| name | mobile-design |
| description | Mobile-first design thinking and decision-making for iOS and Android apps. Touch interaction, performance patterns, platform conventions. Teaches principles, not fixed values. Use when building React Native, Flutter, or native mobile apps. When designing mobile app interfaces for iOS/Android, React Native, or Flutter. Touch interaction and platform conventions. NOT for web apps. |
| allowed-tools | Read, Glob, Grep, Bash |
Mobile Design System
Philosophy: Touch-first. Battery-conscious. Platform-respectful. Offline-capable.
Core Principle: Mobile is NOT a small desktop. THINK mobile constraints, ASK platform choice.
🔧 Runtime Scripts
Execute these for validation (don't read, just run):
| Script | Purpose | Usage |
|---|
scripts/mobile_audit.py | Mobile UX & Touch Audit | python scripts/mobile_audit.py <project_path> |
🔴 MANDATORY: Read Reference Files Before Working!
⛔ DO NOT start development until you read the relevant files:
Universal (Always Read)
| File | Content | Status |
|---|
| mobile-design-thinking.md | ⚠️ ANTI-MEMORIZATION: Forces thinking, prevents AI defaults | ⬜ CRITICAL FIRST |
| touch-psychology.md | Fitts' Law, gestures, haptics, thumb zone | ⬜ CRITICAL |
| mobile-performance.md | RN/Flutter performance, 60fps, memory | ⬜ CRITICAL |
| mobile-backend.md | Push notifications, offline sync, mobile API | ⬜ CRITICAL |
| mobile-testing.md | Testing pyramid, E2E, platform-specific | ⬜ CRITICAL |
| mobile-debugging.md | Native vs JS debugging, RN DevTools, Logcat | ⬜ CRITICAL |
| mobile-navigation.md | Tab/Stack/Drawer, deep linking | ⬜ Read |
| mobile-typography.md | System fonts, Dynamic Type, a11y | ⬜ Read |
| mobile-color-system.md | OLED, dark mode, battery-aware | ⬜ Read |
| decision-trees.md | Framework/state/storage selection | ⬜ Read |
🧠 mobile-design-thinking.md is PRIORITY! This file ensures AI thinks instead of using memorized patterns.
Platform-Specific (Read Based on Target)
| Platform | File | Content | When to Read |
|---|
| iOS | platform-ios.md | Human Interface Guidelines, SF Pro, SwiftUI patterns | Building for iPhone/iPad |
| Android | platform-android.md | Material Design 3, Roboto, Compose patterns | Building for Android |
| Cross-Platform | Both above | Platform divergence points | React Native / Flutter |
🔴 If building for iOS → Read platform-ios.md FIRST!
🔴 If building for Android → Read platform-android.md FIRST!
🔴 If cross-platform → Read BOTH and apply conditional platform logic!
⚠️ CRITICAL: ASK BEFORE ASSUMING (MANDATORY)
STOP! If the user's request is open-ended, DO NOT default to your favorites.
You MUST Ask If Not Specified:
| Aspect | Ask | Why |
|---|
| Platform | "iOS, Android, or both?" | Affects EVERY design decision |
| Framework | "React Native, Flutter, or native?" | Determines patterns and tools |
| Navigation | "Tab bar, drawer, or stack-based?" | Core UX decision |
| State | "What state management? (Zustand/Redux/Riverpod/BLoC?)" | Architecture foundation |
| Offline | "Does this need to work offline?" | Affects data strategy |
| Target devices | "Phone only, or tablet support?" | Layout complexity |
⛔ AI MOBILE ANTI-PATTERNS (BANNED LIST)
🚫 These are AI default tendencies that MUST be avoided!
