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

test_keybindings.py

@@ -0,0 +1,87 @@
+#!/usr/bin/env python3
+
+import unittest
+from pathlib import Path
+
+from engine import controls
+
+
+class DummyBindings(controls.KeyBindings):
+    def spawn_rat(self):
+        pass
+
+    def toggle_audio(self):
+        pass
+
+    def toggle_full_screen(self):
+        pass
+
+    def start_scrolling(self, direction):
+        pass
+
+    def stop_scrolling(self):
+        pass
+
+    def spawn_new_bomb(self):
+        pass
+
+    def spawn_new_nuclear_bomb(self):
+        pass
+
+    def spawn_new_mine(self):
+        pass
+
+    def spawn_new_gas(self):
+        pass
+
+    def spawn_gas(self, parent_id=None):
+        pass
+
+    def toggle_pause(self):
+        pass
+
+    def reset_game(self):
+        pass
+
+    def quit_game(self):
+        pass
+
+    def menu_up(self):
+        pass
+
+    def menu_down(self):
+        pass
+
+    def menu_left(self):
+        pass
+
+    def menu_right(self):
+        pass
+
+
+class KeybindingProfileTests(unittest.TestCase):
+    def test_shipped_profiles_expose_all_weapon_actions(self):
+        dummy = DummyBindings()
+        conf_dir = Path(__file__).resolve().parent / "conf"
+        weapon_actions = {
+            "spawn_new_bomb",
+            "spawn_new_nuclear_bomb",
+            "spawn_new_mine",
+            "spawn_new_gas",
+        }
+
+        for config_path in sorted(conf_dir.glob("keybindings*.json")) + sorted(conf_dir.glob("keybindings*.yaml")):
+            bindings = controls._load_bindings_from_file(config_path)
+            validated = dummy._validate_bindings(bindings, config_path)
+            game_bindings = validated.get("keybinding_game", {})
+            self.assertTrue(game_bindings, f"missing keybinding_game in {config_path.name}")
+
+            actions = set(game_bindings.values())
+            self.assertTrue(
+                weapon_actions.issubset(actions),
+                f"incomplete weapon bindings in {config_path.name}: {sorted(actions)}",
+            )
+
+
+if __name__ == "__main__":
+    unittest.main()