It is a cool idea, and I like how the tutorial teaches you the mechanics without explaining them, but instead making you figure them out in a level.
However, I feel like the complimentary mechanics (elevators and breakable walls) are to restrictive as to make for really interesting puzzles, because they act as locked doors that require a specific size. Maybe if instead they worked differently depending of the player size, like if the elevator launched smaller sizes further, breakable blocks broke more with size or some size-changers (i don't know what to call them) could be moved like boxes it could lead to puzzles with more inventive solutions.
Also the music is beautiful. Good job!