material-3（材料 3）

Material Design 3

This skill guides implementation of Google's Material Design 3 (MD3) — a personal, adaptive, expressive design system. MD3 uses dynamic color, tonal surfaces, rounded shapes, and spring-based motion to create UIs that feel alive and personal.

Philosophy

MD3 is built on three principles:

• Personal: Dynamic color adapts UI to the user's wallpaper or content. Theming is individual, not one-size-fits-all.
• Adaptive: Layouts transform across 5 window size classes. Components resize, reposition, and change form factor responsively.
• Expressive: Shape morphing, spring physics, and emphasized typography create moments of delight without sacrificing usability.

Key differences from MD2:

• Tonal surfaces replace elevation shadows as the primary depth cue
• Dynamic color generates full schemes from a single seed color
• Fully rounded corners by default (not slightly rounded)
• Spring-based motion physics replace fixed easing curves for components
• 3 levels of user-controlled contrast (standard/medium/high)

Relationship with frontend-design skill: When both skills are active, MD3 provides the design system (tokens, components, layout rules) and frontend-design provides creative direction within those constraints. MD3 rules take precedence for component structure and token usage. Note: Roboto/Roboto Flex IS the correct default typeface in MD3 — the frontend-design guidance to avoid Roboto does not apply when implementing MD3.

Decision Tree

What are you building?

Full app scaffold        → See "Common Patterns: App Shell" + references/layout-and-responsive.md
Single component         → See "Component Quick Reference" table → references/component-catalog.md
Custom theme             → See references/theming-and-dynamic-color.md
Form / input layout      → See references/component-catalog.md § Input Components
Navigation structure     → See references/navigation-patterns.md
Data display             → See references/component-catalog.md § Data Display

What platform?

Jetpack Compose          → Primary: androidx.compose.material3, MaterialTheme, references/*
Flutter                  → useMaterial3: true in ThemeData, ColorScheme.fromSeed()
Web (vanilla JS)         → @material/web (limited; maintenance mode) + CSS custom properties
Web (React/Vue/Svelte)   → CSS custom properties + wrapper components (no official React lib)
Web (CSS-only)           → MD3 token values as CSS custom properties (no <md-*> elements)

Design Token System

All MD3 tokens use the md.sys namespace. Jetpack Compose maps roles to MaterialTheme.colorScheme, MaterialTheme.typography, and MaterialTheme.shapes (same semantic roles as the spec). On the web, these map to CSS custom properties (--md-sys-*):

Color Tokens (--md-sys-color-*)

Full details: references/color-system.md

Typography Tokens (--md-sys-typescale-*)

Each style has tokens for: -font, -weight, -size, -line-height, -tracking Plus 15 emphasized variants (higher weight) via --md-sys-typescale-emphasized-*

Full details: references/typography-and-shape.md

Shape Tokens (--md-sys-shape-corner-*)

Elevation Levels

Elevation in MD3 is communicated through tonal surface color, not shadows. Shadows are only used when needed for additional protection against busy backgrounds.

Motion

MD3 Expressive (May 2025) introduced spring-based motion physics for components. The legacy easing/duration system is still used for transitions (enter/exit/shared-axis):

CSS easing values:

• Emphasized: cubic-bezier(0.2, 0, 0, 1)
• Emphasized decelerate: cubic-bezier(0.05, 0.7, 0.1, 1)
• Emphasized accelerate: cubic-bezier(0.3, 0, 0.8, 0.15)
• Standard: cubic-bezier(0.2, 0, 0, 1)
• Standard decelerate: cubic-bezier(0, 0, 0, 1)
• Standard accelerate: cubic-bezier(0.3, 0, 1, 1)

Component Quick Reference

Note: Components marked with — for web element don't have @material/web implementations yet. Use CSS custom properties with standard HTML for these. Compose mappings and examples live in references/component-catalog.md.

Full component details with code examples: references/component-catalog.md

Jetpack Compose (primary)

Use androidx.compose.material3 with MaterialTheme and Material 3 composables (Scaffold, Button, NavigationBar, top app bars, etc.).

• Theming: MaterialTheme(colorScheme = …, typography = …, shapes = …). Prefer dynamicLightColorScheme / dynamicDarkColorScheme on Android 12+ (API 31+) when dynamic color is desired; otherwise lightColorScheme / darkColorScheme or generated theme code from Material Theme Builder.
• Adaptive UI: Window size classes, list-detail and supporting-pane layouts, foldables — see references/layout-and-responsive.md and references/navigation-patterns.md.
• Edge-to-edge & insets: Lay out content with WindowInsets / scaffold padding so bars and IME behave correctly — see references/layout-and-responsive.md.
• Experimental APIs: Some Material 3 APIs require @OptIn(ExperimentalMaterial3Api::class) or expressive opt-ins; match your BOM and compiler.

