private void Awake()
        {
            OnPlaySceneLoaded += StartGame;

            // Play scene is already loaded.
            if (SceneManager.GetSceneByName(playScene).IsValid())
            {
                OnPlaySceneLoaded.Invoke();
                return;
            }
            StartCoroutine(LoadPlayScene());
        }
        /// <summary>
        /// Loads the play scene and sets it as the active one.
        /// </summary>
        /// <returns></returns>
        IEnumerator LoadPlayScene()
        {
            var ls = SceneManager.LoadSceneAsync(playScene, LoadSceneMode.Additive);

            while (!ls.isDone)
            {
                yield return(null);
            }
            yield return(null);

            SceneManager.SetActiveScene(SceneManager.GetSceneByName(playScene));

            OnPlaySceneLoaded.Invoke();
        }