This game is an awesome example of making the player feel clever. It felt as though I was breaking the game, even though it's exactly how we were meant to crack each puzzle. Smooth gameplay (I bet making the expanding and shrinking mechanic so smooth was tough), beautiful and relaxing tone too.
I got stuck on 14 and haven't managed to work it out yet, but I don't want to skip it! Perhaps a tip...?
Otherwise only feedback I can think of is the hitboxes felt slightly awkward at times - like I was only just making it, or only just not making it. And jumps were eaten a little when you jumped against the side of something. But neither mattered, really unique puzzle game!