diff --git a/lifetimer/lib/core/errors/error_mapper.dart b/lifetimer/lib/core/errors/error_mapper.dart
new file mode 100644
index 0000000..53908c8
--- /dev/null
+++ b/lifetimer/lib/core/errors/error_mapper.dart
@@ -0,0 +1,47 @@
+import 'package:supabase_flutter/supabase_flutter.dart';
+import 'failure.dart';
+
+class ErrorMapper {
+  static Failure mapError(dynamic error) {
+    if (error is AuthException) {
+      switch (error.message) {
+        case 'Invalid login credentials':
+          return const AuthFailure('Invalid email or password');
+        case 'Email not confirmed':
+          return const AuthFailure('Please confirm your email address');
+        case 'User already registered':
+          return const AuthFailure('An account with this email already exists');
+        case 'Password should be at least 6 characters':
+          return const AuthFailure('Password must be at least 6 characters');
+        default:
+          return AuthFailure(error.message);
+      }
+    }
+
+    if (error is PostgrestException) {
+      switch (error.code) {
+        case '23505':
+          return const ValidationFailure('This record already exists');
+        case '23503':
+          return const ValidationFailure('Referenced record does not exist');
+        case '42501':
+          return const PermissionFailure('You do not have permission to perform this action');
+        default:
+          return ServerFailure(
+            error.message,
+            statusCode: int.tryParse(error.code ?? ''),
+          );
+      }
+    }
+
+    if (error is Exception) {
+      return NetworkFailure(error.toString().replaceAll('Exception: ', ''));
+    }
+
+    return UnknownFailure(error.toString());
+  }
+
+  static String getUserMessage(Failure failure) {
+    return failure.message;
+  }
+}
diff --git a/lifetimer/lib/core/errors/failure.dart b/lifetimer/lib/core/errors/failure.dart
new file mode 100644
index 0000000..a2d16a6
--- /dev/null
+++ b/lifetimer/lib/core/errors/failure.dart
@@ -0,0 +1,37 @@
+abstract class Failure {
+  final String message;
+  final int? statusCode;
+
+  const Failure(this.message, {this.statusCode});
+
+  @override
+  String toString() => 'Failure: $message';
+}
+
+class ServerFailure extends Failure {
+  const ServerFailure(super.message, {super.statusCode});
+}
+
+class NetworkFailure extends Failure {
+  const NetworkFailure(super.message);
+}
+
+class AuthFailure extends Failure {
+  const AuthFailure(super.message);
+}
+
+class ValidationFailure extends Failure {
+  const ValidationFailure(super.message);
+}
+
+class NotFoundFailure extends Failure {
+  const NotFoundFailure(super.message);
+}
+
+class PermissionFailure extends Failure {
+  const PermissionFailure(super.message);
+}
+
+class UnknownFailure extends Failure {
+  const UnknownFailure(super.message);
+}
diff --git a/lifetimer/lib/core/utils/date_time_utils.dart b/lifetimer/lib/core/utils/date_time_utils.dart
new file mode 100644
index 0000000..a1630d9
--- /dev/null
+++ b/lifetimer/lib/core/utils/date_time_utils.dart
@@ -0,0 +1,77 @@
+import 'package:intl/intl.dart';
+
+class DateTimeUtils {
+  static const int countdownDays = 1356;
+
+  static DateTime calculateEndDate(DateTime startDate) {
+    return startDate.add(const Duration(days: countdownDays));
+  }
+
+  static Duration calculateRemainingTime(DateTime endDate) {
+    return endDate.difference(DateTime.now());
+  }
+
+  static String formatCountdown(Duration duration) {
+    final days = duration.inDays;
+    final hours = duration.inHours % 24;
+    final minutes = duration.inMinutes % 60;
+    final seconds = duration.inSeconds % 60;
+
+    return '${days}d ${hours}h ${minutes}m ${seconds}s';
+  }
+
+  static String formatCountdownCompact(Duration duration) {
+    final days = duration.inDays;
+    final hours = duration.inHours % 24;
+    final minutes = duration.inMinutes % 60;
+
+    if (days > 0) {
+      return '${days}d ${hours}h';
+    } else if (hours > 0) {
+      return '${hours}h ${minutes}m';
+    } else {
+      return '${minutes}m';
+    }
+  }
+
+  static double calculateProgress(DateTime startDate, DateTime endDate) {
+    final now = DateTime.now();
+    final totalDuration = endDate.difference(startDate).inSeconds;
+    final elapsedDuration = now.difference(startDate).inSeconds;
+
+    if (elapsedDuration >= totalDuration) {
+      return 1.0;
+    }
+
+    return elapsedDuration / totalDuration;
+  }
+
+  static String formatDate(DateTime date) {
+    return DateFormat('MMM dd, yyyy').format(date);
+  }
+
+  static String formatDateTime(DateTime dateTime) {
