Prototype

Emil KowalskiCommunityCreated by Emil Kowalski

Skill
Content generator
Software development
MIT
No issues found

From the author

Build multiple genuinely different versions of a UI piece you describe, rendered behind a visual picker so you can flip through them live and promote the one that feels right. Only runs when explicitly invoked; it does not trigger on its own.

— the description by Emil Kowalski

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

The prototype skill enables design engineers to explore multiple, genuinely different UI directions for a single component. By enforcing a strict divergence-based workflow, it ensures that each variant represents a unique design axis—such as layout, personality, or interaction model—rather than minor cosmetic tweaks. The skill manages the creation of an isolated prototype harness, allowing users to flip through fully functional, high-fidelity variants in a realistic context before promoting a final choice into the production codebase.

What it does

Scopes a UI request to a single, high-leverage component.
Maps project tokens and context to ensure prototypes feel native.
Generates 3 to 5 distinct design variants based on unique axes.
Builds an isolated picker harness for live, full-size comparison.
Integrates the chosen variant into the production codebase.
Cleans up prototype artifacts after a selection is made.

When to use it

When you need to explore different UI directions for a specific component.
When you want to compare interaction models or layouts in a realistic context.
When you need to make an informed design decision based on live, functional prototypes.
When you want to ensure a new UI piece aligns with existing design tokens.

Advantages

Prevents design stagnation by forcing genuine divergence.
Maintains high craft standards for motion and interaction in every variant.
Provides a realistic environment for UI evaluation rather than static mockups.
Keeps production code clean by isolating exploration in a separate surface.
Facilitates objective decision-making through side-by-side comparison.

Usage examples

“Create a new pricing card for our dashboard.”: The agent scopes the request, maps the project's design tokens, generates 3 distinct variants (e.g., Quiet, Editorial, Playful), and provides a URL to a picker harness for live comparison.
“riff Editorial”: The agent keeps the existing harness and generates a new set of variants that diverge specifically around the 'Editorial' direction previously explored.
“keep Playful”: The agent integrates the 'Playful' variant into the production codebase following project conventions and deletes the prototype surface.

Install

Download the skill as a ZIP:
https://mp-staging.autogineer.com/agent-skills/emilkowalski/prototype/download
Unzip it into the cross-client skills folder of your project:
```
mkdir -p .agents/skills && unzip prototype.zip -d .agents/skills
```

Documentation by Emil Kowalski

Prototyping Variants

Initial Response

When this skill is first invoked without a specific question, respond only with:

I'm ready to build several genuinely different versions of a UI piece for you to flip through, my craft bar comes from Emil Kowalski's design engineering philosophy.

Do not provide any other information until the user asks a question.

A divergence skill. It does ONE thing: take a described piece of UI ("a toast", "the pricing card", "a hold-to-delete button"), build several genuinely different versions of it, and put them behind a visual picker so the user can flip through them live and choose a winner. It does not review existing UI (that's review-animations), plan fixes for it (that's improve-animations), or choose dependencies (that's pick-ui-library).

Operating Posture

You are a senior design engineer running a design exploration. The entire value of this skill is divergence: three tints of the same idea waste the picker — the user learns nothing by flipping between them. Each variant must be a direction you could defend shipping on its own, exploring a genuinely different answer to the same brief.

Divergence is not an excuse to drop the craft bar. Every variant individually meets Emil Kowalski's standards — right easing (ease-out on entrances, never ease-in), sub-300ms UI motion, correct transform-origin, transform/opacity only, reduced-motion handled. A sloppy variant doesn't widen the exploration; it just loses on execution and teaches nothing about the direction it represents.

Hard Rules

Never touch production code during exploration. Everything lives in an isolated prototype surface (see Phase 4). Integration happens only in Phase 6, only for the variant the user picked.
Variants diverge on a named axis — layout, density, personality, motion, interaction model. Before building, you must be able to state each variant's axis in a phrase. Sharing the project's tokens is not convergence; variants should feel native to the product.
Every variant fully works. Real interactions, real motion, realistic content — actual product-shaped copy, plausible names and numbers. No lorem ipsum, no dead buttons, no "imagine this part".
The picker is chrome, not a contestant. Its exact markup, styles, and behavior are specified in PICKER.md — copy them verbatim. Its look is not a design decision and never adapts to the project.
Clean up after the choice. When a winner is promoted, delete the prototype surface unless the user asks to keep it.

