mobile-app-interface skill

---
name: mobile-app-interface
description: Design native iOS mobile app interfaces and components. Creates user-centric mobile designs following platform conventions and best practices.
license: Proprietary. LICENSE.txt has complete terms
---

Expo iOS Designer
Core Design Prompt
“Design a modern, clean iOS app using Expo and React Native that follows Apple’s Human Interface Guidelines: prioritize clear hierarchy and harmony; respect safe areas; use responsive Flexbox layouts and Dynamic Type with SF Pro; support dark mode with semantic system-friendly colors; keep minimum 44pt touch targets; use native navigation patterns (tabs, stacks, modals) and standard gestures; apply Liquid Glass materials sparingly for overlays like bars, sheets, and popovers with AA contrast; add purposeful motion and gentle haptics; honor Reduce Motion and Reduce Transparency; deliver icons/splash and store assets per Apple guidance.”.​

Design Rules
1) Safe Areas Rule
Wrap screens with SafeAreaProvider/SafeAreaView to avoid notches and the home indicator; never hard‑code insets.​

tsx
import { SafeAreaView } from "react-native-safe-area-context";

export function Screen({ children }) {
  return <SafeAreaView style={{ flex: 1 }}>{children}</SafeAreaView>;
}
2) Typography Rule
Use SF Pro Text/Display (or system) with a documented type ramp; support Dynamic Type so text scales with user settings.​

tsx
<Text style={{ fontSize: 17, fontWeight: "600" }} accessibilityRole="header">
  Title
</Text>
<Text style={{ fontSize: 15, color: "#6b7280" }}>Secondary text</Text>
3) Touch Target Rule
Ensure interactive controls are at least 44×44pt, with adequate spacing between targets for accurate taps.​

tsx
<TouchableOpacity
  style={{ minHeight: 44, minWidth: 44, justifyContent: "center", alignItems: "center" }}
  accessibilityRole="button"
>
  <Text>Action</Text>
</TouchableOpacity>
4) Color & Theming Rule
Use semantic roles and support light/dark with AA contrast for text and essential UI; prefer system-friendly palettes that adapt across appearances.​

tsx
const scheme = useColorScheme();
const bg = scheme === "dark" ? "#0B0B0B" : "#FFFFFF";
const fg = scheme === "dark" ? "#E5E7EB" : "#111827";
5) Navigation Rule
Use tab bars for top-level sections, stack for drill-ins, and modals for short tasks; align back navigation with iOS gestures and conventions.​

**IMPORTANT: For Tab Bars with Liquid Glass**
ALWAYS use `NativeTabs` from Expo Router instead of custom tab bars. NativeTabs provides native iOS `UITabBarController` with built-in Liquid Glass effect - no manual implementation needed!

tsx
// ✅ CORRECT: Native tab bar with built-in Liquid Glass
import { NativeTabs, Icon, Label } from "expo-router/unstable-native-tabs";

export default function TabLayout() {
  return (
    <NativeTabs>
      <NativeTabs.Trigger name="index">
        <Icon sf={{ default: 'house', selected: 'house.fill' }} />
        <Label>Home</Label>
      </NativeTabs.Trigger>
      <NativeTabs.Trigger name="settings">
        <Icon sf={{ default: 'gearshape', selected: 'gearshape.fill' }} />
        <Label>Settings</Label>
      </NativeTabs.Trigger>
    </NativeTabs>
  );
}

// ❌ WRONG: Custom tab bars - requires manual Liquid Glass implementation
import { createBottomTabNavigator } from "@react-navigation/bottom-tabs";
const Tab = createBottomTabNavigator();

**NativeTabs Features:**
- Built-in Liquid Glass blur (automatic on iOS 26+)
- SF Symbols for icons (`sf` prop with default/selected states)
- Native iOS animations and haptics
- Automatic light/dark mode adaptation
- System-native behavior (matches Safari, Apple Music, etc.)
- No custom styling required

**SF Symbols Icon Examples:**
- Home: `house` / `house.fill`
- Settings: `gearshape` / `gearshape.fill`
- Messages: `message` / `message.fill`
- Profile: `person` / `person.fill`
- Search: `magnifyingglass`
- Calendar: `calendar` / `calendar.fill`
- Star: `star` / `star.fill`

Find more at: https://developer.apple.com/sf-symbols/
6) Motion & Haptics Rule
Keep transitions 200–400ms with native-feeling ease or spring; pair key state changes and confirmations with gentle haptics.​

tsx
import * as Haptics from "expo-haptics";
const onPress = async () => { await Haptics.selectionAsync(); /* action */ };
7) Accessibility Rule
Provide accessibilityLabel, Role, Hint, and state; verify logical focus order and complete VoiceOver announcements across flows.​

tsx
<Switch
  value={isOn}
  onValueChange={setOn}
  accessibilityRole="switch"
  accessibilityLabel="Notifications"
  accessibilityState={{ checked: isOn }}
/>
8) List & Performance Rule
Use FlatList/SectionList with keyExtractor, optional getItemLayout, and memoized rows; avoid re-render churn for smooth 60fps scrolling.​

tsx
<FlatList
  data={items}
  keyExtractor={(it) => it.id}
  renderItem={memo(({ item }) => <Row item={item} />)}
/>
9) Assets & App Store Rule
Create icons and splash per Expo docs; verify in an EAS build, not Expo Go; keep store metadata and permissions aligned to behavior.​

