I like the way the game feels to play, and the headphone test + tutorial add a nice level of polish to things!
Requiring headphones limits your potential player base, but that's probably okay for an experimental jam game vs something you want to make more commercial.
There are quite a lot of elements to learn about in a short span of time at the beginning - it was a little overwhelming at first but made more sense the second time around. Adding a new tutorial room to demonstrate doors would definitely help. Speaking of doors: the high-pitched creaking door sound is quite unpleasant - it made me sort of dread closing my eyes, so I'd consider changing that if you continue working on this.
All that said, I love the art style and there's some cool strategy to play with (e.g. positioning yourself in a certain spot to see if an enemy is truly on the left or right). The headphone test and tutorial gave me a really good first impression too - it's a really nice added level of polish.