mobile-first-design-rules

Mobile First Design Rules Skill Always design and implement for mobile screens first, then scale up to larger screens. Use Tailwind's responsive prefixes (sm:, md:, lg:, xl:) to adjust layouts for different screen sizes. Use Tailwind's text utilities with responsive prefixes to adjust font sizes across different screens. Consider using a fluid typography system for seamless scaling. Iron Laws ALWAYS write base styles for mobile first (no Tailwind prefix = mobile) — adding mobile overrides after desktop classes defeats the responsive cascade and creates maintenance debt. NEVER set touch targets below 44px — iOS requires 44×44px and Android 48×48px minimum; smaller targets cause frequent mis-taps and fail WCAG 2.5.5. ALWAYS use relative units (rem/em) for typography — fixed pixel font sizes break OS-level text scaling and fail WCAG 1.4.4 (Resize Text). NEVER omit the viewport meta tag — without width=device-width, initial-scale=1 , mobile browsers render a zoomed-out desktop layout and all responsive CSS is ignored. ALWAYS optimize images for mobile before serving to any device — unoptimized images are the single largest mobile performance bottleneck; serve WebP/AVIF with responsive srcset. Anti-Patterns Anti-Pattern Why It Fails Correct Approach Desktop-first CSS with mobile overrides Mobile overrides fight specificity; cascade order breaks; maintenance burden grows Write base styles for mobile, then use sm: md: lg: prefixes to scale up Touch targets smaller than 44px iOS/Android guidelines violated; WCAG 2.5.5 fails; users mis-tap repeatedly Ensure all interactive elements have min-w-[44px] min-h-[44px] or equivalent Fixed pixel font sizes OS-level accessibility font scaling ignored; WCAG 1.4.4 violation Use text-base (1rem) as mobile base; scale with responsive Tailwind text utilities Missing viewport meta tag Browser renders zoomed-out desktop layout; responsive CSS never activates Always include Unoptimized images served to mobile Largest mobile performance bottleneck; LCP degrades; battery and data consumed Serve WebP/AVIF with responsive srcset; lazy-load below-the-fold images Memory Protocol (MANDATORY) Before starting: cat .claude/context/memory/learnings.md After completing: Record any new patterns or exceptions discovered. ASSUME INTERRUPTION: Your context may reset. If it's not in memory, it didn't happen.