Drag the blanket · drag the room to look around · scroll to zoom
1 Draw
2 The wool decides
The rules, and how the solver works
Overlay mosaic crochet: every row is worked on the right side in one colour, A on odd rows, B on even rows. A plain stitch shows its own row's colour. To put colour where a row can't, you work an X: a long stitch that drops two rows down and covers the stitch below. No X on rows 1–2, none on the edge stitches, and never an X on top of an X.
So most drawings are illegal. For each column, a dynamic program (a Viterbi pass over two states) finds the legal sequence of X stitches that differs from your drawing in the fewest cells: an exact optimum, not a guess. Then a separate check, sharing no code with the solver, re-derives every rule from the finished chart.
The 3D blanket wears a texture drawn stitch by stitch from that legal chart, at the size the gauge gives (16 stitches × 19 rows = 10 cm), on a small Verlet cloth simulation. No AI image anywhere.
∞ Why "6 increases a round" is 2π
Crochet a disc round by round. Each round adds a few stitches. For it to lie flat, its edge must grow by 2π × the round's height, every round.
Too few stitches and the fabric must leave the plane: a bowl. Too many and the edge is longer than any circle: it ruffles, like lettuce or coral. Keep adding at a constant ratio and you get a model of the hyperbolic plane, which the mathematician Daina Taimina first crocheted in 1997.