Mobile UX Optimizer

Mobile-First UX Optimization

Build touch-optimized, performant mobile experiences with proper viewport handling and responsive patterns.

⚠️ TREIDO PROJECT: This project uses Tailwind v4 with CSS variables. Use min-h-(--spacing-touch-md) NOT min-h-[44px]. See globals.css for all tokens.

When to Use

✅ USE this skill for:

• Viewport issues (100vh problems, safe areas, notches)
• Touch target sizing and spacing
• Mobile navigation patterns (bottom nav, drawers, hamburger menus)
• Swipe gestures and pull-to-refresh
• Responsive breakpoint strategies
• Mobile performance optimization

❌ DO NOT use for:

• Native app development → use react-native or swift-executor skills
• Desktop-only features → no skill needed, standard patterns apply
• General CSS/Tailwind questions → use Tailwind docs or web-design-expert
• PWA installation/service workers → use pwa-expert skill

Core Principles

Mobile-First Means Build Up, Not Down

/* ❌ ANTI-PATTERN: Desktop-first (scale down) */
.card { width: 400px; }
@media (max-width: 768px) { .card { width: 100%; } }

/* ✅ CORRECT: Mobile-first (scale up) */
.card { width: 100%; }
@media (min-width: 768px) { .card { width: 400px; } }

The 44px Rule

Apple's Human Interface Guidelines specify 44×44 points as minimum touch target. Google Material suggests 48×48dp.

🎯 TREIDO PROJECT: Tailwind v4 Token Syntax

This project uses Tailwind v4 with CSS variables. Do NOT use arbitrary values.

Touch Target Tokens (from globals.css)

--spacing-touch-xs: 2rem;      /* 32px - minimum WCAG */
--spacing-touch-sm: 2.25rem;   /* 36px - compact */
--spacing-touch: 2.5rem;       /* 40px - default */
--spacing-touch-md: 2.75rem;   /* 44px - Apple minimum */
--spacing-touch-lg: 3rem;      /* 48px - bottom nav */

Correct Tailwind v4 Syntax

// ❌ WRONG - Arbitrary values (v3/generic style)
<button className="min-h-[44px] min-w-[44px] px-4 py-3">

// ✅ CORRECT - Tailwind v4 CSS variable syntax
<button className="min-h-(--spacing-touch-md) px-4 py-3">

// For square touch targets
<button className="size-(--spacing-touch-md)">

Treido-Specific Patterns

Full Touch-Friendly Example

// Touch-friendly button with proper tokens
<button 
  className="
    min-h-(--spacing-touch-md) 
    min-w-(--spacing-touch-md)
    px-4 
    rounded-lg
    active:opacity-80
    transition-opacity
  "
>
  Tap me
</button>

// Touch-friendly link with padding
<Link 
  href="/page" 
  className="inline-flex items-center min-h-(--spacing-touch-md) px-4"
>
  Link text
</Link>

Generic Reference (Non-Treido Projects)

Viewport Handling

The dvh Solution

Mobile browsers have dynamic toolbars. 100vh includes the URL bar, causing content to be cut off.

/* ❌ ANTI-PATTERN: Content hidden behind browser UI */
.full-screen { height: 100vh; }

/* ✅ CORRECT: Responds to browser chrome */
.full-screen { height: 100dvh; }

/* Fallback for older browsers */
.full-screen {
  height: 100vh;
  height: 100dvh;
}

Safe Area Insets (Notches & Home Indicators)

/* Handle iPhone notch and home indicator */
.bottom-nav {
  padding-bottom: env(safe-area-inset-bottom, 0);
}

.header {
  padding-top: env(safe-area-inset-top, 0);
}

/* Full safe area padding */
.safe-container {
  padding: env(safe-area-inset-top)
           env(safe-area-inset-right)
           env(safe-area-inset-bottom)
           env(safe-area-inset-left);
}

Required meta tag:

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

Tailwind Safe Area Classes

// Custom Tailwind utilities (add to globals.css)
@layer utilities {
  .pb-safe { padding-bottom: env(safe-area-inset-bottom); }
  .pt-safe { padding-top: env(safe-area-inset-top); }
  .h-screen-safe { height: calc(100dvh - env(safe-area-inset-top) - env(safe-area-inset-bottom)); }
}

// Usage
<nav className="fixed bottom-0 pb-safe bg-leather-900">
  <BottomNav />
</nav>

Mobile Navigation Patterns

Bottom Navigation (Recommended for Mobile)

// components/BottomNav.tsx - Treido Pattern
'use client';

import { usePathname } from 'next/navigation';
import Link from 'next/link';

const navItems = [
  { href: '/', icon: HomeIcon, label: 'Home' },
  { href: '/meetings', icon: CalendarIcon, label: 'Meetings' },
  { href: '/tools', icon: ToolsIcon, label: 'Tools' },
  { href: '/my', icon: UserIcon, label: 'My Recovery' },
];

export function BottomNav() {
  const pathname = usePathname();

  return (
    <nav className="fixed bottom-0 left-0 right-0 bg-background border-t border-border pb-safe">
      <div className="flex justify-around">
        {navItems.map(({ href, icon: Icon, label }) => {
          const isActive = pathname === href || pathname.startsWith(`${href}/`);
          return (
            <Link
              key={href}
              href={href}
              className={cn(
                "flex flex-col items-center justify-center",
                "h-(--spacing-touch-lg)",           // 48px height
                "min-w-(--spacing-touch-lg)",       // 48px min width
                "px-3",
                "active:opacity-80 transition-opacity",
                isActive ? 'text-primary' : 'text-muted-foreground'
              )}
            >
              <Icon className="size-(--size-icon)" /> {/* 24px icon */}
              <span className="text-xs mt-1">{label}</span>
            </Link>
          );
        })}
      </div>
    </nav>
  );
}

