A good base is there but the game feels very incomplete...
Didn't find anything while exploring, maybe adding hints or art on the walls?
2nd riddle could be "breath" but I had to look at the answer. I'm not sure how a secret is as light as a feather, that was kind of frustrating.
The movement is really smooth, and the environment looks nice, but the invisible walls break immersion a little, which is a huge part of a psychological game imo.