Since you say is not finished is hard to give feeddback because i think most of the stuff you already know, but here it goes:
- Health bar is too big and too centered, it could be very tiny, or better, your remaining shots could be your health bar, so you don't have to have UI.
- Enemies should die when they receive shoots, or at least be pushed/react since right now it feels weird that nothing you do seems to have an impact.
- You should have feedback when you receive damage, and the enemies too (flashing, particles, shake...)
- More randomized enemies (position and patterns)
I think the base idea is really cool (have a limited number of bullets) and i think it could be worked to be awesome. Some ideas I had while playing
- What if the bullets are also like a shield, so if you receive damage while you have bullets in you, you lose a bullet, but if you receive damage without bullets, you lose. This would change the "bullets are evil" mechanic but It could be cool, dunno
- What if if you hit an enemy the bullet recharges faster than if you miss? Then players should be careful and aim better if they want to reload faster.
The art direction is very cool, liked it a lot.