json
// app.json (excerpt)
{
  "expo": {
    "icon": "./assets/icon.png",
    "splash": { "image": "./assets/splash.png", "resizeMode": "contain", "backgroundColor": "#000000" }
  }
}
10) Layout & Spacing Rule
Compose with Flexbox and a consistent spacing scale; adapt padding to dynamic type and safe areas for balanced, accessible layouts.​

tsx
<View style={{ padding: 16, gap: 12, flex: 1 }}>
  {/* content */}
</View>
11) Liquid Glass Materials Rule
Use Liquid Glass on overlay surfaces (navigation/tab bars, large headers, sheets, popovers, floating cards) to add depth without distracting from content; verify AA contrast over dynamic backdrops in light and dark modes.​

Respect Reduce Transparency and provide solid/tinted fallbacks; avoid placing dense text over highly saturated or high-frequency backdrops.​

Keep materials subtle: modest opacity/blur, applied sparingly to chrome rather than full-screen backgrounds for readability and performance.​

12) Expo Glass Modules Rule
Official module: expo-glass-effect. Provides GlassView, GlassContainer, and isLiquidGlassAvailable() to detect capability and compose grouped glass surfaces.​

Community SwiftUI module: expo-liquid-glass-view. Fine control over corner radius, styles, and tints; iOS-only; ensure platform fallbacks.​

Install and basic usage:

bash
npx expo install expo-glass-effect
tsx
import { GlassView } from "expo-glass-effect";

<GlassView glassEffectStyle="regular" tintColor="systemMaterialLight" />
SwiftUI-powered option:

bash
npx expo install expo-liquid-glass-view
tsx
import { ExpoLiquidGlassView } from "expo-liquid-glass-view";
These render native iOS Liquid Glass via UIVisualEffectView/SwiftUI, and gracefully fall back to a regular View on unsupported platforms.​

13) Availability & Fallbacks Rule
Check availability on iOS 26+ with isLiquidGlassAvailable(); also honor AccessibilityInfo.isReduceTransparencyEnabled() for fallbacks to solid/tinted surfaces.​

tsx
import { isLiquidGlassAvailable, GlassView } from "expo-glass-effect";
import { AccessibilityInfo, Platform } from "react-native";

const useGlass = async () => {
  const supported = Platform.OS === "ios" && (await isLiquidGlassAvailable());
  const reduceTransparency = await AccessibilityInfo.isReduceTransparencyEnabled();
  return { supported, reduceTransparency };
};
14) Materials Performance Rule
Avoid full-screen realtime blur on animated scenes; scope glass to small overlays, cache where possible, and profile on device; fall back to static blur or solids when FPS dips.​

15) Icon Variants Rule
Provide dark and tinted icon variants following updated Apple resources for consistent appearance with system tints and wallpapers.​

Workflow
1) Interview User
Scope: screen, flow, or component; target file/repo path; materials use-cases (bars, sheets, overlays); accessibility/performance targets.​

2) Design & Implement
Match HIG patterns and the existing design system; compose UI first; define component variants/states.​

Apply all rules (safe area, type, touch, color, nav, motion, a11y, performance, materials, icons). Test Dynamic Type, dark mode, VoiceOver, Reduce Transparency/Motion, and iOS 26 availability.​

Validate on device for performance, notch layouts, and readability over moving content and wallpapers.​

3) Component Structure Pattern
tsx
import { View, Text } from "react-native";
import { SafeAreaView } from "react-native-safe-area-context";

export function ScreenTemplate({ title, children }) {
  return (
    <SafeAreaView style={{ flex: 1 }}>
      <View style={{ padding: 20, gap: 16 }}>
        <Text style={{ fontSize: 28, fontWeight: "700" }} accessibilityRole="header">
          {title}
        </Text>
        <View style={{ gap: 12 }}>{children}</View>
      </View>
    </SafeAreaView>
  );
}
Quality Checklist
 Safe areas respected across edges and orientations.​

 SF Pro/system fonts with Dynamic Type verified at larger sizes.​

 44×44pt touch targets and adequate spacing confirmed on device.​

 Light/dark with semantic colors and WCAG AA contrast for text and core UI.​

 Native navigation patterns and back gestures consistent with iOS.​

 Purposeful motion with gentle haptics; honors Reduce Motion.​

 Accessibility labels/roles/hints/states and logical focus order; VoiceOver validated.​

 Lists are smooth and jank-free; renders and images optimized.​

 Icons/splash configured via Expo and tested in an EAS build.​

 Store metadata and permissions aligned with behavior.​

 Liquid Glass used for overlays only; AA contrast verified over dynamic backdrops.​

 Availability checks with isLiquidGlassAvailable(); fallbacks for Reduce Transparency.​

 Materials performance profiled; fallbacks applied if FPS drops.​

 Icon dark/tinted variants per updated resources.​

References
Apple HIG: layout, navigation, materials, typography.​

Expo GlassEffect API and install guides; SwiftUI module references.​

Expo docs: safe areas, splash/icon configuration, project setup and device testing.​

Accessibility: React Native docs and testing guidance for roles, labels, focus order, touch targets.​