diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..4f00fd8
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,10 @@
+node_modules/
+.expo/
+dist/
+build/
+.expo-shared/
+.env
+.DS_Store
+web-build/
+*.log
+coverage/
diff --git a/App.tsx b/App.tsx
new file mode 100644
index 0000000..05cbaf8
--- /dev/null
+++ b/App.tsx
@@ -0,0 +1,75 @@
+import { NavigationContainer } from '@react-navigation/native';
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
+import { GestureHandlerRootView } from 'react-native-gesture-handler';
+import { TailwindProvider } from 'nativewind';
+import { StatusBar } from 'expo-status-bar';
+import { LinkingOptions } from '@react-navigation/native';
+import { useMemo } from 'react';
+
+import RootNavigator from '@/navigation/RootNavigator';
+import { AuthProvider } from '@/hooks/useAuth';
+import { RootStackParamList } from '@/types/navigation';
+
+const queryClient = new QueryClient();
+
+const App = () => {
+  const linking = useMemo<LinkingOptions<RootStackParamList>>(
+    () => ({
+      prefixes: ['fetchapp://', 'https://fetchapp.app'],
+      config: {
+        screens: {
+          Auth: {
+            screens: {
+              Login: 'login',
+              Register: 'register'
+            }
+          },
+          Main: {
+            screens: {
+              HomeTab: {
+                screens: {
+                  Home: '',
+                  ScanReceiptModal: 'scan'
+                }
+              },
+              SquadTab: {
+                screens: {
+                  Squad: 'squad/:squadId?',
+                  SquadInvite: 'squad/join/:squadId'
+                }
+              },
+              LeagueTab: {
+                screens: {
+                  League: 'league'
+                }
+              },
+              ProfileTab: {
+                screens: {
+                  Profile: 'profile'
+                }
+              }
+            }
+          }
+        }
+      }
+    }),
+    []
+  );
+
+  return (
+    <GestureHandlerRootView style={{ flex: 1 }}>
+      <TailwindProvider>
+        <QueryClientProvider client={queryClient}>
+          <AuthProvider>
+            <NavigationContainer linking={linking}>
+              <RootNavigator />
+              <StatusBar style="dark" />
+            </NavigationContainer>
+          </AuthProvider>
+        </QueryClientProvider>
+      </TailwindProvider>
+    </GestureHandlerRootView>
+  );
+};
+
+export default App;
diff --git a/README.md b/README.md
index c32ea5a..31410c9 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,94 @@
-# Second
\ No newline at end of file
+# Fetch Rewards MVP – Squads & Leagues
+
+This repository contains a React Native (Expo) MVP for Fetch Rewards that showcases the new **Squads** and **Leagues** experiences. The app is written in TypeScript, styled with NativeWind, and backed by Firebase Authentication and Firestore. Use it to explore receipt-sharing, collaborative goals, and weekly league leaderboards on both iOS and Android via Expo Go.
+
+## ✨ Features
+- Email/password authentication backed by Firebase Auth with automatic Firestore profile creation.
+- **Squads**: create or join teams, share invite links, split receipt points, manage a shared shopping list, and track progress toward group goals with a playful mascot.
+- **Receipt simulator**: quickly award random points and split them across squad members.
+- **Weekly challenges** and duel callouts to encourage friendly competition within squads.
+- **Leagues**: weekly leaderboards, streak multipliers, promotion highlights, and seasonal countdown messaging.
+- Firestore seeding script that creates demo users, squads, and leagues for richer testing data.
+
+## 🧱 Project Structure
+```
+.
+├── App.tsx
+├── app.config.ts
+├── seed.js
+├── src/
+│   ├── components/
+│   ├── hooks/
+│   ├── navigation/
+│   ├── screens/
+│   ├── services/
+│   ├── types/
+│   └── utils/
+└── tailwind.config.js
+```
+
+## 🛠️ Prerequisites
+1. **Node.js** (LTS recommended). Install from [nodejs.org](https://nodejs.org/).
+2. **Expo CLI** – install globally:
+   ```bash
+   npm install -g expo-cli
+   ```
+3. **Firebase project** with:
+   - Web app configuration (API key, project ID, etc.).
+   - Firestore and Authentication enabled.
+4. (Optional for seeding) **Firebase service account JSON** with read/write access to Firestore.
+
+## ⚙️ Setup
+1. Clone the repository and install dependencies:
+   ```bash
+   git clone <repo-url>
+   cd fetch-rewards-mvp
+   npm install
+   ```
+2. Create a `.env` file in the project root and populate it with your Firebase keys:
+   ```env
+   FIREBASE_API_KEY=your-api-key
+   FIREBASE_AUTH_DOMAIN=your-app.firebaseapp.com
+   FIREBASE_PROJECT_ID=your-project-id
+   FIREBASE_STORAGE_BUCKET=your-app.appspot.com
+   FIREBASE_MESSAGING_SENDER_ID=...
+   FIREBASE_APP_ID=...
+   FIREBASE_MEASUREMENT_ID=...
+   # Optional for seeding
+   FIREBASE_SERVICE_ACCOUNT_PATH=path/to/serviceAccount.json
+   ```
+   > On Windows, paths can be absolute (`C:\\path\\to\\serviceAccount.json`) or relative to the project directory.
+
+## 🧪 Seeding Firestore Data
+Populate your Firestore project with 200 demo users, multiple squads, and league groups.
+
+1. Ensure your service account file is accessible and referenced via `FIREBASE_SERVICE_ACCOUNT_PATH` (or set the `GOOGLE_APPLICATION_CREDENTIALS` environment variable).
+2. Run the seeding script:
+   ```bash
+   npm run seed
+   ```
+   The script prints progress as it creates user documents, squads, and league groupings.
+
+## 📱 Running the App
+1. Start the Expo development server:
+   ```bash
+   npm start
+   ```
+2. Press `i` or `a` to open iOS or Android simulators, or scan the QR code using **Expo Go** on your mobile device.
+3. Register a new account directly in the app or sign in with seeded credentials that you manually add to Firebase Authentication.
+
+## 🧭 Navigation Overview
+- **Auth Stack**: Login and registration screens.
+- **Main Tabs**:
+  - **Home**: receipt scanning simulator, squad goal snapshot, weekly highlights.
+  - **Squad**: squad management, mascot, shopping list, weekly challenges.
+  - **League**: weekly leaderboard, promotion summary, reward breakdowns.
+  - **Profile**: personal stats, streak tracker, logout.
+
+## ✅ Notes
+- All Firebase interactions rely on the configuration exposed via `app.config.ts`. Ensure your `.env` values are present **before** launching the app.
+- The seed script creates Firestore documents only; to log in as a seeded user, manually create matching credentials in Firebase Authentication or register through the app and then update the Firestore profile.
+- NativeWind powers the `className` styling on React Native components. Tailwind tokens can be extended via `tailwind.config.js`.
+- Default Expo icon and splash assets are used so the repository stays binary-free for easier pull requests.
+
+Enjoy exploring the Fetch Rewards Squads & Leagues MVP! 💥
diff --git a/app.config.ts b/app.config.ts
new file mode 100644
index 0000000..b494faf
--- /dev/null
+++ b/app.config.ts
@@ -0,0 +1,39 @@
+import 'dotenv/config';
+import type { ExpoConfig } from '@expo/config';
+
+const config: ExpoConfig = {
+  name: 'Fetch Rewards MVP',
+  slug: 'fetch-rewards-mvp',
+  version: '0.1.0',
+  orientation: 'portrait',
+  scheme: 'fetchapp',
+  userInterfaceStyle: 'light',
+  // Using Expo's default icon and splash assets to keep the repository binary-free.
