Good job on this game! I didn't realise there was more than one level until reading some of the comments here, so could be good to have some extra arrows or directions on how to proceed after killing the bosses. I enjoyed the variety of weapons and enemies, nicely done there. I would have liked some SFX and extra feedback when hitting enemies and firing weapons, and some music would not be out of place too. The game also seemed to run at an oddly low resolution, not sure why that was.
Overall, though, good job!