// tailwind.config.ts
theme: {
  extend: {
    colors: {
      brand: { 50: '...', 500: '...', 900: '...' },
      surface: 'hsl(var(--surface))',
      foreground: 'hsl(var(--foreground))',
    },
    fontFamily: { sans: ['var(--font-inter)'] },
    spacing: { '18': '4.5rem' }, // only add if a real gap exists in the default scale
    borderRadius: { xl: '1rem' },
  }
}

For dark mode / multi-theme, drive colors through CSS variables (hsl(var(--x))) so themes swap without a rebuild.

Component variants with class-variance-authority (cva)

Never branch className with long ternary chains. Use cva for variant + size + state matrices:

const button = cva('inline-flex items-center rounded-md font-medium transition-colors', {
  variants: {
    variant: { primary: 'bg-brand-600 text-white hover:bg-brand-700', ghost: 'bg-transparent hover:bg-surface-100' },
    size: { sm: 'h-8 px-3 text-sm', md: 'h-10 px-4', lg: 'h-12 px-6 text-lg' },
  },
  defaultVariants: { variant: 'primary', size: 'md' },
});

Merge with tailwind-merge (cn = (...cls) => twMerge(clsx(cls))) so consumer className overrides win predictably.

Structure a component library

components/ui/          # primitives: Button, Input, Card, Dialog (shadcn-style, headless-first)
components/patterns/    # composed patterns: FormField, DataTable, EmptyState
components/features/    # feature-specific, not reused elsewhere
lib/cn.ts

Base primitives on unstyled/headless behavior (Radix primitives are the standard pairing with Tailwind) and layer Tailwind classes on top — don't reinvent focus trapping, keyboard nav, or ARIA roles.

Governance rules

No arbitrary values (w-[123px], text-[#3a3a3a]) in feature code — if the scale doesn't have it, add the token, don't escape the system.
One typographic scale (text-xs → text-4xl mapped to real heading levels), documented in a Typography stories/reference, not redefined per page.
Spacing follows the 4px base scale everywhere; flag any component using raw margin/padding outside p-*/m-*/gap-* utilities.
Every new primitive gets documented with its variant matrix (a short table: variant × size × state) before being reused across features.

Example prompt this skill should trigger on

"Set up a Tailwind design system for this SaaS app with light/dark themes and a Button, Card, and Input component."

design-system-tailwind

Design System & Tailwind CSS Engineering Skill

Foundation: tokens before components