+  updates: {
+    fallbackToCacheTimeout: 0
+  },
+  assetBundlePatterns: ['**/*'],
+  ios: {
+    supportsTablet: true,
+    bundleIdentifier: 'com.fetchrewards.squadsleagues'
+  },
+  android: {
+    package: 'com.fetchrewards.squadsleagues'
+  },
+  extra: {
+    eas: {
+      projectId: '00000000-0000-0000-0000-000000000000'
+    },
+    firebase: {
+      apiKey: process.env.FIREBASE_API_KEY,
+      authDomain: process.env.FIREBASE_AUTH_DOMAIN,
+      projectId: process.env.FIREBASE_PROJECT_ID,
+      storageBucket: process.env.FIREBASE_STORAGE_BUCKET,
+      messagingSenderId: process.env.FIREBASE_MESSAGING_SENDER_ID,
+      appId: process.env.FIREBASE_APP_ID,
+      measurementId: process.env.FIREBASE_MEASUREMENT_ID
+    }
+  }
+};
+
+export default config;
diff --git a/babel.config.js b/babel.config.js
new file mode 100644
index 0000000..fb57fb2
--- /dev/null
+++ b/babel.config.js
@@ -0,0 +1,18 @@
+module.exports = function (api) {
+  api.cache(true);
+  return {
+    presets: ['babel-preset-expo'],
+    plugins: [
+      'nativewind/babel',
+      [
+        'module-resolver',
+        {
+          root: ['./'],
+          alias: {
+            '@': './src'
+          }
+        }
+      ]
+    ]
+  };
+};
diff --git a/nativewind.d.ts b/nativewind.d.ts
new file mode 100644
index 0000000..a13e313
--- /dev/null
+++ b/nativewind.d.ts
@@ -0,0 +1 @@
+/// <reference types="nativewind/types" />
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..1700307
--- /dev/null
+++ b/package.json
@@ -0,0 +1,53 @@
+{
+  "name": "fetch-rewards-squads-leagues",
+  "version": "0.1.0",
+  "private": true,
+  "main": "expo/AppEntry.js",
+  "scripts": {
+    "start": "expo start",
+    "android": "expo start --android",
+    "ios": "expo start --ios",
+    "web": "expo start --web",
+    "seed": "node seed.js"
+  },
+  "dependencies": {
+    "@react-navigation/bottom-tabs": "^6.5.11",
+    "@react-navigation/native": "^6.1.9",
+    "@react-navigation/native-stack": "^6.9.17",
+    "@react-navigation/stack": "^6.3.21",
+    "@tanstack/react-query": "^5.24.7",
+    "expo": "~50.0.3",
+    "expo-constants": "~15.4.5",
+    "expo-font": "~11.10.3",
+    "expo-linear-gradient": "~12.8.2",
+    "expo-linking": "~6.2.2",
+    "expo-secure-store": "~12.3.1",
+    "expo-splash-screen": "~0.26.5",
+    "expo-status-bar": "~1.11.1",
+    "@react-native-clipboard/clipboard": "^1.13.2",
+    "firebase": "^10.7.2",
+    "firebase-admin": "^11.10.1",
+    "nanoid": "^5.0.6",
+    "dotenv": "^16.3.1",
+    "nativewind": "^2.0.11",
+    "react": "18.2.0",
+    "react-native": "0.73.6",
+    "react-native-gesture-handler": "~2.14.0",
+    "react-native-reanimated": "~3.6.2",
+    "react-native-safe-area-context": "4.7.4",
+    "react-native-screens": "~3.29.0",
+    "react-native-svg": "^14.1.0",
+    "zustand": "^4.4.6"
+  },
+  "devDependencies": {
+    "@babel/core": "^7.20.0",
+    "@types/react": "^18.2.37",
+    "@types/react-native": "^0.73.0",
+    "@types/react-test-renderer": "18.0.0",
+    "autoprefixer": "^10.4.16",
+    "babel-preset-expo": "^10.0.1",
+    "postcss": "^8.4.31",
+    "tailwindcss": "^3.3.3",
+    "typescript": "^5.2.2"
+  }
+}
diff --git a/postcss.config.js b/postcss.config.js
new file mode 100644
index 0000000..5cbc2c7
--- /dev/null
+++ b/postcss.config.js
@@ -0,0 +1,6 @@
+module.exports = {
+  plugins: {
+    tailwindcss: {},
+    autoprefixer: {}
+  }
+};
diff --git a/seed.js b/seed.js
new file mode 100644
index 0000000..6bbb2c5
--- /dev/null
+++ b/seed.js
@@ -0,0 +1,183 @@
+#!/usr/bin/env node
+/* eslint-disable no-console */
+require('dotenv').config();
+const fs = require('fs');
+const path = require('path');
+const { nanoid } = require('nanoid/non-secure');
+const admin = require('firebase-admin');
+
+const serviceAccountPath = process.env.FIREBASE_SERVICE_ACCOUNT_PATH || process.env.GOOGLE_APPLICATION_CREDENTIALS;
+const projectId = process.env.FIREBASE_PROJECT_ID;
+
+if (!projectId) {
+  console.error('FIREBASE_PROJECT_ID is required in your environment variables.');
+  process.exit(1);
+}
+
+if (!admin.apps.length) {
+  if (serviceAccountPath) {
+    const absolutePath = path.isAbsolute(serviceAccountPath)
+      ? serviceAccountPath
+      : path.join(process.cwd(), serviceAccountPath);
+    const serviceAccount = JSON.parse(fs.readFileSync(absolutePath, 'utf-8'));
+    admin.initializeApp({
+      credential: admin.credential.cert(serviceAccount),
+      projectId
+    });
+  } else {
+    admin.initializeApp({
+      credential: admin.credential.applicationDefault(),
+      projectId
+    });
+  }
+}
+
+const db = admin.firestore();
+
+const leagueTiers = ['Bronze', 'Silver', 'Gold', 'Platinum', 'Diamond', 'Elite', 'Legend', 'Mythic'];
+const firstNames = ['Alex', 'Taylor', 'Jordan', 'Morgan', 'Casey', 'River', 'Hayden', 'Skyler', 'Emerson', 'Phoenix'];
+const lastNames = ['Kim', 'Lopez', 'Patel', 'Garcia', 'Nguyen', 'Smith', 'Johnson', 'Martinez', 'Brown', 'Singh'];
+
+const randomFrom = array => array[Math.floor(Math.random() * array.length)];
+
+const generateUsers = count =>
+  Array.from({ length: count }).map(() => {
+    const uid = nanoid(20);
+    const displayName = `${randomFrom(firstNames)} ${randomFrom(lastNames)}`;
+    const league = randomFrom(leagueTiers);
+    const totalPoints = Math.floor(Math.random() * 50000) + 500;
+    const weeklyLeaguePoints = Math.floor(Math.random() * 5000);
+    const scanDays = Math.floor(Math.random() * 7);
+
+    return {
+      uid,
+      email: `${displayName.toLowerCase().replace(/\s/g, '.')}.${Math.floor(Math.random() * 9999)}@example.com`,
+      displayName,
+      totalPoints,
+      league,
+      weeklyLeaguePoints,
+      squadId: null,
+      scanStreak: {
+        days: scanDays,
+        lastScanDate: new Date(Date.now() - scanDays * 86400000).toISOString()
+      },
+      createdAt: new Date().toISOString()
+    };
+  });
+
+const createSquads = (users, squadCount = 6) => {
+  const squads = [];
+  const shuffledUsers = [...users];
+
+  for (let i = 0; i < squadCount; i += 1) {
+    const squadId = nanoid(8);
+    const takeCount = Math.min(shuffledUsers.length, Math.floor(Math.random() * 6) + 4);
+    if (takeCount === 0) break;
+    const members = shuffledUsers.splice(0, takeCount);
+    const goalTarget = [10000, 25000, 50000][Math.floor(Math.random() * 3)];
+
+    members.forEach(member => {
+      // eslint-disable-next-line no-param-reassign
+      member.squadId = squadId;
+    });
+
+    const shoppingList = members.slice(0, Math.min(2, members.length)).map(member => ({
+      id: nanoid(6),
+      itemName: randomFrom(['Energy drinks', 'Snacks', 'Study supplies', 'Party decor', 'Pizza fund']),
+      addedBy: member.uid,
+      createdAt: new Date().toISOString()
+    }));
+
+    squads.push({
+      squadId,
+      squadName: `Squad ${i + 1}`,
+      members: members.map(member => member.uid),
+      mascotStatus: 'happy',
+      sharedGoal: {
+        targetPoints: goalTarget,
+        currentPoints: Math.floor(goalTarget * Math.random())
+      },
+      shoppingList
+    });
+  }
+
+  return squads;
+};
+
+const getWeekRange = () => {
+  const current = new Date();
+  const day = current.getUTCDay();
+  const diffToMonday = (day + 6) % 7;
+  const weekStart = new Date(Date.UTC(current.getUTCFullYear(), current.getUTCMonth(), current.getUTCDate() - diffToMonday));
+  const weekEnd = new Date(weekStart);
+  weekEnd.setUTCDate(weekStart.getUTCDate() + 7);
+  const key = `${weekStart.getUTCFullYear()}-W${String(getWeekNumber(current)).padStart(2, '0')}`;
+  return { weekStart, weekEnd, key };
+};
+
+const getWeekNumber = date => {
+  const tmpDate = new Date(Date.UTC(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate()));
+  const dayNum = tmpDate.getUTCDay() || 7;
+  tmpDate.setUTCDate(tmpDate.getUTCDate() + 4 - dayNum);
+  const yearStart = new Date(Date.UTC(tmpDate.getUTCFullYear(), 0, 1));
+  return Math.ceil(((tmpDate - yearStart) / 86400000 + 1) / 7);
+};
+
+const seed = async () => {
+  const users = generateUsers(200);
+  const squads = createSquads(users);
+  const { weekStart, weekEnd, key } = getWeekRange();
+
+  console.log('Seeding users...');
+  const userWrites = users.map(user =>
+    db
+      .collection('users')
+      .doc(user.uid)
+      .set(user)
+  );
+  await Promise.all(userWrites);
+
+  console.log('Seeding squads...');
+  const squadWrites = squads.map(squad => db.collection('squads').doc(squad.squadId).set(squad));
+  await Promise.all(squadWrites);
+
+  console.log('Seeding leagues...');
+  const leagueGroups = {};
+  users.forEach(user => {
+    const groupNumber = (user.uid.charCodeAt(0) + user.uid.charCodeAt(1)) % 5;
+    const leagueId = `${user.league.toLowerCase()}_${key}_group_${groupNumber + 1}`;
+    if (!leagueGroups[leagueId]) {
+      leagueGroups[leagueId] = {
+        leagueId,
+        leagueName: user.league,
+        members: [],
+        weekStartDate: weekStart.toISOString(),
+        weekEndDate: weekEnd.toISOString(),
+        weekKey: key
+      };
+    }
+    leagueGroups[leagueId].members.push({
+      uid: user.uid,
+      displayName: user.displayName,
+      pointsThisWeek: user.weeklyLeaguePoints,
+      league: user.league,
+      streakMultiplier: user.scanStreak.days >= 5 ? 1.5 : 1
+    });
+  });
+
+  const leagueWrites = Object.values(leagueGroups).map(group =>
+    db
+      .collection('leagues')
+      .doc(group.leagueId)
+      .set(group)
+  );
+  await Promise.all(leagueWrites);
+
+  console.log('Seed complete!');
+  process.exit(0);
+};
+
+seed().catch(error => {
+  console.error('Seeding failed', error);
+  process.exit(1);
+});
diff --git a/src/components/Mascot.tsx b/src/components/Mascot.tsx
new file mode 100644
index 0000000..32c6b13
--- /dev/null
+++ b/src/components/Mascot.tsx
@@ -0,0 +1,27 @@
+import Svg, { Circle, Path } from 'react-native-svg';
