Very very nice. Elegant & creative mechanics, just the right amount of challenge, a lovely, reflective, narrative chaining throughout the game (that frequently plays with metaphors of the obstacles you just cleared, an excellent touch), and a pleasant and uplifting message at the end.
I did run into 1 possibly soft-locking bug on my first playthrough. The second "stage", where you first encounter the 5 suns that you have to place on the scale, I tried to pick up all 5 at the same time and got locked in place and ran out of air. When I respawned, all 5 suns were still overlapped right where I died, so if I tried to pick them up I'd get all 5 again, and get locked in place again. Even after trying to drop them, I stayed locked in that spot till my air ran out. My second playthrough though I was more careful, and finished without issue.
Great job!