Nice art work, and sound matched the theme. I would have liked some more UI elements, to help me track kills/time survived. Good work :)

I liked this game! For your first game Its very Impressive work! But here are my things that I noticed:
-Missing cursor, this type of game needs a cursor to see where are you shooting at. in unity You can Implement that very easily.
-Faster movementspeed for the player or faster gameplay in general. 
-Maybe different styles of shooting or weapons 
Other than these Nice Work!