A zen-garden sand surface you engrave. Drag to press grooves into a height field; every frame a gentle relaxation plus a slow pull toward flat lets the sand creep back and fill the lines, so your marks slowly heal. Surface normals are derived from the height field and lit by a grazing warm key, with fine grain and darkened, compacted groove floors — the crumbling walls read as sand flowing back. Left alone, a virtual finger draws slow enso arcs and parallel rake lines, then pauses while they heal.