Update Project

Assets/Scripts/Core/DeathHandler.cs

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+using UnityEngine;
+using Zenject;
+using FlappyBird.Gameplay.Pipes;
+namespace FlappyBird.Core
+{
+    /// <summary>
+    /// Pure C# service — owns all death side-effects.
+    /// Subscribes to IGameStateManager.OnStateChanged at construction time
+    /// and reacts when the state becomes GameOver.
+    ///
+    /// Side-effects on death:
+    ///   1. Freeze the bird Rigidbody2D (velocity + gravity)
+    ///   2. Reset the pipe spawner timer so pipes start cleanly on restart
+    /// </summary>
+    public sealed class DeathHandler : IDeathHandler, IInitializable
+    {
+        private readonly Rigidbody2D       _birdRigidbody;
+        private readonly IGameStateManager _gameStateManager;
+        private readonly IPipeSpawner      _pipeSpawner;
+        public DeathHandler(
+            Rigidbody2D       birdRigidbody,
+            IGameStateManager gameStateManager,
+            IPipeSpawner      pipeSpawner)
+        {
+            _birdRigidbody    = birdRigidbody;
+            _gameStateManager = gameStateManager;
+            _pipeSpawner      = pipeSpawner;
+        }
+        // ── IInitializable ─────────────────────────────────────────────────
+        public void Initialize()
+        {
+            _gameStateManager.OnStateChanged += OnStateChanged;
+        }
+        // ── IDeathHandler ──────────────────────────────────────────────────
+        /// <inheritdoc/>
+        public void HandleDeath()
+        {
+            FreezeBird();
+            _pipeSpawner.ResetTimer();
+        }
+        // ── Private helpers ────────────────────────────────────────────────
+        private void OnStateChanged(GameState newState)
+        {
+            if (newState == GameState.Playing)
+                UnfreezeBird();
+        }
+        /// <summary>
+        /// Kills velocity and disables gravity so the bird hangs in place
+        /// during the GameOver freeze (Time.timeScale is 0, but we set this
+        /// explicitly so the bird does not drop when timeScale resumes on restart).
+        /// </summary>
+        private void FreezeBird()
+        {
+            _birdRigidbody.linearVelocity = Vector2.zero;
+            _birdRigidbody.angularVelocity = 0f;
+            _birdRigidbody.gravityScale = 0f;
+        }
+        /// <summary>Restore gravity when a new game begins.</summary>
+        private void UnfreezeBird()
+        {
+            _birdRigidbody.gravityScale = 1f;
+        }
+    }
+}

Assets/Scripts/Core/DeathHandler.cs.meta

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+fileFormatVersion: 2
+guid: d023d969944224b458f29abc062d3c07

Assets/Scripts/Core/GameState.cs

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+namespace FlappyBird.Core
+{
+    /// <summary>All possible game states.</summary>
+    public enum GameState
+    {
+        Menu,
+        Playing,
+        GameOver
+    }
+}

Assets/Scripts/Core/GameState.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: b946714168a978e49b501c41b0c81379

Assets/Scripts/Core/GameStateManager.cs

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+using UnityEngine;
+namespace FlappyBird.Core
+{
+    /// <summary>
+    /// Pure C# service — central authority for all game-state transitions.
+    /// No MonoBehaviour, no Unity lifecycle. Injected via Zenject.
+    ///
+    /// Transition side-effects:
+    ///   Playing  -> Time.timeScale = 1  (unfreeze)
+    ///   GameOver -> Time.timeScale = 0  (freeze everything)
+    ///   Menu     -> Time.timeScale = 0  (frozen until game starts)
+    /// </summary>
+    public sealed class GameStateManager : IGameStateManager
+    {
+        // ── IGameStateManager ──────────────────────────────────────────────
+        /// <inheritdoc/>
+        public GameState CurrentState { get; private set; } = GameState.Menu;
+        /// <inheritdoc/>
+        public event System.Action<GameState> OnStateChanged;
+        // ── Constructor ────────────────────────────────────────────────────
+        public GameStateManager()
+        {
+            // Start frozen; gameplay begins only when ChangeState(Playing) is called.
+            Time.timeScale = 0f;
+        }
+        // ── IGameStateManager ──────────────────────────────────────────────
+        /// <inheritdoc/>
+        public void ChangeState(GameState newState)
+        {
+            if (CurrentState == newState) return;
+            CurrentState = newState;
+            ApplyTimeScale(newState);
+            OnStateChanged?.Invoke(newState);
+        }
+        // ── Private helpers ────────────────────────────────────────────────
+        /// <summary>
+        /// Only Playing runs at normal speed.
+        /// Menu and GameOver both freeze Time so no physics or Update logic runs.
+        /// </summary>
+        private static void ApplyTimeScale(GameState state)
+        {
+            Time.timeScale = state == GameState.Playing ? 1f : 0f;
+        }
+    }
+}

Assets/Scripts/Core/GameStateManager.cs.meta

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+fileFormatVersion: 2
+guid: 05899132f4565a94590c4e2a093e54ba

