Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/secondsky/claude-skills --skill mobile-first-design- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads mobile-first-design automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
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
FAQ
What does the mobile-first-design skill do?
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.
How do I install mobile-first-design?
Run npx skills add https://github.com/secondsky/claude-skills --skill mobile-first-design in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/mobile-first-design/ (personal) or .claude/skills/mobile-first-design/ (project).
Which AI agents can use mobile-first-design?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is mobile-first-design safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains mobile-first-design?
It is published by secondsky in secondsky/claude-skills. It has 574 recorded installs.
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