+    return DateFormat('MMM dd, yyyy • HH:mm').format(dateTime);
+  }
+
+  static String formatRelativeTime(DateTime dateTime) {
+    final now = DateTime.now();
+    final difference = now.difference(dateTime);
+
+    if (difference.inSeconds < 60) {
+      return 'Just now';
+    } else if (difference.inMinutes < 60) {
+      return '${difference.inMinutes}m ago';
+    } else if (difference.inHours < 24) {
+      return '${difference.inHours}h ago';
+    } else if (difference.inDays < 7) {
+      return '${difference.inDays}d ago';
+    } else {
+      return formatDate(dateTime);
+    }
+  }
+
+  static bool isCountdownFinished(DateTime endDate) {
+    return DateTime.now().isAfter(endDate);
+  }
+}
diff --git a/lifetimer/lib/core/utils/validators.dart b/lifetimer/lib/core/utils/validators.dart
new file mode 100644
index 0000000..970c32d
--- /dev/null
+++ b/lifetimer/lib/core/utils/validators.dart
@@ -0,0 +1,87 @@
+class Validators {
+  static String? validateEmail(String? value) {
+    if (value == null || value.isEmpty) {
+      return 'Email is required';
+    }
+    
+    final emailRegex = RegExp(r'^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$');
+    if (!emailRegex.hasMatch(value)) {
+      return 'Please enter a valid email address';
+    }
+    
+    return null;
+  }
+
+  static String? validatePassword(String? value) {
+    if (value == null || value.isEmpty) {
+      return 'Password is required';
+    }
+    
+    if (value.length < 6) {
+      return 'Password must be at least 6 characters';
+    }
+    
+    return null;
+  }
+
+  static String? validateUsername(String? value) {
+    if (value == null || value.isEmpty) {
+      return 'Username is required';
+    }
+    
+    if (value.length < 3) {
+      return 'Username must be at least 3 characters';
+    }
+    
+    if (value.length > 20) {
+      return 'Username must not exceed 20 characters';
+    }
+    
+    final usernameRegex = RegExp(r'^[a-zA-Z0-9_]+$');
+    if (!usernameRegex.hasMatch(value)) {
+      return 'Username can only contain letters, numbers, and underscores';
+    }
+    
+    return null;
+  }
+
+  static String? validateGoalTitle(String? value) {
+    if (value == null || value.isEmpty) {
+      return 'Goal title is required';
+    }
+    
+    if (value.length > 100) {
+      return 'Goal title must not exceed 100 characters';
+    }
+    
+    return null;
+  }
+
+  static String? validateGoalDescription(String? value) {
+    if (value != null && value.length > 500) {
+      return 'Description must not exceed 500 characters';
+    }
+    
+    return null;
+  }
+
+  static String? validateGoalProgress(int? value) {
+    if (value == null) {
+      return 'Progress is required';
+    }
+    
+    if (value < 0 || value > 100) {
+      return 'Progress must be between 0 and 100';
+    }
+    
+    return null;
+  }
+
+  static String? validateRequired(String? value, String fieldName) {
+    if (value == null || value.isEmpty) {
+      return '$fieldName is required';
+    }
+    
+    return null;
+  }
+}
diff --git a/lifetimer/lib/core/widgets/app_scaffold.dart b/lifetimer/lib/core/widgets/app_scaffold.dart
new file mode 100644
index 0000000..0f06e9a
--- /dev/null
+++ b/lifetimer/lib/core/widgets/app_scaffold.dart
@@ -0,0 +1,45 @@
+import 'package:flutter/material.dart';
+
+class AppScaffold extends StatelessWidget {
+  final String? title;
+  final Widget body;
+  final List<Widget>? actions;
+  final Widget? floatingActionButton;
+  final bool showBackButton;
+  final VoidCallback? onBackPressed;
+  final Widget? bottomNavigationBar;
+
+  const AppScaffold({
+    super.key,
+    this.title,
+    required this.body,
+    this.actions,
+    this.floatingActionButton,
+    this.showBackButton = false,
+    this.onBackPressed,
+    this.bottomNavigationBar,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: title != null
+          ? AppBar(
+              title: Text(title!),
+              centerTitle: true,
+              automaticallyImplyLeading: showBackButton,
+              leading: showBackButton
+                  ? IconButton(
+                      icon: const Icon(Icons.arrow_back),
+                      onPressed: onBackPressed ?? () => Navigator.pop(context),
+                    )
+                  : null,
+              actions: actions,
+            )
+          : null,
+      body: SafeArea(child: body),
+      floatingActionButton: floatingActionButton,
+      bottomNavigationBar: bottomNavigationBar,
+    );
+  }
+}
diff --git a/lifetimer/lib/core/widgets/bottom_nav_scaffold.dart b/lifetimer/lib/core/widgets/bottom_nav_scaffold.dart