+import { View, Text } from 'react-native';
+
+interface MascotProps {
+  status: 'happy' | 'excited' | 'sleepy';
+}
+
+const Mascot: React.FC<MascotProps> = ({ status }) => {
+  const faceColor = status === 'excited' ? '#FF8F3F' : status === 'sleepy' ? '#A0AEC0' : '#7F5AF0';
+  const smile = status === 'sleepy' ? 'M35 55 Q50 45 65 55' : 'M35 55 Q50 70 65 55';
+
+  return (
+    <View className="items-center">
+      <Svg height={120} width={120} viewBox="0 0 100 100">
+        <Circle cx="50" cy="50" r="40" fill={faceColor} opacity={0.95} />
+        <Circle cx="35" cy="40" r="6" fill="#fff" />
+        <Circle cx="65" cy="40" r="6" fill="#fff" />
+        <Path d="M32 38 Q35 34 38 38" stroke="#333" strokeWidth={2} strokeLinecap="round" />
+        <Path d="M62 38 Q65 34 68 38" stroke="#333" strokeWidth={2} strokeLinecap="round" />
+        <Path d={smile} stroke="#fff" strokeWidth={5} strokeLinecap="round" fill="none" />
+      </Svg>
+      <Text className="text-sm text-gray-600 mt-2 capitalize">Mascot is {status}</Text>
+    </View>
+  );
+};
+
+export default Mascot;
diff --git a/src/components/WeeklyChallengeCard.tsx b/src/components/WeeklyChallengeCard.tsx
new file mode 100644
index 0000000..ac5b563
--- /dev/null
+++ b/src/components/WeeklyChallengeCard.tsx
@@ -0,0 +1,28 @@
+import { View, Text } from 'react-native';
+
+import { Challenge } from '@/types/models';
+
+interface WeeklyChallengeCardProps {
+  challenge: Challenge;
+}
+
+const WeeklyChallengeCard: React.FC<WeeklyChallengeCardProps> = ({ challenge }) => {
+  const progressPercentage = Math.min(100, Math.round((challenge.progress / challenge.target) * 100));
+
+  return (
+    <View className="bg-white rounded-2xl p-4 mb-4 shadow-sm shadow-black/5">
+      <Text className="text-lg font-semibold text-gray-900">{challenge.title}</Text>
+      <Text className="text-sm text-gray-600 mt-1">{challenge.description}</Text>
+      <View className="mt-3">
+        <View className="h-2 rounded-full bg-gray-200 overflow-hidden">
+          <View className="h-full bg-primary" style={{ width: `${progressPercentage}%` }} />
+        </View>
+        <Text className="text-xs text-gray-500 mt-1">
+          {challenge.progress} / {challenge.target}
+        </Text>
+      </View>
+    </View>
+  );
+};
+
+export default WeeklyChallengeCard;
diff --git a/src/hooks/useAuth.tsx b/src/hooks/useAuth.tsx
new file mode 100644
index 0000000..e893fd5
--- /dev/null
+++ b/src/hooks/useAuth.tsx
@@ -0,0 +1,106 @@
+import { createContext, useContext, useEffect, useMemo, useState } from 'react';
+import {
+  User,
+  createUserWithEmailAndPassword,
+  onAuthStateChanged,
+  signInWithEmailAndPassword,
+  signOut,
+  updateProfile
+} from 'firebase/auth';
+import { doc, onSnapshot, setDoc } from 'firebase/firestore';
+
+import { auth, db } from '@/services/firebase';
+import { UserProfile } from '@/types/models';
+
+interface AuthContextValue {
+  user: User | null;
+  profile: UserProfile | null;
+  initializing: boolean;
+  login: (email: string, password: string) => Promise<void>;
+  register: (email: string, password: string, displayName: string) => Promise<void>;
+  logout: () => Promise<void>;
+}
+
+const AuthContext = createContext<AuthContextValue | undefined>(undefined);
+
+export const AuthProvider: React.FC<{ children: React.ReactNode }> = ({ children }) => {
+  const [user, setUser] = useState<User | null>(null);
+  const [profile, setProfile] = useState<UserProfile | null>(null);
+  const [initializing, setInitializing] = useState(true);
+
+  useEffect(() => {
+    const unsubscribe = onAuthStateChanged(auth, currentUser => {
+      setUser(currentUser);
+      setInitializing(false);
+    });
+
+    return unsubscribe;
+  }, []);
+
+  useEffect(() => {
+    if (!user?.uid) {
+      setProfile(null);
+      return;
+    }
+
+    const unsubscribe = onSnapshot(doc(db, 'users', user.uid), snapshot => {
+      if (snapshot.exists()) {
+        setProfile(snapshot.data() as UserProfile);
+      }
+    });
+
+    return unsubscribe;
+  }, [user?.uid]);
+
+  const login = async (email: string, password: string) => {
+    await signInWithEmailAndPassword(auth, email.trim(), password);
+  };
+
+  const register = async (email: string, password: string, displayName: string) => {
+    const credential = await createUserWithEmailAndPassword(auth, email.trim(), password);
+    if (credential.user) {
+      await updateProfile(credential.user, { displayName });
+      const userProfile: UserProfile = {
+        uid: credential.user.uid,
+        email: credential.user.email ?? email,
+        displayName,
+        totalPoints: 0,
+        squadId: null,
+        league: 'Bronze',
+        weeklyLeaguePoints: 0,
+        scanStreak: {
+          days: 0
+        },
+        createdAt: new Date().toISOString()
+      };
+      await setDoc(doc(db, 'users', credential.user.uid), userProfile);
+      setProfile(userProfile);
+    }
+  };
+
+  const logout = async () => {
+    await signOut(auth);
+  };
+
+  const value = useMemo(
+    () => ({
+      user,
+      profile,
+      initializing,
+      login,
+      register,
+      logout
+    }),
+    [user, profile, initializing, login, register, logout]
+  );
+
+  return <AuthContext.Provider value={value}>{children}</AuthContext.Provider>;
+};
+
+export const useAuth = () => {
+  const context = useContext(AuthContext);
+  if (!context) {
+    throw new Error('useAuth must be used within an AuthProvider');
+  }
+  return context;
+};
diff --git a/src/hooks/useLeague.ts b/src/hooks/useLeague.ts
new file mode 100644
index 0000000..f100720
--- /dev/null
+++ b/src/hooks/useLeague.ts
@@ -0,0 +1,54 @@
+import { useCallback, useEffect, useState } from 'react';
+
+import { useAuth } from './useAuth';
+import { LeagueGroup, LeagueGroupMember } from '@/types/models';
+import { fetchLeaderboard, getLeagueRewards, getOrCreateLeagueGroup, getSeasonCountdown } from '@/services/leagueService';
+
+export const useLeague = () => {
+  const { profile } = useAuth();
+  const [group, setGroup] = useState<LeagueGroup | null>(null);
+  const [leaderboard, setLeaderboard] = useState<LeagueGroupMember[]>([]);
+  const [loading, setLoading] = useState(true);
+  const [seasonCountdown, setSeasonCountdown] = useState(getSeasonCountdown());
+
+  useEffect(() => {
+    const interval = setInterval(() => {
+      setSeasonCountdown(getSeasonCountdown());
+    }, 1000 * 60 * 60 * 12);
+    return () => clearInterval(interval);
+  }, []);
+
+  const refresh = useCallback(async () => {
+    if (!profile?.uid) {
+      setLoading(false);
+      return;
+    }
+
+    try {
+      setLoading(true);
+      const currentGroup = await getOrCreateLeagueGroup(profile.league, profile.uid);
+      setGroup(currentGroup);
+      const data = await fetchLeaderboard(currentGroup.leagueId);
+      if (data) {
+        setLeaderboard(data.members);
+      }
+    } finally {
+      setLoading(false);
+    }
+  }, [profile?.league, profile?.uid]);
+
+  useEffect(() => {
+    refresh();
+  }, [refresh]);
+
+  const rewards = profile ? getLeagueRewards(profile.league) : { placementBonus: 0, streakMultiplierBonus: 0 };
+
+  return {
+    group,
+    leaderboard,
+    loading,
+    refresh,
+    rewards,
+    seasonCountdown
+  };
+};
diff --git a/src/hooks/useSquad.ts b/src/hooks/useSquad.ts
new file mode 100644
index 0000000..8f50ad4
--- /dev/null
+++ b/src/hooks/useSquad.ts
@@ -0,0 +1,76 @@
+import { useEffect, useState } from 'react';
+
+import { useAuth } from './useAuth';
+import { Squad } from '@/types/models';
+import {
+  addShoppingListItem,
+  createSquad,
+  distributeReceiptPoints,
+  generateSquadInviteLink,
+  joinSquad,
+  listenToSquad,
+  updateSharedGoal
+} from '@/services/squadService';
+
+export const useSquad = () => {
+  const { user, profile } = useAuth();
+  const [squad, setSquad] = useState<Squad | null>(null);
+  const [loading, setLoading] = useState(true);
+
+  useEffect(() => {
+    if (!profile?.squadId) {
+      setSquad(null);
+      setLoading(false);
+      return;
+    }
+
+    const unsubscribe = listenToSquad(profile.squadId, data => {
+      setSquad(data);
+      setLoading(false);
+    });
+
+    return unsubscribe;
+  }, [profile?.squadId]);
+
+  const createNewSquad = async (squadName: string) => {
+    if (!user) throw new Error('Must be signed in');
+    const newSquad = await createSquad(squadName, user.uid);
+    setSquad(newSquad);
+    return newSquad;
+  };
+
+  const joinExistingSquad = async (squadId: string) => {
+    if (!user) throw new Error('Must be signed in');
+    const updatedSquad = await joinSquad(squadId, user.uid);
+    setSquad(updatedSquad);
+    return updatedSquad;
+  };
+
+  const shareReceiptWithSquad = async (totalPoints: number) => {
+    if (!squad) throw new Error('You need a squad to share points');
+    await distributeReceiptPoints(squad.squadId, totalPoints);
+  };
+
+  const addItemToShoppingList = async (itemName: string) => {
+    if (!squad || !user) throw new Error('You need a squad to add items');
+    await addShoppingListItem(squad.squadId, itemName, user.uid);
+  };
+
+  const setSharedGoalTarget = async (target: number) => {
+    if (!squad) throw new Error('You need a squad to update goals');
+    await updateSharedGoal(squad.squadId, target);
+  };
+
+  const inviteLink = squad ? generateSquadInviteLink(squad.squadId) : null;
+
+  return {
+    squad,
+    loading,
+    createNewSquad,
+    joinExistingSquad,
+    shareReceiptWithSquad,
+    inviteLink,
+    addItemToShoppingList,
+    setSharedGoalTarget
+  };
+};
diff --git a/src/navigation/RootNavigator.tsx b/src/navigation/RootNavigator.tsx
new file mode 100644
index 0000000..0fa0b42
--- /dev/null
+++ b/src/navigation/RootNavigator.tsx
@@ -0,0 +1,29 @@
+import { createNativeStackNavigator } from '@react-navigation/native-stack';
