Overall, I thoroughly enjoyed playing this. But I think the visual language could use some improvement. Specifically incorporating more color with interactive and dynamic assets. The non-moveable cube should be more distinct from the standard moveable cube, a color and/or symbol would most certainly do the trick. This would also help doors and other elements standout from the background. I understand it's more of a style choice, but these minor touches can make the game more accessible.
P.S.: l Love the idea of launching yourself by sizing the block. More of that please!