The literal first thing I do upon booting up the game is get stuck in a wall. Off to a good start!
Mean jabs aside, I do really like the futuristic/low-res aesthetic, and I'd be interested to see real levels in this framework. The battle arena itself is a little hard to judge since it seems to just be there for testing purposes; maybe you could put in some background details like buildings or stars/planets in the distance, but that's about all I can suggest. The shooting controls are smooth and the gameplay loop seems neat, though again it could've used real levels. I think the music is good to have here, but the loop felt rather short and should probably have been extended more.
Really, my biggest issue is probably some UI/UX stuff. The HP counter should probably be more obvious, there were times where the upgrade menu lingered on-screen even after selecting an upgrade (it was still visible even when the game unpaused), and there seems to be no way to pause/exit the game yourself. Aside from that, I'm actually pretty interested to see where this goes.