Higher combos mean higher fire rate but I know what you're saying. It really doesn't make a lot of difference. The system isn't really balanced. Should've increased damage at higher combos. I'll improve on the game later and see if I can manage to balance some things out.
Just to put it out there, the player sprites and arena tiles are by Kenney (link in the description). Did the art for everything else (bullets, blood, bomb, explosion, etc.) myself.
Thanks for playing!