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-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 `<meta name="viewport" content="width=device-width, initial-scale=1">`
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

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.