I'm a big fan of the aesthetic, and level design was quite solid. Combat felt rather awkward though, no feeling of impact to the hits and the lack of telegraphs from the enemies meant it was really easy to get hit point-blank without warning (or worse, killed from behind by an enemy that just respawned mid-fight). My ultimate strategy for beating the boss was to just stand on her head, spamming the attack button.
I know that the lack of music was intentional, but I can't help but feel like some BGM would improve things. The ambient sounds were so low that I couldn't even hear them unless I turned my sound way up, so I spent most of the game in silence.
But like, setting all of that side! This is undeniably very, very impressive for one month's work. Great job, and I'll be sure to check it out again if it gets updated some more