void OnPlayerIsDead()
 {
     Assert.That(_state == GamingStates.Playing);
     _state = GamingStates.GameOver;
     _enemySpawner.Stop();
     Debug.Log("bus Fired");
 }
    void StartGame()
    {
        Assert.That(_state == GamingStates.WaitingToStart || _state == GamingStates.GameOver);

        _player.Position = Vector3.zero;
        _elapsedTime     = 0;
        _player.ChangeState(PlayerStates.Moving);
        _state = GamingStates.Playing;
        _enemySpawner.Start();
    }