Hope you try mine too.
https://itch.io/jam/gmtk-2019/rate/461292?after=20#post-873780
Very fun concept, I really enjoyed the first levels : the learning phase felt natural.
Nevertheless, if you want to extend your game it might a problem if you allow players to jump on cubes indefinitely to gain height. Have you considered adding a maximum number of cubes one can use depending on the levels? It might help creating more puzzles.