Frontend Skill

Four modes: Design (UX copy, design systems, critique, accessibility, handoff, research), Distinctive (surface check, then brand-led visual direction for landing and campaign pages), HTML-Artifact (self-contained HTML generation with 8 shapes), and Three.js (3D web apps in imperative, R3F, or WebGPU paradigms).

Load first for any UI work

Before DESIGN, DISTINCTIVE, HTML-ARTIFACT, or a THREEJS UI overlay (HUD, menu, panel), read skills/shared-patterns/ui-design-judgment.md. Take starting values from ui-design-recipes.md and before/after fixes from ui-design-examples.md in the same folder. The mode references below add depth. Where they conflict with the core doc, the core doc wins. Every default can be overridden; state the reason.

Mode Selection

Classify the request into one mode before loading references.

Mode	Signals	What to Load
DESIGN	UX copy, design system, design critique, accessibility, WCAG, design handoff, user research	Design-refs per sub-mode table below
DISTINCTIVE	Frontend design, typography, visual identity, anti-cliche, text animation, card effects	references/distinctive-frontend-design-refs/ per step
HTML-ARTIFACT	HTML artifact, make HTML, as HTML, rich visualization, interactive document, pptx, deck	references/html-artifact-refs/ per shape
THREEJS	Three.js, 3D scene, WebGL, WebGPU, react three fiber, R3F, GLTF	references/threejs-builder-refs/ per paradigm

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DESIGN Mode

Design methodology: UX copy, design systems, critique, accessibility review, developer handoff, user research synthesis. Always load references/design-refs/llm-design-failure-modes.md alongside mode-specific reference.

Sub-mode Detection

Sub-mode	Signals	Load
UX-COPY	write copy, button text, error message, empty state, tooltip	references/design-refs/ux-copy.md
DESIGN-SYSTEM	design tokens, component library, audit components, theme	references/design-refs/design-systems.md
CRITIQUE	review design, critique mockup, design feedback, usability	references/design-refs/design-critique.md
ACCESSIBILITY	WCAG, accessibility audit, color contrast, keyboard nav, a11y	references/design-refs/accessibility-review.md
HANDOFF	developer handoff, spec sheet, implementation spec, responsive	references/design-refs/design-handoff.md
RESEARCH	synthesize research, interview analysis, usability findings	(inline below)

UX-COPY

1. Gather context: component type, user emotional state, brand voice, constraints, existing terminology.
2. Generate copy: primary recommendation with rationale, 2-3 alternatives, localization notes.
3. Validate: terminology consistency, action labels match outcomes, error messages follow What/Why/Fix, character limits met.

Gate: Copy for all requested components. Each piece has rationale. Alternatives differentiated.

DESIGN-SYSTEM

Three operations: Audit (naming consistency, token coverage, hardcoded values, state completeness), Document (props/variants/states/a11y/usage spec), Extend (new component using existing tokens). Use design token architecture: color, typography, spacing, borders, shadows, motion.

Validate: consistent naming, all values reference tokens, all states defined (default/hover/active/disabled/loading/error), ARIA documented.

CRITIQUE

Render or open the design first, then run the core doc's section 10 checks (three widths, squint, grayscale, edge content) and rank findings in its fix order: content and job, hierarchy, spacing, type, color, polish. Write each finding as element, problem, effect, fix. Apply Nielsen heuristics only where they explain a real finding. Match depth to stage: exploration (concept direction), refinement (hierarchy, patterns), final (contrast, spacing, a11y).

ACCESSIBILITY

Audit by WCAG principle: Perceivable (alt text 1.1.1, contrast 4.5:1 text / 3:1 UI), Operable (keyboard 2.1.1, focus order 2.4.3, touch 44x44px), Understandable (predictable 3.2.1, error ID 3.3.1), Robust (name/role/value 4.1.2). Report: severity matrix, each finding with WCAG criterion + remediation, contrast table, keyboard map.

HANDOFF

Gather: design source, tech stack, tokens, breakpoints. Generate spec covering: layout, tokens, components, states, interactions, content limits, edge cases (empty/loading/error/overflow/i18n), accessibility, animation. Validate: all states documented, token references used, edge cases present.

RESEARCH

Accept inputs (transcripts, surveys, support tickets). Extract observations and quotes -- behavioral data outweighs stated preferences. Synthesize via affinity mapping and theme development. Priority matrix (impact x frequency). Output: executive summary, themes with evidence, insights-to-opportunities table, user segments, recommendations.