new file mode 100644
index 0000000..54c6a8c
--- /dev/null
+++ b/lifetimer/lib/core/widgets/bottom_nav_scaffold.dart
@@ -0,0 +1,74 @@
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+class BottomNavScaffold extends StatefulWidget {
+  final Widget child;
+
+  const BottomNavScaffold({
+    super.key,
+    required this.child,
+  });
+
+  @override
+  State<BottomNavScaffold> createState() => _BottomNavScaffoldState();
+}
+
+class _BottomNavScaffoldState extends State<BottomNavScaffold> {
+  int _currentIndex = 0;
+
+  final List<NavigationDestination> _destinations = const [
+    NavigationDestination(
+      icon: Icon(Icons.home_outlined),
+      selectedIcon: Icon(Icons.home),
+      label: 'Home',
+    ),
+    NavigationDestination(
+      icon: Icon(Icons.flag_outlined),
+      selectedIcon: Icon(Icons.flag),
+      label: 'Goals',
+    ),
+    NavigationDestination(
+      icon: Icon(Icons.people_outline),
+      selectedIcon: Icon(Icons.people),
+      label: 'Social',
+    ),
+    NavigationDestination(
+      icon: Icon(Icons.person_outline),
+      selectedIcon: Icon(Icons.person),
+      label: 'Profile',
+    ),
+  ];
+
+  void _onDestinationSelected(int index) {
+    setState(() {
+      _currentIndex = index;
+    });
+
+    switch (index) {
+      case 0:
+        context.go('/home');
+        break;
+      case 1:
+        context.go('/goals');
+        break;
+      case 2:
+        context.go('/social');
+        break;
+      case 3:
+        context.go('/profile');
+        break;
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: widget.child,
+      bottomNavigationBar: NavigationBar(
+        selectedIndex: _currentIndex,
+        onDestinationSelected: _onDestinationSelected,
+        destinations: _destinations,
+      ),
+    );
+  }
+}
diff --git a/lifetimer/lib/core/widgets/empty_state.dart b/lifetimer/lib/core/widgets/empty_state.dart
new file mode 100644
index 0000000..bad60fb
--- /dev/null
+++ b/lifetimer/lib/core/widgets/empty_state.dart
@@ -0,0 +1,58 @@
+import 'package:flutter/material.dart';
+
+class EmptyState extends StatelessWidget {
+  final IconData icon;
+  final String title;
+  final String? subtitle;
+  final String? actionLabel;
+  final VoidCallback? onAction;
+
+  const EmptyState({
+    super.key,
+    required this.icon,
+    required this.title,
+    this.subtitle,
+    this.actionLabel,
+    this.onAction,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Center(
+      child: Padding(
+        padding: const EdgeInsets.all(32.0),
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            Icon(
+              icon,
+              size: 80,
+              color: Theme.of(context).colorScheme.primary.withOpacity(0.5),
+            ),
+            const SizedBox(height: 24),
+            Text(
+              title,
+              style: Theme.of(context).textTheme.headlineMedium,
+              textAlign: TextAlign.center,
+            ),
+            if (subtitle != null) ...[
+              const SizedBox(height: 8),
+              Text(
+                subtitle!,
+                style: Theme.of(context).textTheme.bodyMedium,
+                textAlign: TextAlign.center,
+              ),
+            ],
+            if (actionLabel != null && onAction != null) ...[
+              const SizedBox(height: 24),
+              ElevatedButton(
+                onPressed: onAction,
+                child: Text(actionLabel!),
+              ),
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+}
diff --git a/lifetimer/lib/core/widgets/loading_indicator.dart b/lifetimer/lib/core/widgets/loading_indicator.dart
new file mode 100644
index 0000000..43748a0
--- /dev/null
+++ b/lifetimer/lib/core/widgets/loading_indicator.dart
@@ -0,0 +1,29 @@
+import 'package:flutter/material.dart';
+
+class LoadingIndicator extends StatelessWidget {
+  final String? message;
+
+  const LoadingIndicator({
+    super.key,
+    this.message,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Center(
+      child: Column(
+        mainAxisAlignment: MainAxisAlignment.center,
+        children: [
+          const CircularProgressIndicator(),
+          if (message != null) ...[
+            const SizedBox(height: 16),
+            Text(
+              message!,
+              style: Theme.of(context).textTheme.bodyMedium,
+            ),
+          ],
+        ],
+      ),
+    );
+  }
+}
diff --git a/lifetimer/lib/data/models/activity_model.dart b/lifetimer/lib/data/models/activity_model.dart
new file mode 100644
index 0000000..76a90bf
--- /dev/null
