The story
First proposed by mathematician, logician, and philosopher Hao Wang in 1961.
Etymology from Wiktionary, CC BY-SA 4.0.
Wang tile
Today it means: A square tile with a colour on each side. Possible sets of such tiles are studied to determine whether they can tile the plane (arranged with like colours touching, and without rotations or reflections) and whether this can be done in a periodic pattern. Full definition →