// 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.
API design principles and decision-making. REST vs GraphQL vs tRPC selection, response formats, versioning, pagination.
Database design principles and decision-making. Schema design, indexing strategy, ORM selection, serverless databases.
Design thinking and decision-making for web UI. Use when designing components, layouts, color schemes, typography, or creating aesthetic interfaces. Teaches principles, not fixed values.
Generative Engine Optimization for AI search engines (ChatGPT, Claude, Perplexity).
Internationalization and localization patterns. Detecting hardcoded strings, managing translations, locale files, RTL support.
Automatic quality control, linting, and static analysis procedures. Use after every code modification to ensure syntax correctness and project standards. Triggers onKeywords: lint, format, check, validate, types, static analysis.
| 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. |
| allowed-tools | Read, Glob, Grep, Bash |
Philosophy: Touch-first. Battery-conscious. Platform-respectful. Offline-capable. Core Principle: Mobile is NOT a small desktop. THINK mobile constraints, ASK platform choice.
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> |
⛔ DO NOT start development until you read the relevant files:
| 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, Flipper, 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 | 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!
STOP! If the user's request is open-ended, DO NOT default to your favorites.
| 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 |
🚫 These are AI default tendencies that MUST be avoided!
| ❌ 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 |
| ❌ 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 |
| ❌ 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 |
| ❌ 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 |
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
| 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 |
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
┌─────────────────────────────┐
│ 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 ]
| 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
// ✅ CORRECT: Memoized renderItem + React.memo wrapper
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} />,
[]
);
// ✅ CORRECT: FlatList with all optimizations
<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}
/>
// ✅ 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!
)
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
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.
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
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.