Prototyping Variants

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

1. Variants live in the real app. Every variant is built on the real route, on the working branch, behind a dev-only ?variant= switch (see Phase 4). Never build a standalone HTML file, a prototype/<slug> branch, or an isolated /prototypes/<slug> route. Only the variant the user picked survives Phase 6.
2. 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.
3. 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".
4. 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.
5. Clean up after the choice. When a winner is promoted, remove the ?variant= switch and the losing variants unless the user asks to keep them.

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), stop and ask for the real app and route the variants will live in.

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

Variants live in the real app, on the real route, on the working branch, behind a dev-only ?variant= switch: one file per variant plus a small switch where the piece renders, which reads ?variant= and shows the picker only in development. Never a standalone HTML file, a prototype/<slug> branch, or an isolated /prototypes/<slug> route.

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 the route URL where the picker is running 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 remove the ?variant= switch and the losing variants 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
combine <variant>:<piece>, <variant>:<piece>	New round: keep the harness, merge the named pieces of those variants into a fresh set
keep <variant>	Promote that variant and remove the ?variant= switch and the losing variants
keep <variant>, leave the picker	Promote, but keep the ?variant= switch and the losing variants around
reject	End the round with no variant kept: remove the ?variant= switch and every variant

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.