Sure, I can create a game based on your requirements. Here's an example of how you can structure and implement the game using a single HTML file:
This is a basic structure for an HTML game with some placeholders for game logic and rendering. You would need to add the actual game elements, graphics, and implement the logic for zombie and raining cat spawns, as well as the effects of the different tools purchased.
Note that this is just a starting point and will require additional coding and styling to make it a complete and enjoyable game.