+++ b/lifetimer/lib/data/models/activity_model.dart
@@ -0,0 +1,56 @@
+import 'package:equatable/equatable.dart';
+
+class Activity extends Equatable {
+  final String id;
+  final String userId;
+  final String type;
+  final Map<String, dynamic>? payload;
+  final DateTime createdAt;
+
+  const Activity({
+    required this.id,
+    required this.userId,
+    required this.type,
+    this.payload,
+    required this.createdAt,
+  });
+
+  Activity copyWith({
+    String? id,
+    String? userId,
+    String? type,
+    Map<String, dynamic>? payload,
+    DateTime? createdAt,
+  }) {
+    return Activity(
+      id: id ?? this.id,
+      userId: userId ?? this.userId,
+      type: type ?? this.type,
+      payload: payload ?? this.payload,
+      createdAt: createdAt ?? this.createdAt,
+    );
+  }
+
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'user_id': userId,
+      'type': type,
+      'payload': payload,
+      'created_at': createdAt.toIso8601String(),
+    };
+  }
+
+  factory Activity.fromJson(Map<String, dynamic> json) {
+    return Activity(
+      id: json['id'] as String,
+      userId: json['user_id'] as String,
+      type: json['type'] as String,
+      payload: json['payload'] as Map<String, dynamic>?,
+      createdAt: DateTime.parse(json['created_at'] as String),
+    );
+  }
+
+  @override
+  List<Object?> get props => [id, userId, type, payload, createdAt];
+}
diff --git a/lifetimer/lib/data/models/goal_model.dart b/lifetimer/lib/data/models/goal_model.dart
index f2556eb..fd6f977 100644
--- a/lifetimer/lib/data/models/goal_model.dart
+++ b/lifetimer/lib/data/models/goal_model.dart
@@ -78,4 +78,38 @@ class Goal extends Equatable {
         createdAt,
         updatedAt,
       ];
+
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'owner_id': ownerId,
+      'title': title,
+      'description': description,
+      'progress': progress,
+      'location_lat': locationLat,
+      'location_lng': locationLng,
+      'location_name': locationName,
+      'image_url': imageUrl,
+      'completed': completed,
+      'created_at': createdAt.toIso8601String(),
+      'updated_at': updatedAt.toIso8601String(),
+    };
+  }
+
+  factory Goal.fromJson(Map<String, dynamic> json) {
+    return Goal(
+      id: json['id'] as String,
+      ownerId: json['owner_id'] as String,
+      title: json['title'] as String,
+      description: json['description'] as String?,
+      progress: json['progress'] as int? ?? 0,
+      locationLat: json['location_lat'] as double?,
+      locationLng: json['location_lng'] as double?,
+      locationName: json['location_name'] as String?,
+      imageUrl: json['image_url'] as String?,
+      completed: json['completed'] as bool? ?? false,
+      createdAt: DateTime.parse(json['created_at'] as String),
+      updatedAt: DateTime.parse(json['updated_at'] as String),
+    );
+  }
 }
diff --git a/lifetimer/lib/data/models/goal_step_model.dart b/lifetimer/lib/data/models/goal_step_model.dart
new file mode 100644
index 0000000..7be4b71
--- /dev/null
+++ b/lifetimer/lib/data/models/goal_step_model.dart
@@ -0,0 +1,62 @@
+import 'package:equatable/equatable.dart';
+
+class GoalStep extends Equatable {
+  final String id;
+  final String goalId;
+  final String title;
+  final bool isDone;
+  final int orderIndex;
+  final DateTime createdAt;
+
+  const GoalStep({
+    required this.id,
+    required this.goalId,
+    required this.title,
+    required this.isDone,
+    required this.orderIndex,
+    required this.createdAt,
+  });
+
+  GoalStep copyWith({
+    String? id,
+    String? goalId,
+    String? title,
+    bool? isDone,
+    int? orderIndex,
+    DateTime? createdAt,
+  }) {
+    return GoalStep(
+      id: id ?? this.id,
+      goalId: goalId ?? this.goalId,
+      title: title ?? this.title,
+      isDone: isDone ?? this.isDone,
+      orderIndex: orderIndex ?? this.orderIndex,
+      createdAt: createdAt ?? this.createdAt,
+    );
+  }
+
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'goal_id': goalId,
+      'title': title,
+      'is_done': isDone,
+      'order_index': orderIndex,
+      'created_at': createdAt.toIso8601String(),
+    };
+  }
+
+  factory GoalStep.fromJson(Map<String, dynamic> json) {
+    return GoalStep(
+      id: json['id'] as String,
+      goalId: json['goal_id'] as String,
+      title: json['title'] as String,
+      isDone: json['is_done'] as bool? ?? false,
+      orderIndex: json['order_index'] as int? ?? 0,
+      createdAt: DateTime.parse(json['created_at'] as String),
+    );
+  }
+
+  @override
+  List<Object?> get props => [id, goalId, title, isDone, orderIndex, createdAt];
