expo routing initialization

frontend/app/(tabs)/_layout.tsx

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+import { Tabs } from 'expo-router';
+import React from 'react';
+import { Platform } from 'react-native';
+
+import { HapticTab } from '@/components/HapticTab';
+import { IconSymbol } from '@/components/ui/IconSymbol';
+import TabBarBackground from '@/components/ui/TabBarBackground';
+import { Colors } from '@/constants/Colors';
+import { useColorScheme } from '@/hooks/useColorScheme';
+
+export default function TabLayout() {
+  const colorScheme = useColorScheme();
+
+  return (
+    <Tabs
+      screenOptions={{
+        tabBarActiveTintColor: Colors[colorScheme ?? 'light'].tint,
+        headerShown: false,
+        tabBarButton: HapticTab,
+        tabBarBackground: TabBarBackground,
+        tabBarStyle: Platform.select({
+          ios: {
+            // Use a transparent background on iOS to show the blur effect
+            position: 'absolute',
+          },
+          default: {},
+        }),
+      }}>
+      <Tabs.Screen
+        name="index"
+        options={{
+          title: 'Home',
+          tabBarIcon: ({ color }) => <IconSymbol size={28} name="house.fill" color={color} />,
+        }}
+      />
+      <Tabs.Screen
+        name="explore"
+        options={{
+          title: 'Explore',
+          tabBarIcon: ({ color }) => <IconSymbol size={28} name="paperplane.fill" color={color} />,
+        }}
+      />
+    </Tabs>
+  );
+}

frontend/app/+not-found.tsx

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+import { Link, Stack } from 'expo-router';
+import { StyleSheet } from 'react-native';
+
+import { ThemedText } from '@/components/ThemedText';
+import { ThemedView } from '@/components/ThemedView';
+
+export default function NotFoundScreen() {
+  return (
+    <>
+      <Stack.Screen options={{ title: 'Oops!' }} />
+      <ThemedView style={styles.container}>
+        <ThemedText type="title">This screen doesn't exist.</ThemedText>
+        <Link href="/" style={styles.link}>
+          <ThemedText type="link">Go to home screen!</ThemedText>
+        </Link>
+      </ThemedView>
+    </>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    alignItems: 'center',
+    justifyContent: 'center',
+    padding: 20,
+  },
+  link: {
+    marginTop: 15,
+    paddingVertical: 15,
+  },
+});

frontend/app/_layout.tsx

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+import { DarkTheme, DefaultTheme, ThemeProvider } from '@react-navigation/native';
+import { useFonts } from 'expo-font';
+import { Stack } from 'expo-router';
+import * as SplashScreen from 'expo-splash-screen';
+import { StatusBar } from 'expo-status-bar';
+import { useEffect } from 'react';
+import 'react-native-reanimated';
+
+import { useColorScheme } from '@/hooks/useColorScheme';
+import { Provider } from 'react-redux';
+import { store } from '@/store';
+
+// Prevent the splash screen from auto-hiding before asset loading is complete.
+SplashScreen.preventAutoHideAsync();
+
+export default function RootLayout() {
+  const colorScheme = useColorScheme();
+  const [loaded] = useFonts({
+    SpaceMono: require('../assets/fonts/SpaceMono-Regular.ttf'),
+  });
+
+  useEffect(() => {
+    if (loaded) {
+      SplashScreen.hideAsync();
+    }
+  }, [loaded]);
+
+  if (!loaded) {
+    return null;
+  }
+
+  return (
+    <Provider store={store}>
+      <ThemeProvider value={colorScheme === 'dark' ? DarkTheme : DefaultTheme}>
+        <Stack>
+          <Stack.Screen name="(tabs)" options={{ headerShown: false }} />
+          <Stack.Screen name="+not-found" />
+        </Stack>
+        <StatusBar style="auto" />
+      </ThemeProvider>
+    </Provider>
+
+  );
+}

frontend/app/index.tsx

@@ -1,10 +1,10 @@
 // index.tsx
 import * as React from 'react';
 import { createNativeStackNavigator } from '@react-navigation/native-stack';
-import LoginScreen from '@/screens/LoginScreen';
-import SignupScreen from '@/screens/SignupScreen';
-import HomeScreen from '@/screens/HomeScreen';
-import ExtraInfoScreen from '@/screens/ExtraInfoScreen';
+import LoginScreen from '@/app/(tabs)/LoginScreen';
+import SignupScreen from '@/app/(tabs)/SignupScreen';
+import HomeScreen from '@/app/(tabs)/HomeScreen';
+import ExtraInfoScreen from '@/app/(tabs)/ExtraInfoScreen';
 import { store } from '@/store';
 import { Provider } from 'react-redux';
 

frontend/components/Collapsible.tsx

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+import { PropsWithChildren, useState } from 'react';
+import { StyleSheet, TouchableOpacity } from 'react-native';
+
+import { ThemedText } from '@/components/ThemedText';
+import { ThemedView } from '@/components/ThemedView';
+import { IconSymbol } from '@/components/ui/IconSymbol';
+import { Colors } from '@/constants/Colors';
+import { useColorScheme } from '@/hooks/useColorScheme';
+
+export function Collapsible({ children, title }: PropsWithChildren & { title: string }) {
+  const [isOpen, setIsOpen] = useState(false);
+  const theme = useColorScheme() ?? 'light';
+
+  return (
+    <ThemedView>
+      <TouchableOpacity
+        style={styles.heading}
+        onPress={() => setIsOpen((value) => !value)}
+        activeOpacity={0.8}>
+        <IconSymbol
+          name="chevron.right"
+          size={18}
+          weight="medium"
+          color={theme === 'light' ? Colors.light.icon : Colors.dark.icon}
+          style={{ transform: [{ rotate: isOpen ? '90deg' : '0deg' }] }}
+        />
+
+        <ThemedText type="defaultSemiBold">{title}</ThemedText>
+      </TouchableOpacity>
+      {isOpen && <ThemedView style={styles.content}>{children}</ThemedView>}
+    </ThemedView>
+  );
+}
+
+const styles = StyleSheet.create({
+  heading: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    gap: 6,
+  },
+  content: {
+    marginTop: 6,
+    marginLeft: 24,
+  },
+});

