Mobile First Design Skill for Claude

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

files

instructions only

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

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different authors, same section of the catalogue

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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.