Refactor code structure for improved readability and maintainability

units/bomb.py

@@ -32,6 +32,8 @@ class Bomb(Unit):
     def draw(self):
         n = self.age // 40
         n= 3 -n +1
+        if n == 0:
+            n = 1
         if n < 0:
             n = 0
         image = self.game.bomb_assets[n]
@@ -123,9 +125,6 @@ class Explosion(Bomb):
             self.die()
             
     def draw(self):
-        if self.game.map.is_tunnel(*self.position):
-            return
-
         image = self.game.assets["BMP_EXPLOSION"]
         image_size = self.game.render_engine.get_image_size(image)
         partial_x, partial_y = 0, 0

units/rat.py

@@ -44,7 +44,7 @@ class Rat(Unit):
             nx, ny = x + dx, y + dy
             if not self.game.map.in_bounds(nx, ny):
                 continue
-            if self.game.map.is_empty(nx, ny) and (nx, ny) != self.position_before:
+            if self.game.map.is_traversable(nx, ny) and (nx, ny) != self.position_before:
                 neighbors.append((nx, ny))
 
         if not neighbors:
@@ -52,11 +52,11 @@ class Rat(Unit):
                 nx, ny = x + dx, y + dy
                 if not self.game.map.in_bounds(nx, ny):
                     continue
-                if self.game.map.is_empty(nx, ny):
+                if self.game.map.is_traversable(nx, ny):
                     neighbors.append((nx, ny))
 
         if not neighbors:
-            print(f"[flow] rat fallback: no empty neighbors from position={self.position}", flush=True)
+            print(f"[flow] rat fallback: no traversable neighbors from position={self.position}", flush=True)
             return self.position
 
         self.position_before = self.position