private void Start()
        {
            IPlayerAction playerAction = new PlayerAction();

            playerAction.Attack();

            // PlayerActionをPoisonで装飾して毒属性を追加
            playerAction = new Poison(playerAction);
            playerAction.Attack();

            // さらに水属性を追加する
            playerAction = new Water(playerAction);
            playerAction.Attack();
        }