Assets/Scripts/Core/IDeathHandler.cs

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+namespace FlappyBird.Core
+{
+    /// <summary>
+    /// Contract for the death-handling service.
+    /// Implementations react to a GameOver state transition and apply
+    /// all necessary side-effects (freeze bird, clear pipes, etc.).
+    /// </summary>
+    public interface IDeathHandler
+    {
+        /// <summary>
+        /// Executes all death side-effects.
+        /// Called by the subscriber wired up in the installer.
+        /// </summary>
+        void HandleDeath();
+    }
+}

Assets/Scripts/Core/IDeathHandler.cs.meta

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+fileFormatVersion: 2
+guid: d145c7d22d47c16479e3be770cfc1cbe

Assets/Scripts/Core/IGameStateManager.cs

@@ -0,0 +1,22 @@
+namespace FlappyBird.Core
+{
+    /// <summary>
+    /// Contract for the central game-state service.
+    /// Matches the interface defined in AI_RULES.md.
+    /// </summary>
+    public interface IGameStateManager
+    {
+        /// <summary>The currently active game state.</summary>
+        GameState CurrentState { get; }
+        /// <summary>
+        /// Transitions to <paramref name="newState"/>.
+        /// Fires <see cref="OnStateChanged"/> after the transition completes.
+        /// </summary>
+        void ChangeState(GameState newState);
+        /// <summary>
+        /// Fired every time the game state changes.
+        /// Passes the new <see cref="GameState"/> value.
+        /// </summary>
+        event System.Action<GameState> OnStateChanged;
+    }
+}

Assets/Scripts/Core/IGameStateManager.cs.meta

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+fileFormatVersion: 2
+guid: 4002324bd9e6d054ea59da95339ab344

Assets/Scripts/Core/IPoolable.cs

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+namespace FlappyBird.Core
+{
+    /// <summary>
+    /// Implement on any Component that is managed by the object pool.
+    /// </summary>
+    public interface IPoolable
+    {
+        /// <summary>Called by the pool just before the object is handed out.</summary>
+        void OnSpawn();
+        /// <summary>Called by the pool just after the object is returned.</summary>
+        void OnDespawn();
+    }
+}

Assets/Scripts/Core/IPoolable.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: 7ea87bd7742f91e4a9550011fb8354fc

Assets/Scripts/Core/IScoreManager.cs

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+namespace FlappyBird.Core
+{
+    /// <summary>
+    /// Contract for the score management service.
+    /// Matches the interface defined in AI_RULES.md.
+    /// </summary>
+    public interface IScoreManager
+    {
+        /// <summary>Current score for this session.</summary>
+        int CurrentScore { get; }
+        /// <summary>All-time high score (persisted via PlayerPrefs).</summary>
+        int HighScore { get; }
+        /// <summary>Adds <paramref name="points"/> to the current score.</summary>
+        void AddScore(int points);
+        /// <summary>Resets the current score to zero (call on game restart).</summary>
+        void ResetScore();
+        /// <summary>Fired whenever the current score changes. Passes the new score value.</summary>
+        event System.Action<int> OnScoreChanged;
+        /// <summary>Fired when a new high score is set. Passes the new high score value.</summary>
+        event System.Action<int> OnHighScoreBeaten;
+    }
+}

Assets/Scripts/Core/IScoreManager.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: c6a5d584113c9e644892894fabe9970b

Assets/Scripts/Core/ScoreManager.cs

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+using UnityEngine;
+namespace FlappyBird.Core
+{
+    /// <summary>
+    /// Pure C# service — all scoring logic lives here.
+    /// No MonoBehaviour, no Unity lifecycle. Injected via Zenject.
+    /// High score is persisted with PlayerPrefs.
+    /// </summary>
+    public sealed class ScoreManager : IScoreManager
+    {
+        private const string HIGH_SCORE_KEY = "HighScore";
+        // ── IScoreManager ──────────────────────────────────────────────────
+        /// <inheritdoc/>
+        public int CurrentScore { get; private set; }
+        /// <inheritdoc/>
+        public int HighScore { get; private set; }
+        /// <inheritdoc/>
+        public event System.Action<int> OnScoreChanged;
+        /// <inheritdoc/>
+        public event System.Action<int> OnHighScoreBeaten;
+        // ── Constructor ────────────────────────────────────────────────────
+        public ScoreManager()
+        {
+            HighScore = PlayerPrefs.GetInt(HIGH_SCORE_KEY, 0);
+        }
+        // ── IScoreManager ──────────────────────────────────────────────────
+        /// <inheritdoc/>
+        public void AddScore(int points)
+        {
+            if (points <= 0) return;
+            CurrentScore += points;
+            OnScoreChanged?.Invoke(CurrentScore);
+            if (CurrentScore > HighScore)
+            {
+                HighScore = CurrentScore;
+                PlayerPrefs.SetInt(HIGH_SCORE_KEY, HighScore);
+                PlayerPrefs.Save();
+                OnHighScoreBeaten?.Invoke(HighScore);
+            }
+        }
+        /// <inheritdoc/>
+        public void ResetScore()
+        {
+            CurrentScore = 0;
+            OnScoreChanged?.Invoke(CurrentScore);
+        }
+    }
+}

Assets/Scripts/Core/ScoreManager.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: 8cb16782bb35543409bdbf67b4f6c2d6