Really great mood, love it. :) Most possible improvements I had in mind have already been mentioned above. I only have two additional ones:
In the room with the many skeletons, the 4th one I think, I got stuck between a wall and all the skeletons the first time and couldn't move anymore. I would suggest making the colliders pretty small, smaller than you'd think they'd need to be when looking at the sprites. You can almost reduce them down to dots and it'll still look okay when they get close to a wall, but feel better when maneuvering between them. That way it's also harder to push the skeletons around by walking against them, which happened many times accidentally. Those little things remind you you're still playing a video game, despite the great atmosphere.
Also I didn't find it immediately obvious that the box at the bottom was a text input, took me a couple moments to realize. The hint the skeleton gives took my attention, so I didn't notice a box had appeared alongside it. So I thought it was just a speech bubble for flavor, like the ones before that with the fresh calcium.
Mood is a make or break aspect in video games for me. It's not easy to get right, because it's influenced by all the other elements. So congrats on nailing that part! If you make use of the feedback you've gotten, your next game could become a really immersive experience that sucks people into it and makes them forget they're sitting in front of a computer.