oof, played it quite a bit. Was really meditative to run around searching for glowing stuff.:D
I find giving feedback always useful (even though this is a jam and time and resources are sparse): Mostly it is just little things, like the torch animation is a tad to slow but the mining animation is ridiculously fast (didn't realize I was swinging a pickax at first). The music worked well, simple, gave the sense of the atmosphere, and didn't started to bother even after a few minutes. But I had the feeling the frequencies clashed a bit with the sfx. At first I wasn't quite sure about the procedural levels. I even died just because there were no fire for ages (maybe it was intended). But after two level it felt nice, how it expanded every time. Giving a sense of progression. Nice would be if there were some unique Assets set in each Level, just to give it a bit more awe.
remember this was a jam, so these a super minor things. I think the biggest improvement would be to make the darkness feel really threatening. At first I didn't even realize it is a real threat until I saw the life bar turn red.
All in all. super solid entry! I lost myself playing it and really liked the idea of the achievements (I'll steal this for my next jam game... hehehehe) :)