Here are my stream of consciousness thoughts on the game.
-I like the little shake when I hit the first panel
-I was expecting the key pipe to spirit me away to the next level, rather than just open the door.
-didn't see the bar in the first level until I smashed into it, still a bit hard to see
-Puzzle 3 was way to easy
-the little plus/minus signs have been a real help
-Puzzle 6 seems like a big jump in difficulty, which is nice, because the previous levels were trivial
-That’s it? Seems like an extended tutorial.
-Also, this reminds me a lot of old flash puzzle platformers, and those often something to keep you playing besides puzzles. Even a text screen at the very beginning can give pathos to a dry puzzle game.
-On that note, give a look to old flash games. Broadening your references can bring unexpected inspirations.