function LayaSample() {

			//初始化引擎

			MiniAdpter.init();

			Laya.init(Browser.width, Browser.height,WebGL);

			Laya.stage.scaleMode = "full";

			Laya.stage.bgColor = "#232628";

			

			//画一个圆

			sprite = new Sprite();

			sprite.pos(500,500);

			var graphics:Graphics = new Graphics();

			graphics.drawCircle(0,0,100,"#00CC33");

			sprite.graphics = graphics;

			Laya.stage.addChild(sprite);

			

			//画一条直线，添加进圆

			var sprite2:Sprite = new Sprite();

			var graphics2:Graphics = new Graphics();

			graphics2.drawLine(500,500,500,400,"#000000",2);

			sprite2.graphics = graphics2;

			Laya.stage.addChild(sprite2);

			Laya.stage.on(Event.MOUSE_UP,this,mouseUP);

				

		}

		

		public var flagCircle:Graphics = new Graphics();

		public var flag:Sprite = new Sprite();

		//让直线在圆内旋转

		public function mouseUP():void{

			

			var point:Point = sprite.globalToLocal(new Point(Laya.stage.mouseX,Laya.stage.mouseY));

			var deltaX:int = point.x-500;

			var deltaY:int = point.x-500;

			//计算旋转角度

			var angle:Number = Math.atan2(deltaX,deltaY)*180/Math.PI;



			//在鼠标的位置生成一个圆来测试本地坐标

			flagCircle.drawCircle(0,0,50,"#000000")

			flag.graphics = flagCircle;

			flag.pos(deltaX,deltaY);

			//添加舞台

			sprite.addChild(flag);

			console.log(point);

		}



	}

}