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Tweaks Skill

Free

Live parameterized controls for HTML design variants.

by nexu-io84.9k stars on nexu-io/open-design
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Updated Aug 10, 2026
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Free · Opens the source repo

What Tweaks Skill does

The Tweaks Skill allows users to wrap any HTML artifact with a sidebar of live controls, enabling real-time adjustments to CSS custom properties. This skill is particularly useful for designers and developers who need to explore different design variants without the need to re-prompt the coding agent. By providing a set of customizable parameters such as accent color, type scale, density, motion, and theme, users can interactively modify their designs and see the effects immediately. The changes are saved to localStorage, ensuring that user preferences persist across sessions.

When utilizing the Tweaks Skill, users will produce a self-contained HTML file that consists of two main components: the original artifact (which could be a landing page, dashboard, or presentation) and a fixed sidebar panel that houses the controls. The panel is designed to be intuitive, allowing users to toggle visibility with keyboard shortcuts and reset to default settings easily. This approach not only enhances the user experience but also allows for a more engaging presentation of design systems or brand elements.

This skill is ideal for situations where a user has a design that is mostly complete but requires fine-tuning. It is also beneficial when showcasing design systems to an audience, allowing them to interact with the design in real time. However, it is less suitable for static artifacts that do not require iteration or for designs where precise ratios are critical, such as infographics. Overall, the Tweaks Skill is a powerful tool for anyone looking to enhance their design workflow with interactive capabilities.

When to use it

Use this skill when you want to fine-tune a design or present multiple design options interactively.

When not to use it

Avoid using it for static designs that won't be modified or where fixed ratios are essential to the design's integrity.

What you can build with it

Fine-Tuning a Design

When a designer has an artifact that is 80% complete, they can use the Tweaks Skill to make precise adjustments to the remaining 20%.

Interactive Design Presentations

When presenting a design system, the Tweaks Skill allows the audience to interact with the design and see live variations.

Standalone Demos

For portfolio pieces or demos, using the Tweaks Skill enables viewers to explore different design options interactively.

How to install Tweaks Skill

View source

1. Install with the skills CLI

npx skills add nexu-io/open-design/tweaks --agent claude-code

2. Or install it manually

Download the skill folder and drop it into ~/.claude/skills/ for all projects, or .claude/skills/ to scope it to one repo. Restart Claude Code so it picks up the new skill.

Anthropic's agentic coding CLI, and the reference implementation of Agent Skills. Drop a skill folder into ~/.claude/skills and Claude Code loads it automatically whenever a task matches the skill's description. Claude Code docs

Inside SKILL.md

Written by nexu-io

Tweaks Skill · 参数化变体面板

Wrap any HTML artifact with a side panel of live controls that rewrite CSS custom properties in real time and persist to localStorage. Inspired by the huashu-design tweak pattern.

What you produce

A single self-contained HTML file with two layers:

  1. Stage — the original artifact (landing page / deck / dashboard) re-keyed so all visual decisions read from CSS custom properties: --accent, --scale, --density, --mode, --motion.
  2. Panel — a fixed sidebar (or drawer on small viewports) with form controls bound to those custom properties via a tiny vanilla-JS bridge. Persists every change to localStorage keyed by the artifact identifier.

The user can:

  • Open the artifact and see the stage rendered with their saved preferences (or sensible defaults).
  • Adjust accent / scale / density / mode / motion in the panel and watch the stage update instantly — no rerender.
  • Press <kbd>T</kbd> to hide / reveal the panel; <kbd>R</kbd> to reset to defaults.
  • Refresh the page — every choice is persisted.

When to use

  • The user generated something they like 80% of, and wants to dial in the last 20% themselves.
  • You're presenting a design system / brand and want the audience to feel the variants live (instead of you re-running the agent).
  • You're shipping a stand-alone demo (e.g. a portfolio piece) and want viewers to play.

When not to use

  • One-shot artifacts that won't be iterated on (e.g. a runbook — parameters don't help).
  • When the artifact's value is in fixed ratios (e.g. an infographic with carefully balanced data viz — knobs would degrade it).

