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
code
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 | ✅ Alway