frontend git:20260919.28d30f9B

Immutable. This exact content is served forever at /api/v1/blob/b1eff3b51234b5bd.

---
name: frontend
description: "Frontend: UI design, distinctive visual styles, HTML artifacts, Three.js 3D."
user-invocable: true
allowed-tools:
  - Read
  - Write
  - Bash
  - Grep
  - Glob
  - Edit
  - Task
  - Agent
  - Skill
routing:
  force_route: false
  not_for: "game UI (use game-dev), backend work (use workflow), brand or logo design without code"
  triggers:
    - "design"
    - "UX copy"
    - "design system"
    - "accessibility"
    - "WCAG"
    - "design handoff"
    - "frontend design"
    - "visual identity"
    - "HTML artifact"
    - "make HTML"
    - "self-contained HTML"
    - "threejs"
    - "three.js"
    - "3D web"
    - "3D scene"
    - "WebGL"
    - "WebGPU"
    - "react three fiber"
    - "r3f"
    - "text animation"
    - "card effects"
    - "pptx"
    - "powerpoint"
    - "slide deck"
    - "design critique"
  category: frontend
  pairs_with:
    - typescript-frontend-engineer
    - ui-frontend-engineer
    - game-dev
---

# Frontend Skill

Four modes: **Design** (UX copy, design systems, critique, accessibility, handoff,
research), **Distinctive** (context-driven aesthetic exploration with anti-cliche
validation), **HTML-Artifact** (self-contained HTML generation with 8 shapes), and
**Three.js** (3D web apps in imperative, R3F, or WebGPU paradigms).

## 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 phase |
| **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 |

---

## 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

Four-step method: Describe (elements, layout -- no judgment), Analyze (hierarchy, contrast, alignment), Interpret (emotional tone, brand alignment), Evaluate (recommendations). Apply Nielsen's 10 heuristics to the specific design. Match feedback 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.

---

## DISTINCTIVE Mode

Systematic aesthetic exploration producing validated design specifications. Every
choice flows from project context, not defaults. Seven phases with gates.

### Phase 1: Context Discovery

1. Gather: purpose, surface type (landing vs app/dashboard), audience, emotion, cultural context, constraints, tech stack, real content, previous projects.
2. Pick one macrostructure from `references/distinctive-frontend-design-refs/macrostructure-catalog.md` by heading anchor. Load only the chosen entry.
3. Define 3-5 aesthetic directions using `references/distinctive-frontend-design-refs/color-inspirations.json` and `references/distinctive-frontend-design-refs/font-catalog.json`. See `references/distinctive-frontend-design-refs/phase-details.md` for examples.
4. Write narrative brief: visual thesis, content plan, interaction thesis.

**Gate**: Macrostructure chosen, aesthetic direction justified, narrative brief written.

### Phase 2: Typography

Load `references/distinctive-frontend-design-refs/font-catalog.json`. Banned fonts: Inter, Roboto, Arial, Helvetica, system fonts, Space Grotesk. Select pairing per `references/distinctive-frontend-design-refs/phase-details.md`. Two typefaces max. Validate against banned list.

### Phase 3: Color Palette

Research inspiration via `references/distinctive-frontend-design-refs/color-inspirations.json`. Build with strict 60/30/10 dominance (dominant, secondary, accent). One accent color only. Check against cliche list in `references/distinctive-frontend-design-refs/preferred-patterns.json`.

### Phase 4: Animation Strategy

2-to-3 rule: ship 2-3 intentional motions per page. Fill three slots (entrance, scroll, interaction). Load `references/distinctive-frontend-design-refs/animation-patterns.md` for patterns. Define easing and timing per `references/distinctive-frontend-design-refs/phase-details.md`.

### Phase 5: Hero & Background

First viewport reads as one composition. See `references/distinctive-frontend-design-refs/app-vs-landing-rules.md` for surface-specific rules. Choose technique from `references/distinctive-frontend-design-refs/background-techniques.md`. Minimum 2 layers. Check contrast against WCAG AA.

### Phase 6: Validation

Run: `python3 ${CLAUDE_SKILL_DIR}/scripts-distinctive-frontend-design/validate_design.py --fonts "Display,Body" --palette palette.json --project NAME --macrostructure macro:ID --animation --background --emitted-css generated.html`

Score must reach 80 (Grade B+). If below, iterate on failed checks.

### Phase 7: Specification Output

Emit design stamp comment. Generate CSS custom properties (tokens). Create base styles. Document specification. Provide framework-specific starter code if requested (see `references/distinctive-frontend-design-refs/implementation-examples.md`).

---

## 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.

### 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}`

Always load `references/html-artifact-refs/design-system.md` and `references/html-artifact-refs/interaction-patterns.md`. Load shape-specific reference from `references/html-artifact-refs/shape-{name}.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

Run: `python3 ${CLAUDE_SKILL_DIR}/scripts-html-artifact/validate-artifact.py {html_file}`

Checks: valid HTML structure, no external deps, has `<title>`, charset, viewport, under 500KB, no broken internal refs, CSS slop scan. Fix failures and re-run (max 3 attempts).

### Phase 5: Deliver

Print absolute file path, 1-line summary, offer browser open. Check `$DISPLAY`/`$SSH_TTY` before offering open on Linux.

### 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`.

---

## 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. Match visual style. Run 4 verification steps: responsive, visual quality, output test, cleanup. See `references/threejs-builder-refs/build-recipes.md`.

---

## 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` | 8 LLM 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` | Selection processes, validation, timing |
| `references/distinctive-frontend-design-refs/css-audit-patterns.md` | Detection commands for CSS slop |
| `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`