Slide-Out Drawer (Side Menu)

'use client';

import { useState, useEffect } from 'react';
import { createPortal } from 'react-dom';

interface DrawerProps {
  isOpen: boolean;
  onClose: () => void;
  children: React.ReactNode;
}

export function Drawer({ isOpen, onClose, children }: DrawerProps) {
  // Prevent body scroll when open
  useEffect(() => {
    if (isOpen) {
      document.body.style.overflow = 'hidden';
    }
    return () => {
      document.body.style.overflow = '';
    };
  }, [isOpen]);

  // Close on escape
  useEffect(() => {
    const handleEscape = (e: KeyboardEvent) => {
      if (e.key === 'Escape') onClose();
    };
    document.addEventListener('keydown', handleEscape);
    return () => document.removeEventListener('keydown', handleEscape);
  }, [onClose]);

  if (!isOpen) return null;

  return createPortal(
    <div className="fixed inset-0 z-50">
      {/* Backdrop */}
      <div
        className="absolute inset-0 bg-overlay-dark backdrop-blur-sm"
       
        aria-hidden="true"
      />

      {/* Drawer - Use Treido token for width */}
      <div
        className="
          absolute left-0 top-0 h-full 
          w-(--width-sheet-mobile)
          bg-background shadow-xl 
          transform transition-transform
          animate-slide-in-left
        "
        role="dialog"
        aria-modal="true"
      >
        <div className="h-full overflow-y-auto pt-safe pb-safe">
          {children}
        </div>
      </div>
    </div>,
    document.body
  );
}

Note: Treido uses vaul Drawer component from components/ui/drawer.tsx for production.

Touch Gestures

Full implementations in references/gestures.md

Quick usage:

// Swipe to dismiss
const { handleTouchStart, handleTouchEnd } = useSwipe({
  onSwipeLeft: () => dismiss(),
  threshold: 50,
});

// Pull to refresh
const { containerRef, pullDistance, isRefreshing, handlers } = 
  usePullToRefresh(async () => await refetchData());

Mobile Performance

Image Optimization

import Image from 'next/image';

// Responsive images with proper sizing
<Image
  src="/hero.jpg"
  alt="Hero"
  fill
  sizes="(max-width: 768px) 100vw, 50vw"
  priority // For above-the-fold images
  className="object-cover"
/>

// Lazy load below-fold images
<Image
  src="/feature.jpg"
  alt="Feature"
  width={400}
  height={300}
  loading="lazy"
/>

Reduce Bundle Size

// Dynamic imports for heavy components
const HeavyChart = dynamic(() => import('@/components/Chart'), {
  loading: () => <ChartSkeleton />,
  ssr: false, // Skip server render for client-only
});

// Lazy load below-fold sections
const Comments = dynamic(() => import('@/components/Comments'));

Skeleton Screens (Not Spinners)

// Skeleton that matches final content layout - Treido pattern
function MeetingCardSkeleton() {
  return (
    <div className="p-4 bg-muted rounded-lg animate-pulse">
      <div className="h-4 bg-muted-foreground/20 rounded w-3/4 mb-2" />
      <div className="h-3 bg-muted-foreground/20 rounded w-1/2 mb-4" />
      <div className="flex gap-2">
        <div className="h-6 w-16 bg-muted-foreground/20 rounded" />
        <div className="h-6 w-16 bg-muted-foreground/20 rounded" />
      </div>
    </div>
  );
}

// Usage
{isLoading ? (
  <div className="space-y-4">
    {[...Array(5)].map((_, i) => <MeetingCardSkeleton key={i} />)}
  </div>
) : (
  meetings.map(m => <MeetingCard key={m.id} meeting={m} />)
)}

Note: Treido uses components/ui/skeleton.tsx for production skeletons.

Responsive Patterns

Tailwind Breakpoint Strategy

sm: 640px   - Large phones (landscape)
md: 768px   - Tablets
lg: 1024px  - Small laptops
xl: 1280px  - Desktops
2xl: 1536px - Large screens

// Mobile: stack, Tablet+: side-by-side
<div className="flex flex-col md:flex-row gap-4">
  <aside className="w-full md:w-64">Sidebar</aside>
  <main className="flex-1">Content</main>
</div>

// Treido pattern: Mobile-only vs Desktop-only
<nav className="md:hidden fixed bottom-0 left-0 right-0">
  <BottomNav />
</nav>
<aside className="hidden md:flex w-(--layout-sidebar-w)">
  <SidebarNav />
</aside>

Container Queries (CSS-only Responsive Components)

/* Component responds to its container, not viewport */
@container (min-width: 400px) {
  .card { flex-direction: row; }
}

<div className="@container">
  <div className="flex flex-col @md:flex-row">
    {/* Responds to parent container width */}
  </div>
</div>

Testing on Real Devices

Chrome DevTools Mobile Emulation

1. Open DevTools (F12)
2. Toggle device toolbar (Ctrl+Shift+M)
3. Select device or set custom dimensions
4. Throttle network/CPU for realistic performance

Must-Test Scenarios

• Content doesn't get cut off by notch/home indicator
• Touch targets are at least 44×44px
• Scrolling is smooth (no jank)
• Bottom nav doesn't block content
• Forms work with virtual keyboard visible
• Landscape orientation works
• Pull-to-refresh doesn't fight with scroll

BrowserStack/Real Device Testing

# Expose local dev server to internet
npx localtunnel --port 3000
# or
ngrok http 3000

Quick Reference

References

See /references/ for detailed guides:

• keyboard-handling.md - Virtual keyboard and form UX
• animations.md - Touch-friendly animations
• accessibility.md - Mobile a11y requirements