練習問題：押すと色が変わるボタン

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

package {
    import flash.display.Sprite;
    import flash.events.MouseEvent;
    import flash.text.TextField;

    public class practice4 extends Sprite {
        public var buttonOff:Circle = new Circle(0x0000ff);
        public var buttonOn:Circle = new Circle(0xff0000);
        public function practice4() {
            buttonOff.x = 232;
            buttonOff.y = 232;
            buttonOff.visible = true;
            buttonOff.buttonMode = true;
            buttonOff.addEventListener(MouseEvent.CLICK,mouseClickOn);
            addChild(buttonOff);
            buttonOn.x = 232;
            buttonOn.y = 232;
            addChild(buttonOn);
            buttonOn.visible = false;
            buttonOn.buttonMode = true;
            buttonOn.addEventListener(MouseEvent.CLICK,mouseClickOff);
        }

        private function mouseClickOn(e:MouseEvent):void {
            buttonOff.visible = false;
            buttonOn.visible = true;
        }
        private function mouseClickOff(e:MouseEvent):void {
            buttonOff.visible = true;
            buttonOn.visible = false;
        }
    } 
}

import flash.display.Sprite;

class Circle extends Sprite {
    public function Circle(color:int ) {
        graphics.beginFill(color);
        graphics.drawCircle(0, 0, 100);
        graphics.endFill();
    }
}