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Assets/_Project/Art/VFX/FX_SellTower.prefab.meta

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Assets/_Project/Scenes/Levels/9Player.unity

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Assets/_Project/Scripts/Gameplay/EnemyMovement.cs

@@ -21,8 +21,10 @@ namespace TD.Gameplay
     ///         and stores the tile waypoint list.</item>
     ///   <item>Each frame: moves toward the world center of <c>remainingPath[0]</c>.
     ///         When within snap distance, pops the waypoint and checks for zone transitions.</item>
-    ///   <item>When <see cref="PathfindingService.OnPathsInvalidated"/> fires (tower placed /
-    ///         sold), <see cref="RecomputePath"/> reruns A* from the current tile.</item>
+    ///   <item>When the maze changes (tower placed / sold), <see cref="PathfindingService"/>'s
+    ///         budgeted scheduler calls <see cref="RecomputePath"/> (registered via
+    ///         <see cref="PathfindingService.RegisterMover"/>), rerunning A* from the current
+    ///         tile — spread across frames so a full wave never spikes.</item>
     ///   <item>When <c>remainingPath</c> is empty after a pop, the enemy has reached the
     ///         goal — <see cref="OnReachedGoal"/> fires and the enemy is despawned.</item>
     /// </list>
@@ -168,15 +170,18 @@ namespace TD.Gameplay
 
             // Recompute when a tower is placed or sold — grounded enemies only.
             // Flyers path on the static baked grid, so tower changes can never affect
-            // their route; subscribing would just trigger needless recomputes.
+            // their route; registering would just trigger needless recomputes.
+            // Registration (not a direct event subscription) lets PathfindingService
+            // spread the recomputes across frames under a per-frame budget, so a maze
+            // change with a full wave present never spikes a single frame.
             if (!isFlying && PathfindingService.Instance != null)
-                PathfindingService.Instance.OnPathsInvalidated += RecomputePath;
+                PathfindingService.Instance.RegisterMover(this);
         }
 
         public override void OnNetworkDespawn()
         {
             if (PathfindingService.Instance != null)
-                PathfindingService.Instance.OnPathsInvalidated -= RecomputePath;
+                PathfindingService.Instance.UnregisterMover(this);
         }
 
         // ----- Server update --------------------------------------------------
@@ -274,8 +279,9 @@ namespace TD.Gameplay
 
         // ----- Path invalidation ----------------------------------------------
 
-        // Called on server when LevelLoader.OnWalkabilityChanged fires (tower placed/sold).
-        private void RecomputePath()
+        // Called by PathfindingService's budgeted scheduler after a walkability change
+        // (tower placed/sold). Public so the scheduler can drive it across frames.
+        public void RecomputePath()
         {
             if (!IsServer) return;
 

Assets/_Project/Scripts/Gameplay/PathfindingService.cs

@@ -26,13 +26,15 @@ namespace TD.Gameplay
     /// <b>Who calls this:</b>
     /// <list type="bullet">
     ///   <item><see cref="EnemyMovement"/> calls <see cref="ComputePath"/> once on
-    ///         spawn and again whenever <see cref="OnPathsInvalidated"/> fires.</item>
+    ///         spawn, then registers via <see cref="RegisterMover"/> to be re-pathed when
+    ///         the maze changes.</item>
     /// </list>
     ///
     /// <b>Invalidation:</b> Subscribes to <see cref="LevelLoader.OnWalkabilityChanged"/>.
-    /// When a tower is placed or sold, <c>LevelLoader.SetWalkable</c> fires that event
-    /// and <see cref="OnPathsInvalidated"/> is relayed to all active enemies, which
-    /// each recompute their own path from their current tile.
+    /// When a tower is placed or sold, <c>LevelLoader.SetWalkable</c> fires that event; the
+    /// service then enqueues every registered grounded enemy and recomputes them under a
+    /// per-frame time budget (<c>recomputeBudgetMs</c>), draining across frames so a maze
+    /// change with a full wave present never spikes a single frame.
     ///
     /// <b>Goal tile set:</b> Built once on <c>Start</c> from
     /// <c>LevelLoader.LevelData.Goals[].TileArea</c>. Goal tiles never change at
@@ -52,7 +54,10 @@ namespace TD.Gameplay
 
