Interesting concept. There's always a bit of dread when there's darkness all around you. Then you heart starts beating a bit faster when that beating/clicking picks up pace because you know "something" is getting closer. I also thought it was a nice touch that I didn't seem to be able to run while holding a gem. It made for an interesting mechanic of dropping what you need to get away knowing that you'd eventually have to loop back later to pick up what you dropped.
Nice work