+import { ActivityIndicator, View } from 'react-native';
+
+import AuthNavigator from './stacks/AuthNavigator';
+import MainNavigator from './stacks/MainNavigator';
+import { RootStackParamList } from '@/types/navigation';
+import { useAuth } from '@/hooks/useAuth';
+
+const Stack = createNativeStackNavigator<RootStackParamList>();
+
+const RootNavigator = () => {
+  const { user, initializing } = useAuth();
+
+  if (initializing) {
+    return (
+      <View className="flex-1 items-center justify-center bg-background">
+        <ActivityIndicator size="large" color="#FF8F3F" />
+      </View>
+    );
+  }
+
+  return (
+    <Stack.Navigator screenOptions={{ headerShown: false }}>
+      {user ? <Stack.Screen name="Main" component={MainNavigator} /> : <Stack.Screen name="Auth" component={AuthNavigator} />}
+    </Stack.Navigator>
+  );
+};
+
+export default RootNavigator;
diff --git a/src/navigation/stacks/AuthNavigator.tsx b/src/navigation/stacks/AuthNavigator.tsx
new file mode 100644
index 0000000..06bcbba
--- /dev/null
+++ b/src/navigation/stacks/AuthNavigator.tsx
@@ -0,0 +1,21 @@
+import { createNativeStackNavigator } from '@react-navigation/native-stack';
+
+import LoginScreen from '@/screens/auth/LoginScreen';
+import RegisterScreen from '@/screens/auth/RegisterScreen';
+import { AuthStackParamList } from '@/types/navigation';
+
+const Stack = createNativeStackNavigator<AuthStackParamList>();
+
+const AuthNavigator = () => (
+  <Stack.Navigator
+    screenOptions={{
+      headerShown: false,
+      contentStyle: { backgroundColor: '#F7F7FF' }
+    }}
+  >
+    <Stack.Screen name="Login" component={LoginScreen} />
+    <Stack.Screen name="Register" component={RegisterScreen} />
+  </Stack.Navigator>
+);
+
+export default AuthNavigator;
diff --git a/src/navigation/stacks/MainNavigator.tsx b/src/navigation/stacks/MainNavigator.tsx
new file mode 100644
index 0000000..e9e5d96
--- /dev/null
+++ b/src/navigation/stacks/MainNavigator.tsx
@@ -0,0 +1,71 @@
+import { createBottomTabNavigator } from '@react-navigation/bottom-tabs';
+import { createNativeStackNavigator } from '@react-navigation/native-stack';
+import { Ionicons } from '@expo/vector-icons';
+
+import HomeScreen from '@/screens/main/HomeScreen';
+import ScanReceiptModal from '@/screens/main/ScanReceiptModal';
+import SquadScreen from '@/screens/squads/SquadScreen';
+import SquadInviteScreen from '@/screens/squads/SquadInviteScreen';
+import LeagueScreen from '@/screens/leagues/LeagueScreen';
+import ProfileScreen from '@/screens/main/ProfileScreen';
+import { HomeStackParamList, LeagueStackParamList, MainTabParamList, ProfileStackParamList, SquadStackParamList } from '@/types/navigation';
+
+const Tab = createBottomTabNavigator<MainTabParamList>();
+const HomeStack = createNativeStackNavigator<HomeStackParamList>();
+const SquadStack = createNativeStackNavigator<SquadStackParamList>();
+const LeagueStack = createNativeStackNavigator<LeagueStackParamList>();
+const ProfileStack = createNativeStackNavigator<ProfileStackParamList>();
+
+const HomeNavigator = () => (
+  <HomeStack.Navigator>
+    <HomeStack.Screen name="Home" component={HomeScreen} options={{ headerShown: false }} />
+    <HomeStack.Screen name="ScanReceiptModal" component={ScanReceiptModal} options={{ presentation: 'modal', title: 'Scan Receipt' }} />
+  </HomeStack.Navigator>
+);
+
+const SquadNavigator = () => (
+  <SquadStack.Navigator>
+    <SquadStack.Screen name="Squad" component={SquadScreen} options={{ headerShown: false }} />
+    <SquadStack.Screen name="SquadInvite" component={SquadInviteScreen} options={{ title: 'Join Squad' }} />
+  </SquadStack.Navigator>
+);
+
+const LeagueNavigator = () => (
+  <LeagueStack.Navigator>
+    <LeagueStack.Screen name="League" component={LeagueScreen} options={{ headerShown: false }} />
+  </LeagueStack.Navigator>
+);
+
+const ProfileNavigator = () => (
+  <ProfileStack.Navigator>
+    <ProfileStack.Screen name="Profile" component={ProfileScreen} options={{ headerShown: false }} />
+  </ProfileStack.Navigator>
+);
+
+const MainNavigator = () => (
+  <Tab.Navigator
+    screenOptions={({ route }) => ({
+      headerShown: false,
+      tabBarActiveTintColor: '#FF8F3F',
+      tabBarInactiveTintColor: '#7F8C8D',
+      tabBarStyle: { backgroundColor: '#FFFFFF' },
+      tabBarIcon: ({ color, size }) => {
+        const icons: Record<string, keyof typeof Ionicons.glyphMap> = {
+          HomeTab: 'home',
+          SquadTab: 'people',
+          LeagueTab: 'trophy',
+          ProfileTab: 'person-circle'
+        };
+        const iconName = icons[route.name] ?? 'ellipse';
+        return <Ionicons name={iconName} color={color} size={size} />;
+      }
+    })}
+  >
+    <Tab.Screen name="HomeTab" component={HomeNavigator} options={{ title: 'Home' }} />
+    <Tab.Screen name="SquadTab" component={SquadNavigator} options={{ title: 'Squad' }} />
+    <Tab.Screen name="LeagueTab" component={LeagueNavigator} options={{ title: 'League' }} />
+    <Tab.Screen name="ProfileTab" component={ProfileNavigator} options={{ title: 'Profile' }} />
+  </Tab.Navigator>
+);
+
+export default MainNavigator;
diff --git a/src/screens/auth/LoginScreen.tsx b/src/screens/auth/LoginScreen.tsx
new file mode 100644
index 0000000..7c3b5d0
--- /dev/null
+++ b/src/screens/auth/LoginScreen.tsx
@@ -0,0 +1,72 @@
+import { useState } from 'react';
+import { Alert, Text, TextInput, TouchableOpacity, View } from 'react-native';
+import { NativeStackScreenProps } from '@react-navigation/native-stack';
+import { LinearGradient } from 'expo-linear-gradient';
+
+import { useAuth } from '@/hooks/useAuth';
+import { AuthStackParamList } from '@/types/navigation';
+
+const LoginScreen = ({ navigation }: NativeStackScreenProps<AuthStackParamList, 'Login'>) => {
+  const { login } = useAuth();
+  const [email, setEmail] = useState('');
+  const [password, setPassword] = useState('');
+  const [loading, setLoading] = useState(false);
+
+  const handleLogin = async () => {
+    try {
+      setLoading(true);
+      await login(email, password);
+    } catch (error) {
+      Alert.alert('Login failed', (error as Error)?.message ?? 'Unable to log in.');
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <LinearGradient colors={['#FFE0C2', '#F7F7FF']} style={{ flex: 1, justifyContent: 'flex-end' }}>
+      <View className="bg-surface/90 rounded-t-3xl p-6">
+        <Text className="text-3xl font-bold text-primary mb-4">Fetch Squads</Text>
+        <Text className="text-base text-gray-600 mb-6">Sign in to reunite with your crew and chase rewards together.</Text>
+
+        <View className="space-y-3">
+          <View>
+            <Text className="text-sm font-semibold text-gray-500 mb-1">Email</Text>
+            <TextInput
+              value={email}
+              onChangeText={setEmail}
+              autoCapitalize="none"
+              keyboardType="email-address"
+              placeholder="you@email.com"
+              className="bg-white/80 rounded-xl px-4 py-3"
+            />
+          </View>
+          <View>
+            <Text className="text-sm font-semibold text-gray-500 mb-1">Password</Text>
+            <TextInput
+              value={password}
+              onChangeText={setPassword}
+              secureTextEntry
+              placeholder="••••••••"
+              className="bg-white/80 rounded-xl px-4 py-3"
+            />
+          </View>
+        </View>
+
+        <TouchableOpacity
+          onPress={handleLogin}
+          disabled={loading}
+          className="mt-6 bg-primary rounded-xl py-3 items-center"
+        >
+          <Text className="text-white font-semibold text-lg">{loading ? 'Signing in...' : 'Sign In'}</Text>
+        </TouchableOpacity>
+
+        <TouchableOpacity onPress={() => navigation.navigate('Register')} className="mt-4 items-center">
+          <Text className="text-secondary font-semibold">New to Fetch? Create an account</Text>
+        </TouchableOpacity>
+      </View>
+    </LinearGradient>
+  );
+};
+
+export default LoginScreen;
diff --git a/src/screens/auth/RegisterScreen.tsx b/src/screens/auth/RegisterScreen.tsx
new file mode 100644
index 0000000..db32260
--- /dev/null
+++ b/src/screens/auth/RegisterScreen.tsx
@@ -0,0 +1,98 @@
+import { useState } from 'react';
+import { Alert, Text, TextInput, TouchableOpacity, View } from 'react-native';
+import { NativeStackScreenProps } from '@react-navigation/native-stack';
+import { LinearGradient } from 'expo-linear-gradient';
+
+import { useAuth } from '@/hooks/useAuth';
+import { AuthStackParamList } from '@/types/navigation';
+
+const RegisterScreen = ({ navigation }: NativeStackScreenProps<AuthStackParamList, 'Register'>) => {
+  const { register } = useAuth();
+  const [displayName, setDisplayName] = useState('');
+  const [email, setEmail] = useState('');
+  const [password, setPassword] = useState('');
+  const [confirmPassword, setConfirmPassword] = useState('');
+  const [loading, setLoading] = useState(false);
+
+  const handleRegister = async () => {
+    if (password !== confirmPassword) {
+      Alert.alert('Oops!', 'Passwords do not match.');
+      return;
+    }
+
+    try {
+      setLoading(true);
+      await register(email, password, displayName);
+    } catch (error) {
+      Alert.alert('Registration failed', (error as Error)?.message ?? 'Unable to register.');
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <LinearGradient colors={['#FFF4D9', '#F7F7FF']} style={{ flex: 1, justifyContent: 'flex-end' }}>
+      <View className="bg-surface/95 rounded-t-3xl p-6">
+        <Text className="text-3xl font-bold text-secondary mb-4">Ready to Squad Up?</Text>
+        <Text className="text-base text-gray-600 mb-6">Create your Fetch account and invite friends to earn rewards faster.</Text>
+
+        <View className="space-y-3">
