UI Design System

When to Use

Activate this skill when:

Creating new UI components that must follow a design system
Building page layouts with consistent spacing and structure
Setting up or extending design tokens (colors, typography, spacing)
Choosing colors, fonts, or spacing values for a project
Reviewing UI code for design consistency and accessibility
Integrating shadcn/ui components into existing layouts

Do NOT use this skill for:

Backend API implementation (use
```
python-backend-expert
```
)
Component or hook testing (use
```
react-testing-patterns
```
)
E2E browser testing (use
```
e2e-testing
```
)
General React patterns unrelated to design system (use
```
react-frontend-expert
```
)
Deployment or CI/CD (use
```
deployment-pipeline
```
)

Instructions

Step 0: Read Existing Design Tokens

Before generating any UI code, check the project for existing tokens:

Read
```
tailwind.config.ts
```
(or
```
.js
```
) for custom theme extensions
Read
```
src/styles/globals.css
```
or
```
app/globals.css
```
for CSS custom properties
Read
```
components.json
```
if shadcn/ui is configured

If no design tokens exist, generate a starter set and ask the user to confirm before proceeding (see Edge Cases).

Design Tokens

Color Tokens

Define colors as CSS custom properties consumed by Tailwind. Never use hardcoded hex/rgb values in components.

CSS custom properties (HSL format for shadcn/ui compatibility):

css

/* globals.css */
@layer base {
  :root {
    --background: 0 0% 100%;
    --foreground: 222 47% 11%;
    --primary: 221 83% 53%;
    --primary-foreground: 210 40% 98%;
    --secondary: 210 40% 96%;
    --secondary-foreground: 222 47% 11%;
    --muted: 210 40% 96%;
    --muted-foreground: 215 16% 47%;
    --accent: 210 40% 96%;
    --accent-foreground: 222 47% 11%;
    --destructive: 0 84% 60%;
    --destructive-foreground: 210 40% 98%;
    --border: 214 32% 91%;
    --input: 214 32% 91%;
    --ring: 221 83% 53%;
    --radius: 0.5rem;
  }

  .dark {
    --background: 222 47% 11%;
    --foreground: 210 40% 98%;
    --primary: 217 91% 60%;
    --primary-foreground: 222 47% 11%;
    --secondary: 217 33% 17%;
    --secondary-foreground: 210 40% 98%;
    --muted: 217 33% 17%;
    --muted-foreground: 215 20% 65%;
    --accent: 217 33% 17%;
    --accent-foreground: 210 40% 98%;
    --destructive: 0 63% 31%;
    --destructive-foreground: 210 40% 98%;
    --border: 217 33% 17%;
    --input: 217 33% 17%;
    --ring: 224 76% 48%;
  }
}

Tailwind config mapping:

// tailwind.config.ts
export default {
  theme: {
    extend: {
      colors: {
        background: "hsl(var(--background))",
        foreground: "hsl(var(--foreground))",
        primary: {
          DEFAULT: "hsl(var(--primary))",
          foreground: "hsl(var(--primary-foreground))",
        },
        secondary: {
          DEFAULT: "hsl(var(--secondary))",
          foreground: "hsl(var(--secondary-foreground))",
        },
        muted: {
          DEFAULT: "hsl(var(--muted))",
          foreground: "hsl(var(--muted-foreground))",
        },
        accent: {
          DEFAULT: "hsl(var(--accent))",
          foreground: "hsl(var(--accent-foreground))",
        },
        destructive: {
          DEFAULT: "hsl(var(--destructive))",
          foreground: "hsl(var(--destructive-foreground))",
        },
        border: "hsl(var(--border))",
        input: "hsl(var(--input))",
        ring: "hsl(var(--ring))",
      },
    },
  },
} satisfies Config;

Color usage rules:

Always use semantic token classes:
```
bg-primary
```
,
```
text-foreground
```
,
```
border-border
```
Never use raw Tailwind palette colors (
```
bg-blue-500
```
) in component code
Every color must have a dark mode variant defined
Use
```
foreground
```
variants for text on colored backgrounds

Typography Scale

Define a typographic scale using Tailwind's font-size utilities:

Token	Size	Line Height	Usage
`text-xs`	12px	16px	Captions, helper text
`text-sm`	14px	20px	Secondary text, labels
`text-base`	16px	24px	Body text (default)
`text-lg`	18px	28px	Subheadings
`text-xl`	20px	28px	Section headings
`text-2xl`	24px	32px	Page headings
`text-3xl`	30px	36px	Hero headings

Typography rules:

Set a base font in

tailwind.config.ts

fontFamily: { sans: ["Inter", "system-ui", "sans-serif"] }

Use
```
font-medium
```
(500) for headings and labels,
```
font-normal
```
(400) for body
Use
```
tracking-tight
```
for headings
```
text-2xl
```
and above
Limit line length with
```
max-w-prose
```
(65ch) for readability

Spacing (8pt Grid)

All spacing values follow an 8pt base grid:

Tailwind Class	Value	Use Case
`p-1` / `gap-1`	4px	Inline icon padding, tight gaps
`p-2` / `gap-2`	8px	Compact element spacing
`p-3` / `gap-3`	12px	Input padding, small card padding
`p-4` / `gap-4`	16px	Standard component padding
`p-6` / `gap-6`	24px	Card padding, section gaps
`p-8` / `gap-8`	32px	Section padding
`p-12` / `gap-12`	48px	Page section spacing
`p-16` / `gap-16`	64px	Major layout spacing

Spacing rules:

Use
```
gap-*
```
for flex/grid children instead of individual margins
Prefer
```
space-y-*
```
for vertical stacking of sibling elements
Cards:
```
p-6
```
padding with
```
gap-4
```
between internal elements
Page sections:
```
py-12
```
or
```
py-16
```
vertical padding
Never mix spacing systems (no
```
margin: 13px
```
)

Component Structure

Hierarchy: Container > Layout > Content

Every component follows a three-layer structure:

tsx

// Container: outer wrapper with spacing, background, border
<Card className="p-6">
  {/* Layout: flex/grid arrangement */}
  <div className="flex items-center gap-4">
    {/* Content: actual UI elements */}
    <Avatar src={user.avatar} alt={user.name} />
    <div className="space-y-1">
      <h3 className="text-sm font-medium">{user.name}</h3>
      <p className="text-sm text-muted-foreground">{user.role}</p>
    </div>
  </div>
</Card>

Semantic HTML

Use the correct HTML element for every purpose:

Element	Use For	Not
`<button>`	Clickable actions	`<div onClick>`
`<a>`	Navigation links	`<button>` for links
`<nav>`	Navigation regions	`<div>`
`<main>`	Primary page content	`<div>`
`<article>`	Self-contained content (card, post)	`<div>`
`<section>`	Thematic grouping with heading	`<div>`
`<aside>`	Sidebar or tangential content	`<div>`
`<header>`	Introductory content for a section	`<div>`
`<footer>`	Footer content for a section	`<div>`
`<ul>` / `<ol>`	Lists of items	`<div>` for each item

shadcn/ui Primitives

Prefer shadcn/ui components over custom implementations:

Need	Use	Not
Buttons	`<Button>`	Custom `<button>` with styles
Modals	`<Dialog>`	Custom modal with portal
Dropdowns	`<DropdownMenu>`	Custom dropdown
Cards	`<Card>`	Styled `<div>`
Inputs	`<Input>`	Styled `<input>`
Selects	`<Select>`	Native `<select>`
Tooltips	`<Tooltip>`	Custom tooltip
Tabs	`<Tabs>`	Custom tab component
Tables	`<Table>`	Plain `<table>`
Alerts	`<Alert>`	Custom banner div

If shadcn/ui is not installed, fall back to plain Tailwind with equivalent patterns and consistent class ordering.

TypeScript Component Interfaces

Export props as TypeScript interfaces with JSDoc descriptions:

tsx

/** Props for the UserProfileCard component. */
interface UserProfileCardProps {
  /** User data to display. */
  user: User;
  /** Called when the edit button is clicked. */
  onEdit?: (userId: string) => void;
  /** Visual variant of the card. */
  variant?: "default" | "compact";
  /** Additional CSS classes applied to the root element. */
  className?: string;
}

export function UserProfileCard({
  user,
  onEdit,
  variant = "default",
  className,
}: UserProfileCardProps) {
  // ...
}

Props rules:

Name interface
```
{ComponentName}Props
```
Include
```
className?: string
```
on every component for composition
Use
```
variant
```
prop for visual variations, not separate components
Default optional props in destructuring, not in interface
Use union types for constrained string values:
```
"sm" | "md" | "lg"
```

Responsive Design

Breakpoints

Use Tailwind's mobile-first breakpoints:

Prefix	Min Width	Target
(none)	0px	Mobile (default)
`sm:`	640px	Large phones / small tablets
`md:`	768px	Tablets
`lg:`	1024px	Desktops
`xl:`	1280px	Large desktops

Responsive rules:

Design mobile-first: base styles for mobile, then add breakpoint overrides

Use

grid-cols-1 md:grid-cols-2 lg:grid-cols-3

for responsive grids

Stack navigation vertically on mobile:
```
flex-col md:flex-row
```
Hide non-essential elements on mobile:
```
hidden md:block
```
Set max container width:
```
max-w-7xl mx-auto px-4 sm:px-6 lg:px-8
```

Responsive Layout Pattern

tsx

<div className="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8">
  <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-6">
    {items.map((item) => (
      <ItemCard key={item.id} item={item} />
    ))}
  </div>
</div>

Accessibility (WCAG 2.1 AA)

Contrast Ratios

Normal text (< 18px or < 14px bold): minimum 4.5:1 contrast ratio
Large text (>= 18px or >= 14px bold): minimum 3:1 contrast ratio
UI components and graphical objects: minimum 3:1 contrast ratio

Interactive Element Requirements

Every interactive element must have:

Visible label or aria-label:

<Button aria-label="Close dialog">X</Button>

Focus indicator: Tailwind's

ring

utilities:

focus-visible:ring-2 focus-visible:ring-ring

Keyboard access: Reachable via Tab, activatable via Enter/Space
Disabled state: Both visual and
```
aria-disabled
```
or
```
disabled
```
attribute

ARIA Patterns

Icon-only buttons:
```
aria-label="Delete item"
```
Loading states:
```
aria-busy="true"
```
on the loading container
Dynamic content updates:
```
aria-live="polite"
```
on the container
Form errors:
```
aria-invalid="true"
```
on the input,
```
role="alert"
```
on the message
Modals:
```
aria-modal="true"
```
, focus trap, Escape to close
Navigation landmarks:
```
<nav aria-label="Main navigation">
```

Examples

User Profile Card

tsx

interface UserProfileCardProps {
  user: { id: string; name: string; role: string; avatarUrl: string };
  onEdit?: (userId: string) => void;
  className?: string;
}

export function UserProfileCard({ user, onEdit, className }: UserProfileCardProps) {
  return (
    <Card className={cn("p-6", className)}>
      <div className="flex items-center gap-4">
        <Avatar className="h-12 w-12">
          <AvatarImage src={user.avatarUrl} alt={user.name} />
          <AvatarFallback>{user.name.charAt(0)}</AvatarFallback>
        </Avatar>
        <div className="space-y-1">
          <h3 className="text-sm font-medium leading-none">{user.name}</h3>
          <p className="text-sm text-muted-foreground">{user.role}</p>
        </div>
      </div>
      {onEdit && (
        <div className="mt-4">
          <Button
            variant="outline"
            size="sm"
            onClick={() => onEdit(user.id)}
            aria-label={`Edit ${user.name}'s profile`}
          >
            Edit Profile
          </Button>
        </div>
      )}
    </Card>
  );
}

SaaS Dashboard Design Tokens Setup

Tailwind config extension:

// tailwind.config.ts
import type { Config } from "tailwindcss";

export default {
  theme: {
    extend: {
      colors: {
        background: "hsl(var(--background))",
        foreground: "hsl(var(--foreground))",
        primary: {
          DEFAULT: "hsl(var(--primary))",
          foreground: "hsl(var(--primary-foreground))",
        },
        secondary: {
          DEFAULT: "hsl(var(--secondary))",
          foreground: "hsl(var(--secondary-foreground))",
        },
        muted: {
          DEFAULT: "hsl(var(--muted))",
          foreground: "hsl(var(--muted-foreground))",
        },
        accent: {
          DEFAULT: "hsl(var(--accent))",
          foreground: "hsl(var(--accent-foreground))",
        },
        destructive: {
          DEFAULT: "hsl(var(--destructive))",
          foreground: "hsl(var(--destructive-foreground))",
        },
        border: "hsl(var(--border))",
        input: "hsl(var(--input))",
        ring: "hsl(var(--ring))",
      },
      fontFamily: {
        sans: ["Inter", "system-ui", "sans-serif"],
      },
      borderRadius: {
        lg: "var(--radius)",
        md: "calc(var(--radius) - 2px)",
        sm: "calc(var(--radius) - 4px)",
      },
    },
  },
} satisfies Config;

Responsive Dashboard Layout

tsx

export function DashboardLayout({ children }: { children: React.ReactNode }) {
  return (
    <div className="min-h-screen bg-background">
      <nav className="border-b border-border" aria-label="Main navigation">
        <div className="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 h-16 flex items-center">
          {/* nav content */}
        </div>
      </nav>
      <div className="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-8">
        <div className="grid grid-cols-1 lg:grid-cols-[240px_1fr] gap-8">
          <aside className="hidden lg:block" aria-label="Sidebar">
            {/* sidebar content */}
          </aside>
          <main>{children}</main>
        </div>
      </div>
    </div>
  );
}

Edge Cases

No existing design tokens: Generate a starter token set (see
```
references/design-tokens-reference.md
```
) and present it to the user for confirmation before writing any component code. Ask: "No design tokens found. Here's a starter set — should I apply these?"
shadcn/ui not installed: Fall back to plain Tailwind with equivalent patterns. Use
```
<button className="...">
```
instead of
```
<Button>
```
, styled
```
<div>
```
instead of
```
<Card>
```
. Maintain the same spacing and color token approach.
Component overlap: If a requested component duplicates an existing one, flag it: "A similar
```
UserCard
```
component exists at
```
src/components/UserCard.tsx
```
. Should I extend it or create a separate component?"
Dark mode tokens missing: If
```
:root
```
tokens exist but
```
.dark
```
variants are absent, generate matching dark variants before proceeding. Every semantic color token must have both light and dark values.
Custom brand colors: When the user provides specific brand hex values, convert them to HSL and integrate into the token system. Never use the hex values directly in components.
Inconsistent spacing in existing code: Flag the inconsistency, suggest the closest 8pt grid values, and ask whether to normalize existing components or only apply the grid to new code.

See

references/design-tokens-reference.md

for starter token sets, color palette guide, and typography scales.

ui-design-system

NPX Install

Tags

SKILL.md Content