End game after livesLeft = 0

Hi

I have a game that is currently working with a countdown timer using Time.deltaTime. But I need to use a life counter as opposed to a time counter.

I have a destroyer script which is based outside of the visible screen to that GameObjects are destroyed if they manage to get past the player, and if they do the player loses a life, but I cannot get the game to end when livesLeft = 0.

Currently the timer version has the countdown timer on the GameController script: void Start () {

         if (cam == null) {
             cam = Camera.main;        
         }
         Vector3 upperCorner = new Vector3 (Screen.width, Screen.height, 0.0f);
         Vector3 targetWidth = cam.ScreenToWorldPoint (upperCorner);    
         float flapWidth = flap.renderer.bounds.extents.x;
         maxWidth = targetWidth.x - flapWidth;
         StartCoroutine (Spawn());
         timerText.text = "LIVES: " + Mathf.RoundToInt (timeLeft);
         timerText.text = "Time Left:\n" + Mathf.RoundToInt (timeLeft);
         
     }
 
     void FixedUpdate () {
         timeLeft -= Time.deltaTime;
         if (timeLeft < 0) {
                 timeLeft = 0;
                 }
         timerText.text = "Time Left:\n" + Mathf.RoundToInt (timeLeft);
         }
     
     IEnumerator Spawn () {
         yield return new WaitForSeconds (2.0f);
         while (timeLeft > 0) {
                         Vector3 spawnPosition = new Vector3 (Random.Range (-maxWidth, maxWidth), transform.position.y, 0.0f);
                         Quaternion spawnRotation = Quaternion.identity;
                         Instantiate (flap, spawnPosition, spawnRotation);
             yield return new WaitForSeconds (Random.Range(1.0f, 1.0f));
                 }
         yield return new WaitForSeconds (1.0f);
         gameOverText.SetActive (true);
         yield return new WaitForSeconds (1.0f);
         restartButton.SetActive (true);
     }

And the destroyer also has the life lost script: void Start () { lifescore = 5; UpdateScore ();

     }
     
     void OnTriggerEnter2D () {
         lifescore -= lifeValue;
         UpdateScore ();
     }
     
     void UpdateScore () {
         livesText.text = "LIVES: " + lifescore;
         if (lifescore < 0) {
             lifescore = 0;
             gameController.CancelInvoke("Spawn");
         }
         livesText.text = "LIVES: " + lifescore;
     }

If I put them both together the timer counts down as expected and also the players lives are reduced every time they miss a target, but I need the game to end after all the lives are lost so that I can remove the timer section, as this is not a timed game.

Any help would be appreciated. Thanks.