Loved the changing music between modes and the creative sprites for different platform shapes! Also, the little player sprites are very cute!
It would have felt a bit better to play if you could drag the pieces directly off of their spots in the menu. I also think that there should have been a way to reset the position of the players without removing all the placed blocks. Often I just needed to move a platform over by a grid square or two, but the game made me have to re-place everything again. Coupled with the extra click to spawn the piece, starting over each time felt like a lot of work. Pre-specifying how the players would move would also reduce frustration, for example when introducing each player for the first time (“this guy loves to jump”, etc.)