Hey I played this for a bit until I unlocked the ancient matter store. Fun game! It's fast and hectic in a great way, but mostly after you unlock auto-shoot. It's easy enough to get, but makes a massive difference to how enjoyable the game is imo so I really think you should start off with auto-shoot.
Lots of nice feedback when shots collide and things die.
I also think changing some of the font and text size would also be a relatively easy upgrade to polish it up. The pixel fonts in game don't really suit the game graphics, and are very different from the shop and tutorial and menu fonts. Also some of sir sluggers tutorial texts are very small and hard to read. Personally I'd suggest a different thick cartoony font for the floating damage text but even just using the UI fonts during the waves might look nice. The more important thing would be clarity of reading the tutorial texts though.
Oh and I don't know what to call these but the like lines of shuriken things from wave 6+ disappearing monsters felt pretty brutal. I'd have liked some more windup or something to help me dodge out of the way.