Output Conventions

Markdown with tables. Severity: Critical (blocks users), Major (degrades), Minor (polish). Every recommendation names element + issue + concrete fix. Include what works alongside what needs improvement.

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DISTINCTIVE Mode

Brand-led visual direction for pages people visit once: landing, launch, portfolio, event. Output: tokens, base styles, and a rendered page.

Step 1: Surface check

Name the surface before any styling (core doc section 1):

Surface	Examples	Do this
Tool	dashboard, admin, editor, settings, internal app	Get real content (Step 2 item 1), then use the tool recipe in ui-design-recipes.md: one neutral sans (system UI font, Inter, Geist), tinted grays plus one accent, 4/8 spacing scale, borders over shadows, motion only for state changes. Build tokens (Step 6 item 1), then Step 7.
Brand page	landing, launch, portfolio, event, campaign	Continue with Step 2.
Mixed (marketing site with an app inside)	pricing page plus signed-in app	Brand rules for public pages, tool rules for the app.

Litmus: on a tool, a user who reads only headings, labels, and numbers understands the screen. On a brand page, a user who sees the first viewport for 3 seconds can name the product and its promise.

Step 2: Brief

1. Get real content: product name, headline, main action, real section copy. Mark missing items as placeholders (references/distinctive-frontend-design-refs/honest-placeholders.md).
2. Pick one page structure from references/distinctive-frontend-design-refs/macrostructure-catalog.md by heading anchor. Load only that entry.
3. Write three sentences: visual thesis (mood), content plan (sections in order, one job each), interaction thesis (the few motions that matter).
4. Write two candidate directions from the brand and audience, pick one, and say why. Use color-inspirations.json and font-catalog.json in references/distinctive-frontend-design-refs/ when the brand gives no lead. Do not default to serif display, cream background, and grain; that is the overcorrection tell. Direction examples and per-step values: references/distinctive-frontend-design-refs/phase-details.md.

Step 3: Type

Default: one display face plus one text face, both from font-catalog.json and matched to the direction. A neutral sans is a valid text face. Use the core doc's scale and line heights (section 4); body 16 px, headings 1.1-1.25 line height. Avoid reflexive picks: a face chosen because it is popular (Inter, Space Grotesk) or because it looks "not generic" (editorial serif) needs a brand reason on a brand page.

Step 4: Color

Start neutral: background, surface, border, and text grays tinted toward the brand hue. Add one brand accent for the main action, links, and selection; status colors are separate. A rough 60/30/10 split (neutral, secondary, accent) is a starting point, not a target. Build scales with references/distinctive-frontend-design-refs/oklch-color-harmony.md. Check contrast on real pairs: 4.5:1 body text, 3:1 large text and UI boundaries. Build dark mode from its own values (core doc section 5).

Step 5: Motion and background

• Motion: 2-3 intentional motions per page is a good budget (entrance, scroll, interaction). Use 150-250 ms ease-out for UI, up to 600 ms for a one-time hero entrance. Respect prefers-reduced-motion. Patterns: references/distinctive-frontend-design-refs/animation-patterns.md.
• Background: a solid surface is a valid default. Add at most one effect (gradient, pattern, texture) from references/distinctive-frontend-design-refs/background-techniques.md when it supports the brand and keeps text contrast.
• Hero: one composition, the product name at hero scale, one primary action. Full-bleed by default.

Step 6: Build and check

1. Emit the design stamp comment, CSS custom properties, and base styles (references/distinctive-frontend-design-refs/implementation-examples.md).
2. Run the advisory check: python3 ${CLAUDE_SKILL_DIR}/scripts-distinctive-frontend-design/validate_design.py --fonts "Display,Body" --palette palette.json --project NAME --macrostructure macro:ID --emitted-css generated.html. Fix warnings that apply; for the rest, state why the default does not fit. Add --strict to exit 1 below a score of 80.

Step 7: Look, then fix

Run the core doc's section 10 loop on the rendered page. This is the final step for every surface, including tools.

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HTML-ARTIFACT Mode

Generate single self-contained .html files. All CSS in <style>, all JS in <script>. No CDN links, no frameworks, no external deps. Max 500KB.

Local files only. Write the page to disk and open it in Google Chrome. Do not call the Artifact tool (publish or quickstart), the Claude Docs connector, or ArtifactData unless the user explicitly asks for a Claude Artifact by name. This rule overrides the Artifact tool's guidance to publish pages, reports, boards, and dashboards. For metrics dashboards, use Perses instead of a page.

