Very nice, I assume this was a LD48 entry? Just found out about Patrick's Parabox so I appreciate being able to play with the idea! In this one I can push... TWO boxes at ONCE?!? In my sokoban? Imagine that. Anyway, I don't think the physics is breaking the boxes... just the other way around!
(Speaking of breaking things, I broke the ending screen by pushing the recursive box against the wall, then trying to push another box out through the blocked side, and I ended up way out of bounds with no idea where I was.)