This isn't working

private bool gameStarted =  false;
[SerializeField]
private Text gameStateText;
[SerializeField]
private GameObject player;
[SerializeField]
private BirdMovement birdMovement;
[SerializeField]
private FollowCamera followCamera;
private float restartDelay = 3f;
private float restartTimer;
private PlayerMovement playerMovement;
private PlayerHealth playerHealth;

// Use this for initialization
void Start () {
    Cursor.visible = false;
    playerMovement = player.GetComponent<PlayerMovement>();
    playerHealth = player.GetComponent<PlayerHealth>();
    playerMovement.enabled = false;
    birdMovement.enabled = false;
    followCamera.enabled = false;

}

// Update is called once per frame
void Update () {
    if (gameStarted == false && Input.GetKeyUp (KeyCode.Space))
    {
        StartGame();
    }
    if (playerHealth.alive == false)
    {
        EndGame();
        restartTimer = restartTimer + Time.deltaTime;

        if (restartTimer >= restartDelay)
        {
            Application.LoadLevel (Application.loadedLevel);
        }
    }
}

private void StartGame()
{
    gameStarted = true;

    gameStateText.color = Color.clear;

    playerMovement.enabled = true;
    birdMovement.enabled = true;
}

private void EndGame()
{
    gameStarted = false;

    gameStateText.color = Color.white;

    gameStateText.text = "Game Over!";
    player.SetActive(false);
}