Hi there, I tried your game.
Overall it is an okay game for 5 minutes. This game can grow greatly if you will plan to develop it further.
There are some notes regarding the game which could be improved:
- Sound: Sound effects are repetitive. Do not know if Unity has it, but adding some random modulation (and potential other sound alterations) will greatly improve the auditory experience without the need to go and search extra sounds.
-Lack of enemy variety: Although they look different, they act in similar fashion. Different rates of fire, or occasional alteration in their movement velocity would greatly improve it.
I hope I am not too harsh on you. I wish you to grow further as a game dev :)