UX Design Systems

Build consistent, maintainable design systems with tokens, components, and theming.

Design Tokens

CSS Variables

:root {
  /* Colors */
  --color-primary-50: #eff6ff;
  --color-primary-500: #3b82f6;
  --color-primary-900: #1e3a8a;
  
  /* Typography */
  --font-sans: 'Inter', system-ui, sans-serif;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  
  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-4: 1rem;
  --space-8: 2rem;
  
  /* Border Radius */
  --radius-sm: 0.25rem;
  --radius-md: 0.375rem;
  --radius-lg: 0.5rem;
  --radius-full: 9999px;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
}

TypeScript Token System

export const tokens = {
  colors: {
    primary: {
      50: '#eff6ff',
      500: '#3b82f6',
      900: '#1e3a8a',
    },
    gray: {
      50: '#f9fafb',
      500: '#6b7280',
      900: '#111827',
    },
  },
  spacing: {
    1: '0.25rem',
    2: '0.5rem',
    4: '1rem',
    8: '2rem',
  },
  fontSize: {
    sm: '0.875rem',
    base: '1rem',
    lg: '1.125rem',
    xl: '1.25rem',
  },
} as const;

type ColorToken = keyof typeof tokens.colors;
type SpaceToken = keyof typeof tokens.spacing;

Component Patterns

Button Component

import { cva, type VariantProps } from 'class-variance-authority';

const buttonVariants = cva(
  'inline-flex items-center justify-center rounded-md font-medium transition-colors focus-visible:outline-none focus-visible:ring-2 disabled:pointer-events-none disabled:opacity-50',
  {
    variants: {
      variant: {
        primary: 'bg-primary-500 text-white hover:bg-primary-600',
        secondary: 'bg-gray-100 text-gray-900 hover:bg-gray-200',
        outline: 'border border-gray-300 bg-transparent hover:bg-gray-50',
        ghost: 'hover:bg-gray-100',
        destructive: 'bg-red-500 text-white hover:bg-red-600',
      },
      size: {
        sm: 'h-8 px-3 text-sm',
        md: 'h-10 px-4 text-base',
        lg: 'h-12 px-6 text-lg',
      },
    },
    defaultVariants: {
      variant: 'primary',
      size: 'md',
    },
  }
);

interface ButtonProps
  extends React.ButtonHTMLAttributes<HTMLButtonElement>,
    VariantProps<typeof buttonVariants> {
  isLoading?: boolean;
}

export function Button({
  className,
  variant,
  size,
  isLoading,
  children,
  ...props
}: ButtonProps) {
  return (
    <button
      className={buttonVariants({ variant, size, className })}
      disabled={isLoading}
      {...props}
    >
      {isLoading && <Spinner className="mr-2 h-4 w-4" />}
      {children}
    </button>
  );
}

Dark Mode

CSS-Based Theme Switching

:root {
  --bg-primary: #ffffff;
  --text-primary: #111827;
  --border-color: #e5e7eb;
}

[data-theme='dark'] {
  --bg-primary: #111827;
  --text-primary: #f9fafb;
  --border-color: #374151;
}

React Theme Provider

import { createContext, useContext, useEffect, useState } from 'react';

type Theme = 'light' | 'dark' | 'system';

const ThemeContext = createContext<{
  theme: Theme;
  setTheme: (theme: Theme) => void;
}>({ theme: 'system', setTheme: () => {} });

export function ThemeProvider({ children }: { children: React.ReactNode }) {
  const [theme, setTheme] = useState<Theme>('system');

  useEffect(() => {
    const root = document.documentElement;
    
    if (theme === 'system') {
      const systemTheme = window.matchMedia('(prefers-color-scheme: dark)').matches
        ? 'dark'
        : 'light';
      root.setAttribute('data-theme', systemTheme);
    } else {
      root.setAttribute('data-theme', theme);
    }
  }, [theme]);

  return (
    <ThemeContext.Provider value={{ theme, setTheme }}>
      {children}
    </ThemeContext.Provider>
  );
}

export const useTheme = () => useContext(ThemeContext);

Resources

• Tailwind CSS: https://tailwindcss.com
• CVA (Class Variance Authority): https://cva.style