The 5 standard knobs

Pick a subset that suits the artifact. Don't ship all 5 if only 2 matter — clutter is a regression.

1. --accent — Accent color

A select with 5–8 curated swatches (don't ship a free color picker — the user will pick a bad color and blame you).

const ACCENT_PRESETS = [
  { id: 'rust',    val: '#c96442', label: 'Rust' },
  { id: 'cobalt',  val: '#2c4d8e', label: 'Cobalt' },
  { id: 'sage',    val: '#4a7a3f', label: 'Sage' },
  { id: 'plum',    val: '#7a3f6a', label: 'Plum' },
  { id: 'graphite',val: '#3a3a3a', label: 'Graphite' },
];

The artifact uses var(--accent) everywhere it had a hard-coded accent before. Border / link / pull-quote rule / CTA all flip together.

2. --scale — Type scale (0.85 / 1.0 / 1.15)

Three settings: Compact (0.85), Normal (1.0), Generous (1.15). All font-size declarations multiply by var(--scale) via calc(... * var(--scale)).

Don't go beyond ±15% — beyond that the layout breaks (column flow, breakpoints, line counts).

3. --density — Layout density (Tight / Normal / Roomy)

Three settings that swap the spacing scale: Tight (0.75) / Normal (1.0) / Roomy (1.4). All padding / gap / margin declarations multiply by var(--density).

This is the highest-impact knob — it's also the most fragile, so every layout-critical container must declare its base spacing in custom properties before you wrap.

4. --mode — Light / Dark

A 2-state toggle. Sets data-mode="light" vs "dark" on the <html> element and the artifact's :root selector responds with two color sets.

If the artifact already has a media-query-based dark mode, replace it with the data-attr version — the user's choice should win over their OS.

5. --motion — Off / Subtle / Lively

Three settings. Maps to a CSS variable --motion-mult that scales all transition-duration / animation-duration declarations:

  • Off — 0s (also disables WebGL canvases / decorative animation).
  • Subtle — 1.0 (the artifact's authored timing).
  • Lively — 1.6 (slower transitions, more visible motion).

Respect prefers-reduced-motion: default to Off if the user has that set, regardless of stored preference.

Host integration contract (REQUIRED)

The Open Design viewer toolbar has a Tweaks toggle that drives panel visibility from outside the iframe. For the toggle to bind to your panel, your artifact must speak one of these two protocols (pick one; don't mix). The toolbar enables itself the moment it sees either signal.

Protocol A — postMessage (recommended for agent-generated artifacts)

Use this when the panel mounts via JS (React, vanilla, anything dynamic).

Artifact → host:

  • On mount, post { type: '__edit_mode_available', visible?: boolean } to window.parent. Tells the toolbar a panel exists; the optional visible reports the panel's initial state so the toolbar toggle starts in sync. Omit visible for the common "panel is already on screen" case (the host treats a missing field as true so the legacy zero-arg message keeps working). Pass visible: false to declare a default-closed panel.
  • When the user closes the panel locally (× button, Esc, etc.), post { type: '__edit_mode_dismissed' }. Toolbar flips to "off".

Host → artifact:

  • { type: '__activate_edit_mode' } — open the panel (setOpen(true)).
  • { type: '__deactivate_edit_mode' } — close the panel (setOpen(false)).

Minimal listener:

window.addEventListener('message', (e) => {
  const t = e?.data?.type;
  if (t === '__activate_edit_mode') setOpen(true);
  else if (t === '__deactivate_edit_mode') setOpen(false);
});
// Or, for a default-closed panel:
//   window.parent.postMessage({ type: '__edit_mode_available', visible: open }, '*');
window.parent.postMessage({ type: '__edit_mode_available' }, '*');
// in your close handler:
const dismiss = () => {
  setOpen(false);
  window.parent.postMessage({ type: '__edit_mode_dismissed' }, '*');
};

Panel may default to open or closed — the host syncs its toggle to whichever state the artifact reports.

Protocol B — class-based (used by assets/wrap.html)

Use this only when you wrap the template verbatim. The artifact ships a .tw-panel element and toggles a .tw-hidden class for visibility. The viewer's iframe bridge (in apps/web/src/runtime/srcdoc.ts) hides the panel on initial paint, watches the class via MutationObserver, and relays state both directions. No JS required in the artifact beyond what the template already includes.

