Truchet tiles, dealt by π. Each tile is a square carrying a pair of arcs, and each digit of π picks which tile goes in the next cell. Because the arcs always meet at the edge midpoints, neighbouring tiles join into long curving paths and closed loops — a different labyrinth for every stretch of π. Switch the colour mode to Loops to see the regions it draws.
Inspired by the tiles of Sébastien Truchet (1704) and Cyril Stanley Smith's revival in Leonardo, 1987.