+}
diff --git a/lifetimer/lib/data/models/user_model.dart b/lifetimer/lib/data/models/user_model.dart
index a0fe255..d2a5f2d 100644
--- a/lifetimer/lib/data/models/user_model.dart
+++ b/lifetimer/lib/data/models/user_model.dart
@@ -76,4 +76,38 @@ class User extends Equatable {
         createdAt,
         updatedAt,
       ];
+
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'username': username,
+      'email': email,
+      'avatar_url': avatarUrl,
+      'bio': bio,
+      'is_public_profile': isPublicProfile,
+      'countdown_start_date': countdownStartDate?.toIso8601String(),
+      'countdown_end_date': countdownEndDate?.toIso8601String(),
+      'created_at': createdAt.toIso8601String(),
+      'updated_at': updatedAt.toIso8601String(),
+    };
+  }
+
+  factory User.fromJson(Map<String, dynamic> json) {
+    return User(
+      id: json['id'] as String,
+      username: json['username'] as String,
+      email: json['email'] as String,
+      avatarUrl: json['avatar_url'] as String?,
+      bio: json['bio'] as String?,
+      isPublicProfile: json['is_public_profile'] as bool? ?? false,
+      countdownStartDate: json['countdown_start_date'] != null
+          ? DateTime.parse(json['countdown_start_date'] as String)
+          : null,
+      countdownEndDate: json['countdown_end_date'] != null
+          ? DateTime.parse(json['countdown_end_date'] as String)
+          : null,
+      createdAt: DateTime.parse(json['created_at'] as String),
+      updatedAt: DateTime.parse(json['updated_at'] as String),
+    );
+  }
 }
diff --git a/lifetimer/lib/data/repositories/countdown_repository.dart b/lifetimer/lib/data/repositories/countdown_repository.dart
new file mode 100644
index 0000000..4f38c10
--- /dev/null
+++ b/lifetimer/lib/data/repositories/countdown_repository.dart
@@ -0,0 +1,62 @@
+import 'package:supabase_flutter/supabase_flutter.dart' as supabase;
+import '../models/user_model.dart' as app;
+import '../../core/utils/date_time_utils.dart';
+import '../../core/errors/failure.dart';
+
+class CountdownRepository {
+  final supabase.SupabaseClient _client;
+
+  CountdownRepository(this._client);
+
+  Future<app.User> startCountdown(String userId) async {
+    try {
+      final startDate = DateTime.now();
+      final endDate = DateTimeUtils.calculateEndDate(startDate);
+
+      final response = await _client
+          .from('users')
+          .update({
+            'countdown_start_date': startDate.toIso8601String(),
+            'countdown_end_date': endDate.toIso8601String(),
+            'updated_at': DateTime.now().toIso8601String(),
+          })
+          .eq('id', userId)
+          .select()
+          .single();
+
+      return app.User.fromJson(response);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<app.User> getCountdownInfo(String userId) async {
+    try {
+      final response = await _client
+          .from('users')
+          .select()
+          .eq('id', userId)
+          .single();
+
+      return app.User.fromJson(response);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<bool> hasCountdownStarted(String userId) async {
+    try {
+      final user = await getCountdownInfo(userId);
+      return user.countdownStartDate != null;
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Failure _handleError(dynamic error) {
+    if (error is supabase.PostgrestException) {
+      return ServerFailure(error.message);
+    }
+    return UnknownFailure(error.toString());
+  }
+}
diff --git a/lifetimer/lib/data/repositories/goals_repository.dart b/lifetimer/lib/data/repositories/goals_repository.dart
new file mode 100644
index 0000000..1c3616d
--- /dev/null
+++ b/lifetimer/lib/data/repositories/goals_repository.dart
@@ -0,0 +1,153 @@
+import 'package:supabase_flutter/supabase_flutter.dart' as supabase;
+import '../models/goal_model.dart';
+import '../models/goal_step_model.dart';
+import '../../core/errors/failure.dart';
+
+class GoalsRepository {
+  final supabase.SupabaseClient _client;
+  static const int maxGoals = 20;
+
+  GoalsRepository(this._client);
+
+  Future<List<Goal>> getGoals(String userId) async {
+    try {
+      final response = await _client
+          .from('goals')
+          .select()
+          .eq('owner_id', userId)
+          .order('created_at', ascending: false);
+
+      return (response as List).map((json) => Goal.fromJson(json)).toList();
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<Goal> getGoal(String goalId) async {
+    try {
+      final response = await _client
+          .from('goals')
+          .select()
+          .eq('id', goalId)
