Great atmosphere. The sound design and art take the player to a serene yet eerie place.
Could improve the platforming physics. Look up "coyote time" and consider a similar tweak for when players press the "jump" button a little too early before landing. Holding a direction against a wall in mid-air also sticks you to the wall - probably a quirk when using Unity's rigidbodies for character movement.
I like how the gameplay loop fits the theme well and contributes to the overall tone. But I do think there's more potential for puzzle/problem solving and just "fun" factor. The most optimal approach is basically to hold right and jump until eventually you can reach the goal. It stops being interesting after a handful of levels.