Added a strategic pygame.event.pump() in level.py. Levels 4-7 added, will probably need refining.

src/level.py

@@ -268,6 +268,9 @@ class Level:
 
     def handle_collisions(self):
         """Handle all collision checks and return True if level is complete."""
+        # Add a pump here so it gets called reasonably often.
+        pygame.event.pump()
+
         # First check if player is dead
         if self.player.get_health() <= 0:
             return False