+          .single();
+
+      return Goal.fromJson(response);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<Goal> createGoal(Goal goal) async {
+    try {
+      final response = await _client
+          .from('goals')
+          .insert(goal.toJson())
+          .select()
+          .single();
+
+      return Goal.fromJson(response);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<Goal> updateGoal(Goal goal) async {
+    try {
+      final updates = goal.toJson();
+      updates['updated_at'] = DateTime.now().toIso8601String();
+
+      final response = await _client
+          .from('goals')
+          .update(updates)
+          .eq('id', goal.id)
+          .select()
+          .single();
+
+      return Goal.fromJson(response);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<void> deleteGoal(String goalId) async {
+    try {
+      await _client.from('goals').delete().eq('id', goalId);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<List<GoalStep>> getGoalSteps(String goalId) async {
+    try {
+      final response = await _client
+          .from('goal_steps')
+          .select()
+          .eq('goal_id', goalId)
+          .order('order_index', ascending: true);
+
+      return (response as List).map((json) => GoalStep.fromJson(json)).toList();
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<GoalStep> createGoalStep(GoalStep step) async {
+    try {
+      final response = await _client
+          .from('goal_steps')
+          .insert(step.toJson())
+          .select()
+          .single();
+
+      return GoalStep.fromJson(response);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<GoalStep> updateGoalStep(GoalStep step) async {
+    try {
+      final response = await _client
+          .from('goal_steps')
+          .update(step.toJson())
+          .eq('id', step.id)
+          .select()
+          .single();
+
+      return GoalStep.fromJson(response);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<void> deleteGoalStep(String stepId) async {
+    try {
+      await _client.from('goal_steps').delete().eq('id', stepId);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<int> getGoalsCount(String userId) async {
+    try {
+      final response = await _client
+          .from('goals')
+          .select('id')
+          .eq('owner_id', userId);
+
+      return (response as List).length;
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Failure _handleError(dynamic error) {
+    if (error is supabase.PostgrestException) {
+      if (error.code == '23505') {
+        return const ValidationFailure('A goal with this title already exists');
+      }
+      return ServerFailure(error.message);
+    }
+    return UnknownFailure(error.toString());
+  }
+}
diff --git a/lifetimer/lib/data/repositories/notifications_repository.dart b/lifetimer/lib/data/repositories/notifications_repository.dart
new file mode 100644
index 0000000..1fcf0d1
--- /dev/null
+++ b/lifetimer/lib/data/repositories/notifications_repository.dart
@@ -0,0 +1,156 @@
+import 'package:flutter_local_notifications/flutter_local_notifications.dart';
+import 'package:timezone/timezone.dart' as tz;
+import 'package:timezone/data/latest.dart' as tz_data;
+
+class NotificationsRepository {
+  final FlutterLocalNotificationsPlugin _notificationsPlugin;
+
+  NotificationsRepository() : _notificationsPlugin = FlutterLocalNotificationsPlugin() {
+    _initialize();
+  }
+
+  Future<void> _initialize() async {
+    tz_data.initializeTimeZones();
+
+    const androidSettings = AndroidInitializationSettings('@mipmap/ic_launcher');
+    const iosSettings = DarwinInitializationSettings();
+
+    const initSettings = InitializationSettings(
+      android: androidSettings,
+      iOS: iosSettings,
+    );
+
+    await _notificationsPlugin.initialize(initSettings);
+  }
+
+  Future<void> showNotification({
+    required int id,
+    required String title,
+    required String body,
+    String? payload,
+  }) async {
+    const androidDetails = AndroidNotificationDetails(
+      'lifetimer_channel',
+      'LifeTimer Notifications',
+      channelDescription: 'Notifications for LifeTimer app',
+      importance: Importance.high,
+      priority: Priority.high,
+    );
+
+    const iosDetails = DarwinNotificationDetails();
+
+    const notificationDetails = NotificationDetails(
+      android: androidDetails,
+      iOS: iosDetails,
+    );
+
+    await _notificationsPlugin.show(
+      id,
+      title,
+      body,
+      notificationDetails,
+      payload: payload,
+    );
+  }
+
+  Future<void> scheduleNotification({
+    required int id,
