跳ね返りの練習

/**
 * Copyright Nowloading_ ( http://wonderfl.net/user/Nowloading_ )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/bQ6s
 */

package {
    import flash.display.Sprite;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
    import flash.events.Event;
    
    public class Bouncing extends Sprite{
        private var ball:Ball;
        private var vx:Number;
        private var vy:Number;    
        public function Bouncing(){
            init();
        }
        private function init():void{
            stage.scaleMode = StageScaleMode.NO_SCALE;
            stage.align = StageAlign.TOP_LEFT;
            ball = new Ball();
            ball.x = stage.stageWidth/2;
            ball.y = stage.stageHeight/2;
            vx = Math.random()*10-5;
            vy = Math.random()*10-5;
            addChild(ball);
            addEventListener(Event.ENTER_FRAME,onEnterFrame);
        }
        private function onEnterFrame(e:Event):void{        
            ball.x += vx;
            ball.y += vy;
            var left:Number = 0;
            var right:Number = stage.stageWidth;
            var top:Number = 0;
            var bottom:Number = stage.stageHeight;
            if(ball.x+ball.radius>right){
                ball.x = right-ball.radius;
                vx *= -1;
            }else if(ball.x - ball.radius<left){
                ball.x = left + ball.radius;    
                vx *= -1;
            }
            if(ball.y + ball.radius>bottom){
                ball.y = bottom-ball.radius;
                vy *= -1;
            }else if(ball.y - ball.radius<top){
                ball.y = top + ball.radius;
                vy *= -1;
            }
        }
    }
}

    import flash.display.Sprite;
    class Ball extends Sprite{
        public var radius:Number;
        public var color:uint;
        public var vx:Number =0;
        public var vy:Number =0;
        
        public function Ball(radius:Number = 40,color:uint = 0xff0000){
            this.radius = radius;
            this.color = color;
            init();
        }
        public function init():void{
            graphics.beginFill(color);
            graphics.drawCircle(0,0,radius);
            graphics.endFill();
        }
    }