MaterialTheme(
    colorScheme = colorScheme, // from dynamicLightColorScheme / lightColorScheme / etc.
    typography = Typography(),
    shapes = Shapes(),
) {
    // M3 content — prefer references for Scaffold, navigation, text fields
}

Web (limited): @material/web

Important: Per Material Design 3 for Web, Material Web Components are in maintenance mode and M3 Expressive is not implemented on Web. Use @material/web for token-backed web UIs when appropriate, but do not treat it as equivalent to Compose for current Expressive features.

Setup

npm install @material/web

Import Components Individually

Always import only the components you use — importing the entire package bloats the bundle:

// Good — individual imports
import '@material/web/button/filled-button.js';
import '@material/web/button/outlined-button.js';
import '@material/web/textfield/outlined-text-field.js';
import '@material/web/icon/icon.js';

// Bad — never do this
import '@material/web'; // imports everything

Basic Usage

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link href="https://fonts.googleapis.com/css2?family=Roboto+Flex:wght@400;500;700&display=swap" rel="stylesheet">
  <link href="https://fonts.googleapis.com/icon?family=Material+Symbols+Outlined" rel="stylesheet">
</head>
<body>
  <md-filled-button>Get started</md-filled-button>
  <md-outlined-text-field label="Email" type="email"></md-outlined-text-field>

  <script type="module">
    import '@material/web/button/filled-button.js';
    import '@material/web/textfield/outlined-text-field.js';
  </script>
</body>
</html>

Theming with CSS Custom Properties

Apply a custom theme by setting CSS custom properties on :root or any ancestor:

:root {
  /* Color scheme (generate with @material/material-color-utilities) */
  --md-sys-color-primary: #6750A4;
  --md-sys-color-on-primary: #FFFFFF;
  --md-sys-color-primary-container: #EADDFF;
  --md-sys-color-on-primary-container: #21005D;
  --md-sys-color-secondary: #625B71;
  --md-sys-color-on-secondary: #FFFFFF;
  --md-sys-color-secondary-container: #E8DEF8;
  --md-sys-color-on-secondary-container: #1D192B;
  --md-sys-color-surface: #FEF7FF;
  --md-sys-color-on-surface: #1D1B20;
  --md-sys-color-surface-container: #F3EDF7;
  --md-sys-color-outline: #79747E;
  --md-sys-color-outline-variant: #CAC4D0;

  /* Typography */
  --md-sys-typescale-body-large-font: 'Roboto Flex', sans-serif;
  --md-sys-typescale-body-large-size: 1rem;
  --md-sys-typescale-body-large-weight: 400;
  --md-sys-typescale-body-large-line-height: 1.5rem;

  /* Shape */
  --md-sys-shape-corner-full: 9999px;
  --md-sys-shape-corner-medium: 12px;
}

Component-Level Overrides

Override individual component tokens for specific customization:

md-filled-button {
  --md-filled-button-container-color: var(--md-sys-color-primary);
  --md-filled-button-label-text-color: var(--md-sys-color-on-primary);
  --md-filled-button-container-shape: var(--md-sys-shape-corner-full);
  --md-filled-button-container-height: 40px;
}

md-outlined-text-field {
  --md-outlined-text-field-container-shape: var(--md-sys-shape-corner-small);
  --md-outlined-text-field-focus-outline-color: var(--md-sys-color-primary);
}

Dark Theme

Apply dark theme by overriding color tokens on a class or media query:

@media (prefers-color-scheme: dark) {
  :root {
    --md-sys-color-primary: #D0BCFF;
    --md-sys-color-on-primary: #381E72;
    --md-sys-color-primary-container: #4F378B;
    --md-sys-color-on-primary-container: #EADDFF;
    --md-sys-color-surface: #141218;
    --md-sys-color-on-surface: #E6E0E9;
    --md-sys-color-surface-container: #211F26;
    --md-sys-color-outline: #938F99;
    --md-sys-color-outline-variant: #49454F;
  }
}

Full theming guide: references/theming-and-dynamic-color.md

Common Patterns

App Shell

Standard MD3 app with responsive navigation + top app bar + content area:

<div class="md3-app">
  <nav class="md3-nav-rail" aria-label="Main navigation">
    <!-- Navigation rail for medium+ screens -->
    <md-fab size="small" aria-label="Compose">
      <md-icon slot="icon">edit</md-icon>
    </md-fab>
    <md-navigation-bar>
      <md-navigation-tab label="Home">
        <md-icon slot="active-icon">home</md-icon>
        <md-icon slot="inactive-icon">home</md-icon>
      </md-navigation-tab>
      <md-navigation-tab label="Search">
        <md-icon slot="active-icon">search</md-icon>
        <md-icon slot="inactive-icon">search</md-icon>
      </md-navigation-tab>
    </md-navigation-bar>
  </nav>
  <main class="md3-content">
    <header class="md3-top-app-bar">
      <h1 class="md3-top-app-bar__title" style="font: var(--md-sys-typescale-title-large)">
        Page Title
      </h1>
    </header>
    <div class="md3-body">
      <!-- Content here -->
    </div>
  </main>
</div>