Performance Sins
| ❌ NEVER DO | Why It's Wrong | ✅ ALWAYS DO |
|---|
| ScrollView for long lists | Renders ALL items, memory explodes | Use FlatList / FlashList / ListView.builder |
| Inline renderItem function | New function every render, all items re-render | useCallback + React.memo |
| Missing keyExtractor | Index-based keys cause bugs on reorder | Unique, stable ID from data |
| Skip getItemLayout | Async layout = janky scroll | Provide when items have fixed height |
| setState() everywhere | Unnecessary widget rebuilds | Targeted state, const constructors |
| Native driver: false | Animations blocked by JS thread | useNativeDriver: true always |
| console.log in production | Blocks JS thread severely | Remove before release build |
| Skip React.memo/const | Every item re-renders on any change | Memoize list items ALWAYS |
Touch/UX Sins
| ❌ NEVER DO | Why It's Wrong | ✅ ALWAYS DO |
|---|
| Touch target < 44px | Impossible to tap accurately, frustrating | Minimum 44pt (iOS) / 48dp (Android) |
| Spacing < 8px between targets | Accidental taps on neighbors | Minimum 8-12px gap |
| Gesture-only interactions | Motor impaired users excluded | Always provide button alternative |
| No loading state | User thinks app crashed | ALWAYS show loading feedback |
| No error state | User stuck, no recovery path | Show error with retry option |
| No offline handling | Crash/block when network lost | Graceful degradation, cached data |
| Ignore platform conventions | Users confused, muscle memory broken | iOS feels iOS, Android feels Android |
Security Sins
| ❌ NEVER DO | Why It's Wrong | ✅ ALWAYS DO |
|---|
| Token in AsyncStorage | Easily accessible, stolen on rooted device | SecureStore / Keychain / EncryptedSharedPreferences |
| Hardcode API keys | Reverse engineered from APK/IPA | Environment variables, secure storage |
| Skip SSL pinning | MITM attacks possible | Pin certificates in production |
| Log sensitive data | Logs can be extracted | Never log tokens, passwords, PII |
Architecture Sins
| ❌ NEVER DO | Why It's Wrong | ✅ ALWAYS DO |
|---|
| Business logic in UI | Untestable, unmaintainable | Service layer separation |
| Global state for everything | Unnecessary re-renders, complexity | Local state default, lift when needed |
| Deep linking as afterthought | Notifications, shares broken | Plan deep links from day one |
| Skip dispose/cleanup | Memory leaks, zombie listeners | Clean up subscriptions, timers |
📱 Platform Decision Matrix
When to Unify vs Diverge
UNIFY (same on both) DIVERGE (platform-specific)
─────────────────── ──────────────────────────
Business Logic ✅ Always -
Data Layer ✅ Always -
Core Features ✅ Always -
Navigation - ✅ iOS: edge swipe, Android: back button
Gestures - ✅ Platform-native feel
Icons - ✅ SF Symbols vs Material Icons
Date Pickers - ✅ Native pickers feel right
Modals/Sheets - ✅ iOS: bottom sheet vs Android: dialog
Typography - ✅ SF Pro vs Roboto (or custom)
Error Dialogs - ✅ Platform conventions for alerts
Quick Reference: Platform Defaults
| Element | iOS | Android |
|---|
| Primary Font | SF Pro / SF Compact | Roboto |
| Min Touch Target | 44pt × 44pt | 48dp × 48dp |
| Back Navigation | Edge swipe left | System back button/gesture |
| Bottom Tab Icons | SF Symbols | Material Symbols |
| Action Sheet | UIActionSheet from bottom | Bottom Sheet / Dialog |
| Progress | Spinner | Linear progress (Material) |
| Pull to Refresh | Native UIRefreshControl | SwipeRefreshLayout |
🧠 Mobile UX Psychology (Quick Reference)
Fitts' Law for Touch
Desktop: Cursor is precise (1px)
Mobile: Finger is imprecise (~7mm contact area)
→ Touch targets MUST be 44-48px minimum
→ Important actions in THUMB ZONE (bottom of screen)
→ Destructive actions AWAY from easy reach
Thumb Zone (One-Handed Usage)
┌─────────────────────────────┐
│ HARD TO REACH │ ← Navigation, menu, back
│ (stretch) │
├─────────────────────────────┤
│ OK TO REACH │ ← Secondary actions
│ (natural) │
├─────────────────────────────┤
│ EASY TO REACH │ ← PRIMARY CTAs, tab bar
│ (thumb's natural arc) │ ← Main content interaction
└─────────────────────────────┘
[ HOME ]
Mobile-Specific Cognitive Load
| Desktop | Mobile Difference |
|---|
| Multiple windows | ONE task at a time |
| Keyboard shortcuts | Touch gestures |
| Hover states | NO hover (tap or nothing) |
| Large viewport | Limited space, scroll vertical |
| Stable attention | Interrupted constantly |
For deep dive: touch-psychology.md
⚡ Performance Principles (Quick Reference)
React Native Critical Rules
const ListItem = React.memo(({ item }: { item: Item }) => (
<View style={styles.item}>
<Text>{item.title}</Text>
</View>
));
const renderItem = useCallback(
({ item }: { item: Item }) => <ListItem item={item} />,
[]
);
<FlatList
data={items}
renderItem={renderItem}
keyExtractor={(item) => item.id} // Stable ID, NOT index
getItemLayout={(data, index) => ({
length: ITEM_HEIGHT,
offset: ITEM_HEIGHT * index,
index,
})}
removeClippedSubviews={true}
maxToRenderPerBatch={10}
windowSize={5}
/>
Flutter Critical Rules
// ✅ CORRECT: const constructors prevent rebuilds
class MyWidget extends StatelessWidget {
const MyWidget({super.key}); // CONST!
