Definition
Plain language
A famous unsolved geometry puzzle about the biggest piece of furniture you can drag around a right-angle hallway.
As stated in the literature
Moser's 1966 problem on the largest area of a connected region that can be moved around a right-angle corner in a hallway of unit width.
Why it matters: It's a famously simple-sounding open problem that remains unsolved, making it a target for AI-assisted mathematical search.
For example, the question is roughly: what's the largest sofa shape you could slide around an L-shaped corridor whose halls are one meter wide?