I really like the combat system! Punching the aliens feels very satisfying and has a nice punching sound effect. I like the art design a lot, although the colors feel a little flat.
I also came across the bug where if you hold down the left mouse button, the fist will be raised and you'll just kind of glide around very slowly depending on where your mouse is pointing. Also, I noticed the "!" icon for entering doors felt like it was appearing too far out from the actual doors; I would be in between two buildings and the "!" would pop up even if I wasn't closer to one door vs the other.
The camera also is a bit inconsistent; like, it'll pass through most of a building when I swing it around, but it is blocked by the building's frames, the doors, and even the window textures.
Overall I really like it, and I can't wait to see it develop even further! This is a really cool idea :)