         /// <summary>
         /// Fired on every peer when the walkability grid changes (tower placed/sold).
-        /// <see cref="EnemyMovement"/> subscribes per-instance to recompute its path.
+        /// Enemies no longer subscribe here — they register with the budgeted re-path
+        /// scheduler (<see cref="RegisterMover"/>) so recomputes spread across frames.
+        /// This event remains as an extension point for any non-enemy listener that wants
+        /// immediate notification of a maze change.
         /// </summary>
         public event System.Action OnPathsInvalidated;
 
@@ -79,6 +84,28 @@ namespace TD.Gameplay
         private readonly Dictionary<Vector2Int, float>       gScore    = new Dictionary<Vector2Int, float>();
         private readonly SimplePriorityQueue                  openSet   = new SimplePriorityQueue();
 
+        // ----- Deferred re-path scheduler ---------------------------------
+        //
+        // Grounded enemies register here (flyers never re-path — baked grid). On a
+        // walkability change we enqueue every registered enemy and recompute a
+        // TIME-BUDGETED number of them per frame, draining the backlog over subsequent
+        // frames. Recomputing them all synchronously on the change frame spiked to ~0.5s
+        // with a full wave on this large grid whenever a tower was sold/placed — this
+        // caps the per-frame cost so no single frame ever hitches. The maze can only be
+        // opened (sell) or narrowed with a guaranteed remaining route (placement, BFS-
+        // validated), so an enemy briefly following its slightly-stale path for a few
+        // frames until its turn comes up is safe and visually negligible.
+
+        [Tooltip("Max wall-clock milliseconds spent recomputing enemy paths per frame " +
+                 "after a maze change. The backlog drains over following frames; at least " +
+                 "one enemy is always processed per frame so it converges. Lower = smoother " +
+                 "but slower to fully update; higher = faster to update but larger frame cost.")]
+        [SerializeField] private float recomputeBudgetMs = 1.5f;
+
+        private readonly HashSet<EnemyMovement> movers          = new HashSet<EnemyMovement>();
+        private readonly Queue<EnemyMovement>   recomputeQueue  = new Queue<EnemyMovement>();
+        private readonly HashSet<EnemyMovement> queued          = new HashSet<EnemyMovement>();
+
         // ----- Lifecycle --------------------------------------------------
 
         private void Awake()
@@ -115,6 +142,48 @@ namespace TD.Gameplay
                 loader.OnWalkabilityChanged -= HandleWalkabilityChanged;
         }
 
+        // Drains the deferred re-path backlog under a per-frame time budget. Runs on all
+        // peers, but the queue is only ever populated on the server (clients never register
+        // movers), so this is a no-op cost on clients. At least one enemy is processed per
+        // frame whenever the queue is non-empty, so it always converges.
+        private void Update()
+        {
+            if (recomputeQueue.Count == 0) return;
+
+            double startMs = Time.realtimeSinceStartupAsDouble * 1000.0;
+            do
+            {
+                var mover = recomputeQueue.Dequeue();
+                if (!queued.Remove(mover)) continue;      // unregistered/cancelled after enqueue
+                if (mover != null) mover.RecomputePath(); // reads the CURRENT grid state
+            }
+            while (recomputeQueue.Count > 0
+                   && Time.realtimeSinceStartupAsDouble * 1000.0 - startMs < recomputeBudgetMs);
+        }
+
+        // ----- Deferred re-path scheduler API -----------------------------
+
+        /// <summary>
+        /// Registers a grounded enemy to be re-pathed (budgeted, over following frames)
+        /// whenever the maze changes. Flyers must NOT register — their baked-grid route
+        /// never changes. Called on the server from <see cref="EnemyMovement"/>.
+        /// </summary>
+        public void RegisterMover(EnemyMovement mover)
+        {
+            if (mover != null) movers.Add(mover);
+        }
+
+        /// <summary>
+        /// Removes an enemy from the scheduler (on despawn). Any stale entry still sitting
+        /// in the pending queue is skipped when dequeued (the <c>queued</c> membership check).
+        /// </summary>
+        public void UnregisterMover(EnemyMovement mover)
+        {
+            if (mover == null) return;
+            movers.Remove(mover);
+            queued.Remove(mover);
+        }
+
         // ----- Public API -------------------------------------------------
 
