Good job man, this is great! I shat myself when I first saw the hallucinations lmao, great job on the dissolve effect too.
My main piece of feedback is that the amount of sanity given back when standing next to a light is incredibly slow to go up, and it seems as if you're powerless to do anything about dying once you've gone deep enough. Perhaps instead of instantly losing, reaching 0 sanity could turn all the lights out and cause hallucinations to start chasing you down - which means you'd still have a slight chance of escaping with the right amount of skill and luck.
Regardless, I loved the art and music, and the sound design was solid. The mood was spot on. Good Game!