I really liked the concept and had fun playing it!
Other commenters have pointed out that the rebounding bullets are quite hard to see, and that it seems odd that they don't hit the slimes once they ricochet. While I don't necessarily think they need to be able to hit the slimes, the ricochets are rather punishing as it is. By combination of the speed and low visibility, the ricocheting bullets don't become a hazard, more just something that will eventually hit you. I actually think it could be improved by slowing the ricocheting bullets down, so that there's time for the player to account for and dodge them.