+          <View>
+            <Text className="text-sm font-semibold text-gray-500 mb-1">Display name</Text>
+            <TextInput
+              value={displayName}
+              onChangeText={setDisplayName}
+              placeholder="Vlad the Fetcher"
+              className="bg-white/85 rounded-xl px-4 py-3"
+            />
+          </View>
+          <View>
+            <Text className="text-sm font-semibold text-gray-500 mb-1">Email</Text>
+            <TextInput
+              value={email}
+              onChangeText={setEmail}
+              autoCapitalize="none"
+              keyboardType="email-address"
+              placeholder="you@email.com"
+              className="bg-white/85 rounded-xl px-4 py-3"
+            />
+          </View>
+          <View>
+            <Text className="text-sm font-semibold text-gray-500 mb-1">Password</Text>
+            <TextInput
+              value={password}
+              onChangeText={setPassword}
+              secureTextEntry
+              placeholder="Create a strong password"
+              className="bg-white/85 rounded-xl px-4 py-3"
+            />
+          </View>
+          <View>
+            <Text className="text-sm font-semibold text-gray-500 mb-1">Confirm Password</Text>
+            <TextInput
+              value={confirmPassword}
+              onChangeText={setConfirmPassword}
+              secureTextEntry
+              placeholder="Repeat your password"
+              className="bg-white/85 rounded-xl px-4 py-3"
+            />
+          </View>
+        </View>
+
+        <TouchableOpacity
+          onPress={handleRegister}
+          disabled={loading}
+          className="mt-6 bg-secondary rounded-xl py-3 items-center"
+        >
+          <Text className="text-white font-semibold text-lg">{loading ? 'Creating account...' : 'Create Account'}</Text>
+        </TouchableOpacity>
+
+        <TouchableOpacity onPress={() => navigation.navigate('Login')} className="mt-4 items-center">
+          <Text className="text-primary font-semibold">Already have an account? Sign in</Text>
+        </TouchableOpacity>
+      </View>
+    </LinearGradient>
+  );
+};
+
+export default RegisterScreen;
diff --git a/src/screens/leagues/LeagueScreen.tsx b/src/screens/leagues/LeagueScreen.tsx
new file mode 100644
index 0000000..d5e2ee3
--- /dev/null
+++ b/src/screens/leagues/LeagueScreen.tsx
@@ -0,0 +1,84 @@
+import { useMemo } from 'react';
+import { RefreshControl, ScrollView, Text, View } from 'react-native';
+
+import { useAuth } from '@/hooks/useAuth';
+import { useLeague } from '@/hooks/useLeague';
+
+const LeagueScreen = () => {
+  const { profile } = useAuth();
+  const { leaderboard, loading, refresh, rewards, seasonCountdown } = useLeague();
+
+  const promotionCutoff = useMemo(() => Math.min(10, leaderboard.length), [leaderboard.length]);
+
+  return (
+    <ScrollView
+      className="bg-background flex-1"
+      contentContainerStyle={{ padding: 20, paddingBottom: 120 }}
+      refreshControl={<RefreshControl refreshing={loading} onRefresh={refresh} />}
+    >
+      <Text className="text-3xl font-bold text-gray-900">{profile?.league ?? 'Bronze'} League</Text>
+      <Text className="text-gray-600 mt-1">Season ends in {seasonCountdown} • Weekly reset every Monday</Text>
+
+      <View className="mt-5 bg-white rounded-3xl p-5 shadow-sm shadow-black/5">
+        <Text className="text-xl font-semibold text-gray-900">This Week&apos;s Leaderboard</Text>
+        <Text className="text-sm text-gray-600 mt-1">
+          Top {promotionCutoff} advance to the next league. Everyone keeps their hard-earned tier.
+        </Text>
+
+        <View className="mt-4 space-y-3">
+          {leaderboard.map((member, index) => {
+            const isCurrentUser = member.uid === profile?.uid;
+            const promoted = index < promotionCutoff;
+            return (
+              <View
+                key={member.uid}
+                className={`flex-row items-center justify-between rounded-2xl px-4 py-3 ${
+                  promoted ? 'bg-primary/10 border border-primary/40' : 'bg-gray-50'
+                }`}
+              >
+                <View>
+                  <Text className={`text-base font-semibold ${isCurrentUser ? 'text-secondary' : 'text-gray-900'}`}>
+                    {index + 1}. {isCurrentUser ? 'You' : member.displayName ?? 'Fetcher'}
+                  </Text>
+                  <Text className="text-xs text-gray-500">{member.pointsThisWeek} pts • Streak x{member.streakMultiplier.toFixed(1)}</Text>
+                </View>
+                {promoted && <Text className="text-sm font-semibold text-primary">Promoted!</Text>}
+              </View>
+            );
+          })}
+          {!leaderboard.length && <Text className="text-gray-500">No leaderboard data yet. Scan a receipt to get started!</Text>}
+        </View>
+      </View>
+
+      <View className="mt-6 bg-white rounded-3xl p-5">
+        <Text className="text-xl font-semibold text-gray-900">Weekly Rewards</Text>
+        <Text className="text-sm text-gray-600 mt-2">Top players earn a promotion bonus.</Text>
+        <View className="flex-row justify-between mt-4">
+          <View className="bg-primary/10 rounded-2xl px-4 py-3 flex-1 mr-2">
+            <Text className="text-xs text-primary font-semibold">Placement Bonus</Text>
+            <Text className="text-xl font-bold text-primary mt-1">+{rewards.placementBonus} pts</Text>
+          </View>
+          <View className="bg-secondary/10 rounded-2xl px-4 py-3 flex-1">
+            <Text className="text-xs text-secondary font-semibold">Streak Bonus</Text>
+            <Text className="text-xl font-bold text-secondary mt-1">+{rewards.streakMultiplierBonus} pts</Text>
+          </View>
+        </View>
+      </View>
+
+      <View className="mt-6 bg-white rounded-3xl p-5">
+        <Text className="text-xl font-semibold text-gray-900">How Leagues Work</Text>
+        <Text className="text-sm text-gray-600 mt-2">
+          Every Monday you&apos;re grouped with 30-50 players at your tier. Earn weekly points to climb the board.
+        </Text>
+        <Text className="text-sm text-gray-600 mt-2">
+          Scan on at least 5 of 7 days to receive a 1.5x streak multiplier on your weekly points.
+        </Text>
+        <Text className="text-sm text-gray-600 mt-2">
+          Finish in the top 10 to earn a promotion badge and bonus points. No demotions in this MVP.
+        </Text>
+      </View>
+    </ScrollView>
+  );
+};
+
+export default LeagueScreen;
diff --git a/src/screens/main/HomeScreen.tsx b/src/screens/main/HomeScreen.tsx
new file mode 100644
index 0000000..24e336a
--- /dev/null
+++ b/src/screens/main/HomeScreen.tsx
@@ -0,0 +1,88 @@
+import { LinearGradient } from 'expo-linear-gradient';
+import { NativeStackScreenProps } from '@react-navigation/native-stack';
+import { useNavigation } from '@react-navigation/native';
+import { useMemo } from 'react';
+import { ScrollView, Text, TouchableOpacity, View } from 'react-native';
+
+import { useAuth } from '@/hooks/useAuth';
+import { useSquad } from '@/hooks/useSquad';
+import { HomeStackParamList } from '@/types/navigation';
+import WeeklyChallengeCard from '@/components/WeeklyChallengeCard';
+import { Challenge } from '@/types/models';
+
+const demoChallenges: Challenge[] = [
+  {
+    id: 'weekly-quest',
+    title: 'Squad Quest: Scan 5 receipts',
+    description: 'Team up and scan five receipts together to earn a 1.2x multiplier!',
+    progress: 3,
+    target: 5
+  },
+  {
+    id: 'duel',
+    title: 'Duel of the Week',
+    description: 'Challenge a squadmate to beat your points by Sunday night.',
+    progress: 1,
+    target: 1
+  }
+];
+
+const HomeScreen = () => {
+  const navigation = useNavigation<NativeStackScreenProps<HomeStackParamList>['navigation']>();
+  const { profile } = useAuth();
+  const { squad } = useSquad();
+
+  const squadProgress = useMemo(() => {
+    if (!squad) return 0;
+    const { currentPoints, targetPoints } = squad.sharedGoal;
+    return Math.min(1, currentPoints / targetPoints);
+  }, [squad]);
+
+  return (
+    <LinearGradient colors={['#FFE6D5', '#F7F7FF']} style={{ flex: 1 }}>
+      <ScrollView contentContainerStyle={{ padding: 20, paddingBottom: 120 }}>
+        <View className="bg-white rounded-3xl p-5 shadow-sm shadow-black/10">
+          <Text className="text-2xl font-bold text-gray-900">Hey {profile?.displayName ?? 'Fetcher'} 👋</Text>
+          <Text className="text-gray-600 mt-1">You have {profile?.totalPoints ?? 0} lifetime points.</Text>
+
+          <TouchableOpacity
+            onPress={() => navigation.navigate('ScanReceiptModal')}
+            className="mt-5 bg-secondary rounded-2xl py-4 items-center"
+          >
+            <Text className="text-white font-semibold text-lg">Scan Receipt</Text>
+          </TouchableOpacity>
+
+          {squad ? (
+            <View className="mt-6">
+              <Text className="text-lg font-semibold text-gray-800">Squad Goal</Text>
+              <View className="mt-2 h-3 bg-gray-200 rounded-full overflow-hidden">
+                <View className="h-full bg-accent" style={{ width: `${squadProgress * 100}%` }} />
+              </View>
+              <Text className="mt-2 text-sm text-gray-500">
+                {squad.sharedGoal.currentPoints.toLocaleString()} / {squad.sharedGoal.targetPoints.toLocaleString()} points saved
+              </Text>
+            </View>
+          ) : (
+            <TouchableOpacity
+              onPress={() => navigation.getParent()?.navigate('SquadTab' as never)}
+              className="mt-6 bg-accent/20 border border-dashed border-accent rounded-2xl p-4"
+            >
+              <Text className="text-accent font-semibold text-center">
+                Create or join a squad to start sharing points!
