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Mobile First Design

secondsky/mobile-first-design

Designs responsive interfaces starting from mobile screens with progressive enhancement for larger devices. Use when building responsive websites, optimizing for mobile users, or implementing adaptive layouts.

493 tokens
context cost
the whole folder, loaded on every use
1
files
instructions only
0
copies elsewhere
how many repositories repackaged it
202
stars on the repo
on the repository, not the skill itself

Install

one command, takes just this skill from the repository 
npx skills add https://github.com/secondsky/claude-skills --skill mobile-first-design

The instruction itself

7 sections, as written by the author

Mobile-First Design

Design interfaces starting with mobile as the foundation, then enhance for larger screens.

Breakpoints

| Name | Width | Devices |

|------|-------|---------|

| Mobile | 320-480px | iPhone SE, small Android |

| Tablet | 481-768px | iPad mini |

| Desktop | 769-1024px | iPad Pro, laptops |

| Large | 1025px+ | Desktop monitors |

Mobile-First CSS

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

.nav {
  display: none; /* Hidden on mobile */
}

.nav-toggle {
  display: block; /* Hamburger visible */
}

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

  .nav {
    display: flex;
  }

  .nav-toggle {
    display: none;
  }
}

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

Touch-Friendly Design

/* Minimum touch target: 48x48px */
.button {
  min-height: 48px;
  min-width: 48px;
  padding: 12px 24px;
}

/* Adequate spacing */
.list-item {
  padding: 16px;
  margin-bottom: 8px;
}

Performance Requirements

| Metric | Target |

|--------|--------|

| First Contentful Paint | <3s on 3G |

| JS bundle | <100KB gzipped |

| Total page weight | <500KB |

Progressive Enhancement

<!-- Layer 1: Semantic HTML (works without CSS/JS) -->
<nav>
  <a href="/home">Home</a>
  <a href="/about">About</a>
</nav>

<!-- Layer 2: CSS enhances appearance -->
<!-- Layer 3: JS adds interactivity -->

Best Practices

  • Start design at 320px width
  • Use relative units (rem, %, vw)
  • Test on real devices
  • Optimize images for mobile
  • Minimize JavaScript for initial load
  • Ensure readable text without zooming

How to use it

Copy the folder

Take secondsky/mobile-first-design from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.