Thread

sew each pair of buttons together. leave no linen bare.

connect each pair of same-coloured buttons with a thread through the grid of an embroidery hoop, filling every cell; four hoops against the clock

The classic connect-the-dots pipe puzzle, stitched: join every pair of buttons with one thread, threads never cross, and the hoop is done only when every cell holds a thread. Drawing through another thread cuts it back; back off and it returns. The clock runs from your first touch on the first hoop, and from the moment each later hoop settles in.

Concepts: constraint, partition.

An interactive you play with one thumb, on Wundr.