dithercn

dithercn is a dither engine. dither-core (installed into lib/dither) turns a tone you compute into ordered dither dots, in your theme's colours, with motion, resizing and reduced motion handled. You build the dither the user asked for on top of it. The dithercn components are examples of what the engine can do, not a menu to pick from. Install one only when it is exactly what the user asked for. Otherwise write your own, and borrow technique from the closest example's source.

1. Set up the engine

Find the engine: lib/dither/index.ts, under the lib alias in components.json (imports below use @/lib/dither; use the project's alias). If it is missing, install it from the dithercn registry:

npx shadcn@latest add https://dithercn.dev/r/dither-core.json

If it exists, check that it is current: grep -q colorField lib/dither/shader.tsx (with the project's path). An engine installed before colorField existed lacks it and the spectrum and paletteColor helpers, and TypeScript reports Property 'colorField' does not exist. Replace the engine's files; this keeps the project's lib/utils.ts (yes n answers no to every question about overwriting a file) and restores lib/dither/export.ts:

rm -rf lib/dither && yes n | npx shadcn@latest add https://dithercn.dev/r/dither-core.json https://dithercn.dev/r/dither-export.json

Don't use --overwrite: it also replaces lib/utils.ts. If the project edited files inside lib/dither, tell the user before replacing them.

That also installs dither-tokens: the CSS variables --dither-ink, --dither-paper, --dither-cell, --dither-bloom and --dither-color-<name>, written into the project's global CSS and mapped to the shadcn --primary and --background. The engine needs React 19 and Tailwind CSS v4.

Done when lib/dither/index.ts exists, lib/dither/shader.tsx mentions colorField, and the global CSS defines --dither-ink.

2. Pick the technique

Combine them freely: a dashboard card can hold an SVG meter with FillPattern over a DitherShader glow.

The examples in examples.md (written when the skill is installed; if it's missing, read https://dithercn.dev/.well-known/agent-skills/dithercn/references/examples.md) are references. If the user asked for exactly one of them, install it. If not, write your own: read the closest example's source for its field or SVG, then build the design the user described. Never swap the request for an example that is merely nearby, and never guess at an example's props; read its docs page or source.

Done when every visual in the request has a technique.

3. Build it

If the dither is for a landing page, or a section of one, read landing-pages.md before anything else. A good dither on a generic page still looks generated: the page has to be about the product, and the dither has to come from it.

1. Read the reference named for your technique, and recipes.md for complete, working components to adapt.
2. Write the component in its own file. "use client" when it uses DitherShader, hooks or a canvas; FillPattern, DitherPattern, fillStyle and ditherMaskStyle render on the server.
3. Give it typed props for what the user would tweak (colour, intensity, speed, scale, value), with defaults that already look good.
4. Place it with placement.md: a shader fills a positioned parent (absolute inset-0), and content sits in a sibling above it.
5. Colour it with theme.md: palette names such as "ink" and "blue", or CSS variables, so it follows light and dark.

Done when the component renders the requested look with no [dither-core] errors in the console.

4. Check it in a browser

Open the page and look at it. Screenshot it if you can, at desktop and phone widths, in light and dark mode, and once with reduced motion (prefers-reduced-motion: reduce). Hold it to quality.md.

Done when every check in quality.md passes. A screenshot that shows flat colour, a solid block or an empty box means the field returns the wrong range or the parent has no size: fix it and look again.

Rules for every dither

• A field returns a continuous tone in [0, 1]: 0 paper, 1 ink. The engine quantises and dithers it, so write smooth math (smoothstep, exp, mix) and leave thresholds and Bayer matrices to the engine.
• uv runs 0 to 1 on both axes with y up. Multiply x by res.x / res.y before measuring distances, or circles stretch into ovals.
• Paint with theme colours ("ink", palette names, --css-variables). Literal colours, and spectrum() in a colorField, are for when the user asks for specific colours or a rainbow.
• Text sits on clear ground. Fade the tone down where text goes: to 0 for lines and sparse patterns, to 0.2 or less for soft fills. Text contrast stays at 4.5:1 or better.
• Motion is slow, a drift of a few percent of the box per second. Choose stillTime so the reduced-motion frame looks finished.