+              </Text>
+            </TouchableOpacity>
+          )}
+        </View>
+
+        <View className="mt-6">
+          <Text className="text-xl font-bold text-gray-900 mb-3">Weekly Highlights</Text>
+          {demoChallenges.map(challenge => (
+            <WeeklyChallengeCard key={challenge.id} challenge={challenge} />
+          ))}
+        </View>
+      </ScrollView>
+    </LinearGradient>
+  );
+};
+
+export default HomeScreen;
diff --git a/src/screens/main/ProfileScreen.tsx b/src/screens/main/ProfileScreen.tsx
new file mode 100644
index 0000000..f5f5ac4
--- /dev/null
+++ b/src/screens/main/ProfileScreen.tsx
@@ -0,0 +1,41 @@
+import { LinearGradient } from 'expo-linear-gradient';
+import { ScrollView, Text, TouchableOpacity, View } from 'react-native';
+
+import { useAuth } from '@/hooks/useAuth';
+
+const ProfileScreen = () => {
+  const { profile, logout } = useAuth();
+
+  return (
+    <LinearGradient colors={['#F7F7FF', '#EAF8FF']} style={{ flex: 1 }}>
+      <ScrollView contentContainerStyle={{ padding: 20 }}>
+        <View className="bg-white rounded-3xl p-6 shadow-sm shadow-black/10">
+          <Text className="text-3xl font-bold text-gray-900">{profile?.displayName ?? 'Fetcher'}</Text>
+          <Text className="text-gray-500 mt-1">{profile?.email}</Text>
+
+          <View className="mt-6 space-y-4">
+            <View className="bg-primary/10 rounded-2xl p-4">
+              <Text className="text-primary font-semibold text-sm">Lifetime Points</Text>
+              <Text className="text-2xl font-bold text-primary mt-1">{profile?.totalPoints ?? 0}</Text>
+            </View>
+            <View className="bg-secondary/10 rounded-2xl p-4">
+              <Text className="text-secondary font-semibold text-sm">League</Text>
+              <Text className="text-xl font-bold text-secondary mt-1">{profile?.league ?? 'Bronze'}</Text>
+              <Text className="text-sm text-gray-600 mt-1">Weekly points: {profile?.weeklyLeaguePoints ?? 0}</Text>
+            </View>
+            <View className="bg-accent/10 rounded-2xl p-4">
+              <Text className="text-accent font-semibold text-sm">Scan Streak</Text>
+              <Text className="text-xl font-bold text-accent mt-1">{profile?.scanStreak.days ?? 0} days</Text>
+            </View>
+          </View>
+
+          <TouchableOpacity onPress={logout} className="mt-8 bg-gray-900 rounded-2xl py-3 items-center">
+            <Text className="text-white font-semibold">Log out</Text>
+          </TouchableOpacity>
+        </View>
+      </ScrollView>
+    </LinearGradient>
+  );
+};
+
+export default ProfileScreen;
diff --git a/src/screens/main/ScanReceiptModal.tsx b/src/screens/main/ScanReceiptModal.tsx
new file mode 100644
index 0000000..3d25f92
--- /dev/null
+++ b/src/screens/main/ScanReceiptModal.tsx
@@ -0,0 +1,69 @@
+import { useNavigation } from '@react-navigation/native';
+import { NativeStackScreenProps } from '@react-navigation/native-stack';
+import { useState } from 'react';
+import { Alert, Text, TouchableOpacity, View } from 'react-native';
+
+import { useSquad } from '@/hooks/useSquad';
+import { HomeStackParamList } from '@/types/navigation';
+
+const generatePoints = () => Math.floor(Math.random() * 400) + 100;
+
+const ScanReceiptModal = () => {
+  const navigation = useNavigation<NativeStackScreenProps<HomeStackParamList>['navigation']>();
+  const { squad, shareReceiptWithSquad } = useSquad();
+  const [isScanning, setIsScanning] = useState(false);
+  const [points, setPoints] = useState<number | null>(null);
+
+  const handleSimulateScan = () => {
+    setIsScanning(true);
+    setTimeout(() => {
+      setPoints(generatePoints());
+      setIsScanning(false);
+    }, 1200);
+  };
+
+  const handleShare = async () => {
+    if (!squad || !points) return;
+    try {
+      await shareReceiptWithSquad(points);
+      Alert.alert('Success', `Shared ${points} points with your squad!`);
+      navigation.goBack();
+    } catch (error) {
+      Alert.alert('Error', (error as Error)?.message ?? 'Failed to share points.');
+    }
+  };
+
+  return (
+    <View className="flex-1 bg-white p-6">
+      <Text className="text-2xl font-bold text-gray-900">Scan Receipt</Text>
+      <Text className="text-gray-600 mt-1">Use this simulator to award points and share them with your squad.</Text>
+
+      <View className="mt-6 bg-gray-100 rounded-3xl h-72 items-center justify-center border border-dashed border-gray-300">
+        <Text className="text-gray-500 text-lg">Camera simulation</Text>
+        <TouchableOpacity onPress={handleSimulateScan} className="mt-4 bg-secondary px-6 py-3 rounded-full">
+          <Text className="text-white font-semibold">{isScanning ? 'Scanning...' : 'Tap to Scan'}</Text>
+        </TouchableOpacity>
+      </View>
+
+      {points && (
+        <View className="mt-6 bg-primary/10 border border-primary/40 rounded-2xl p-4">
+          <Text className="text-primary font-semibold text-lg">Receipt Points Awarded</Text>
+          <Text className="text-2xl font-bold text-primary mt-2">{points} pts</Text>
+          <Text className="text-sm text-gray-600 mt-1">
+            Share them with your squad to split evenly across all members.
+          </Text>
+
+          <TouchableOpacity
+            onPress={handleShare}
+            disabled={!squad}
+            className={`mt-4 rounded-xl py-3 items-center ${squad ? 'bg-primary' : 'bg-gray-400'}`}
+          >
+            <Text className="text-white font-semibold">Share with Squad</Text>
+          </TouchableOpacity>
+        </View>
+      )}
+    </View>
+  );
+};
+
+export default ScanReceiptModal;
diff --git a/src/screens/squads/SquadInviteScreen.tsx b/src/screens/squads/SquadInviteScreen.tsx
new file mode 100644
index 0000000..e2b288b
--- /dev/null
+++ b/src/screens/squads/SquadInviteScreen.tsx
@@ -0,0 +1,33 @@
+import { useEffect } from 'react';
+import { Alert, Text, View } from 'react-native';
+import { NativeStackScreenProps } from '@react-navigation/native-stack';
+
+import { useSquad } from '@/hooks/useSquad';
+import { SquadStackParamList } from '@/types/navigation';
+
+const SquadInviteScreen = ({ route, navigation }: NativeStackScreenProps<SquadStackParamList, 'SquadInvite'>) => {
+  const { joinExistingSquad } = useSquad();
+  const { squadId } = route.params;
+
+  useEffect(() => {
+    const join = async () => {
+      try {
+        await joinExistingSquad(squadId);
+        navigation.replace('Squad');
+      } catch (error) {
+        Alert.alert('Unable to join squad', (error as Error)?.message ?? 'Please try again.');
+        navigation.goBack();
+      }
+    };
+
+    join();
+  }, [joinExistingSquad, navigation, squadId]);
+
+  return (
+    <View className="flex-1 items-center justify-center bg-background">
+      <Text className="text-gray-700">Joining squad...</Text>
+    </View>
+  );
+};
+
+export default SquadInviteScreen;
diff --git a/src/screens/squads/SquadScreen.tsx b/src/screens/squads/SquadScreen.tsx
new file mode 100644
index 0000000..763a27d
--- /dev/null
+++ b/src/screens/squads/SquadScreen.tsx
@@ -0,0 +1,204 @@
+import Clipboard from '@react-native-clipboard/clipboard';
+import { useState } from 'react';
+import { Alert, FlatList, ScrollView, Text, TextInput, TouchableOpacity, View } from 'react-native';
+
+import Mascot from '@/components/Mascot';
+import { useAuth } from '@/hooks/useAuth';
+import { useSquad } from '@/hooks/useSquad';
+
+const SquadScreen = () => {
+  const { profile } = useAuth();
+  const { squad, loading, createNewSquad, joinExistingSquad, inviteLink, addItemToShoppingList, setSharedGoalTarget } = useSquad();
+  const [squadName, setSquadName] = useState('');
+  const [joinId, setJoinId] = useState('');
+  const [itemName, setItemName] = useState('');
+  const [updatingGoal, setUpdatingGoal] = useState(false);
+
+  const members = squad?.members ?? [];
+
+  const handleCreate = async () => {
+    if (!squadName.trim()) return;
+    try {
+      await createNewSquad(squadName.trim());
+      setSquadName('');
+    } catch (error) {
+      Alert.alert('Unable to create squad', (error as Error)?.message ?? 'Please try again.');
+    }
+  };
+
+  const handleJoin = async () => {
+    if (!joinId.trim()) return;
+    try {
+      await joinExistingSquad(joinId.trim());
+      setJoinId('');
+    } catch (error) {
+      Alert.alert('Unable to join squad', (error as Error)?.message ?? 'Check the invite ID and try again.');
+    }
+  };
+
+  const handleCopyInvite = () => {
+    if (inviteLink) {
+      Clipboard.setString(inviteLink);
+      Alert.alert('Invite link copied', 'Share it with your friends to squad up!');
+    }
+  };
+
+  const handleAddItem = async () => {
+    if (!itemName.trim()) return;
+    try {
+      await addItemToShoppingList(itemName.trim());
+      setItemName('');
+    } catch (error) {
+      Alert.alert('Unable to add item', (error as Error)?.message ?? 'Please try again.');
+    }
+  };
+
+  const handleUpdateGoal = async (target: number) => {
+    try {
+      setUpdatingGoal(true);
+      await setSharedGoalTarget(target);
+    } catch (error) {
+      Alert.alert('Unable to update goal', (error as Error)?.message ?? 'Please try again later.');
+    } finally {
+      setUpdatingGoal(false);
+    }
+  };
+
+  if (loading) {
+    return (
+      <View className="flex-1 items-center justify-center bg-background">
+        <Text className="text-gray-600">Loading your squad...</Text>
+      </View>
+    );
+  }
+
+  if (!squad) {
+    return (
+      <ScrollView contentContainerStyle={{ padding: 20 }} className="bg-background flex-1">
+        <Text className="text-3xl font-bold text-gray-900">Build your Squad</Text>
+        <Text className="text-gray-600 mt-2">
+          Create a new squad or join an existing one to start splitting points, setting goals, and completing weekly quests.