+    required String title,
+    required String body,
+    required DateTime scheduledDate,
+    String? payload,
+  }) async {
+    const androidDetails = AndroidNotificationDetails(
+      'lifetimer_channel',
+      'LifeTimer Notifications',
+      channelDescription: 'Notifications for LifeTimer app',
+      importance: Importance.high,
+      priority: Priority.high,
+    );
+
+    const iosDetails = DarwinNotificationDetails();
+
+    const notificationDetails = NotificationDetails(
+      android: androidDetails,
+      iOS: iosDetails,
+    );
+
+    await _notificationsPlugin.zonedSchedule(
+      id,
+      title,
+      body,
+      tz.TZDateTime.from(scheduledDate, tz.local),
+      notificationDetails,
+      uiLocalNotificationDateInterpretation:
+          UILocalNotificationDateInterpretation.absoluteTime,
+      payload: payload,
+    );
+  }
+
+  Future<void> scheduleDailyReminder({
+    required int id,
+    required String title,
+    required String body,
+    required int hour,
+    required int minute,
+  }) async {
+    const androidDetails = AndroidNotificationDetails(
+      'lifetimer_daily_channel',
+      'Daily Reminders',
+      channelDescription: 'Daily reminder notifications',
+      importance: Importance.high,
+      priority: Priority.high,
+    );
+
+    const iosDetails = DarwinNotificationDetails();
+
+    const notificationDetails = NotificationDetails(
+      android: androidDetails,
+      iOS: iosDetails,
+    );
+
+    await _notificationsPlugin.zonedSchedule(
+      id,
+      title,
+      body,
+      _nextInstanceOfTime(hour, minute),
+      notificationDetails,
+      uiLocalNotificationDateInterpretation:
+          UILocalNotificationDateInterpretation.absoluteTime,
+      matchDateTimeComponents: DateTimeComponents.time,
+      payload: 'daily_reminder',
+    );
+  }
+
+  Future<void> cancelNotification(int id) async {
+    await _notificationsPlugin.cancel(id);
+  }
+
+  Future<void> cancelAllNotifications() async {
+    await _notificationsPlugin.cancelAll();
+  }
+
+  Future<List<PendingNotificationRequest>> getPendingNotifications() async {
+    return await _notificationsPlugin.pendingNotificationRequests();
+  }
+
+  tz.TZDateTime _nextInstanceOfTime(int hour, int minute) {
+    final now = tz.TZDateTime.now(tz.local);
+    final scheduledDate = tz.TZDateTime(
+      tz.local,
+      now.year,
+      now.month,
+      now.day,
+      hour,
+      minute,
+      0,
+    );
+
+    if (scheduledDate.isBefore(now)) {
+      return scheduledDate.add(const Duration(days: 1));
+    }
+
+    return scheduledDate;
+  }
+
+}
diff --git a/lifetimer/lib/data/repositories/social_repository.dart b/lifetimer/lib/data/repositories/social_repository.dart
new file mode 100644
index 0000000..a355825
--- /dev/null
+++ b/lifetimer/lib/data/repositories/social_repository.dart
@@ -0,0 +1,154 @@
+import 'package:supabase_flutter/supabase_flutter.dart' as supabase;
+import '../models/user_model.dart' as app;
+import '../models/activity_model.dart';
+import '../../core/errors/failure.dart';
+
+class SocialRepository {
+  final supabase.SupabaseClient _client;
+
+  SocialRepository(this._client);
+
+  Future<void> followUser(String userId, String targetUserId) async {
+    try {
+      await _client.from('followers').insert({
+        'user_id': targetUserId,
+        'follower_id': userId,
+        'created_at': DateTime.now().toIso8601String(),
+      });
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<void> unfollowUser(String userId, String targetUserId) async {
+    try {
+      await _client
+          .from('followers')
+          .delete()
+          .eq('user_id', targetUserId)
+          .eq('follower_id', userId);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<bool> isFollowing(String userId, String targetUserId) async {
+    try {
+      final response = await _client
+          .from('followers')
+          .select('id')
+          .eq('user_id', targetUserId)
+          .eq('follower_id', userId)
+          .maybeSingle();
+
+      return response != null;
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<List<app.User>> getFollowers(String userId) async {
+    try {
+      final response = await _client
+          .from('followers')
+          .select('follower_id, users!followers_follower_id_fkey(*)')
+          .eq('user_id', userId);
+
+      return (response as List)
+          .map((json) => app.User.fromJson(json['users']))
+          .toList();
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<List<app.User>> getFollowing(String userId) async {