Selectors are fixed: .tw-panel (the panel root) and .tw-hidden (the hidden state). If you rename either, the bridge can't find it.

Anti-pattern

Don't invent a third protocol or rename either set of identifiers. The toolbar toggle only binds to A or B. Custom panels with custom classes and no postMessage will leave the toolbar greyed out.

Implementation primitives

Read assets/wrap.html — it ships the panel + bridge as an inert template. Your job is to:

  1. Take the user's existing artifact HTML.
  2. Lift its accent / mode / spacing / scale into custom properties (search for hard-coded #hex / Npx / Nrem and convert).
  3. Paste the contents into the marked region of wrap.html.
  4. Edit assets/wrap.html's KNOBS array to keep only the knobs you decided are relevant to this artifact. Don't ship 5 if 2 matter.
  5. Patch the STORAGE_KEY to a unique slug (tweaks-<artifact-slug>).

The bridge in wrap.html:

  • Loads localStorage[STORAGE_KEY] JSON on first paint.
  • Applies values as document.documentElement.style.setProperty('--accent', ...).
  • Listens to every form control's change event and writes back.
  • Exposes <kbd>T</kbd> (toggle panel) and <kbd>R</kbd> (reset).

Workflow

Step 1 — Acquire the artifact

Same options as the critique skill:

  1. Project file (index.html in the project folder).
  2. Pasted HTML in the chat.
  3. Generated by you in this turn.

Step 2 — Decide which knobs apply

Read the artifact's CSS first. For each knob, decide yes / no:

  • --accent — yes if the artifact has 1 accent color used ≥ 3 times.
  • --scale — yes if the artifact is type-driven (article, deck, pricing page).
  • --density — yes if the artifact has consistent gap / padding rhythm (deck, dashboard, landing). No for runbooks (already dense).
  • --mode — yes if the artifact has authored dark mode tokens, or you're willing to derive them.
  • --motion — yes if the artifact has any transition / animation worth scaling. No for static reports / critique reports.

Default: 3 knobs is the sweet spot. Five is too busy, one is not worth a panel.

Step 3 — Lift hard-coded values into custom properties

Open assets/wrap.html's <style> block — copy its custom-property naming scheme (--accent, --scale, etc.). In the user's artifact, find every place those concerns live and rewrite:

  • color: #c96442 → color: var(--accent)
  • font-size: 18px → font-size: calc(18px * var(--scale))
  • padding: 24px 32px → padding: calc(24px * var(--density)) calc(32px * var(--density))
  • transition: opacity 200ms → transition: opacity calc(200ms * var(--motion-mult))

If the artifact uses clamp() or vw already, multiply the outer value by the custom property — don't tear apart clamp(...).

Step 4 — Paste into the wrap

Copy the artifact's <style> and <body> into the marked regions of wrap.html. Keep the panel + bridge intact.

Step 5 — Test the loop

Open the result, click each knob at least once, refresh the page, confirm the choice persists. If a knob breaks the layout — remove it, don't ship it.

Output contract

<artifact identifier="tweaks-<artifact-slug>" type="text/html" title="<Artifact Title> · Tweaks">
<!doctype html>
<html>...</html>
</artifact>

One sentence before the artifact ("Wrapped X with a 3-knob tweak panel — accent / scale / mode."). Stop after </artifact>.

Hard rules

  • Don't ship a free color picker — only curated swatches. Users pick bad colors when given freedom; saving them from that is the whole point.
  • Persist by artifact identifier — tweaks-<slug>, not a global key. Two artifacts open in two tabs must not share state.
  • Respect prefers-reduced-motion — default to Off for motion if the user has that set, override only on explicit click.
  • Single-file — no external CSS / JS / fonts beyond the artifact's existing imports. Inline the panel + bridge.
  • Panel hidden by default on viewports < 720px — slide-in drawer via a "T" button at top-right.
  • Don't ship more than 5 knobs. Three is the sweet spot.

Frequently asked questions about Tweaks Skill

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