Hi!
First of all, i really like the shooting mechanic, it is very polished. The simple artstyle also looks good. But i think the gameplay is a bit too generic.
A tutorial in-game would have been really helpful, it is easy to implement and makes a better impression on your game. Also, an idea i had is, that you need too shoot red enemeis, but you can't shoot green enemies because that would give you minus points or something. That would have been really chaotic.
I hope my feedback helped you, it would be nice if you could check out my submission too. Thanks. :)