.md3-app {
  display: flex;
  min-height: 100vh;
  background: var(--md-sys-color-surface);
  color: var(--md-sys-color-on-surface);
}

.md3-nav-rail {
  width: 80px;
  background: var(--md-sys-color-surface);
  border-right: 1px solid var(--md-sys-color-outline-variant);
  display: flex;
  flex-direction: column;
  align-items: center;
  padding-top: 12px;
  gap: 12px;
}

.md3-content {
  flex: 1;
  display: flex;
  flex-direction: column;
}

.md3-top-app-bar {
  height: 64px;
  padding: 0 16px;
  display: flex;
  align-items: center;
  background: var(--md-sys-color-surface);
}

.md3-body {
  padding: 24px;
  flex: 1;
}

/* Responsive: switch to bottom nav on compact */
@media (max-width: 599px) {
  .md3-app { flex-direction: column; }
  .md3-nav-rail {
    order: 1;
    width: 100%;
    flex-direction: row;
    justify-content: center;
    border-right: none;
    border-top: 1px solid var(--md-sys-color-outline-variant);
    padding: 0;
  }
}

Card Grid

<div class="md3-card-grid">
  <div class="md3-card md3-card--outlined">
    <img src="image.jpg" alt="Description" class="md3-card__media">
    <div class="md3-card__content">
      <h3 style="font: var(--md-sys-typescale-title-medium)">Card Title</h3>
      <p style="font: var(--md-sys-typescale-body-medium); color: var(--md-sys-color-on-surface-variant)">
        Supporting text for this card.
      </p>
    </div>
    <div class="md3-card__actions">
      <md-text-button>Learn more</md-text-button>
      <md-filled-tonal-button>Action</md-filled-tonal-button>
    </div>
  </div>
</div>

.md3-card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 16px;
}

.md3-card--outlined {
  border: 1px solid var(--md-sys-color-outline-variant);
  border-radius: var(--md-sys-shape-corner-medium, 12px);
  background: var(--md-sys-color-surface);
  overflow: hidden;
}

.md3-card__content { padding: 16px; }
.md3-card__actions { padding: 8px 16px 16px; display: flex; gap: 8px; justify-content: flex-end; }
.md3-card__media { width: 100%; aspect-ratio: 16/9; object-fit: cover; }

Form Layout

<form class="md3-form">
  <md-outlined-text-field label="Full name" required></md-outlined-text-field>
  <md-outlined-text-field label="Email" type="email" required></md-outlined-text-field>
  <md-outlined-text-field label="Message" type="textarea" rows="4"></md-outlined-text-field>
  <div class="md3-form__actions">
    <md-text-button type="reset">Cancel</md-text-button>
    <md-filled-button type="submit">Submit</md-filled-button>
  </div>
</form>

.md3-form {
  display: flex;
  flex-direction: column;
  gap: 16px;
  max-width: 560px;
}

.md3-form__actions {
  display: flex;
  gap: 8px;
  justify-content: flex-end;
  margin-top: 8px;
}

More patterns: references/navigation-patterns.md, references/layout-and-responsive.md

Anti-Patterns

Never do these when implementing MD3:

• Mix MD2 and MD3 libraries: Don't use @material/mdc-* (MD2) alongside @material/web (MD3). They have incompatible APIs and styling.
• Hardcode colors: Always use var(--md-sys-color-*) tokens, never raw hex/rgb values. Hardcoded colors break dynamic theming, dark mode, and contrast adjustment.
• Ignore tonal pairing: Only combine colors in their intended pairs (e.g., primary + on-primary, surface-container + on-surface). Arbitrary pairings break contrast in dynamic color and high contrast modes.
• Use outline for dividers: Use outline-variant for dividers. outline is for important boundaries like text field borders.
• Import all of @material/web: Always import individual component modules. Barrel imports include every component and destroy bundle size.
• Use border-radius directly: Use shape tokens (var(--md-sys-shape-corner-medium)) so shapes stay consistent with theming.
• Use shadows for elevation by default: MD3 communicates elevation through tonal surface color, not shadows. Only add shadows when elements need extra separation from busy backgrounds.
• Apply frontend-design "avoid Roboto" rule: On Android, Roboto is the default Material typeface; web often uses Roboto or Roboto Flex with MD3 tokens. Replace only when intentionally customizing the type scale.
• Assume SSR compatibility: @material/web uses Web Components (custom elements) which require JavaScript to render. They won't produce meaningful HTML in SSR without additional hydration strategies.
• Ignore foldables and large screens: MD3 is designed for all screen sizes. Don't ship phone-only layouts — use canonical layouts, multi-pane at 600dp+, and test on foldable/tablet emulators. Place no interactive content across the fold/hinge.
• Stretch content to fill wide screens: On Large (1200dp+) and Extra-large (1600dp+) windows, constrain content to a max width (840–1040dp). Endless-width text lines are unreadable.

