Design (entry)

Use this skill when the user asks to build or style web UIs: components, pages, dashboards, landing pages, React/Vue/HTML-CSS layouts, or any frontend interface. Goal: distinctive, production-grade output that avoids generic AI aesthetics.

Before reporting any design "done": render it and have a separate judge critique the image (not the code, not self-grading) — see design-spatial §1. Blind generation can't see its own collisions; this applies to all design output, not just spatial work.

MANDATORY HORIZONTAL-OVERFLOW GATE — runs before ANY web UI is "done". Measure document.documentElement.scrollWidth - document.documentElement.clientWidth at a narrow width (~390px and ~1024px), this turn, and confirm it's 0. This bug is invisible at desktop width and re-appears every time a row (header, nav, toolbar) gains an item, so it ships repeatedly. Default to flex-wrap:wrap on header/toolbar rows + body{overflow-x:clip}, and re-measure after adding any element to a horizontal row. Full procedure + recurrence cases: design-spatial §4. If you haven't measured narrow, you are not done — don't claim it.

Sub-skills (load when relevant)

• design-thinking — Load for every design task. Defines purpose, tone, domain, color world, review bar, and cross-domain lens (cinema, architecture, marketing, UX, automotive, industrial design). See design-thinking/SKILL.md.
• design-system — Load when implementing: tokens, typography, motion, color semantics, backgrounds. Use when building components, pages, or design systems. See design-system/SKILL.md.
• design-spatial — Load when composing layout: explicit grid + 8-point spacing constraints, visual-weight/balance/alignment, and a render-then-critique vision loop. The fix for "spatial understanding is off" — generated layout that's centered mush, misaligned, or breaks at some widths. See design-spatial/SKILL.md.
• design-ux — Load when auditing USABILITY (not just looks): a UI that "feels off"/"sucks to use", is hard to learn, needs an instruction wall, or any interactive tool/editor/app before shipping. Scores the rendered UI against Nielsen's 10 + interaction heuristics via a SEPARATE fresh-eyes judge → prioritized fix list. Usability ≠ aesthetics. See design-ux/SKILL.md.
• design-philosophy — Load for high-concept work, campaigns, or when the user asks for a visual philosophy, manifesto, or unmistakable art-like aesthetic. See design-philosophy/SKILL.md.

Visual assets — generate or source

When design-thinking identifies a need for visual assets (logos, icons, hero images, textures, backgrounds):

1. Generate → use an image-generation model or API for synthetic/branded assets.
2. Source a real/archival one → free stock or archival image search, often cheaper and more authentic than generating.
3. Use design-thinking output (tone, domain, color world) to craft prompts / queries.
4. Evaluate against the design philosophy, refine, integrate into the build.

LLM-assisted work — always annotate model + cost

When design work involves running an LLM (generative assets, VLM analysis, layout critique, prompt generation, etc.):

• Before running: state which model will be used and the estimated cost (e.g., "gpt-4o-mini · ~$0.005/image" or "FLUX v1 · ~$0.006 per gen").
• After results: annotate the output with the model used, actual cost if different from estimate, and any key params (seed, prompt, settings). Cost goes visible to the user (in the message, contact sheet header, or asset caption), not buried in logs.
• Why: the user is deciding whether the cost-to-quality trade-off is worth it. Unlabeled or hidden costs hide the most important lever. This rule mirrors media-attribution-rule for generative assets and extends it to any LLM operation in the design workflow.

Examples:

• "Running gpt-4o-mini layout critique on 8 designs · est. ~$0.04 total" (before).
• Contact sheet header: "FLUX v1 · $0.48 total (6 gen × $0.08)" (after).
• Asset caption: "hero_banner_flux-dev_seed3891.jpg" (seeds enable reproducibility).
• Uncertainty slider result: "VLM triage on 46,978 images · gpt-4o-mini · ~$9.40" (before); "✓ Completed: 12,447 images classified · gpt-4o-mini · $7.62" (after).

Algorithm / model explainers — show the equation, annotate the terms

Whenever a UI surfaces an algorithm or model to the user (an "ⓘ how this works" panel, a model breakdown, a methods note), include the actual equation, typeset, with its key terms annotated — don't settle for prose. A scorer described only in words ("ranks by how much of the picked color is present") is unfalsifiable hand- waving; the formula score = Σ fracᵢ · max(0, 1 − ΔEᵢ/τ) with each term labelled tells the user exactly what the knob does and builds trust that there's real math under the hood.

How to apply:

• Render one clean, central equation per algorithm — the "sexy" core, not every detail. Use proper notation: σ for sigmoid, Σ for sums, ‖·‖ for norms, superscripts, ΔE, ∇²; a monospace/serif-math block set off from the prose.
• Annotate every symbol immediately below: what e_x, w, τ, Q each are, in one line each. An unlabelled equation is decoration; a labelled one is a spec.
• Keep it dependency-light — styled HTML/Unicode math is fine and works offline; only reach for KaTeX/MathJax if the expressions genuinely need it.
• State the decision rule alongside the score (e.g. "personal if P ≥ 0.55").
• This composes with the model+cost annotation above: the equation says what it computes, the model/cost line says what ran it and for how much.

Example (a logistic head):

P(personal │ x) = σ(w·eₓ + b), σ(z) = 1 / (1 + e⁻ᶻ) • eₓ — the image's 768-d embedding · w, b — weights learned from your labels · decision: personal if P ≥ 0.55, reference if P ≤ 0.40.

Select-all always has a deselect — no dead-end selections

Any "Select all" affordance MUST be paired with a way to clear the selection — preferably the same button, label-flipped when everything is already selected ("Select all" ⇄ "Deselect all"). A select-all with no inverse is a trap: the user over-selects (or hits it by reflex), then has to un-click items one by one, or reload the page, to get back. The cost is silent — it only bites after they've committed to the wrong set.

How to apply:

• Toggle the same button (simplest, fewest controls): when all visible items are selected, the button reads "Deselect all" and clears; otherwise "Select all". One control, no dead end.
• Or a separate Clear/Deselect shown whenever the selection is non-empty.
• The deselect must reach the same scope the select-all did (all shown, all filtered, all on this page) — don't let "Select all" grab 500 but "Clear" only drop the 50 on screen.
• This generalizes: any reversible bulk toggle (select, expand-all, mute-all, check-all) needs its inverse one tap away. Symmetry of action — see restraint-rule (don't strand the user mid-task).