Great atmosphere. The cave is very dark which makes movement challenging but is also a huge part of the mood. I think it's great how you introduce new mechanics...with explanation and in game signs. The wall climb and dash are a bit hard to get comfortable with.
I was at the door and rusty keep map. After the block at the top of the screen crumbled below me, I wasn't able to make the dash over to the key. It would be a good idea for crumbling platforms to regenerate after awhile.
Even though we are told that we can light the lanterns, I didn't see any way to light them. Maybe they are supposed to light just by touching them? In the webGL version there was never any light from lanterns. No light from the lanterns left where you die either. The idea to leave lanterns that add more light to the map is a great idea...but unfortunately it didn't work on my browser.
The red eyes fleeing from the light felt a little inconsistent. Sometimes I would shine my light directly on the eyes and they would fade away; other times they would be moving toward me and still get me. I think they need to be in the brightest part of the light a certain amount of time?? it's unclear.
The background music was a perfect fit to your game. The art style was really nice to look at.