The moving sofa problem
Of course, in the real world, furniture is 3D, and the obstacles you move move furniture around are also 3D. Bannister that's 3 feet high, couches with curved arms, ceilings have heights, stairwells...<p>Part of the fun of moving is trying to figure out how to orientate furniture to get it into a room - or out of the room, since someone already got in there so of course it must come out.