As a jam-game, it’s almost perfect (subjective opinion of course :-) … ) – The fluid movement, the little squish on the dot when jumping, the cohesive art-style, the sound effects … it just all blends together so well.
The idea is also one of those once where once you see it, it should have been obvious, but you also know not everyone would have come up with it.
The only negative points, and I strain to come up with something, is that the last (or next-to-last if the ‘thank you for playing’ level is counted – which as an aside, reminded me of ‘Manifold Garden’) can get a little tedious. Since I messed up near the end, then have to go all the way back, and repeatedly, despite knowing what to do there.
I also think that if you want to expand on this later, you might want to add another gimmick/thing as well, as I think the sorts of puzzles you can make with this may in the end be somewhat limited.