Very nice! The weapons are balanced really well. One thing I would do differently is the difficulty. It increased too slowly for me. Maybe, more enemies could spawn at the same time in later waves to make them more dangerous.
Thank you! I spent much time monkeying with the weapon stats to find a good balance.
Yeah, right now each wave adds about 5 zombies. I wanted to do something resembling a curve, but ran out of time :c