マウスカーソル位置を通る曲線

/**
 * Copyright toburau ( http://wonderfl.net/user/toburau )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/aU4P
 */

package {
    import flash.display.Sprite;
    import flash.events.MouseEvent;
    public class FlashTest extends Sprite {
        private var x0:Number = 100;
        private var y0:Number = stage.stageHeight/2;
        private var x1:Number;
        private var y1:Number;
        private var x2:Number = 300;
        private var y2:Number = y0;
        public function FlashTest() {
            stage.addEventListener(MouseEvent.MOUSE_MOVE, onMouseMove);
        }
        private function onMouseMove(event:MouseEvent):void {
            x1 = mouseX*2 - (x0+x2)/2;
            y1 = mouseY*2 - (y0+y2)/2;

            graphics.clear();
            graphics.lineStyle(1);
            graphics.moveTo(x0,y0);
            graphics.curveTo(x1,y1,x2,y2);
        }
    }
}