I love the little taily guy. Does he have a name?
All in all this is a lovely entry into the gamejam with respect to the time alloted (good idea to recycle the block sprite for slopes as well), but I would like to point out a few things for next gamejam that you could improve on :)
1) In level 3, why can't I push blocks over other blocks? It is such a staple in other block pushing games that it really caught me off-guard.
2) Everything feels really floaty: Speed goes from 0 to 100 and gravity is surprisingly low, which makes for some (frustratingly) surprising falling trajectories. To top that off: you can't change your falling trajectory which exacerbates the floaty feeling. Being able to correct trajectory mid-air would be more in line with modern platformers. This way it feels like an oldschool game, which I guess could be seen as a plus if done intentional.
3) The death animation, although (morbidly) cute, felt rally lengthy and I found myself skipping over it everytime with the reset button.
Did you already find out that if you get stuck in a switch wall you float up as if it were an escalator...?
About the puzzles itself, most were quite neat, others a bit on the simple side. I saw in another comment that the tail-holding-down button appears only in the introductory level, but I also used it in the last level, skipping the need for the box, and that move scratched that typical "puzzler"-itch. Thanks!