Driftology/Assets/RaceCountdownManager.cs

using UnityEngine;
using TMPro;
using Fusion;
using System.Collections;

public class RaceCountdownManager : NetworkBehaviour
{
    public static RaceCountdownManager Instance;

    [SerializeField] private TextMeshProUGUI countdownText;

    [Networked, OnChangedRender(nameof(OnCountdownChanged))]
    private int CountdownTimer { get; set; }

    [Networked] public bool RaceStarted { get; private set; }

    private void Awake()
    {
        Instance = this;
        if (countdownText != null)
            countdownText.gameObject.SetActive(false);
    }

    public override void Spawned()
    {
        if (Object.HasStateAuthority)
        {
            StartCoroutine(CountdownCoroutine());
        }
    }

    private IEnumerator CountdownCoroutine()
    {
        CountdownTimer = 3;
        countdownText.gameObject.SetActive(true);

        while (CountdownTimer > 0)
        {
            yield return new WaitForSeconds(1f);
            CountdownTimer--;
        }

        RaceStarted = true;
        countdownText.gameObject.SetActive(false);
    }

    private void OnCountdownChanged()
    {
        if (CountdownTimer > 0)
        {
            countdownText.text = CountdownTimer.ToString();
            countdownText.gameObject.SetActive(true);
        }
        else
        {
            countdownText.gameObject.SetActive(false);
        }
    }
}