遊戲時間倒數

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using TMPro;
using UnityEngine.SceneManagement;

public class timer : MonoBehaviour
{
    public static bool IsGameOver = false;
    public GameObject DontDestroy_Obj;
    public TMP_Text timer_Text;
    
    int time = 60;
    // Start is called before the first frame update
    void Start()
    {
        timer_Text = GetComponent<TMP_Text>();
    }

    // Update is called once per frame
    void Update()
    {
        timer_Text.text = "Time:0" + time / 60 + ":" + time % 60;

        if(time < 0.5)
        {
            timer_Text.text = "";
            IsGameOver = true;
            CancelInvoke();
        }
    }

    void Countdown()
    {
        time--;
    }

    public void StartGame()
    {
        InvokeRepeating("Countdown", 0, 1);
    }
}