I really enjoyed this one. The later puzzles were well thought out and showed a lot of potential. As a proof of concept for a puzzle game, this is really well done.
As another here mentioned, it might cause issues for colorblind people. It's understandable for a jam, but if you expand on this in future please consider adding symbols as well to each cube face. Also, physics were a bit wonky, which was an issue when I had to make a staircase of blocks. Jumping on blocks occasionally sent them flying into each other and combining when I didn't want them to.