diff --git a/lib/function/login_controller.dart b/lib/function/login_controller.dart
index 9e95b97..2cbbbe4 100644
--- a/lib/function/login_controller.dart
+++ b/lib/function/login_controller.dart
@@ -16,18 +16,21 @@ class LoginResult {
   final String? name;
   final bool isDeviceMatched;
   final String? errorMessage;
+  final int? grade; // 🎓 공부 타이머 학년별 랭킹에서 본인 학년을 기본값으로 쓰기 위함.
 
   const LoginResult.masterSuccess({required this.studentId, required this.name})
     : outcome = LoginOutcome.masterSuccess,
       role = null,
       isDeviceMatched = true,
-      errorMessage = null;
+      errorMessage = null,
+      grade = null;
 
   const LoginResult.needsPasswordChange({
     required this.studentId,
     required this.name,
     required this.role,
     required this.isDeviceMatched,
+    this.grade,
   }) : outcome = LoginOutcome.needsPasswordChange,
        errorMessage = null;
 
@@ -36,6 +39,7 @@ class LoginResult {
     required this.studentId,
     required this.name,
     required this.isDeviceMatched,
+    this.grade,
   }) : outcome = LoginOutcome.success,
        errorMessage = null;
 
@@ -44,7 +48,8 @@ class LoginResult {
       role = null,
       studentId = null,
       name = null,
-      isDeviceMatched = false;
+      isDeviceMatched = false,
+      grade = null;
 }
 
 class LoginController extends ChangeNotifier {
@@ -101,6 +106,7 @@ class LoginController extends ChangeNotifier {
         String name = '';
         String studentId = '';
         int isFirstLogin = 0;
+        int? grade;
 
         var userObj = resData['user'];
         if (userObj != null) {
@@ -114,6 +120,7 @@ class LoginController extends ChangeNotifier {
               userObj['studentId']?.toString() ??
               userObj['student_id']?.toString() ??
               id;
+          grade = int.tryParse(userObj['grade']?.toString() ?? '');
 
           var rawFirst = userObj['isFirstLogin'] ?? userObj['is_first_login'];
           isFirstLogin = (rawFirst is bool)
@@ -126,6 +133,7 @@ class LoginController extends ChangeNotifier {
               resData['studentName']?.toString() ??
               '';
           studentId = resData['studentId']?.toString() ?? id;
+          grade = int.tryParse(resData['grade']?.toString() ?? '');
 
           var rawFirst = resData['isFirstLogin'] ?? resData['is_first_login'];
           isFirstLogin = (rawFirst is bool)
@@ -153,6 +161,7 @@ class LoginController extends ChangeNotifier {
             name: name,
             role: role,
             isDeviceMatched: isDeviceMatched,
+            grade: grade,
           );
         }
 
@@ -161,6 +170,7 @@ class LoginController extends ChangeNotifier {
           studentId: studentId,
           name: name,
           isDeviceMatched: isDeviceMatched,
+          grade: grade,
         );
       } else {
         String errorMsg = '로그인에 실패했습니다.';
diff --git a/lib/function/session_store.dart b/lib/function/session_store.dart
index 42b61a0..a3a3348 100644
--- a/lib/function/session_store.dart
+++ b/lib/function/session_store.dart
@@ -9,12 +9,14 @@ class SavedSession {
   final String userName;
   final String role;
   final bool isDeviceMatched;
+  final int? grade; // 🎓 공부 타이머 학년별 랭킹에서 본인 학년을 기본값으로 쓰기 위함.
 
   const SavedSession({
     required this.userId,
     required this.userName,
     required this.role,
     required this.isDeviceMatched,
+    this.grade,
   });
 
   Map<String, dynamic> toJson() => {
@@ -22,6 +24,7 @@ class SavedSession {
     'userName': userName,
     'role': role,
     'isDeviceMatched': isDeviceMatched,
+    'grade': grade,
   };
 
   factory SavedSession.fromJson(Map<String, dynamic> json) => SavedSession(
@@ -29,6 +32,7 @@ class SavedSession {
     userName: json['userName'] as String,
     role: json['role'] as String,
     isDeviceMatched: json['isDeviceMatched'] as bool? ?? true,
+    grade: json['grade'] as int?,
   );
 }
 