+    try {
+      final response = await _client
+          .from('followers')
+          .select('user_id, users!followers_user_id_fkey(*)')
+          .eq('follower_id', userId);
+
+      return (response as List)
+          .map((json) => app.User.fromJson(json['users']))
+          .toList();
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<List<Activity>> getActivityFeed(String userId) async {
+    try {
+      final response = await _client
+          .from('activities')
+          .select()
+          .eq('user_id', userId)
+          .order('created_at', ascending: false)
+          .limit(50);
+
+      return (response as List).map((json) => Activity.fromJson(json)).toList();
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<Activity> logActivity({
+    required String userId,
+    required String type,
+    Map<String, dynamic>? payload,
+  }) async {
+    try {
+      final response = await _client
+          .from('activities')
+          .insert({
+            'user_id': userId,
+            'type': type,
+            'payload': payload,
+            'created_at': DateTime.now().toIso8601String(),
+          })
+          .select()
+          .single();
+
+      return Activity.fromJson(response);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<List<app.User>> getLeaderboard({
+    required String sortBy,
+    int limit = 50,
+  }) async {
+    try {
+      String orderBy;
+      switch (sortBy) {
+        case 'goals_completed':
+          orderBy = 'goals_completed_count';
+          break;
+        case 'streak':
+          orderBy = 'streak_days';
+          break;
+        default:
+          orderBy = 'created_at';
+      }
+
+      final response = await _client
+          .from('users')
+          .select()
+          .eq('is_public_profile', true)
+          .order(orderBy, ascending: false)
+          .limit(limit);
+
+      return (response as List).map((json) => app.User.fromJson(json)).toList();
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Failure _handleError(dynamic error) {
+    if (error is supabase.PostgrestException) {
+      return ServerFailure(error.message);
+    }
+    return UnknownFailure(error.toString());
+  }
+}
diff --git a/lifetimer/lib/data/repositories/user_repository.dart b/lifetimer/lib/data/repositories/user_repository.dart
new file mode 100644
index 0000000..049b878
--- /dev/null
+++ b/lifetimer/lib/data/repositories/user_repository.dart
@@ -0,0 +1,83 @@
+import 'package:supabase_flutter/supabase_flutter.dart' as supabase;
+import '../models/user_model.dart' as app;
+import '../../core/errors/failure.dart';
+
+class UserRepository {
+  final supabase.SupabaseClient _client;
+
+  UserRepository(this._client);
+
+  Future<app.User> getProfile(String userId) async {
+    try {
+      final response = await _client
+          .from('users')
+          .select()
+          .eq('id', userId)
+          .single();
+
+      return app.User.fromJson(response);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<app.User> updateProfile({
+    required String userId,
+    String? username,
+    String? avatarUrl,
+    String? bio,
+    bool? isPublicProfile,
+  }) async {
+    try {
+      final updates = <String, dynamic>{};
+      if (username != null) updates['username'] = username;
+      if (avatarUrl != null) updates['avatar_url'] = avatarUrl;
+      if (bio != null) updates['bio'] = bio;
+      if (isPublicProfile != null) updates['is_public_profile'] = isPublicProfile;
+      updates['updated_at'] = DateTime.now().toIso8601String();
+
+      final response = await _client
+          .from('users')
+          .update(updates)
+          .eq('id', userId)
+          .select()
+          .single();
+
+      return app.User.fromJson(response);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<bool> isUsernameAvailable(String username) async {
+    try {
+      final response = await _client
+          .from('users')
+          .select('id')
+          .eq('username', username)
+          .maybeSingle();
+
+      return response == null;
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Future<void> deleteAccount(String userId) async {
+    try {
+      await _client.from('users').delete().eq('id', userId);
+    } catch (e) {
+      throw _handleError(e);
+    }
+  }
+
+  Failure _handleError(dynamic error) {
+    if (error is supabase.PostgrestException) {
+      if (error.code == '23505') {
+        return const ValidationFailure('Username already taken');
+      }
+      return ServerFailure(error.message);
+    }
+    return UnknownFailure(error.toString());
+  }
+}