I enjoyed playing this game. The risk versus reward type playstyle definitely intrigued me. It lead to me trying to calculate how much damage I would take at a time, to get the next upgrade without dying. This playstyle was very incorporated with the limitation. The art style was very good I loved the shop keeper, the enemies, and the guns. This is just my opinion but I really like games where the walking or running animations are small squash and stretches, and seeing this game had that made me happy.
I would say for some reason I couldn't make the connection of space/action to going to the next stage for about a minute I don't know why I didn't but its my only criticism for this game.
Overall good game!