It has some audio strangeness, for instance with footsteps at the start
Enemies get knocked back in a weird way. U and I aren't easy to press without taking the right hand off the cursor but ig that may be intentional. Also why do I drop all my weapons at the strat of the level? It's a little annoying picking them up. Some upgrades are a little unbalanced. Somewhat limited number of level layouts. Meellee weapon hitboxes are a bit hard to understand.
Most of the game is pretty good though.