Workflow

Phase 1 — Scope

One thing per run. If the description spans multiple components ("the dashboard"), narrow it: pick the single highest-leverage piece, say which and why, and offer the rest as follow-up runs. Restate the brief in one sentence — what the thing is, where it will live, what it must do.

Phase 2 — Recon

Before designing anything, map the ground the variants must stand on:

Stack: framework, styling system (Tailwind, CSS modules, vanilla), motion library if any.
Tokens: colors, radii, spacing, fonts, easing/duration variables. Variants use these — every variant should look like it could ship in this product tomorrow.
Personality: playful consumer app or crisp dashboard? This bounds how far the boldest variant may go.
Context: where the piece renders — against what background, beside what neighbors, at what sizes.

If there is no project (empty directory, or the user is just exploring), skip to the standalone branch in Phase 4 and choose a restrained default look: neutral grays, one accent, system font stack.

Phase 3 — Choose directions

Default 3 variants; up to 5 when the user asks or the design space is genuinely wide. More than 5 dilutes the comparison.

Before writing any code, list the set: a name and an axis for each. Names describe the direction — "Quiet", "Editorial", "Playful", "Dense" — never "Option A/B/C". If two proposed directions would differ only in accent color or copy, they are one direction; replace one with a real alternative (different layout, different interaction model, different motion story).

Completion criterion: every variant has a name and a stated axis, and no two variants share an axis position.

Phase 4 — Build the picker harness

Two branches, by what exists:

In a project with a dev server — an isolated route or page (/prototypes/<slug>, or the framework's equivalent), one file per variant plus a small harness file. Nothing imports from the prototype surface into production code.
No project / static context — a single self-contained HTML file (inline CSS/JS) the user can open directly in a browser.

The picker's markup, styles, keyboard wiring, and placement come from PICKER.md, verbatim — load it now and build exactly that. Beyond the picker itself, the harness must render one variant at a time, full size, in realistic surrounding context — a toast needs a page behind it, a card needs siblings, a button needs a form. Side-by-side thumbnails distort spacing and scale; never judge UI at postage-stamp size. Switching is instant — flipping is a 100+/session action; by the frequency rule the variant swap gets no animation.

Phase 5 — Verify and hand off

Run the harness. Confirm every variant renders, every interaction responds, and the console is clean — flip through all of them yourself before showing the user. If browser tooling is available, screenshot each variant.

Then present the set and stop — the choice belongs to the user:

#	Variant	Axis	When it's the right choice	Its cost
1	Quiet	Minimal motion, borders over shadows	The product is a daily-use tool	Least memorable
2	Editorial	Large type, generous whitespace	The moment deserves weight	Eats vertical space

Close with where the picker is running (URL or file path) and the keys to flip.

Completion criterion: every variant is reachable from the picker and behaves correctly; no console errors; the table names each variant's tradeoff honestly.

Phase 6 — Promote on selection

When the user picks: integrate that variant where it belongs, following the project's existing conventions (file layout, naming, token usage), then delete the prototype surface per Hard Rule 5. If the user instead wants another round, keep the harness and run Phase 3 again, diverging around the direction they gravitated to.

Invocation Variants

Invocation	Behavior
`<description>`	Full workflow: scope → recon → 3 variants → picker → wait for choice
`<description> x5`	Same, with that many variants (capped at 5)
`riff <variant>`	New round: keep the harness, generate a fresh set diverging around the named variant's direction
`keep <variant>`	Promote that variant into the codebase and delete the prototype surface
`keep <variant>, leave the picker`	Promote, but keep the prototype surface around

Tone

Sell each variant honestly — one line on when it wins, one on what it costs. Never pre-pick a favorite in the table; if the user asks which you'd choose, answer with a reason rooted in the product's personality and frequency of use, not aesthetics alone. If two variants converged while you built them, cut one and say so: a picker with two truly distinct directions beats one padded to three.

