design-tokens - Claude MCP Skill

# Design Tokens

**Design tokens are the single source of truth for design decisions.**

## Philosophy

- **CSS-first**: Define tokens in CSS `@theme`, not JavaScript config
- **Semantic naming**: `--color-primary` not `--color-blue-500`
- **Brand-tinted neutrals**: Add imperceptible brand hue (chroma 0.005-0.02), not pure gray
- **OKLCH colors**: Perceptually uniform, better than RGB/HSL

## Why Tailwind CSS 4 @theme

- CSS-native (no build step overhead)
- Type-safe auto-completion
- CSS variable integration (`var(--color-primary)`)
- Dark mode built-in

**Migration from Tailwind 3**: Delete `tailwind.config.js`, move to CSS `@theme`.

## Basic @theme Structure

```css
@import "tailwindcss";

@theme {
  /* Brand hue - single source of truth */
  --brand-hue: 250;

  /* Colors - OKLCH with semantic names */
  --color-primary: oklch(0.6 0.2 var(--brand-hue));
  --color-background: oklch(0.995 0.005 var(--brand-hue));  /* Brand-tinted */
  --color-foreground: oklch(0.15 0.02 var(--brand-hue));

  /* Typography */
  --font-sans: "Inter Variable", system-ui, sans-serif;
  --font-size-base: 1rem;

  /* Spacing (8-point grid) */
  --spacing-md: 1rem;
  --radius-md: 0.5rem;
}
```

## Best Practices

### Do
- Use semantic names (`--color-primary`)
- Use OKLCH colors
- Tint neutrals with brand hue
- Follow 8-point spacing grid
- Support dark mode from start
- Create component tokens

### Don't
- Hardcode values
- Use pure grays (chroma 0)
- Use generic fonts (Inter/Roboto)
- Skip dark mode
- Create too many tokens initially

## Dark Mode Pattern

Same brand hue, inverted lightness:

```css
@theme {
  --brand-hue: 250;
  --color-background: oklch(0.995 0.005 var(--brand-hue));

  @media (prefers-color-scheme: dark) {
    --color-background: oklch(0.12 0.015 var(--brand-hue));
  }
}
```

## References

Detailed patterns:
- `references/color-system.md` — OKLCH, semantic colors, brand-tinted neutrals
- `references/typography.md` — Type scale, font pairings, font loading
- `references/spacing.md` — 8-point grid, radius, shadows, breakpoints, z-index
- `references/dark-mode.md` — System preference, manual toggle, component
- `references/component-tokens.md` — Button, input, card, animation, WebGL

## Integration

**Design tokens provide the foundation; frontend-design provides aesthetic direction.**

1. Load design-tokens for the system
2. Load frontend-design for aesthetic execution
3. Result: Consistent system + distinctive design

**"Design tokens are contracts between design and development."**