It looks like game inspiration is took by space shooter. I don't have a problem with that but tell if I am right.
Ok so as an average I gave you 4 star rating. Somehow reason can feel me this game more better:-
1. Please Give a sprint key. Cause without sprint it feels me slow a lot. That's why I give 4 star in entertainment
2. Yeah player looks Sci-Fi and his gun. Also alien crash looks but I think enemies feels me bitwise different. Is your player comes from alien and we have to kill earth people's then tell me if I am wrong. Otherwise could improve it.
3. I mind you could give some power ups as restore health, increase bullets, laser etc.