# Tailwind CSS Pattern

> Apply Tailwind CSS utility-first patterns for consistent, maintainable component styling

## When to Use

- Styling React components without writing custom CSS files
- Building consistent UIs using a design system constraint
- Rapid prototyping with immediate visual feedback
- Maintaining styles that are co-located with component markup

## Instructions

1. Apply utilities directly on elements. Group by concern: layout, spacing, typography, color, effects.
2. Extract repeated utility combinations into React components, not `@apply` directives. Components are the abstraction layer.
3. Use Tailwind's design tokens (spacing scale, color palette, typography scale) instead of arbitrary values.
4. When arbitrary values are needed, use bracket notation: `w-[calc(100%-2rem)]`, `bg-[#1a1a2e]`.
5. Order utilities consistently: layout > positioning > sizing > spacing > typography > color > effects > responsive > state.
6. Use `@apply` only in base layer styles (global resets, typography defaults), not in component styles.

```tsx
// Good — utilities grouped by concern
function Card({ title, children }: { title: string; children: React.ReactNode }) {
  return (
    <div
      className="
      flex flex-col              /* layout */
      rounded-lg                 /* shape */
      p-6 gap-4                  /* spacing */
      bg-white shadow-md         /* visual */
      border border-gray-200     /* border */
      hover:shadow-lg            /* interaction */
      transition-shadow          /* animation */
    "
    >
      <h3 className="text-lg font-semibold text-gray-900">{title}</h3>
      <div className="text-sm text-gray-600">{children}</div>
    </div>
  );
}

// Component is the abstraction — reuse Card, not @apply
function FeatureCard({ feature }: { feature: Feature }) {
  return (
    <Card title={feature.name}>
      <p>{feature.description}</p>
      <Badge variant={feature.status}>{feature.status}</Badge>
    </Card>
  );
}
```

```tsx
// Using Tailwind's design tokens vs arbitrary values
// Prefer tokens
<div className="p-4 text-sm text-gray-700 rounded-md" />

// Use arbitrary only when tokens don't cover it
<div className="p-[18px] text-[13px] text-[#334155] rounded-[5px]" />
```

## Details

**Why utility-first works:** Every utility maps to one CSS property. You never need to name things. You never wonder where a style comes from — it is right on the element. Dead code elimination is automatic (unused utilities are purged).

**Tailwind v4 changes:** Tailwind v4 uses CSS-first configuration instead of `tailwind.config.js`. Theme values are defined in CSS with `@theme`:

```css
@import 'tailwindcss';

@theme {
  --color-primary: #3b82f6;
  --font-sans: 'Inter', sans-serif;
  --breakpoint-3xl: 1920px;
}
```

**Tailwind v3 config:**

```typescript
// tailwind.config.ts
import type { Config } from 'tailwindcss';

const config: Config = {
  content: ['./src/**/*.{ts,tsx}'],
  theme: {
    extend: {
      colors: {
        primary: { 50: '#eff6ff', 500: '#3b82f6', 900: '#1e3a8a' },
      },
      spacing: { '18': '4.5rem' },
    },
  },
  plugins: [],
};

export default config;
```

**When to use @apply:** Almost never in components. Use it for:

- Base styles on `body`, `h1`-`h6`, `a` tags in a global stylesheet
- Third-party component overrides where you cannot add classes
- Prose/article content where utility classes are impractical

**Performance:** Tailwind's output is a single CSS file with only the utilities you use. Typical production size: 10-30 KB gzipped. No runtime cost.

## Source

https://tailwindcss.com/docs/utility-first

## Process

1. Read the instructions and examples in this document.
2. Apply the patterns to your implementation, adapting to your specific context.
3. Verify your implementation against the details and edge cases listed above.

## Harness Integration

- **Type:** knowledge — this skill is a reference document, not a procedural workflow.
- **No tools or state** — consumed as context by other skills and agents.

## Success Criteria

- The patterns described in this document are applied correctly in the implementation.
- Edge cases and anti-patterns listed in this document are avoided.