         /// <summary>
@@ -471,7 +540,16 @@ namespace TD.Gameplay
 
         private void HandleWalkabilityChanged()
         {
+            // Notify any non-enemy listeners immediately (kept for API compatibility).
             OnPathsInvalidated?.Invoke();
+
+            // Enqueue every registered grounded enemy for a budgeted, deferred recompute
+            // instead of recomputing them all on this frame. Already-queued enemies are
+            // deduped, so rapid successive maze changes just lengthen the drain rather
+            // than compounding into a spike.
+            foreach (var mover in movers)
+                if (queued.Add(mover))
+                    recomputeQueue.Enqueue(mover);
         }
     }
 

Assets/_Project/Scripts/VFX/SellEffectSpawner.cs

@@ -65,7 +65,15 @@ namespace TD.VFX
 
             if (coinBurstPrefab != null)
             {
-                Instantiate(coinBurstPrefab, spawnPos, Quaternion.identity);
+                var instance = Instantiate(coinBurstPrefab, spawnPos, Quaternion.identity);
+
+                // Force the burst to play. The spawner's whole job is to play this effect, so
+                // it shouldn't depend on the prefab's ParticleSystem having "Play On Awake"
+                // ticked — if that's off, the effect would silently never appear. Harmless when
+                // Play On Awake is already on (a freshly instantiated one-shot just restarts at
+                // t=0). VFX Graph effects play from their own settings, so a null PS is fine.
+                var ps = instance.GetComponentInChildren<ParticleSystem>();
+                if (ps != null) ps.Play(withChildren: true);
             }
             else
             {

Assets/_Project/Scripts/VFX/TransientEffect.cs

@@ -0,0 +1,30 @@
+// Assets/_Project/Scripts/VFX/TransientEffect.cs
+using UnityEngine;
+
+namespace TD.VFX
+{
+    /// <summary>
+    /// Destroys its GameObject a fixed time after it spawns. Drop this onto any one-shot
+    /// effect prefab — a particle burst, a VFX Graph effect, a sound-only object — so it
+    /// cleans itself up without any bespoke code. Designed for prefabs spawned by
+    /// <see cref="SellEffectSpawner"/> (and any future effect spawner) that fire once and
+    /// should disappear.
+    /// </summary>
+    /// <remarks>
+    /// <b>Shuriken shortcut:</b> a plain <see cref="ParticleSystem"/> can instead self-destroy
+    /// with no component at all — set <i>Main → Stop Action → Destroy</i> and make sure Looping
+    /// is off. Use this component for <b>VFX Graph</b> effects (which have no Stop Action) or for
+    /// prefabs that combine several systems and need one predictable lifetime.
+    ///
+    /// <para>Set <see cref="lifetime"/> to comfortably exceed the effect's visible duration so it
+    /// isn't cut off mid-play.</para>
+    /// </remarks>
+    public class TransientEffect : MonoBehaviour
+    {
+        [Tooltip("Seconds after spawn before this GameObject destroys itself. Set it a little " +
+                 "longer than the effect's visible length so nothing is cut off.")]
+        [SerializeField, Min(0f)] private float lifetime = 1.5f;
+
+        private void Start() => Destroy(gameObject, lifetime);
+    }
+}

Assets/_Project/Scripts/VFX/TransientEffect.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: 739f3145f66002d47850b603164d07b8