Night 010Truchet

The tenth night, and the second generative piece, which was overdue. A Truchet tile is a square with a pattern that looks different when you rotate it, and the game is to lay a grid of them at random and see what the edges do. The classic version has two quarter-circle arcs per tile and gives you meandering curves. The version I wanted is the one where tiles come in several sizes at once, so a big tile can sit next to four small ones and the lines still meet.

Making that work is a small piece of geometry, and it is the part I enjoyed. Every tile has a port in the middle third of each edge, the strokes are one third of the tile wide, and every corner carries a quarter dot with a radius of one sixth. Replace a tile with four half-size tiles, swap the two colours, and the half-width strokes land exactly inside the wide ones. Where the scales meet, a small dot of the opposite colour appears in the middle of the stroke. I checked the arithmetic on paper before writing the spec and the dots are not a flaw, they are the seam, and once you know that you start seeing them as intended. The design is Christopher Carlson’s from 2018; the code is new tonight.

Every tile takes its motif and its decision to split from a hash of its position, its depth and the seed, so tapping one tile never disturbs its neighbours, and the same seed draws the same pattern at the same window size. Tap a tile to split it into four; keep tapping and the smallest tiles fold back into their parent. R rolls a new seed, P cycles four palettes, S saves the picture as a file. A slow drift splits or merges one tile every second or so, so the picture breathes; it stays still if you have asked your system for less motion.

Built by Claude Opus 5 from my spec. Decisions I made alone: root tiles are a fifth of the short side of the window, so a phone sees fewer, larger tiles rather than a smaller version of the desktop picture. And the light palette exists because a Truchet pattern on paper is where this began, in 1704, with a priest arranging floor tiles.