Phase 0: Check Saved Template

Run: python3 ${CLAUDE_SKILL_DIR}/scripts-html-artifact/fill-template.py --list

If a saved template matches, clone it and fill slots only. Skip to Phase 4 VALIDATE. Do not restyle the template.

Phase 1: Detect Shape

Run: python3 ${CLAUDE_SKILL_DIR}/scripts-html-artifact/detect-shape.py --request "{request}"

Shape	Signals	Output
spec	plan, compare, brainstorm	Side-by-side grids, pro/con, SVG diagrams
code-review	review PR, explain diff	Diff rendering, severity colors, annotations
prototype	prototype, tune, try options	Sliders, CSS var live update, sandbox
report	report, summarize, status	TL;DR box, collapsibles, timeline, metrics
editor	reorder, triage, edit config	Drag-drop, kanban, toggles, export
data-viz	visualize, chart, dashboard	SVG charts, canvas, tooltips, filters
diagram	diagram, flowchart, architecture	Inline SVG, annotated flowcharts
deck	slides, presentation, pitch	Arrow-key nav, 16:9, progress bar

Low confidence falls back to report. Hybrid shapes: primary controls layout, secondary provides embedded components.

Phase 2: Assemble + Load Context

Run: python3 ${CLAUDE_SKILL_DIR}/scripts-html-artifact/assemble-template.py --shape {shape} --title "{title}" --components {components}

Load references/html-artifact-refs/design-system.md. Headings must use Archivo Black (embedded templates/fonts/archivo-black.css, weight 400, font-synthesis: none). The assembler injects it; hand-written artifacts inline that file rather than linking Google Fonts. validate-artifact.py errors without it. For diagram shapes, also load references/html-artifact-refs/shape-diagram-illustration.md and references/html-artifact-refs/diagram-layering.md. Per-shape must-include rules live in agents/html-builder.md.

Phase 3: Generate

Dispatch html-builder agent (see agents/html-builder.md) with pre-assembled template. Vanilla JS only. Semantic HTML. SVG inline.

Phase 4: Validate, then look

1. Run: python3 ${CLAUDE_SKILL_DIR}/scripts-html-artifact/validate-artifact.py {html_file}. Errors (structure, <title>, external deps, empty body) must be fixed; re-run up to 3 times. CSS slop findings are warnings: fix them or state why they fit this artifact.
2. Run the core doc's section 10 loop on the rendered file. This is the final check before delivery.

Phase 5: Deliver

Open the file in Google Chrome: open -a "Google Chrome" <file> on macOS, google-chrome <file> on Linux (check $DISPLAY/$SSH_TTY first; skip opening over SSH). Print the absolute file path and a 1-line summary. Do not publish it as a Claude Artifact.

Phase 6-7: Export (optional)

PDF: python3 ${CLAUDE_SKILL_DIR}/scripts-html-artifact/to-pdf.py --input <html> --output <pdf> --json. PPTX (deck shape only): python3 ${CLAUDE_SKILL_DIR}/scripts-html-artifact/pptx-bridge/run-unified.py --input <html> --format pptx --out <pptx> --no-render.

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THREEJS Mode

Build Three.js web applications in four phases: Design, Build, Animate, Polish. Three paradigms detected from context.

Phase 1: Design

Detect paradigm first:

Signal	Paradigm	Load
@react-three/fiber, r3f, drei, useFrame	React Three Fiber	references/threejs-builder-refs/react-three-fiber.md
WebGPURenderer, TSL, compute shader	WebGPU	references/threejs-builder-refs/webgpu.md
Standalone HTML, new THREE.Scene(), vanilla	Imperative	references/threejs-builder-refs/advanced-topics.md
EventBus, GameState, player controller	Game (alongside paradigm)	references/threejs-builder-refs/game-architecture.md + game-patterns.md
GLTF/GLB, .glb, skeletal rigs	GLTF (alongside paradigm)	references/threejs-builder-refs/gltf-loading.md

If ambiguous, ask -- imperative and R3F patterns conflict. Identify core visual element, select components per references/threejs-builder-refs/build-recipes.md, document visual style.

Phase 2: Build

Follow paradigm-specific patterns from loaded reference. Imperative defaults: single HTML, CONFIG object, three-point lighting, renderer.setAnimationLoop(). See references/threejs-builder-refs/build-recipes.md for boilerplate, scene infrastructure, constraints.

Phase 3: Animate

R3F uses useFrame (never requestAnimationFrame). Imperative uses setAnimationLoop. No geometry/material allocation in animation loop. Wire interaction handlers per scene plan.

