Mobile First Design

by secondsky88378361314fMIT227 starsListed Oct 8, 2026Updated Oct 8, 2026Repository updated 10 days ago

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.

Instructions onlyDesign & Creative
AI-generated overview

Guidance for designing responsive interfaces mobile-first with progressive enhancement for larger screens.

What it does
This skill provides instructions and reference material for designing responsive web interfaces starting from mobile screens and enhancing them for larger devices. It defines breakpoint widths, mobile-first CSS patterns, touch-friendly sizing, performance targets, and progressive enhancement layers. It produces design guidance rather than files or code artifacts.
When to use it
Use it when building responsive websites, optimizing layouts for mobile users, or implementing adaptive layouts that scale from small screens to desktop.
Requirements
No scripts or tools are required; it is instructions only. Applying the CSS and HTML examples assumes a web project and browser testing environment.

Mobile-First Design

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

Breakpoints

NameWidthDevices
Mobile320-480pxiPhone SE, small Android
Tablet481-768pxiPad mini
Desktop769-1024pxiPad Pro, laptops
Large1025px+Desktop monitors

Mobile-First CSS

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

css
/* 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

MetricTarget
First Contentful Paint<3s on 3G
JS bundle<100KB gzipped
Total page weight<500KB

Progressive Enhancement

html
<!-- 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

Source and attribution

Source:secondsky/claude-skillsinplugins/mobile-first-design/skills/mobile-first-designat commit8837836

License: MIT

Content belongs to its original authors. SourceWeft indexes it from a public repository.

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