responsive-design

What this skill does

# Responsive Design Skill

## When to Use This Skill

Use this skill when you need to:

- Design and implement mobile-first responsive layouts
- Create fluid, adaptive interfaces that work across all device sizes
- Implement modern CSS layout techniques (Flexbox, Grid)
- Optimize images and media for different screen sizes
- Build accessible, touch-friendly interfaces
- Implement responsive typography and spacing systems
- Create container-based responsive components
- Optimize performance for mobile devices
- Ensure consistent user experience across devices
- Implement responsive navigation patterns
- Design responsive forms and data tables
- Create adaptive card layouts and galleries
- Build responsive dashboards and admin interfaces

## Core Concepts

### Mobile-First Philosophy

Mobile-first design means starting with mobile layout and progressively enhancing for larger screens.

**Why Mobile-First?**

- Forces focus on essential content and features
- Easier to scale up than scale down
- Better performance on mobile devices
- Aligns with modern usage patterns (mobile-first world)
- Simpler CSS with fewer overrides

**Mobile-First Approach:**

```css
/* Base styles for mobile (320px+) */
.container {
  padding: 1rem;
  width: 100%;
}

/* Tablet (768px+) */
@media (min-width: 768px) {
  .container {
    padding: 2rem;
    max-width: 720px;
    margin: 0 auto;
  }
}

/* Desktop (1024px+) */
@media (min-width: 1024px) {
  .container {
    max-width: 960px;
    padding: 3rem;
  }
}

/* Large Desktop (1280px+) */
@media (min-width: 1280px) {
  .container {
    max-width: 1200px;
  }
}
```

### Breakpoint Strategy

Standard breakpoints based on common device sizes:

```css
/* Extra Small (Mobile) - Default */
/* No media query needed */

/* Small (Large Mobile) */
@media (min-width: 480px) { }

/* Medium (Tablet) */
@media (min-width: 768px) { }

/* Large (Desktop) */
@media (min-width: 1024px) { }

/* Extra Large (Wide Desktop) */
@media (min-width: 1280px) { }

/* XXL (Ultra-wide) */
@media (min-width: 1536px) { }
```

**Custom Breakpoints:**

```css
/* Use custom breakpoints based on content, not devices */

/* When text becomes too long to read comfortably */
@media (min-width: 40em) { /* 640px */ }

/* When sidebar can fit alongside content */
@media (min-width: 60em) { /* 960px */ }

/* When multi-column layout makes sense */
@media (min-width: 75em) { /* 1200px */ }
```

### Fluid Layouts

Create layouts that adapt smoothly to any screen size:

```css
/* Fluid container with constraints */
.container {
  width: 100%;
  max-width: 1200px;
  margin-left: auto;
  margin-right: auto;
  padding-left: clamp(1rem, 5vw, 3rem);
  padding-right: clamp(1rem, 5vw, 3rem);
}

/* Fluid grid */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: clamp(1rem, 3vw, 2rem);
}

/* Fluid typography */
.heading {
  font-size: clamp(1.5rem, 4vw + 1rem, 3rem);
  line-height: 1.2;
}
```

## CSS Techniques

### Flexbox for Responsive Layouts

Flexbox excels at one-dimensional layouts (row or column):

```css
/* Responsive navigation */
.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: space-between;
  align-items: center;
}

.nav-links {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  list-style: none;
}

@media (max-width: 767px) {
  .nav {
    flex-direction: column;
    align-items: stretch;
  }

  .nav-links {
    flex-direction: column;
  }
}

/* Flexible card layout */
.card-container {
  display: flex;
  flex-wrap: wrap;
  gap: 1.5rem;
}

.card {
  flex: 1 1 300px; /* grow, shrink, base width */
  min-width: 0; /* Allow flex items to shrink below content size */
}

/* Responsive sidebar layout */
.layout {
  display: flex;
  flex-wrap: wrap;
  gap: 2rem;
}

.sidebar {
  flex: 1 1 250px;
}

.main-content {
  flex: 3 1 500px;
}
```