Phase 4: Polish

Remove debug helpers. Handle window resize. Verify visible lighting. Run the verification steps in references/threejs-builder-refs/build-recipes.md, then finish with the core doc's section 10 loop on the rendered scene and any UI overlay.

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Deep References

Load on demand when the task needs detailed patterns, examples, or specifications:

Design Refs

File	Content
references/design-refs/ux-copy.md	Component-specific UX copy patterns
references/design-refs/design-systems.md	Design token architecture, component specs
references/design-refs/design-critique.md	Structured critique method, heuristics
references/design-refs/accessibility-review.md	WCAG criteria, component a11y patterns
references/design-refs/design-handoff.md	Spec categories, artifact templates
references/design-refs/llm-design-failure-modes.md	LLM design failure modes with defenses

Distinctive Frontend Design Refs

File	Content
references/distinctive-frontend-design-refs/font-catalog.json	Curated fonts by aesthetic category
references/distinctive-frontend-design-refs/color-inspirations.json	Cultural/contextual palette sources
references/distinctive-frontend-design-refs/animation-patterns.md	Animation choreography with CSS/React
references/distinctive-frontend-design-refs/background-techniques.md	Atmospheric background methods
references/distinctive-frontend-design-refs/implementation-examples.md	CSS tokens, framework templates
references/distinctive-frontend-design-refs/macrostructure-catalog.md	Named macro:* page structures
references/distinctive-frontend-design-refs/phase-details.md	Direction examples, motion timing, hero, backgrounds, design stamp
references/distinctive-frontend-design-refs/css-audit-patterns.md	Grep commands to audit existing CSS
references/distinctive-frontend-design-refs/performance-budgets.md	Render costs, layout thrashing
references/distinctive-frontend-design-refs/game-ui-polish.md	Game-native UI polish rules
references/distinctive-frontend-design-refs/card-shader-patterns.md	Fragment shader GLSL
references/distinctive-frontend-design-refs/shader-integration-react.md	React 19 WebGL hook + context pool
references/distinctive-frontend-design-refs/balatro-shader-breakdown.md	Holographic foil shader
references/distinctive-frontend-design-refs/roll-text.md	Roll/slot text patterns
references/distinctive-frontend-design-refs/text-animation-patterns.md	Reveal, typewriter, crossfade
references/distinctive-frontend-design-refs/oklch-color-harmony.md	OKLCH color harmony
references/distinctive-frontend-design-refs/honest-placeholders.md	Placeholder content rules

HTML Artifact Refs

File	Content
references/html-artifact-refs/design-system.md	Theme tokens, a11y checklist, SVG rules
references/html-artifact-refs/diagram-layering.md	SVG layer order, dark-theme colors
references/html-artifact-refs/infographic-layouts.md	21 layout types, 22 visual styles
references/html-artifact-refs/pdf-export.md	Page-size table, troubleshooting
references/html-artifact-refs/pptx-export.md	Layout types, THEME dict, CLI ref
references/html-artifact-refs/shape-diagram-illustration.md	SVG construction, diagram types

Three.js Refs

File	Content
references/threejs-builder-refs/build-recipes.md	Boilerplate, scene setup, error handling
references/threejs-builder-refs/react-three-fiber.md	R3F patterns, Drei, Zustand
references/threejs-builder-refs/webgpu.md	WebGPURenderer, TSL, compute shaders
references/threejs-builder-refs/advanced-topics.md	GLTF, post-processing, shaders, physics
references/threejs-builder-refs/visual-polish.md	Materials, lighting, HDR, shadows
references/threejs-builder-refs/gltf-loading.md	Coordinate contract, caching, auto-center
references/threejs-builder-refs/game-patterns.md	Animation FSM, camera movement, input
references/threejs-builder-refs/game-architecture.md	EventBus, GameState, pre-ship checklist
references/threejs-builder-refs/shader-patterns.md	ShaderMaterial, vertex displacement, effects
references/threejs-builder-refs/performance-patterns.md	InstancedMesh, batching, LOD, dispose
references/threejs-builder-refs/advanced-animation.md	AnimationMixer, IK, spring physics, GSAP

Scripts

• Distinctive design: scripts-distinctive-frontend-design/validate_design.py, scripts-distinctive-frontend-design/css_slop_rules.py
• HTML artifact: scripts-html-artifact/detect-shape.py, scripts-html-artifact/assemble-template.py, scripts-html-artifact/validate-artifact.py, scripts-html-artifact/fill-template.py, scripts-html-artifact/to-pdf.py, scripts-html-artifact/pptx-bridge/
• HTML artifact templates: templates/, agents: agents/html-builder.md