frontend-design

# Frontend Design

This skill enables the agent to design and implement frontend interfaces that are visually polished, responsive, accessible, and maintainable. The agent works with design systems — component libraries, spacing scales, color tokens, and typography scales — to produce consistent UI code. It outputs production-ready HTML, CSS (including Tailwind CSS), and framework components (React, Vue, Svelte) with WCAG-compliant accessibility and dark mode support built in.

## Workflow

1. **Analyze Requirements and Constraints**: Identify the target platforms (desktop, tablet, mobile), the framework in use (React, Vue, plain HTML), the styling approach (Tailwind, CSS Modules, styled-components), and any existing design tokens or brand guidelines. Determine the key pages or components needed and their priority order.

2. **Establish the Design System Foundation**: Define the core tokens before writing any component code. This includes a spacing scale (4px base: 4, 8, 12, 16, 24, 32, 48, 64), a type scale (xs through 4xl with corresponding line-heights), a color palette with semantic tokens (primary, secondary, success, warning, error, neutral) in both light and dark variants, and border-radius and shadow tokens. These tokens ensure every component is visually consistent.

3. **Build Components with Variants**: Implement each component with clearly defined variants (size, color, state). Use props or CSS classes to control variants rather than duplicating markup. Include all interactive states: default, hover, focus-visible, active, disabled. Ensure every interactive element has a visible focus ring for keyboard navigation.

4. **Implement Responsive Layouts**: Use CSS Grid for two-dimensional page layouts and Flexbox for one-dimensional component alignment. Define breakpoints (sm: 640px, md: 768px, lg: 1024px, xl: 1280px) and design mobile-first, layering complexity at larger breakpoints. Test that no horizontal scrolling occurs and that tap targets meet the 44x44px minimum on touch devices.

5. **Integrate Accessibility from the Start**: Apply semantic HTML elements (nav, main, article, section, aside) before adding ARIA attributes. Ensure color contrast meets WCAG 2.1 AA (4.5:1 for normal text, 3:1 for large text). Add `aria-label`, `aria-describedby`, and `role` attributes only where semantic HTML is insufficient. Test keyboard navigation order with Tab and Shift+Tab.

6. **Add Dark Mode Support**: Implement dark mode using a CSS custom property strategy or Tailwind's `dark:` variant. Swap background, text, and border tokens while preserving sufficient contrast ratios. Avoid pure black (`#000`) backgrounds — use a dark gray (`#0f172a` or `#1e293b`) for reduced eye strain. Ensure images, shadows, and elevation levels adapt appropriately.

## Usage

Provide the agent with a description of the interface you need, including the framework, styling approach, and any existing design tokens. The agent will produce component code with responsive behavior, accessibility attributes, and dark mode support included.

## Examples

### Example 1: React Card Component with Tailwind CSS Variants

**User Request**: "Create a reusable Card component in React with Tailwind CSS. I need default, elevated, and outlined variants, plus support for dark mode."

**Agent Response**:

```jsx
function Card({ variant = 'default', children, className = '' }) {
  const base = 'rounded-lg p-6 transition-colors duration-200';

  const variants = {
    default:
      'bg-white text-gray-900 dark:bg-slate-800 dark:text-gray-100',
    elevated:
      'bg-white text-gray-900 shadow-lg hover:shadow-xl dark:bg-slate-800 dark:text-gray-100 dark:shadow-slate-900/30',
    outlined:
      'bg-transparent text-gray-900 border border-gray-200 dark:text-gray-100 dark:border-slate-700',
  };

  return (
    <div className={`${base} ${variants[variant]} ${className}`}>
      {children}
    </div>
  );
}

function CardHeader({ title, subtitle }) {
  return (
    <div className="mb-4">
      <h3 className="text-lg font-semibold leading-tight">{title}</h3>
      {subtitle && (
        <p className="mt-1 text-sm text-gray-500 dark:text-gray-400">
          {subtitle}
        </p>
      )}
    </div>
  );
}

function CardFooter({ children }) {
  return (
    <div className="mt-6 flex items-center gap-3 pt-4 border-t border-gray-100 dark:border-slate-700">
      {children}
    </div>
  );
}
```

**Usage of the component**:
```jsx
<Card variant="elevated">
  <CardHeader title="Monthly Revenue" subtitle="Jan 2026" />
  <p className="text-3xl font-bold">$48,250</p>
  <CardFooter>
    <span className="text-sm text-green-600 dark:text-green-400">+12.5% from last month</span>
  </CardFooter>
</Card>
```

### Example 2: Responsive Dashboard Layout with CSS Grid

**User Request**: "Build a responsive dashboard layout with a sidebar, top nav, and main content area. Sidebar should collapse on mobile."

**Agent Response**:

```html
<div class="dashboard">
  <nav class="dashboard__topbar" role="navigation" aria-label="Primary">
    <button class="sidebar-toggle" aria-label="Toggle sidebar" aria-expanded="false">☰</button>
    <h1 class="topbar-title">Dashboard</h1>
    <div class="topbar-actions"><!-- user avatar, notifications --></div>
  </nav>
  <aside class="dashboard__sidebar" role="navigation" aria-label="Sidebar">
    <ul role="list">
      <li><a href="/overview" aria-current="page">Overview</a></li>
      <li><a href="/analytics">Analytics</a></li>
      <li><a href="/settings">Settings</a></li>
    </ul>
  </aside>
  <main class="dashboard__content" id="main-content" role="main">
    <!-- page content -->
  </main>
</div>
```

```css
.dashboard {
  display: grid;
  grid-template-columns: 1fr;
  grid-template-rows: 56px 1fr;
  min-height: 100vh;
}
.dashboard__topbar { grid-column: 1 / -1; }
.dashboard__sidebar { display: none; }

@media (min-width: 768px) {
  .dashboard {
    grid-template-columns: 240px 1fr;
    grid-template-rows: 56px