Platform Notes

Flutter

MaterialApp(
  theme: ThemeData(
    useMaterial3: true,
    colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
  ),
);

Jetpack Compose

See Jetpack Compose (primary) above. Use LocalContext.current with dynamicLightColorScheme / dynamicDarkColorScheme only when Build.VERSION.SDK_INT >= Build.VERSION_CODES.S and dynamic color is enabled; otherwise supply static light/dark schemes.

Component Name Mapping

M3 Expressive (May 2025)

The Expressive update adds visual richness while maintaining usability. Availability differs by platform — do not assume one stack implements everything.

Web: Material Web is maintenance-only; M3 Expressive is not on Web. Use CSS easing/duration tokens as fallback for motion, not spring parity.

Legacy easing/duration remains valid for transitions (enter/exit/shared-axis) where the spec still references them; see the Motion table below.

MD3 Compliance Audit

When invoked with audit as the argument (e.g., /material-3 audit), or when asked to audit/review MD3 compliance, analyze the target app or page and produce a compliance report.

Audit Procedure

1. Identify the target: The user provides a URL (use browser tools to inspect), file paths (read source), or a running app.
2. Inspect the following categories and score each 0–10:

1. Generate the report:

# MD3 Compliance Audit Report

Target: [URL or file path]
Date: [date]
Overall Score: [X/100]

## Scores by Category
| Category       | Score | Status |
|----------------|-------|--------|
| Color tokens   | X/10  | [pass/warn/fail] |
| Typography     | X/10  | [pass/warn/fail] |
| Shape          | X/10  | [pass/warn/fail] |
| Elevation      | X/10  | [pass/warn/fail] |
| Components     | X/10  | [pass/warn/fail] |
| Layout         | X/10  | [pass/warn/fail] |
| Navigation     | X/10  | [pass/warn/fail] |
| Motion         | X/10  | [pass/warn/fail] |
| Accessibility  | X/10  | [pass/warn/fail] |
| Theming        | X/10  | [pass/warn/fail] |

## Critical Issues
[List items scoring 0-3 with specific file:line references and fixes]

## Warnings
[List items scoring 4-6 with recommendations]

## Passing
[List items scoring 7-10 with notes on what's done well]

## Recommended Fixes (Priority Order)
1. [Most impactful fix first]
2. ...

Audit Methods

For a live URL (browser or devtools):

• Inspect computed styles and CSS variables (--md-sys-*)
• Resize viewport or use responsive mode for breakpoints
• Capture screenshots at key widths if helpful

For source code (file paths provided):

• Compose/Kotlin: .kt files — MaterialTheme, composables, Color(0x…) abuse, hard-coded Dp, missing Modifier.semantics where needed
• Flutter: .dart — ThemeData, ColorScheme
• Web: HTML/JSX/Vue/Svelte; CSS/SCSS for tokens
• Check web imports for @material/web vs @material/mdc-* (MD2)

Quick checks (adapt paths to your stack):

# Web: hardcoded colors
grep -rn '#[0-9a-fA-F]\{3,8\}' --include='*.css' --include='*.scss'

# Compose: raw Color(...) audits (sample — tune for your codebase)
grep -rn 'Color(0x' --include='*.kt'

# MD2 on web
grep -rn '@material/mdc-' --include='*.js' --include='*.ts'

Browser automation (if your environment exposes MCP browser tools): navigate, snapshot DOM/CSS variables, resize for breakpoints — optional, not required.

Scoring Guide

• 9-10: Fully MD3 compliant, uses correct tokens and patterns
• 7-8: Mostly compliant, minor issues (e.g., a few hardcoded values)
• 4-6: Partially compliant, some MD3 patterns but significant gaps
• 1-3: Major violations, mostly non-MD3 or MD2 patterns
• 0: Not applicable or completely absent

Status thresholds: pass (7+), warn (4-6), fail (0-3)

Reference Documents

• references/color-system.md — Color roles, tonal palettes, dynamic color, Compose + CSS mapping
• references/typography-and-shape.md — Type scale, shape corners, elevation, motion, Expressive notes
• references/component-catalog.md — Components: Compose + @material/web where applicable
• references/navigation-patterns.md — Navigation selection, Compose-first adaptive patterns
• references/layout-and-responsive.md — Breakpoints, canonical layouts, insets, foldables
• references/theming-and-dynamic-color.md — Theming: Compose first, then Flutter and web