Add NPC and Power-Up features with associated prefabs and effects

Assets/Scripts/Core/Domain/GameSession.cs

@@ -7,6 +7,8 @@ namespace Core.Domain
     public class GameSession
     {
         private const string HighScoreKey = "HighScore";
+        private const float NpcSpawnTime = 4f;
+        private const float PowerUpSpawnInterval = 25f;
         
         public int Score { get; private set; }
         public int HighScore { get; private set; }
@@ -16,11 +18,16 @@ namespace Core.Domain
         public event Action<string> OnOrbSpawned;
         public event Action OnOrbReset;
         public event Action OnGameOver;
+        public event Action OnSpawnNpc;
+        public event Action<PowerUpType, string> OnSpawnPowerUp;
 
         private readonly List<Tile> _tiles;
         private readonly IPersistenceService _persistenceService;
         private readonly Random _rng = new();
         private int _playerFloorIndex = 0;
+        private float _timeSinceStart;
+        private bool _npcSpawned;
+        private float _powerUpTimer;
 
         public GameSession(List<Tile> tiles, IPersistenceService persistenceService)
         {
@@ -35,9 +42,32 @@ namespace Core.Domain
 
         public void StartGame()
         {
+            _timeSinceStart = 0f;
+            _powerUpTimer = 0f;
+            _npcSpawned = false;
+            
             SpawnNextOrb();
         }
 
+        public void Tick(float deltaTime)
+        {
+            if (IsGameOver) return;
+            
+            _timeSinceStart += deltaTime;
+            if (!_npcSpawned && _timeSinceStart >= NpcSpawnTime)
+            {
+                _npcSpawned = true;
+                OnSpawnNpc?.Invoke();
+            }
+            
+            _powerUpTimer += deltaTime;
+            if (_powerUpTimer >= PowerUpSpawnInterval)
+            {
+                _powerUpTimer = 0f;
+                SpawnRandomPowerUp();
+            }
+        }
+
         public void OrbCollected()
         {
             if (IsGameOver) return;
@@ -95,5 +125,17 @@ namespace Core.Domain
             OnOrbReset?.Invoke();
             SpawnNextOrb();
         }
+
+        private void SpawnRandomPowerUp()
+        {
+            var validTiles = _tiles.FindAll(t => t.CurrentState == TileState.Stable);
+            if (validTiles.Count == 0) return;
+            
+            var tile = validTiles[_rng.Next(validTiles.Count)];
+            
+            var type = _rng.Next(0, 2) == 0 ? PowerUpType.LightFooted : PowerUpType.SpeedBoost;
+            
+            OnSpawnPowerUp?.Invoke(type, tile.Id);
+        }
     }
 }