TITLE: Sumi — Ink in Water FILE: 005-sumi-ink-in-water.html === PROMPT (exact prompt used) === Make "Sumi — Ink in Water", a meditative fluid simulation. A full-screen canvas showing warm washi paper (#f4efe6 with procedurally generated fibre noise). Clicking or tapping drops ink that blooms, curls and diffuses like sumi ink in water — implement a small grid-based stable-fluids solver (advection, diffusion, pressure projection) at reduced resolution with smooth upscaling, or an equivalent dye-advection approach; dragging the pointer stirs the water. Default ink is deep sumi black-indigo (#1b1f2a); a minimal vertical toolbar on the right, set in a quiet serif, switches to indigo (#2c3e75), vermillion (#d23c26) or pale gold (#b89b5e). A red hanko seal in the corner (SVG, carved-looking characters approximated with geometric strokes) signs the piece; a "Still the water" button slowly fades the ink away. Typography: an elegant vertical title using writing-mode: vertical-rl. Delight: an occasional falling ink droplet when idle; ink leaves faint tidelines at its edges. Must run smoothly on laptops and lower its resolution on mobile. SHARED REQUIREMENTS (apply to every page in this 100-page collection): 1. One standalone HTML5 file. All CSS inline in