Files

ATTRIBUTION.mdAdded by AutoGineer859 B
LICENSELicence file added by AutoGineer1.0 KiB
PICKER.md7.4 KiB
SKILL.md7.6 KiB

PICKER.md

The Picker

The picker's appearance is not a design decision — it is this spec. Copy the markup, CSS, and wiring below verbatim; the only values that change per run are the variant names and count. It stays identical across every project so it always reads as harness chrome, never as part of the design being judged. Do not restyle it with the project's tokens, fonts, or colors.

It is a floating dark pill, bottom-center. Dark glass works on top of any page — light or dark — which is why it is not theme-aware.

Markup

The sliding highlight span first, one button per variant, a hairline divider, then the replay button (only when at least one variant has motion to re-trigger):

<nav class="proto-picker" aria-label="Prototype variants">
  <span class="proto-picker-highlight" aria-hidden="true"></span>
  <button class="proto-picker-item" data-active aria-current="true">Quiet</button>
  <button class="proto-picker-item">Editorial</button>
  <button class="proto-picker-item">Playful</button>
  <span class="proto-picker-divider" aria-hidden="true"></span>
  <button class="proto-picker-item proto-picker-replay" aria-label="Replay animation (R)">↻</button>
</nav>

In a framework, keep the class names and structure; only the rendering syntax changes.

Styles

.proto-picker {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 2147483647;
  display: flex;
  align-items: center;
  gap: 2px;
  padding: 4px;
  border-radius: 999px;
  background: rgba(10, 10, 10, 0.82);
  -webkit-backdrop-filter: blur(12px) saturate(1.4);
  backdrop-filter: blur(12px) saturate(1.4);
  box-shadow:
    0 0 0 1px rgba(255, 255, 255, 0.08) inset,
    0 8px 24px rgba(0, 0, 0, 0.24),
    0 2px 6px rgba(0, 0, 0, 0.12);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 13px;
  line-height: 1;
  -webkit-font-smoothing: antialiased;
  user-select: none;
  -webkit-user-select: none;
}

.proto-picker-highlight {
  position: absolute;
  top: 4px;
  left: 0;
  height: 28px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.12);
  will-change: transform;
}

/* The slide is enabled only after first paint (data-ready), so load doesn't animate. */
.proto-picker[data-ready] .proto-picker-highlight {
  transition:
    transform 250ms cubic-bezier(0.23, 1, 0.32, 1),
    width 250ms cubic-bezier(0.23, 1, 0.32, 1);
}

@media (prefers-reduced-motion: reduce) {
  .proto-picker[data-ready] .proto-picker-highlight { transition: none; }
}

.proto-picker-item {
  position: relative; /* sits above the highlight */
  display: flex;
  align-items: center;
  height: 28px;
  padding: 0 12px;
  border: 0;
  border-radius: 999px;
  background: transparent;
  color: rgba(255, 255, 255, 0.55);
  font: inherit;
  cursor: pointer;
  transition: color 150ms ease-out;
}

.proto-picker-item:hover {
  color: rgba(255, 255, 255, 0.85);
}

.proto-picker-item:active {
  transform: scale(0.97);
}

.proto-picker-item:focus-visible {
  outline: 2px solid rgba(255, 255, 255, 0.4);
  outline-offset: 2px;
}

.proto-picker-item[data-active] {
  color: #fff;
}

.proto-picker-divider {
  width: 1px;
  height: 16px;
  margin: 0 4px;
  background: rgba(255, 255, 255, 0.12);
}

.proto-picker-replay {
  padding: 0 10px;
  font-size: 14px;
}

.proto-picker[data-position="top"] {
  bottom: auto;
  top: 24px;
}

Rules

Verbatim. These values are the spec. No project fonts, no brand colors, no theme switching, no extra shadows or borders.
The highlight slides; the variant swap stays instant. The active pill animates between buttons (250ms, strong ease-out) as spatial feedback on the picker itself — but the variant being previewed still switches with no transition. The width transition is a deliberate exception to the transform/opacity rule: the element is 28px tall, absolutely positioned, and has no layout dependents, so the paint cost is negligible.
One allowed modification: if a variant occupies the bottom-center of the screen (a toast stack, a bottom sheet, a dock), set data-position="top" so the picker never covers the work. Nothing else about it may move or change.
Replay is conditional. Render the replay button and its divider only when at least one variant has an entrance or state animation worth re-triggering; a static comparison gets a shorter pill.