+        </Text>
+
+        <View className="mt-6 bg-white rounded-3xl p-5 shadow-sm shadow-black/5">
+          <Text className="text-xl font-semibold text-gray-900">Create Squad</Text>
+          <TextInput
+            placeholder="Name your squad"
+            value={squadName}
+            onChangeText={setSquadName}
+            className="mt-3 bg-gray-100 rounded-xl px-4 py-3"
+          />
+          <TouchableOpacity onPress={handleCreate} className="mt-4 bg-primary rounded-xl py-3 items-center">
+            <Text className="text-white font-semibold">Create</Text>
+          </TouchableOpacity>
+        </View>
+
+        <View className="mt-6 bg-white rounded-3xl p-5 shadow-sm shadow-black/5">
+          <Text className="text-xl font-semibold text-gray-900">Join Squad</Text>
+          <TextInput
+            placeholder="Enter invite ID"
+            value={joinId}
+            onChangeText={setJoinId}
+            className="mt-3 bg-gray-100 rounded-xl px-4 py-3"
+          />
+          <TouchableOpacity onPress={handleJoin} className="mt-4 bg-secondary rounded-xl py-3 items-center">
+            <Text className="text-white font-semibold">Join</Text>
+          </TouchableOpacity>
+        </View>
+      </ScrollView>
+    );
+  }
+
+  return (
+    <ScrollView className="bg-background flex-1" contentContainerStyle={{ padding: 20, paddingBottom: 160 }}>
+      <Text className="text-3xl font-bold text-gray-900">{squad.squadName}</Text>
+      <Text className="text-gray-600 mt-1">Invite friends with the link below and start earning faster.</Text>
+
+      <View className="mt-5 bg-white rounded-3xl p-5 shadow-sm shadow-black/5">
+        <View className="items-center">
+          <Mascot status={squad.mascotStatus} />
+        </View>
+        <TouchableOpacity onPress={handleCopyInvite} className="mt-6 bg-secondary/10 rounded-xl px-4 py-3">
+          <Text className="text-secondary font-semibold text-center">Copy invite link</Text>
+          <Text className="text-xs text-gray-500 text-center mt-1">{inviteLink}</Text>
+        </TouchableOpacity>
+      </View>
+
+      <View className="mt-6 bg-white rounded-3xl p-5">
+        <Text className="text-xl font-semibold text-gray-900">Members</Text>
+        <FlatList
+          data={members}
+          keyExtractor={item => item}
+          renderItem={({ item }) => (
+            <Text className="mt-2 text-gray-700">{item === profile?.uid ? `${item} (you)` : item}</Text>
+          )}
+        />
+      </View>
+
+      <View className="mt-6 bg-white rounded-3xl p-5">
+        <Text className="text-xl font-semibold text-gray-900">Shared Goal</Text>
+        <Text className="text-sm text-gray-600 mt-1">Current: {squad.sharedGoal.targetPoints.toLocaleString()} pts</Text>
+        <View className="mt-2 h-3 bg-gray-200 rounded-full overflow-hidden">
+          <View
+            className="h-full bg-accent"
+            style={{ width: `${Math.min(100, (squad.sharedGoal.currentPoints / squad.sharedGoal.targetPoints) * 100)}%` }}
+          />
+        </View>
+        <View className="flex-row flex-wrap mt-4 gap-2">
+          {[10000, 25000, 50000].map(goal => (
+            <TouchableOpacity
+              key={goal}
+              onPress={() => handleUpdateGoal(goal)}
+              className={`px-4 py-2 rounded-full border ${
+                squad.sharedGoal.targetPoints === goal ? 'bg-accent text-white border-accent' : 'border-gray-200'
+              }`}
+            >
+              <Text className={`${squad.sharedGoal.targetPoints === goal ? 'text-white' : 'text-gray-700'}`}>{goal.toLocaleString()} pts</Text>
+            </TouchableOpacity>
+          ))}
+        </View>
+        {updatingGoal && <Text className="text-xs text-gray-500 mt-2">Updating goal...</Text>}
+      </View>
+
+      <View className="mt-6 bg-white rounded-3xl p-5">
+        <Text className="text-xl font-semibold text-gray-900">Squad Shopping List</Text>
+        <View className="flex-row items-center mt-3">
+          <TextInput
+            placeholder="Add grocery item"
+            value={itemName}
+            onChangeText={setItemName}
+            className="flex-1 bg-gray-100 rounded-xl px-4 py-3"
+          />
+          <TouchableOpacity onPress={handleAddItem} className="ml-3 bg-primary rounded-xl px-4 py-3">
+            <Text className="text-white font-semibold">Add</Text>
+          </TouchableOpacity>
+        </View>
+        <View className="mt-4 space-y-2">
+          {squad.shoppingList.map(entry => (
+            <View key={entry.id} className="flex-row justify-between bg-gray-50 rounded-xl px-4 py-3">
+              <Text className="text-gray-800">{entry.itemName}</Text>
+              <Text className="text-xs text-gray-500">by {entry.addedBy}</Text>
+            </View>
+          ))}
+        </View>
+      </View>
+
+      <View className="mt-6 bg-white rounded-3xl p-5">
+        <Text className="text-xl font-semibold text-gray-900">Weekly Challenges</Text>
+        <View className="mt-4">
+          <Text className="text-base font-semibold text-gray-800">Quest</Text>
+          <Text className="text-sm text-gray-600 mt-1">Scan 5 receipts together this week.</Text>
+          <Text className="text-sm text-gray-500 mt-1">Progress updates automatically after each scan.</Text>
+        </View>
+        <View className="mt-4">
+          <Text className="text-base font-semibold text-gray-800">Squad Duel</Text>
+          <Text className="text-sm text-gray-600 mt-1">
+            Challenge a teammate and see who collects more points before Sunday night.
+          </Text>
+        </View>
+      </View>
+    </ScrollView>
+  );
+};
+
+export default SquadScreen;
diff --git a/src/services/firebase.ts b/src/services/firebase.ts
new file mode 100644
index 0000000..9c8d226
--- /dev/null
+++ b/src/services/firebase.ts
@@ -0,0 +1,26 @@
+import { initializeApp, getApps, FirebaseApp } from 'firebase/app';
+import { getAuth } from 'firebase/auth';
+import { getFirestore } from 'firebase/firestore';
+import Constants from 'expo-constants';
+
+let app: FirebaseApp;
+
+const initFirebase = () => {
+  if (!getApps().length) {
+    const firebaseConfig = Constants?.expoConfig?.extra?.firebase;
+
+    if (!firebaseConfig) {
+      throw new Error('Firebase configuration is missing. Make sure to define it in the .env file.');
+    }
+
+    app = initializeApp(firebaseConfig);
+  } else {
+    app = getApps()[0];
+  }
+
+  return app;
+};
+
+export const firebaseApp = initFirebase();
+export const auth = getAuth(firebaseApp);
+export const db = getFirestore(firebaseApp);
diff --git a/src/services/leagueService.ts b/src/services/leagueService.ts
new file mode 100644
index 0000000..df8652d
--- /dev/null
+++ b/src/services/leagueService.ts
@@ -0,0 +1,89 @@
+import { doc, getDoc, setDoc, updateDoc } from 'firebase/firestore';
+
+import { db } from './firebase';
+import { LeagueGroup, LeagueGroupMember, LeagueTier } from '@/types/models';
+import { getWeekRange } from '@/utils/date';
+import { hashStringToNumber } from '@/utils/hash';
+
+const leagueTiers: LeagueTier[] = ['Bronze', 'Silver', 'Gold', 'Platinum', 'Diamond', 'Elite', 'Legend', 'Mythic'];
+
+export const getNextLeague = (current: LeagueTier): LeagueTier => {
+  const index = leagueTiers.indexOf(current);
+  return leagueTiers[Math.min(index + 1, leagueTiers.length - 1)];
+};
+
+export const getLeagueGroupId = (league: LeagueTier, weekKey: string, groupNumber: number) =>
+  `${league.toLowerCase()}_${weekKey}_group_${groupNumber}`;
+
+export const getOrCreateLeagueGroup = async (league: LeagueTier, uid: string) => {
+  const { key, weekStart, weekEnd } = getWeekRange();
+  const groupNumber = hashStringToNumber(uid + key + league, 5) + 1;
+  const targetGroupId = getLeagueGroupId(league, key, groupNumber);
+
+  const groupRef = doc(db, 'leagues', targetGroupId);
+  const groupSnapshot = await getDoc(groupRef);
+  if (!groupSnapshot.exists()) {
+    const newGroup: LeagueGroup = {
+      leagueId: targetGroupId,
+      leagueName: league,
+      members: [],
+      weekStartDate: weekStart.toISOString(),
+      weekEndDate: weekEnd.toISOString(),
+      weekKey: key
+    };
+    await setDoc(groupRef, newGroup);
+  }
+
+  const groupData = (await getDoc(groupRef)).data() as LeagueGroup;
+  const members = groupData.members ?? [];
+
+  const member: LeagueGroupMember = {
+    uid,
+    displayName: 'You',
+    pointsThisWeek: 0,
+    league,
+    streakMultiplier: 1
+  };
+
+  await updateDoc(groupRef, {
+    members: [...members.filter(existing => existing.uid !== uid), member]
+  });
+
+  return { ...groupData, members: [...members.filter(existing => existing.uid !== uid), member] };
+};
+
+export const updateWeeklyPoints = async (leagueId: string, member: LeagueGroupMember) => {
+  const groupRef = doc(db, 'leagues', leagueId);
+  const snapshot = await getDoc(groupRef);
+  if (!snapshot.exists()) return;
+
+  const group = snapshot.data() as LeagueGroup;
+  const members = (group.members ?? []).filter(existing => existing.uid !== member.uid);
+  await updateDoc(groupRef, { members: [...members, member] });
+};
+
+export const fetchLeaderboard = async (leagueId: string) => {
+  const snapshot = await getDoc(doc(db, 'leagues', leagueId));
+  if (!snapshot.exists()) return null;
+  const group = snapshot.data() as LeagueGroup;
