Not bad. I did manage to cheese a bit I think by just standing still and shooting, I managed to survive for more than five minutes doing that, which I'm sure someone can beat but it felt like I shouldn't be able to survive for that long if I just stand and shoot at the enemies that approach me.
The idea of losing bullets if you're not careful is pretty interesting. I did find myself out of bullets the first time I played because I just fired wherever haha
Good job! :)