Overall, a really cool game concept! My main feedback is to make the game timer more lenient when it comes to not killing enough enemies, as I found myself dying extremely quickly as I was trying to either hit enemies or on my way to get more. That, and maybe make enemy bullets much easier to dodge, as I found myself getting hit in the back with them several times.
Either way, it's a really cool game with a really cool concept! I just feel like the mechanics could use some tuning since I found it extremely hard to get into, as I kept on dying just after I started.