Добавил возможность проиграть

Assets/Scripts/Tower.cs

@@ -1,14 +1,29 @@
 using System;
 using UnityEngine;
+using UnityEngine.Events;
 
 [RequireComponent(typeof(TowerHealth))]
 public class Tower : MonoBehaviour
 {
+    [SerializeField] private UnityEvent _onGameOver;
+
+    public event UnityAction OnGameOver
+    {
+        add => _onGameOver.AddListener(value);
+        remove => _onGameOver.RemoveListener(value);
+    }
+
     private TowerHealth _towerHealth;
 
-    private void Start()
+    private void OnEnable()
     {
         _towerHealth = GetComponent<TowerHealth>();
+        _towerHealth.OnHealthChanged += OnHealthChanged;
+    }
+
+    private void OnDisable()
+    {
+        _towerHealth.OnHealthChanged -= OnHealthChanged;
     }
 
     private void OnTriggerEnter(Collider other)
@@ -16,4 +31,10 @@ public class Tower : MonoBehaviour
         if (other.TryGetComponent(out Enemy enemy))
             _towerHealth.TakeDamage(enemy.Damage);
     }
+
+    private void OnHealthChanged(TowerHealth.OnHealthChangedEventArgs args)
+    {
+        if (args.CurrentHealth <= 0)
+            _onGameOver?.Invoke();
+    }
 }