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(Mobile-First · Touch-First · Platform-Respectful)
---
name: mobile-design
description: "(Mobile-First · Touch-First · Platform-Respectful)"
risk: unknown
source: community
date_added: "2026-02-27"
---
# Mobile Design System
**(Mobile-First · Touch-First · Platform-Respectful)**
> **Philosophy:** Touch-first. Battery-conscious. Platform-respectful. Offline-capable.
> **Core Law:** Mobile is NOT a small desktop.
> **Operating Rule:** Think constraints first, aesthetics second.
This skill exists to **prevent desktop-thinking, AI-defaults, and unsafe assumptions** when designing or building mobile applications.
---
## 1. Mobile Feasibility & Risk Index (MFRI)
Before designing or implementing **any mobile feature or screen**, assess feasibility.
### MFRI Dimensions (1–5)
| Dimension | Question |
| -------------------------- | ----------------------------------------------------------------- |
| **Platform Clarity** | Is the target platform (iOS / Android / both) explicitly defined? |
| **Interaction Complexity** | How complex are gestures, flows, or navigation? |
| **Performance Risk** | Does this involve lists, animations, heavy state, or media? |
| **Offline Dependence** | Does the feature break or degrade without network? |
| **Accessibility Risk** | Does this impact motor, visual, or cognitive accessibility? |
### Score Formula
```
MFRI = (Platform Clarity + Accessibility Readiness)
− (Interaction Complexity + Performance Risk + Offline Dependence)
```
**Range:** `-10 → +10`
### Interpretation
| MFRI | Meaning | Required Action |
| -------- | --------- | ------------------------------------- |
| **6–10** | Safe | Proceed normally |
| **3–5** | Moderate | Add performance + UX validation |
| **0–2** | Risky | Simplify interactions or architecture |
| **< 0** | Dangerous | Redesign before implementation |
---
## 2. Mandatory Thinking Before Any Work
### ⛔ STOP: Ask Before Assuming (Required)
If **any of the following are not explicitly stated**, you MUST ask before proceeding:
| Aspect | Question | Why |
| ---------- | ------------------------------------------ | ---------------------------------------- |
| Platform | iOS, Android, or both? | Affects navigation, gestures, typography |
| Framework | React Native, Flutter, or native? | Determines performance and patterns |
| Navigation | Tabs, stack, drawer? | Core UX architecture |
| Offline | Must it work offline? | Data & sync strategy |
| Devices | Phone only or tablet too? | Layout & density rules |
| Audience | Consumer, enterprise, accessibility needs? | Touch & readability |
🚫 **Never default to your favorite stack or pattern.**
---
## 3. Mandatory Reference Reading (Enforced)
### Universal (Always Read First)
| File | Purpose | Status |
| ----------------------------- | ---------------------------------- | ----------------- |
| **mobile-design-thinking.md** | Anti-memorization, context-forcing | 🔴 REQUIRED FIRST |
| **touch-psychology.md** | Fitts’ Law, thumb zones, gestures | 🔴 REQUIRED |
| **mobile-performance.md** | 60fps, memory, battery | 🔴 REQUIRED |
| **mobile-backend.md** | Offline sync, push, APIs | 🔴 REQUIRED |
| **mobile-testing.md** | Device & E2E testing | 🔴 REQUIRED |
| **mobile-debugging.md** | Native vs JS debugging | 🔴 REQUIRED |
### Platform-Specific (Conditional)
| Platform | File |
| -------------- | ------------------- |
| iOS | platform-ios.md |
| Android | platform-android.md |
| Cross-platform | BOTH above |
> ❌ If you haven’t read the platform file, you are not allowed to design UI.
