Wait, didn't you made something similar before? Or maybe all the unreal engine sokoban felt the same to me.
Okay, I give up on the last level, that was just mindbogglingly hard. Exceptional good idea! As the other comment mentioned, I would actually shrink the inner levels and put them on the cube. I think this is one of the few games that could benefits from less visual clutters - like for example, it was never really that clear to me which direction is the laser coming from and going, and where are they supposed to go, etc. Overall I still really liked it though.