Implement optimized collision detection system using NumPy

- Introduced a hybrid collision detection approach that utilizes NumPy for vectorized operations, improving performance for games with many entities (200+).
- Added a spatial grid for efficient lookups and AABB (Axis-Aligned Bounding Box) collision detection.
- Implemented a new `CollisionSystem` class with methods for registering units, checking collisions, and managing spatial data.
- Created performance tests to benchmark the new collision system against the old O(n²) method, demonstrating significant speed improvements.
- Updated existing code to integrate the new collision detection system and ensure compatibility with game logic.

units/gas.py

@@ -1,5 +1,6 @@
 from .unit import Unit
 from .rat import Rat
+from engine.collision_system import CollisionLayer
 import random
 
 # Costanti
@@ -7,7 +8,7 @@ AGE_THRESHOLD = 200
 
 class Gas(Unit):
     def __init__(self, game, position=(0,0), id=None, parent_id=None):
-        super().__init__(game, position, id)
+        super().__init__(game, position, id, collision_layer=CollisionLayer.GAS)
         self.parent_id = parent_id
         # Specific attributes for gas
         self.speed = 50
@@ -24,13 +25,29 @@ class Gas(Unit):
             self.die()  
             return
         self.age += 1
-        #victims = self.game.unit_positions.get(self.position, [])
-        victims = [rat for rat in self.game.unit_positions.get(self.position, []) if rat.partial_move>0.5]
-        for rat in self.game.unit_positions_before.get(self.position, []):
-            if rat.partial_move<0.5 and rat is Rat:
-                victims.append(rat)
-        for victim in victims:
-            victim.gassed += 1
+        
+        # Use optimized collision system to find rats in gas cloud
+        victim_ids = self.game.collision_system.get_units_in_cell(
+            self.position, use_before=False
+        )
+        
+        for victim_id in victim_ids:
+            victim = self.game.get_unit_by_id(victim_id)
+            if victim and isinstance(victim, Rat):
+                if victim.partial_move > 0.5:
+                    victim.gassed += 1
+        
+        # Check position_before as well
+        victim_ids_before = self.game.collision_system.get_units_in_cell(
+            self.position, use_before=True
+        )
+        
+        for victim_id in victim_ids_before:
+            victim = self.game.get_unit_by_id(victim_id)
+            if victim and isinstance(victim, Rat):
+                if victim.partial_move < 0.5:
+                    victim.gassed += 1
+        
         if self.age % self.speed:
             return
         parent = self.game.get_unit_by_id(self.parent_id)