Behavior contract

The contract is fixed regardless of how the harness renders:

Number keys 1–N and ←/→ switch variants; R replays. Ignore key events when focus is in an input, textarea, select, or contenteditable, or when a modifier is held.
Clicking an item switches to it; exactly one item carries data-active and aria-current="true" at all times, and the highlight slides to it.
Selection persists across reload via a URL param (?v=2), falling back to variant 1. The highlight takes its initial position without animating (data-ready is added after first paint).
Switching re-mounts the variant (so entrance animations re-run); the replay key re-mounts without switching.

Reference wiring

Verbatim for the standalone-HTML branch; in a framework, keep the same behavior but express it idiomatically (state instead of innerHTML, a keyed re-mount instead of requestAnimationFrame, refs + a layout effect for the highlight measurement).

// `variants` is an array of render functions, one per variant, in picker order.
const stage = document.getElementById('stage');
const picker = document.querySelector('.proto-picker');
const highlight = picker.querySelector('.proto-picker-highlight');
const items = [...picker.querySelectorAll('.proto-picker-item:not(.proto-picker-replay)')];
const replay = picker.querySelector('.proto-picker-replay');
let current = 0;

function moveHighlight() {
  const el = items[current];
  highlight.style.width = el.offsetWidth + 'px';
  highlight.style.transform = `translateX(${el.offsetLeft}px)`;
}

function mount(i) {
  stage.innerHTML = '';
  // Clear first, render next frame, so entrance animations re-run.
  requestAnimationFrame(() => { stage.innerHTML = variants[i](); });
}

function setActive(i) {
  if (i < 0 || i >= variants.length) return;
  current = i;
  items.forEach((el, j) => {
    el.toggleAttribute('data-active', j === i);
    if (j === i) el.setAttribute('aria-current', 'true');
    else el.removeAttribute('aria-current');
  });
  moveHighlight();
  const url = new URL(location);
  url.searchParams.set('v', i + 1);
  history.replaceState(null, '', url);
  mount(i);
}

items.forEach((el, i) => el.addEventListener('click', () => setActive(i)));
replay?.addEventListener('click', () => mount(current));
window.addEventListener('resize', moveHighlight);

document.addEventListener('keydown', (e) => {
  if (/^(INPUT|TEXTAREA|SELECT)$/.test(e.target.tagName) || e.target.isContentEditable) return;
  if (e.metaKey || e.ctrlKey || e.altKey) return;
  const num = parseInt(e.key, 10);
  if (num >= 1 && num <= variants.length) setActive(num - 1);
  else if (e.key === 'ArrowRight') setActive((current + 1) % variants.length);
  else if (e.key === 'ArrowLeft') setActive((current - 1 + variants.length) % variants.length);
  else if (e.key === 'r' || e.key === 'R') mount(current);
});

setActive((parseInt(new URLSearchParams(location.search).get('v'), 10) || 1) - 1);
// Enable the slide only after first paint, so load doesn't animate.
requestAnimationFrame(() => requestAnimationFrame(() => picker.setAttribute('data-ready', '')));

Requirements and compatibility

Written for: Claude Code

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Claude Code frontmatter

Security

No issues found by our static scan· No issues found

A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.

Attribution and licence

Created by

Emil Kowalski

Publisher

Emil Kowalski (Community)

Source

emilkowalski/skills · skills/prototype · commit c8a7962

Licence

MIT License (redistribution allowed)

LICENSE (added by AutoGineer from LICENSE)
ATTRIBUTION.md (written by AutoGineer)

Synced

2026-11-08

AutoGineer is not affiliated with or endorsed by Emil Kowalski.

Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download prototype.zip