@override
Widget build(BuildContext context) {
return const Column( // CONST!
children: [
Text('Static content'),
MyConstantWidget(),
],
);
}
}
// ✅ CORRECT: Targeted state with ValueListenableBuilder
ValueListenableBuilder<int>(
valueListenable: counter,
builder: (context, value, child) => Text('$value'),
child: const ExpensiveWidget(), // Won't rebuild!
)
Animation Performance
GPU-accelerated (FAST): CPU-bound (SLOW):
├── transform ├── width, height
├── opacity ├── top, left, right, bottom
└── (use these ONLY) ├── margin, padding
└── (AVOID animating these)
For complete guide: mobile-performance.md
📝 CHECKPOINT (MANDATORY Before Any Mobile Work)
Before writing ANY mobile code, you MUST complete this checkpoint:
🧠 CHECKPOINT:
Platform: [ iOS / Android / Both ]
Framework: [ React Native / Flutter / SwiftUI / Kotlin ]
Files Read: [ List the skill files you've read ]
3 Principles I Will Apply:
1. _______________
2. _______________
3. _______________
Anti-Patterns I Will Avoid:
1. _______________
2. _______________
Example:
🧠 CHECKPOINT:
Platform: iOS + Android (Cross-platform)
Framework: React Native + Expo
Files Read: touch-psychology.md, mobile-performance.md, platform-ios.md, platform-android.md
3 Principles I Will Apply:
1. FlatList with React.memo + useCallback for all lists
2. 48px touch targets, thumb zone for primary CTAs
3. Platform-specific navigation (edge swipe iOS, back button Android)
Anti-Patterns I Will Avoid:
1. ScrollView for lists → FlatList
2. Inline renderItem → Memoized
3. AsyncStorage for tokens → SecureStore
🔴 Can't fill the checkpoint? → GO BACK AND READ THE SKILL FILES.
🔧 Framework Decision Tree
WHAT ARE YOU BUILDING?
│
├── Need OTA updates + rapid iteration + web team
│ └── ✅ React Native + Expo
│
├── Need pixel-perfect custom UI + performance critical
│ └── ✅ Flutter
│
├── Deep native features + single platform focus
│ ├── iOS only → SwiftUI
│ └── Android only → Kotlin + Jetpack Compose
│
├── Existing RN codebase + new features
│ └── ✅ React Native (bare workflow)
│
└── Enterprise + existing Flutter codebase
└── ✅ Flutter
For complete decision trees: decision-trees.md
📋 Pre-Development Checklist
Before Starting ANY Mobile Project
Before Every Screen
Before Release
📚 Reference Files
For deeper guidance on specific areas:
| File | When to Use |
|---|
| mobile-design-thinking.md | FIRST! Anti-memorization, forces context-based thinking |
| touch-psychology.md | Understanding touch interaction, Fitts' Law, gesture design |
| mobile-performance.md | Optimizing RN/Flutter, 60fps, memory/battery |
| platform-ios.md | iOS-specific design, HIG compliance |
| platform-android.md | Android-specific design, Material Design 3 |
| mobile-navigation.md | Navigation patterns, deep linking |
| mobile-typography.md | Type scale, system fonts, accessibility |
| mobile-color-system.md | OLED optimization, dark mode, battery |
| decision-trees.md | Framework, state, storage decisions |
Remember: Mobile users are impatient, interrupted, and using imprecise fingers on small screens. Design for the WORST conditions: bad network, one hand, bright sun, low battery. If it works there, it works everywhere.
