Back button bug fix

Assets/Darkmatter/Code/Features/GameplayFlow/Systems/GameplayFlowController.cs

@@ -46,6 +46,7 @@ namespace Darkmatter.Features.GameplayFlow.Systems
         private string _templateId;
         private DrawingPhase _phase = DrawingPhase.ShapeBuilding;
         private bool _allContentReported;
+        private bool _navigating;
         private float _lastThumbnailTime = float.NegativeInfinity;
 
         private IDisposable _assembledSub;
@@ -166,12 +167,24 @@ namespace Darkmatter.Features.GameplayFlow.Systems
 
         public async UniTask BackAsync(CancellationToken ct)
         {
-            await SaveCurrentAsync(CancellationToken.None);
-            _loadingScreen.Show();
-            _shapeBuilder.Clear();
-            _coloring.Clear();
-            await _scenes.LoadSceneAsync(nameof(GameScene.Colorbook), progress: null, cancellationToken: ct);
-            await _scenes.UnloadSceneAsync(nameof(GameScene.Gameplay), progress: null, cancellationToken: ct);
+            // A second navigation while one runs (e.g. Back pressed during the completion
+            // animation inside NextAsync) would interleave two saves and two Colorbook loads,
+            // and Clear() would rip the celebration apart mid-flight. First navigation wins.
+            if (_navigating) return;
+            _navigating = true;
+            try
+            {
+                await SaveCurrentAsync(CancellationToken.None);
+                _loadingScreen.Show();
+                _shapeBuilder.Clear();
+                _coloring.Clear();
+                await _scenes.LoadSceneAsync(nameof(GameScene.Colorbook), progress: null, cancellationToken: ct);
+                await _scenes.UnloadSceneAsync(nameof(GameScene.Gameplay), progress: null, cancellationToken: ct);
+            }
+            finally
+            {
+                _navigating = false;
+            }
         }
 
         public async UniTask SaveAsync(CancellationToken ct)
@@ -184,48 +197,48 @@ namespace Darkmatter.Features.GameplayFlow.Systems
 
         public async UniTask NextAsync(CancellationToken ct)
         {
-            // Drop any debounced autosave so it can't fire during/after the completion
-            // animation and capture the animation (or an empty paper) into the thumbnail.
-            _autosaveCts?.Cancel();
-            _autosaveCts?.Dispose();
-            _autosaveCts = null;
-
-            await SaveCurrentAsync(ct);
-            _refs.Confetti.Play();
-            _sfx.Play(SfxId.FireWorkLaunch);
-            _sfx.Play(SfxId.LevelComplete);
-            await _coloring.PlayCompletionAnimationAsync(ct);
-            _progression.MarkCompleted(_templateId);
-            var progressAfter = _progression.GetProgress(_templateId);
-            _bus.Publish(new DrawingCompletedSignal(_templateId, progressAfter?.completionCount ?? 1));
-
-            // Player has cleared the whole catalog → surface the "ran out of content" milestone. Guarded
-            // per session here; analytics dedupes it to once-ever.
-            if (!_allContentReported &&
-                _catalog.AllTemplateIds.Count > 0 &&
-                _progression.CompletedTemplateIds.Count >= _catalog.AllTemplateIds.Count)
+            if (_navigating) return;
+            _navigating = true;
+            try
             {
-                _allContentReported = true;
-                _bus.Publish(new AllContentCompletedSignal(_progression.CompletedTemplateIds.Count));
-            }
+                // Drop any debounced autosave so it can't fire during/after the completion
+                // animation and capture the animation (or an empty paper) into the thumbnail.
+                _autosaveCts?.Cancel();
+                _autosaveCts?.Dispose();
+                _autosaveCts = null;
 
-            var nextId = _catalog.GetNextTemplate(_templateId);
-            if (string.IsNullOrEmpty(nextId))
-            {
+                await SaveCurrentAsync(ct);
+                _refs.Confetti.Play();
+                _sfx.Play(SfxId.FireWorkLaunch);
+                _sfx.Play(SfxId.LevelComplete);
+                await _coloring.PlayCompletionAnimationAsync(ct);
+                _progression.MarkCompleted(_templateId);
+                var progressAfter = _progression.GetProgress(_templateId);
+                _bus.Publish(new DrawingCompletedSignal(_templateId, progressAfter?.completionCount ?? 1));
+
+                // Player has cleared the whole catalog → surface the "ran out of content" milestone. Guarded
+                // per session here; analytics dedupes it to once-ever.
+                if (!_allContentReported &&
+                    _catalog.AllTemplateIds.Count > 0 &&
+                    _progression.CompletedTemplateIds.Count >= _catalog.AllTemplateIds.Count)
+                {
+                    _allContentReported = true;
+                    _bus.Publish(new AllContentCompletedSignal(_progression.CompletedTemplateIds.Count));
+                }
+
+                var nextId = _catalog.GetNextTemplate(_templateId);
                 _loadingScreen.Show();
                 _shapeBuilder.Clear();
                 _coloring.Clear();
                 await _scenes.LoadSceneAsync(nameof(GameScene.Colorbook), progress: null, cancellationToken: default);
                 await _scenes.UnloadSceneAsync(nameof(GameScene.Gameplay), progress: null, cancellationToken: default);
-                return;
+                if (!string.IsNullOrEmpty(nextId))
+                    _bus.Publish(new DrawingSelectedSignal(nextId));
+            }
+            finally
+            {
+                _navigating = false;
             }
-
-            _loadingScreen.Show();
-            _shapeBuilder.Clear();
-            _coloring.Clear();
-            await _scenes.LoadSceneAsync(nameof(GameScene.Colorbook), progress: null, cancellationToken: default);
-            await _scenes.UnloadSceneAsync(nameof(GameScene.Gameplay), progress: null, cancellationToken: default);
-            _bus.Publish(new DrawingSelectedSignal(nextId));
         }
         
         
@@ -270,13 +283,22 @@ namespace Darkmatter.Features.GameplayFlow.Systems
 
         private async UniTaskVoid EditAsync(string newTemplateId)
         {
-            await SaveCurrentAsync(CancellationToken.None);
-            _loadingScreen.Show();
-            _shapeBuilder.Clear();
-            _coloring.Clear();
-            await _scenes.LoadSceneAsync(nameof(GameScene.Colorbook), progress: null, cancellationToken: default);
-            await _scenes.UnloadSceneAsync(nameof(GameScene.Gameplay), progress: null, cancellationToken: default);
-            _bus.Publish(new DrawingSelectedSignal(newTemplateId));
+            if (_navigating) return;
+            _navigating = true;
+            try
+            {
+                await SaveCurrentAsync(CancellationToken.None);
+                _loadingScreen.Show();
+                _shapeBuilder.Clear();
+                _coloring.Clear();
+                await _scenes.LoadSceneAsync(nameof(GameScene.Colorbook), progress: null, cancellationToken: default);
+                await _scenes.UnloadSceneAsync(nameof(GameScene.Gameplay), progress: null, cancellationToken: default);
+                _bus.Publish(new DrawingSelectedSignal(newTemplateId));
+            }
+            finally
+            {
+                _navigating = false;
+            }
         }
 
         private async UniTaskVoid DebouncedAutosaveAsync(CancellationToken ct)