readme.md

quarter turns

Truchet tiles: one tile, four rotations, endless plumbing.

what you're looking at

Every square holds the same two arcs. Each arc starts and ends at the middle of a side, so whichever way a tile is rotated, its arcs always meet the arcs next door. No tile knows anything about its neighbours, yet the whole wall reads as continuous loops.

A tile turns every tenth of a second. One quarter turn reroutes two paths at once, so a single orange flicker can merge two loops into one or snap one loop in two.

things worth stealing from the prompt

Describing the rule, not the picture. The prompt never says "draw loops". It describes one tile and one rule, and explains why loops emerge. Agents do better when they understand the mechanism.
"Flat ends so arcs meet cleanly" heads off the most common flaw: round caps that bulge at every tile border.
Colour only while moving. The orange is how you find the change in a busy field.

try changing

turn two arcs into a diagonal line for the classic maze version
flip tiles in a travelling wave instead of at random
fill the regions between paths with two alternating colours

Make a single self-contained HTML file: a full-window canvas artwork called "quarter turns". No libraries, no text on screen, no controls. Fill the window with a grid of square tiles, about 14 tiles along the longer side, centered so the grid bleeds off every edge. Black background. Every tile carries the same drawing: two thick white quarter-circle arcs, each connecting the midpoints of two neighbouring sides. Give each tile a random starting rotation of 0, 90, 180 or 270 degrees. Because every arc ends at the middle of a side, the tiles join into long wandering loops and blobs with no loose ends. About ten times a second, pick one random tile and rotate it a quarter turn, taking 0.7 seconds with an ease-in-out. While a tile is turning, draw its arcs in orange (#ff5a1f); when it lands, it goes back to white. The paths should visibly break apart and reconnect as tiles turn. The stroke should be heavy, about 12% of the tile size, with flat ends so arcs meet cleanly at tile borders. Handle window resize and high-density screens.