HighGroundRoyaleNetcode/Assets/StartingTimer.cs

using System.Collections;
using UnityEngine;
using UnityEngine.UI;
using TMPro;
using DG.Tweening;
using Unity.Netcode;
using Unity.Multiplayer.Samples.Utilities;

public class StartingTimer : NetworkBehaviour
{
    public ServerAdditiveSceneLoader serverAdditiveSceneLoader;
    private Image BlackScreen;
    public TextMeshProUGUI TimerText;

    private NetworkVariable<int> timerValue = new NetworkVariable<int>(0, NetworkVariableReadPermission.Everyone, NetworkVariableWritePermission.Server);
    private bool coroutineStartedBool = false;

    private void Start()
    {
        BlackScreen = GetComponent<Image>();
    }

    private void Update()
    {
        if (serverAdditiveSceneLoader.m_SceneState == ServerAdditiveSceneLoader.SceneState.Loaded && coroutineStartedBool == false)
        {
            if (IsServer)
            {
            coroutineStartedBool = true;
                StartCoroutine(ServerTimerCoroutine());
            }
        }

        // Update the UI on all clients
        UpdateTimerUI();
    }

    private IEnumerator ServerTimerCoroutine()
    {
        const int countdownStart = 3;

        for (int i = countdownStart; i > 0; i--)
        {
            timerValue.Value = i;
            yield return new WaitForSeconds(1);
        }

        timerValue.Value = -1; // Indicate "GO"
        yield return new WaitForSeconds(0.5f);

        // Notify clients to disable the black screen
        BlackScreenAlphaDisablerClientRpc();
    }

    private void UpdateTimerUI()
    {
        if (timerValue.Value > 0)
        {
            TimerText.text = timerValue.Value.ToString();
        }
        else if (timerValue.Value == -1)
        {
            TimerText.text = "GO";
        }
    }

    [ClientRpc]
    private void BlackScreenAlphaDisablerClientRpc()
    {
        BlackScreen.DOFade(0, 0.25f).OnComplete(() =>
        {
            gameObject.SetActive(false);
        });
    }
}