Ui Mobile

# Mobile UI Design Skill (React Native)


---

## MANDATORY: Mobile Accessibility Standards

**These rules are NON-NEGOTIABLE. Every UI element must pass these checks.**

### 1. Touch Targets (CRITICAL)
```typescript
// MINIMUM 44x44 points for ALL interactive elements
const MINIMUM_TOUCH_SIZE = 44;

// EVERY button, link, icon button must meet this
const styles = StyleSheet.create({
  button: {
    minHeight: MINIMUM_TOUCH_SIZE,
    minWidth: MINIMUM_TOUCH_SIZE,
    paddingVertical: 12,
    paddingHorizontal: 16,
  },
  iconButton: {
    width: MINIMUM_TOUCH_SIZE,
    height: MINIMUM_TOUCH_SIZE,
    justifyContent: 'center',
    alignItems: 'center',
  },
});

// NEVER DO THIS:
style={{ height: 30 }}  // ✗ TOO SMALL
style={{ padding: 4 }}  // ✗ RESULTS IN TINY TARGET
```

### 2. Color Contrast (CRITICAL)
```typescript
// WCAG 2.1 AA: 4.5:1 for text, 3:1 for large text/UI

// SAFE COMBINATIONS:
const colors = {
  // Light mode
  textPrimary: '#000000',     // on white = 21:1 ✓
  textSecondary: '#374151',   // gray-700 on white = 9.2:1 ✓

  // Dark mode
  textPrimaryDark: '#FFFFFF', // on gray-900 = 16:1 ✓
  textSecondaryDark: '#E5E7EB', // gray-200 on gray-900 = 11:1 ✓
};

// FORBIDDEN - FAILS CONTRAST:
// ✗ '#9CA3AF' (gray-400) on white = 2.6:1
// ✗ '#6B7280' (gray-500) on '#111827' = 4.0:1
// ✗ Any text below 4.5:1 ratio
```

### 3. Visibility Rules
```typescript
// ALL BUTTONS MUST HAVE visible boundaries

// PRIMARY: Solid background with contrasting text
<Pressable style={styles.primaryButton}>
  <Text style={{ color: '#FFFFFF' }}>Submit</Text>
</Pressable>

const styles = StyleSheet.create({
  primaryButton: {
    backgroundColor: '#1F2937', // gray-800
    paddingVertical: 16,
    paddingHorizontal: 24,
    borderRadius: 12,
    minHeight: 44,
  },
});

// SECONDARY: Visible background
<Pressable style={styles.secondaryButton}>
  <Text style={{ color: '#1F2937' }}>Cancel</Text>
</Pressable>

const styles = StyleSheet.create({
  secondaryButton: {
    backgroundColor: '#F3F4F6', // gray-100
    minHeight: 44,
  },
});

// GHOST: MUST have visible border
<Pressable style={styles.ghostButton}>
  <Text style={{ color: '#374151' }}>Skip</Text>
</Pressable>

const styles = StyleSheet.create({
  ghostButton: {
    borderWidth: 1,
    borderColor: '#D1D5DB', // gray-300
    minHeight: 44,
  },
});

// NEVER CREATE invisible buttons:
// ✗ backgroundColor: 'transparent' without border
// ✗ Text color matching background
```

### 4. Accessibility Labels (REQUIRED)
```tsx
// EVERY interactive element needs accessibility props

// Buttons
<Pressable
  accessible={true}
  accessibilityRole="button"
  accessibilityLabel="Submit form"
  accessibilityHint="Double tap to submit your information"
>
  <Text>Submit</Text>
</Pressable>

// Icon buttons (NO visible text = MUST have label)
<Pressable
  accessible={true}
  accessibilityRole="button"
  accessibilityLabel="Close menu"
>
  <CloseIcon />
</Pressable>

// Images
<Image
  accessible={true}
  accessibilityRole="image"
  accessibilityLabel="User profile photo"
  source={...}
/>
```

### 5. Focus/Selection States
```tsx
// EVERY Pressable needs visible pressed state
<Pressable
  style={({ pressed }) => [
    styles.button,
    pressed && styles.buttonPressed,
  ]}
>
  {children}
</Pressable>

const styles = StyleSheet.create({
  button: {
    backgroundColor: '#1F2937',
  },
  buttonPressed: {
    opacity: 0.7,
    // OR
    backgroundColor: '#374151',
  },
});
```

---

## Core Philosophy

**Mobile UI is about touch, speed, and focus.** No hover states, smaller screens, thumb-friendly targets. Design for one-handed use and interruption recovery.

## Platform Differences

### iOS vs Android
```typescript
import { Platform } from 'react-n