GameManager.cs

using UnityEngine;
using UnityEngine.UI;

public class GameManager : MonoBehaviour
{

    //bikin array untuk sprite2 mobil nya/

    public Sprite[] carSprites;

    //Reference to our game objects
    public GameObject playButton;

    public GameObject playerCar;
    public GameObject enemySpawner;
    public GameObject GameOverGO;
    public GameObject TimeCountdown;
    public GameObject CongratulationMessage;
    public GameObject FailedMessage;
    private GameObject GameMaster;
    public Button ReturnButton;

    public static GameManager GM;
    public int carSelected;

    private GameScore ScoreManager;

    // Use this for initialization

    private void Awake()
    {
    }
    private void Start()
    {
        GM = this;
        GameMaster = GameObject.Find("GameMaster");
        StartGamePlay();
        ScoreManager = FindObjectOfType<GameScore>();
        Debug.Log(carSelected);

    }

    // Function to update the game manager state
    public void GamePlay()
    {
         //Count the timer
        TimeCountdown.GetComponent<TimeCounter>().StartTimeCounter();

        //show the player while game start
        playerCar.GetComponent<PlayerController>().Init();

        //Start Enemy Spawner
        enemySpawner.GetComponent<EnemySpawner>().ScheduleEnemySpawner();
    }

    public void GameOver()
    {
        //Stop score when player die
        ScoreManager.scoreIncrease = false;

        //Stop enemy Spawn
        enemySpawner.GetComponent<EnemySpawner>().UnscheduleEnemySpawner();

        //Display Game Over
        GameOverGO.SetActive(true);

        // ***** tombol return muncul kalo mati (cuma buat debug) *****
        ReturnButton.gameObject.SetActive(true);


        // ***** Kalau dapet highscore, munculin kata2 selamat. *****
        if (ScoreManager.scoreCount >= ScoreManager.highScoreCount)
        {
            CongratulationMessage.SetActive(true);

            // ***** sekalian write highsscore nya ke playerpref *****
            PlayerPrefs.SetFloat("HighScore", ScoreManager.highScoreCount);

            FailedMessage.SetActive(false);
        }
        else
        {
            FailedMessage.SetActive(true);
            CongratulationMessage.SetActive(false);
        }

        //Change game manager state to opening state
        Invoke("ChangeToMainMenu", 8f);

        TimeCountdown.GetComponent<TimeCounter>().StopTimeCounter();
    }

    public void StartGamePlay()
    {
        carSelected = GameMaster.GetComponent<GameMaster>().carSelected;
        playerCar.GetComponent<SpriteRenderer>().sprite = carSprites[carSelected];
        GamePlay();
    }

    //Function to change game manager state to opening state
    public void ChangeToMainMenu()
    {
        Application.LoadLevel("mainmenu");
    }
}