frontend/components/ExternalLink.tsx

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+import { Link } from 'expo-router';
+import { openBrowserAsync } from 'expo-web-browser';
+import { type ComponentProps } from 'react';
+import { Platform } from 'react-native';
+
+type Props = Omit<ComponentProps<typeof Link>, 'href'> & { href: string };
+
+export function ExternalLink({ href, ...rest }: Props) {
+  return (
+    <Link
+      target="_blank"
+      {...rest}
+      href={href}
+      onPress={async (event) => {
+        if (Platform.OS !== 'web') {
+          // Prevent the default behavior of linking to the default browser on native.
+          event.preventDefault();
+          // Open the link in an in-app browser.
+          await openBrowserAsync(href);
+        }
+      }}
+    />
+  );
+}

frontend/components/HapticTab.tsx

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+import { BottomTabBarButtonProps } from '@react-navigation/bottom-tabs';
+import { PlatformPressable } from '@react-navigation/elements';
+import * as Haptics from 'expo-haptics';
+
+export function HapticTab(props: BottomTabBarButtonProps) {
+  return (
+    <PlatformPressable
+      {...props}
+      onPressIn={(ev) => {
+        if (process.env.EXPO_OS === 'ios') {
+          // Add a soft haptic feedback when pressing down on the tabs.
+          Haptics.impactAsync(Haptics.ImpactFeedbackStyle.Light);
+        }
+        props.onPressIn?.(ev);
+      }}
+    />
+  );
+}

frontend/components/HelloWave.tsx

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+import { useEffect } from 'react';
+import { StyleSheet } from 'react-native';
+import Animated, {
+  useSharedValue,
+  useAnimatedStyle,
+  withTiming,
+  withRepeat,
+  withSequence,
+} from 'react-native-reanimated';
+
+import { ThemedText } from '@/components/ThemedText';
+
+export function HelloWave() {
+  const rotationAnimation = useSharedValue(0);
+
+  useEffect(() => {
+    rotationAnimation.value = withRepeat(
+      withSequence(withTiming(25, { duration: 150 }), withTiming(0, { duration: 150 })),
+      4 // Run the animation 4 times
+    );
+  }, []);
+
+  const animatedStyle = useAnimatedStyle(() => ({
+    transform: [{ rotate: `${rotationAnimation.value}deg` }],
+  }));
+
+  return (
+    <Animated.View style={animatedStyle}>
+      <ThemedText style={styles.text}>👋</ThemedText>
+    </Animated.View>
+  );
+}
+
+const styles = StyleSheet.create({
+  text: {
+    fontSize: 28,
+    lineHeight: 32,
+    marginTop: -6,
+  },
+});

frontend/components/ParallaxScrollView.tsx

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+import type { PropsWithChildren, ReactElement } from 'react';
+import { StyleSheet } from 'react-native';
+import Animated, {
+  interpolate,
+  useAnimatedRef,
+  useAnimatedStyle,
+  useScrollViewOffset,
+} from 'react-native-reanimated';
+
+import { ThemedView } from '@/components/ThemedView';
+import { useBottomTabOverflow } from '@/components/ui/TabBarBackground';
+import { useColorScheme } from '@/hooks/useColorScheme';
+
+const HEADER_HEIGHT = 250;
+
+type Props = PropsWithChildren<{
+  headerImage: ReactElement;
+  headerBackgroundColor: { dark: string; light: string };
+}>;
+
+export default function ParallaxScrollView({
+  children,
+  headerImage,
+  headerBackgroundColor,
+}: Props) {
+  const colorScheme = useColorScheme() ?? 'light';
+  const scrollRef = useAnimatedRef<Animated.ScrollView>();
+  const scrollOffset = useScrollViewOffset(scrollRef);
+  const bottom = useBottomTabOverflow();
+  const headerAnimatedStyle = useAnimatedStyle(() => {
+    return {
+      transform: [
+        {
+          translateY: interpolate(
+            scrollOffset.value,
+            [-HEADER_HEIGHT, 0, HEADER_HEIGHT],
+            [-HEADER_HEIGHT / 2, 0, HEADER_HEIGHT * 0.75]
+          ),
+        },
+        {
+          scale: interpolate(scrollOffset.value, [-HEADER_HEIGHT, 0, HEADER_HEIGHT], [2, 1, 1]),
+        },
+      ],
+    };
+  });
+
+  return (
+    <ThemedView style={styles.container}>
+      <Animated.ScrollView
+        ref={scrollRef}
+        scrollEventThrottle={16}
+        scrollIndicatorInsets={{ bottom }}
+        contentContainerStyle={{ paddingBottom: bottom }}>
+        <Animated.View
+          style={[
+            styles.header,
+            { backgroundColor: headerBackgroundColor[colorScheme] },
+            headerAnimatedStyle,
+          ]}>
+          {headerImage}
+        </Animated.View>
+        <ThemedView style={styles.content}>{children}</ThemedView>
+      </Animated.ScrollView>
+    </ThemedView>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+  },
+  header: {
+    height: HEADER_HEIGHT,
+    overflow: 'hidden',
+  },
+  content: {
+    flex: 1,
+    padding: 32,
+    gap: 16,
+    overflow: 'hidden',
+  },
+});