Hey! Really solid game. I enjoyed playing it. It was fun.
Let me share some feedback that could make the game even better:
- In tutorial, information about collection of money should appear fist time the money drops.
- Not sure why you don't display coins counter in the tutorial - I was confused about that, and was looking for one. Which appeared after the tutorial
- I think game should pause when you are in the shop and select upgrades/weapons. I did not have much time to read and check all options available, decide on the best tactics before next round starting. I think you should give a player an option to rest a bit, analyse.
- Not sure if return on investment for ammunition is balanced. It might be very difficult to defeat later waves if you run out of ammunition for your upgraded weapons and cannot afford new ammo. Personally I would find it more fun if I could just focus on upgrades, instead of buying extra ammo, instead of other upgrades.
- I was not able to test later stages, as I was getting killed a lot :)
Good job!