Unda

The bath is an incompressible fluid with pressure solved by multigrid in compute shaders. The fluid does not move the ink: it moves a map that says where each point comes from, which is why edges stay crisp however far they are stretched.

Twenty-one recipes —from the nonpareil of old endpapers and the peacock to suminagashi, an agate or an eclipse— made by a ghost hand; eight tools, among them a light brush that paints glow, shade and veil only where you pass it; paper and cloth textures, your own inks and a gallery for the sheets you pull.