Very nice game. Probably one of the nicer things I've found on itch.io.
You really should compress your audio. You can drastically reduce the size of the game that way. The ambience file (by far the largest) dropped to about 22 MB when I compressed to .ogg. I'd suggest compressing the other larger files as well.
I also noticed that the light used underground tends to slow the game down quite a bit, including when the lantern is in use. I also noticed most of the sound cutting out several times, but I suspect you already know about that.