I'll start off by praising the visuals and the atmosphere, I think you really nailed these! The little blue humans had me laughing, really cool designs.
While I think that the shooting and the moving aspectsof the game are solid and as a standard survival shooter with upgrades it would work well, I think that without there being an actual way to lose the game lacks meaning and interest. At first I was trying to avoid being hit and shoot back at enemies but after realizing that them killing me makes ME STRONGER without any kind of setback whatsoever ( if anything, the enemies actually disappear when you "die") it kind of stopped making sense since it actually does benefit me to continue dying and getting all the upgrades. I get that you can potentially look at it as a simple "score- chaser" but without there being any kind of setback I don't see much point. I do think that if the player was at sent back to the starting room with all of their score reset (waves, kills, etc) but with an upgrade to choose from it would be more interesting since this way you're actually trying to survive and get further but if you do die you at least get a bit stronger for the next run.
Anyways, I hope this feedback was useful to you. In general I think the game has a solid core interaction (moving, shooting, getting stronger) that could simply use a better gameplay loop!