Responsive Design Advisor

Responsive Design Advisor

Design responsive layouts that work across all device sizes.

Quick Start

Use mobile-first approach, flexible units (rem, %), CSS Grid/Flexbox, and test on real devices.

Instructions

Mobile-First Approach

Start with mobile, enhance for larger screens:

/* Base styles (mobile) */
.container {
  padding: 1rem;
}

/* Tablet */
@media (min-width: 768px) {
  .container {
    padding: 2rem;
  }
}

/* Desktop */
@media (min-width: 1024px) {
  .container {
    padding: 3rem;
    max-width: 1200px;
    margin: 0 auto;
  }
}

Common Breakpoints

Standard breakpoints:

/* Mobile: 0-639px (default) */

/* Tablet: 640px+ */
@media (min-width: 640px) { }

/* Laptop: 1024px+ */
@media (min-width: 1024px) { }

/* Desktop: 1280px+ */
@media (min-width: 1280px) { }

/* Large: 1536px+ */
@media (min-width: 1536px) { }

Tailwind breakpoints:

  Content

Flexible Layouts

CSS Grid:

.grid {
  display: grid;
  gap: 1rem;
  
  /* Mobile: 1 column */
  grid-template-columns: 1fr;
}

@media (min-width: 768px) {
  .grid {
    /* Tablet: 2 columns */
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .grid {
    /* Desktop: 3 columns */
    grid-template-columns: repeat(3, 1fr);
  }
}

Auto-fit grid:

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1rem;
}

Flexbox:

.flex-container {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
}

.flex-item {
  flex: 1 1 100%; /* Mobile: full width */
}

@media (min-width: 768px) {
  .flex-item {
    flex: 1 1 calc(50% - 0.5rem); /* Tablet: 2 columns */
  }
}

@media (min-width: 1024px) {
  .flex-item {
    flex: 1 1 calc(33.333% - 0.667rem); /* Desktop: 3 columns */
  }
}

Responsive Typography

Fluid typography:

h1 {
  font-size: clamp(2rem, 5vw, 4rem);
}

p {
  font-size: clamp(1rem, 2vw, 1.125rem);
}

Responsive scale:

/* Mobile */
h1 { font-size: 2rem; }
h2 { font-size: 1.5rem; }
p { font-size: 1rem; }

/* Desktop */
@media (min-width: 1024px) {
  h1 { font-size: 3rem; }
  h2 { font-size: 2rem; }
  p { font-size: 1.125rem; }
}

Responsive Images

Responsive image:

img {
  max-width: 100%;
  height: auto;
}

Art direction:

Responsive background:

.hero {
  background-image: url('mobile.jpg');
}

@media (min-width: 768px) {
  .hero {
    background-image: url('tablet.jpg');
  }
}

@media (min-width: 1024px) {
  .hero {
    background-image: url('desktop.jpg');
  }
}

Container Queries

Component-based responsive:

.card-container {
  container-type: inline-size;
}

.card {
  padding: 1rem;
}

@container (min-width: 400px) {
  .card {
    display: grid;
    grid-template-columns: 1fr 2fr;
  }
}

Navigation Patterns

Mobile menu:

function Navigation() {
  const [isOpen, setIsOpen] = useState(false);
  
  return (
    
      {/* Mobile: Hamburger */}
       setIsOpen(!isOpen)}
      >
        Menu
      
      
      {/* Mobile: Drawer */}
      
        
          Home
          About
          Contact
        
      
    
  );
}

Touch Targets

Minimum size:

button, a {
  min-height: 44px; /* iOS recommendation */
  min-width: 44px;
  padding: 0.75rem 1rem;
}

Touch-friendly spacing:

.button-group button {
  margin: 0.5rem; /* Space between touch targets */
}

Viewport Units

Full height:

.hero {
  height: 100vh; /* Viewport height */
  height: 100dvh; /* Dynamic viewport (mobile) */
}

Responsive spacing:

.section {
  padding: 5vw; /* Scales with viewport */
}

Common Patterns

Sidebar layout:

.layout {
  display: grid;
  gap: 2rem;
  
  /* Mobile: Stack */
  grid-template-columns: 1fr;
}

@media (min-width: 1024px) {
  .layout {
    /* Desktop: Sidebar + main */
    grid-template-columns: 250px 1fr;
  }
}

Card grid:

.cards {
  display: grid;
  gap: 1rem;
  
  /* Mobile: 1 column */
  grid-template-columns: 1fr;
}

@media (min-width: 640px) {
  .cards {
    /* Tablet: 2 columns */
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .cards {
    /* Desktop: 3 columns */
    grid-template-columns: repeat(3, 1fr);
  }
}

@media (min-width: 1280px) {
  .cards {
    /* Large: 4 columns */
    grid-template-columns: repeat(4, 1fr);
  }
}

Hero section:

.hero {
  padding: 2rem 1rem;
  text-align: center;
}

@media (min-width: 768px) {
  .hero {
    padding: 4rem 2rem;
  }
}

@media (min-width: 1024px) {
  .hero {
    padding: 6rem 3rem;
    text-align: left;
    display: grid;
    grid-template-columns: 1fr 1fr;
    align-items: center;
  }
}

Testing

Browser DevTools:

• Chrome: Device toolbar (Cmd+Shift+M)
• Firefox: Responsive Design Mode
• Safari: Enter Responsive Design Mode

Test on real devices:

• iPhone (various sizes)
• Android phones
• Tablets
• Different browsers

Responsive testing tools:

• BrowserStack
• LambdaTest
• Responsively App

Responsive Checklist

Layout:

• [ ] Mobile-first approach
• [ ] Flexible grid system
• [ ] No horizontal scrolling
• [ ] Content readable at all sizes

Typography:

• [ ] Readable font sizes (16px+ body)
• [ ] Appropriate line height
• [ ] Fluid typography for headings
• [ ] Proper text wrapping

Images:

• [ ] Responsive images
• [ ] Appropriate sizes for devices
• [ ] Fast loading
• [ ] Art direction where needed

Navigation:

• [ ] Mobile menu pattern
• [ ] Touch-friendly targets (44px+)
• [ ] Easy to use on mobile
• [ ] Accessible

Performance:

• [ ] Fast on mobile networks
• [ ] Optimized images
• [ ] Minimal layout shifts
• [ ] Touch interactions smooth

Best Practices

Use relative units:

/* Good */
padding: 1rem;
font-size: 1.125rem;
width: 80%;

/* Avoid */
padding: 16px;
font-size: 18px;
width: 800px;

Test early and often:

• Test on mobile first
• Use real devices
• Test different orientations
• Test with slow connections

Progressive enhancement:

• Core functionality works on all devices
• Enhanced features for larger screens
• Graceful degradation

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [armanzeroeight](https://github.com/armanzeroeight)
- **Source:** [armanzeroeight/fastagent-plugins](https://github.com/armanzeroeight/fastagent-plugins)
- **License:** MIT

Install and usage instructions live in the source repository linked above.