+  return {
+    ...group,
+    members: [...group.members].sort((a, b) => b.pointsThisWeek - a.pointsThisWeek)
+  };
+};
+
+export const getSeasonCountdown = () => {
+  const seasonEnd = new Date();
+  seasonEnd.setDate(seasonEnd.getDate() + (30 - (seasonEnd.getDate() % 30)));
+  const diff = seasonEnd.getTime() - Date.now();
+  const days = Math.max(0, Math.floor(diff / (1000 * 60 * 60 * 24)));
+  return `${days} days`;
+};
+
+export const getLeagueRewards = (league: LeagueTier) => {
+  const base = (leagueTiers.indexOf(league) + 1) * 100;
+  return {
+    placementBonus: base,
+    streakMultiplierBonus: base / 2
+  };
+};
diff --git a/src/services/squadService.ts b/src/services/squadService.ts
new file mode 100644
index 0000000..1ed1d78
--- /dev/null
+++ b/src/services/squadService.ts
@@ -0,0 +1,110 @@
+import { nanoid } from 'nanoid/non-secure';
+import {
+  Timestamp,
+  arrayUnion,
+  collection,
+  doc,
+  getDoc,
+  increment,
+  onSnapshot,
+  setDoc,
+  updateDoc
+} from 'firebase/firestore';
+
+import { db } from './firebase';
+import { Squad } from '@/types/models';
+
+export const squadsCollection = collection(db, 'squads');
+
+export const generateSquadInviteLink = (squadId: string) => `fetchapp://squad/join/${squadId}`;
+
+export const createSquad = async (squadName: string, ownerId: string) => {
+  const squadId = nanoid(8);
+  const squadRef = doc(squadsCollection, squadId);
+  const squad: Squad = {
+    squadId,
+    squadName,
+    members: [ownerId],
+    mascotStatus: 'happy',
+    sharedGoal: {
+      targetPoints: 25000,
+      currentPoints: 0
+    },
+    shoppingList: []
+  };
+
+  await setDoc(squadRef, squad);
+  await updateDoc(doc(db, 'users', ownerId), { squadId });
+
+  return squad;
+};
+
+export const listenToSquad = (squadId: string, callback: (squad: Squad | null) => void) =>
+  onSnapshot(doc(squadsCollection, squadId), snapshot => {
+    if (snapshot.exists()) {
+      callback(snapshot.data() as Squad);
+    } else {
+      callback(null);
+    }
+  });
+
+export const joinSquad = async (squadId: string, userId: string) => {
+  const squadRef = doc(squadsCollection, squadId);
+  const squadSnap = await getDoc(squadRef);
+  if (!squadSnap.exists()) {
+    throw new Error('Squad not found');
+  }
+
+  const squad = squadSnap.data() as Squad;
+  if (squad.members.includes(userId)) {
+    return squad;
+  }
+
+  await updateDoc(squadRef, {
+    members: arrayUnion(userId)
+  });
+
+  await updateDoc(doc(db, 'users', userId), { squadId });
+  return (await getDoc(squadRef)).data() as Squad;
+};
+
+export const addShoppingListItem = async (squadId: string, itemName: string, addedBy: string) => {
+  const squadRef = doc(squadsCollection, squadId);
+  const itemId = nanoid();
+  await updateDoc(squadRef, {
+    shoppingList: arrayUnion({
+      id: itemId,
+      itemName,
+      addedBy,
+      createdAt: Timestamp.now().toDate().toISOString()
+    })
+  });
+};
+
+export const updateSharedGoal = async (squadId: string, targetPoints: number) => {
+  await updateDoc(doc(squadsCollection, squadId), {
+    'sharedGoal.targetPoints': targetPoints
+  });
+};
+
+export const distributeReceiptPoints = async (squadId: string, totalPoints: number) => {
+  const squadSnap = await getDoc(doc(squadsCollection, squadId));
+  if (!squadSnap.exists()) {
+    throw new Error('Squad not found');
+  }
+  const squad = squadSnap.data() as Squad;
+  const perMember = Math.floor(totalPoints / squad.members.length);
+
+  const batchUpdates = squad.members.map(memberId =>
+    updateDoc(doc(db, 'users', memberId), {
+      totalPoints: increment(perMember),
+      weeklyLeaguePoints: increment(perMember)
+    })
+  );
+
+  await Promise.all(batchUpdates);
+  await updateDoc(doc(squadsCollection, squadId), {
+    'sharedGoal.currentPoints': increment(totalPoints),
+    mascotStatus: totalPoints > 400 ? 'excited' : 'happy'
+  });
+};
diff --git a/src/types/models.ts b/src/types/models.ts
new file mode 100644
index 0000000..75ae5d9
--- /dev/null
+++ b/src/types/models.ts
@@ -0,0 +1,66 @@
+export type LeagueTier =
+  | 'Bronze'
+  | 'Silver'
+  | 'Gold'
+  | 'Platinum'
+  | 'Diamond'
+  | 'Elite'
+  | 'Legend'
+  | 'Mythic';
+
+export interface UserProfile {
+  uid: string;
+  email: string;
+  displayName: string;
+  totalPoints: number;
+  squadId?: string | null;
+  league: LeagueTier;
+  weeklyLeaguePoints: number;
+  scanStreak: {
+    days: number;
+    lastScanDate?: string;
+  };
+  createdAt: string;
+}
+
+export interface Squad {
+  squadId: string;
+  squadName: string;
+  members: string[];
+  mascotStatus: 'happy' | 'excited' | 'sleepy';
+  sharedGoal: {
+    targetPoints: number;
+    currentPoints: number;
+  };
+  shoppingList: Array<{
+    id: string;
+    itemName: string;
+    addedBy: string;
+    createdAt: string;
+  }>;
+}
+
+export interface LeagueGroupMember {
+  uid: string;
+  displayName: string;
+  pointsThisWeek: number;
+  league: LeagueTier;
+  streakMultiplier: number;
+}
+
+export interface LeagueGroup {
+  leagueId: string;
+  leagueName: LeagueTier;
+  members: LeagueGroupMember[];
+  weekStartDate: string;
+  weekEndDate: string;
+  weekKey?: string;
+}
+
+export interface Challenge {
+  id: string;
+  title: string;
+  description: string;
+  progress: number;
+  target: number;
+}
diff --git a/src/types/navigation.ts b/src/types/navigation.ts
new file mode 100644
index 0000000..bccf038
--- /dev/null
+++ b/src/types/navigation.ts
@@ -0,0 +1,34 @@
+export type RootStackParamList = {
+  Auth: undefined;
+  Main: undefined;
+};
+
+export type AuthStackParamList = {
+  Login: undefined;
+  Register: undefined;
+};
+
+export type MainTabParamList = {
+  HomeTab: undefined;
+  SquadTab: { squadId?: string } | undefined;
+  LeagueTab: undefined;
+  ProfileTab: undefined;
+};
+
+export type HomeStackParamList = {
+  Home: undefined;
+  ScanReceiptModal: undefined;
+};
+
+export type SquadStackParamList = {
+  Squad: { squadId?: string } | undefined;
+  SquadInvite: { squadId: string };
+};
+
+export type LeagueStackParamList = {
+  League: undefined;
+};
+
+export type ProfileStackParamList = {
+  Profile: undefined;
+};
diff --git a/src/utils/date.ts b/src/utils/date.ts
new file mode 100644
index 0000000..e05533e
--- /dev/null
+++ b/src/utils/date.ts
@@ -0,0 +1,22 @@
+export const getWeekRange = (date: Date = new Date()) => {
+  const current = new Date(date);
+  const day = current.getUTCDay();
+  const diffToMonday = (day + 6) % 7;
+  const weekStart = new Date(Date.UTC(current.getUTCFullYear(), current.getUTCMonth(), current.getUTCDate() - diffToMonday));
+  const weekEnd = new Date(weekStart);
+  weekEnd.setUTCDate(weekStart.getUTCDate() + 7);
+
+  return {
+    weekStart,
+    weekEnd,
+    key: `${weekStart.getUTCFullYear()}-W${String(getWeekNumber(current)).padStart(2, '0')}`
+  };
+};
+
+export const getWeekNumber = (date: Date) => {
+  const tmpDate = new Date(Date.UTC(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate()));
+  const dayNum = tmpDate.getUTCDay() || 7;
+  tmpDate.setUTCDate(tmpDate.getUTCDate() + 4 - dayNum);
+  const yearStart = new Date(Date.UTC(tmpDate.getUTCFullYear(), 0, 1));
+  return Math.ceil(((tmpDate.getTime() - yearStart.getTime()) / 86400000 + 1) / 7);
+};
diff --git a/src/utils/hash.ts b/src/utils/hash.ts
new file mode 100644
index 0000000..2fd148c
--- /dev/null
+++ b/src/utils/hash.ts
@@ -0,0 +1,8 @@
+export const hashStringToNumber = (value: string, max: number) => {
+  let hash = 0;
+  for (let i = 0; i < value.length; i += 1) {
+    hash = (hash << 5) - hash + value.charCodeAt(i);
+    hash |= 0;
+  }
+  return Math.abs(hash) % max;
+};
diff --git a/tailwind.config.js b/tailwind.config.js
new file mode 100644
index 0000000..04964b7
--- /dev/null
+++ b/tailwind.config.js
@@ -0,0 +1,16 @@
+/** @type {import('tailwindcss').Config} */
+module.exports = {
+  content: ['./App.{ts,tsx}', './src/**/*.{ts,tsx}'],
+  theme: {
+    extend: {
+      colors: {
+        primary: '#FF8F3F',
+        secondary: '#7F5AF0',
+        accent: '#2CB9B0',
+        background: '#F7F7FF',
+        surface: '#FFFFFF'
+      }
+    }
+  },
+  plugins: []
+};
diff --git a/todo.md b/todo.md
new file mode 100644
index 0000000..e97ad89
--- /dev/null
+++ b/todo.md
@@ -0,0 +1,16 @@
+# TODO
+
+## Plan
+- [x] Initialize Expo React Native TypeScript project structure within repo
+- [x] Configure NativeWind, React Navigation, Firebase dependencies
+- [x] Implement authentication flow with Firebase Auth integration
+- [x] Build Squad feature screens and logic (creation, join, sharing, mascot, challenges)
+- [x] Build League feature screens and logic (leaderboard, weekly reset simulation)
+- [x] Implement Firestore data models, hooks, and utilities
+- [x] Add seeding script for Firestore fake data (seed.js)
+- [x] Create README with setup and launch instructions
+- [x] Update assets (mascot animation placeholder) and UI components
+- [x] Final review and testing instructions
+
+## Review Notes
+- Seed script generates demo data for Firestore using Firebase Admin. Provide service account via env variables.
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..8030269
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,9 @@
+{
+  "extends": "expo/tsconfig.base",
+  "compilerOptions": {
+    "strict": true,
+    "paths": {
+      "@/*": ["src/*"]
+    }
+  }
+}