I completed it! (so smart)
Really like games that make you think, the walking on wood sound is a bit repetitive, loved the shader!
I noticed that in the upside down level, the lights seem to ghost, from far away you see them but not when coming closer. Anyway, I got it! Really clever ;)
Edit: Now replaying it, for a future version of the game, it would be cool if the doors and puzzles were random.