The game is great, and you've got some really good ideas in here - also, I love the aesthetic of a slime picking up a key.  However, I think that given more time, the level design could be tightened up a bit - every level can be solved with at least one less bullet than given, in a few cases with 2 or 5 less bullets.  Also, I encountered a bug where, despite neither being blocked, only one of the PC/monster would move, which is probably something you should fix if you plan to do a post-jam version.  Very cool ideas, and I hope you make something more out of this!