Update keybindings and enhance loading screen functionality

- Refactor keybindings for gas spawning across multiple configurations
- Implement new loading screen updates during game initialization
- Add tests to ensure all weapon actions are exposed in keybinding profiles
- Introduce new assets for explosion effects

engine/controls.py

@@ -278,6 +278,9 @@ class KeyBindings:
     def spawn_new_nuclear_bomb(self):
         self.spawn_nuclear_bomb(self.pointer)
 
+    def spawn_new_gas(self):
+        self.spawn_gas()
+
     def toggle_audio(self):
         self.render_engine.audio = not self.render_engine.audio
         self.audio = self.render_engine.audio
@@ -287,7 +290,19 @@ class KeyBindings:
             self.render_engine.stop_sound()
 
     def toggle_pause(self):
-        self.game_status = "paused" if self.game_status == "game" else "game"
+        if getattr(self, "game_end", (False, None))[0]:
+            return
+
+        if self.game_status == "game":
+            self.game_status = "paused"
+            return
+
+        if self.game_status == "paused":
+            self.game_status = "game"
+            return
+
+        if self.game_status == "start_menu" and getattr(self, "menu_screen", None) == "start":
+            self.reset_game()
 
     def toggle_full_screen(self):
         self.full_screen = not self.full_screen