### CSS Grid for Complex Layouts

Grid is perfect for two-dimensional layouts:

```css
/* Auto-responsive grid */
.grid-auto {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 2rem;
}

/* Named grid areas for semantic layouts */
.page-layout {
  display: grid;
  grid-template-areas:
    "header"
    "nav"
    "main"
    "aside"
    "footer";
  gap: 1rem;
}

@media (min-width: 768px) {
  .page-layout {
    grid-template-areas:
      "header header"
      "nav nav"
      "main aside"
      "footer footer";
    grid-template-columns: 2fr 1fr;
  }
}

@media (min-width: 1024px) {
  .page-layout {
    grid-template-areas:
      "header header header"
      "nav main aside"
      "footer footer footer";
    grid-template-columns: 200px 1fr 250px;
  }
}

.header { grid-area: header; }
.nav { grid-area: nav; }
.main { grid-area: main; }
.aside { grid-area: aside; }
.footer { grid-area: footer; }

/* Responsive grid with precise control */
.gallery {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: 1rem;
}

.gallery-item {
  grid-column: span 12; /* Full width on mobile */
}

@media (min-width: 480px) {
  .gallery-item {
    grid-column: span 6; /* Half width on small screens */
  }
}

@media (min-width: 768px) {
  .gallery-item {
    grid-column: span 4; /* Third width on tablets */
  }
}

@media (min-width: 1024px) {
  .gallery-item {
    grid-column: span 3; /* Quarter width on desktop */
  }
}

/* Featured item spans more columns */
.gallery-item.featured {
  grid-column: span 12;
}

@media (min-width: 768px) {
  .gallery-item.featured {
    grid-column: span 8;
  }
}
```

### Media Queries Advanced Techniques

```css
/* Orientation-based queries */
@media (orientation: portrait) {
  .image-hero {
    aspect-ratio: 3/4;
  }
}

@media (orientation: landscape) {
  .image-hero {
    aspect-ratio: 16/9;
  }
}

/* Hover capability detection */
@media (hover: hover) and (pointer: fine) {
  /* Desktop with mouse */
  .button:hover {
    transform: scale(1.05);
  }
}

@media (hover: none) and (pointer: coarse) {
  /* Touch devices */
  .button:active {
    transform: scale(0.95);
  }
}

/* Prefers reduced motion */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* Prefers color scheme */
@media (prefers-color-scheme: dark) {
  :root {
    --bg-color: #1a1a1a;
    --text-color: #f0f0f0;
  }
}

/* Combining media queries */
@media (min-width: 768px) and (max-width: 1023px) {
  /* Tablet only styles */
  .container {
    padding: 2rem;
  }
}

/* Print styles */
@media print {
  .no-print {
    display: none;
  }

  body {
    font-size: 12pt;
    color: black;
    background: white;
  }
}
```

### Container Queries

Modern alternative to viewport-based media queries:

```css
/* Define container */
.card-container {
  container-type: inline-size;
  container-name: card;
}

/* Query based on container size */
.card {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

@container card (min-width: 400px) {
  .card {
    flex-direction: row;
    align-items: center;
  }

  .card-image {
    width: 40%;
  }

  .card-content {
    width: 60%;
  }
}

@container card (min-width: 600px) {
  .card-title {
    font-size: 1.5rem;
  }
}

/* Multiple containers */
.sidebar {
  container-type: inline-size;
  container-name: sidebar;
}

.main-content {
  container-type: inline-size;
  container-name: main;
}

@container sidebar (min-width: 300px) {
  .widget {
    padding: 1.5rem;
  }
}

@container main (min-width: 600px) {
  .article {
    column-count: 2;
  }
}
```

## Responsive Images

### Srcset and Sizes

Provide different image sizes for different viewport widths:

```html
<!-- Responsive image with srcset -->
<img
  src="image-800.jpg"
  srcset="
    image-400.jpg 400w,
    image-800.jpg 800w,
    image-1200.jpg 1200w,
    image-1600.jpg 1600w
  "
  sizes="
    (max-width: 480px) 100vw,
    (max-width: 768px) 90vw,
    (max-width: 1024px) 700px,
    1000px
  "
  alt="Re