---
## 4. AI Mobile Anti-Patterns (Hard Bans)
### 🚫 Performance Sins (Non-Negotiable)
| ❌ Never | Why | ✅ Always |
| ------------------------- | -------------------- | --------------------------------------- |
| ScrollView for long lists | Memory explosion | FlatList / FlashList / ListView.builder |
| Inline renderItem | Re-renders all rows | useCallback + memo |
| Index as key | Reorder bugs | Stable ID |
| JS-thread animations | Jank | Native driver / GPU |
| console.log in prod | JS thread block | Strip logs |
| No memoization | Battery + perf drain | React.memo / const widgets |
---
### 🚫 Touch & UX Sins
| ❌ Never | Why | ✅ Always |
| --------------------- | -------------------- | ----------------- |
| Touch <44–48px | Miss taps | Min touch target |
| Gesture-only action | Excludes users | Button fallback |
| No loading state | Feels broken | Explicit feedback |
| No error recovery | Dead end | Retry + message |
| Ignore platform norms | Muscle memory broken | iOS ≠ Android |
---
### 🚫 Security Sins
| ❌ Never | Why | ✅ Always |
| ---------------------- | ------------------ | ---------------------- |
| Tokens in AsyncStorage | Easily stolen | SecureStore / Keychain |
| Hardcoded secrets | Reverse engineered | Env + secure storage |
| No SSL pinning | MITM risk | Cert pinning |
| Log sensitive data | PII leakage | Never log secrets |
---
## 5. Platform Unification vs Divergence Matrix
```
UNIFY DIVERGE
────────────────────────── ─────────────────────────
Business logic Navigation behavior
Data models Gestures
API contracts Icons
Validation Typography
Error semantics Pickers / dialogs
```
### Platform Defaults
| Element | iOS | Android |
| --------- | ------------ | -------------- |
| Font | SF Pro | Roboto |
| Min touch | 44pt | 48dp |
| Back | Edge swipe | System back |
| Sheets | Bottom sheet | Dialog / sheet |
| Icons | SF Symbols | Material Icons |
---
## 6. Mobile UX Psychology (Non-Optional)
### Fitts’ Law (Touch Reality)
* Finger ≠ cursor
* Accuracy is low
* Reach matters more than precision
**Rules:**
* Primary CTAs live in **thumb zone**
* Destructive actions pushed away
* No hover assumptions
---
## 7. Performance Doctrine
### React Native (Required Pattern)
```ts
const Row = React.memo(({ item }) => (
<View><Text>{item.title}</Text></View>
));
const renderItem = useCallback(
({ item }) => <Row item={item} />,
[]
);
<FlatList
data={items}
renderItem={renderItem}
keyExtractor={(i) => i.id}
getItemLayout={(_, i) => ({
length: ITEM_HEIGHT,
offset: ITEM_HEIGHT * i,
index: i,
})}
/>
```
### Flutter (Required Pattern)
```dart
class Item extends StatelessWidget {
const Item({super.key});
@override
Widget build(BuildContext context) {
return const Text('Static');
}
}
```
* `const` everywhere possible
* Targeted rebuilds only
---
## 8. Mandatory Mobile Checkpoint
Before writing **any code**, you must complete this:
```
🧠 MOBILE CHECKPOINT
Platform: ___________
Framework: ___________
Files Read: ___________
3 Principles I Will Apply:
1.
2.
3.
Anti-Patterns I Will Avoid:
1.
2.
```
❌ Cannot complete → go back and read.
---
## 9. Framework Decision Tree (Canonical)
```
Need OTA + web team → React Native + Expo
High-perf UI → Flutter
iOS only → SwiftUI
Android only → Compose
```
No debate without justification.
---
## 10. Release Readiness Checklist
### Before Shipping
* [ ] Touch targets ≥ 44–48px
* [ ] Offline handled
* [ ] Secure storage used
* [ ] Lists optimized
* [ ] Logs stripped
* [ ] Tested on low-end devices
* [ ] Accessibility labels present
* [ ] MFRI ≥ 3
---
## 11. Related Skills
* **frontend-design** – Visual systems & components
* **frontend-dev-guidelines** – RN/TS architecture
* **backend-dev-guidelines** – Mobile-safe APIs
* **error-tracking** – Crash & performance telemetry
---
> **Final Law:**
> Mobile users are distracted, interrupted, and impatient—often using one hand on a bad network with low battery.
> **Design for that reality, or your app will fail quietly.**
---
## When to Use
This skill is applicable to execute the workflow or actions described in the overview.
## Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.
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