Very solid entry. I really liked the idea and it is a fun experience to spawn hordes of zombies. Here are some things I would improve:
- Add keyboard controls to select the type of zombie. In this way you can focus more with the mouse on spawning them at the right place and changing between types of zombies faster.
- After you died there should be a retry functionality.
- I would also enable fullscreen play on your itch.io page.
Anyway, I had fun playing this. Congrats to this game!