unity项目实现“再按一次退出程序”提示功能

    float _waitTime = 2f;//前后两次按退出间隔时间
    void OnGUI()
    {
        if (_waitTime < 2)
        {
            GUI.Label(new Rect(Screen.width / 2 - 100, Screen.height / 2 - 30, 200, 60), "再按一次退出");
            _waitTime -= Time.deltaTime;
            if (_waitTime < 0)
            {
                _waitTime = 2;
            }
            if (Input.GetKeyDown(KeyCode.Escape))
            {
                Application.Quit();
            }
        }
        if (Input.GetKeyUp(KeyCode.Escape) && _waitTime == 2)
        {
            _waitTime -= Time.deltaTime;
        }
    }