diff --git a/lib/function/study_ranking_controller.dart b/lib/function/study_ranking_controller.dart
new file mode 100644
index 0000000..13c5f25
--- /dev/null
+++ b/lib/function/study_ranking_controller.dart
@@ -0,0 +1,46 @@
+// 🏆 학년별 공부시간 랭킹 화면의 기능(서버 통신/상태) 담당 컨트롤러.
+import 'dart:convert';
+import 'package:flutter/foundation.dart';
+import 'package:http/http.dart' as http;
+import '../config.dart';
+
+class StudyRankingController extends ChangeNotifier {
+  final int grade;
+
+  StudyRankingController({required this.grade});
+
+  bool _isLoading = true;
+  String _period = 'today'; // today / week / total
+  List<dynamic> _ranking = [];
+
+  bool get isLoading => _isLoading;
+  String get period => _period;
+  List<dynamic> get ranking => _ranking;
+
+  Future<void> init() => fetchRanking();
+
+  Future<void> setPeriod(String period) async {
+    if (_period == period) return;
+    _period = period;
+    await fetchRanking();
+  }
+
+  Future<void> fetchRanking() async {
+    _isLoading = true;
+    notifyListeners();
+    try {
+      final response = await http.get(
+        Uri.parse('$baseUrl/api/study/ranking?grade=$grade&period=$_period'),
+      );
+      if (response.statusCode == 200) {
+        final data = jsonDecode(utf8.decode(response.bodyBytes));
+        _ranking = data['ranking'] ?? [];
+      }
+    } catch (_) {
+      // 조용히 무시 - 마지막으로 받아온 랭킹을 유지한다.
+    } finally {
+      _isLoading = false;
+      notifyListeners();
+    }
+  }
+}
diff --git a/lib/function/study_timer_controller.dart b/lib/function/study_timer_controller.dart
new file mode 100644
index 0000000..ecd0fa4
--- /dev/null
+++ b/lib/function/study_timer_controller.dart
@@ -0,0 +1,146 @@
+// ⏱️ 우리 학교 전용 "열품타" 공부 타이머 화면의 기능(서버 통신/상태) 담당 컨트롤러.
+import 'dart:async';
+import 'dart:convert';
+import 'package:flutter/foundation.dart';
+import 'package:http/http.dart' as http;
+import '../config.dart';
+
+class StudyTimerController extends ChangeNotifier {
+  final String studentId;
+  final String studentName;
+
+  StudyTimerController({required this.studentId, required this.studentName});
+
+  bool _isLoading = true;
+  bool _isBusy = false; // 시작/종료 버튼 눌러서 서버 응답 기다리는 중
+  bool _isRunning = false;
+  DateTime? _startTime;
+  int _todaySeconds = 0;
+  int _weekSeconds = 0;
+  int _totalSeconds = 0;
+  Timer? _ticker;
+  bool _disposed = false;
+
+  bool get isLoading => _isLoading;
+  bool get isBusy => _isBusy;
+  bool get isRunning => _isRunning;
+
+  /// 지금 진행 중인 세션까지 포함한 "오늘" 누적 초. 실시간으로 똑딱거린다.
+  int get todaySecondsLive =>
+      _todaySeconds + (_isRunning ? _liveElapsedSeconds : 0);
+  int get weekSecondsLive =>
+      _weekSeconds + (_isRunning ? _liveElapsedSeconds : 0);
+  int get totalSecondsLive =>
+      _totalSeconds + (_isRunning ? _liveElapsedSeconds : 0);
+
+  /// 지금 세션 하나만의 경과 시간(타이머 화면 큰 숫자용).
+  int get _liveElapsedSeconds {
+    if (_startTime == null) return 0;
+    final diff = DateTime.now().difference(_startTime!).inSeconds;
+    return diff > 0 ? diff : 0;
+  }
+
+  int get liveElapsedSeconds => _liveElapsedSeconds;
+
+  void _safeNotify() {
+    if (!_disposed) notifyListeners();
+  }
+
+  Future<void> init() async {
+    await _fetchStatus();
+  }
+
+  @override
+  void dispose() {
+    _disposed = true;
+    _ticker?.cancel();
+    super.dispose();
+  }
+
+  Future<void> _fetchStatus() async {
+    try {
+      final response = await http.get(
+        Uri.parse('$baseUrl/api/study/status?studentId=$studentId'),
+      );
+      if (response.statusCode == 200) {
+        final data = jsonDecode(utf8.decode(response.bodyBytes));
+        _isRunning = data['isRunning'] == true;
+        _startTime = data['startTime'] != null
+            ? DateTime.tryParse(data['startTime'])
+            : null;
+        _todaySeconds = (data['todaySeconds'] as num?)?.toInt() ?? 0;
+        _weekSeconds = (data['weekSeconds'] as num?)?.toInt() ?? 0;
+        _totalSeconds = (data['totalSeconds'] as num?)?.toInt() ?? 0;
+        _restartTickerIfNeeded();
+      }
+    } catch (_) {
+      // 조용히 무시 - 마지막으로 알던 상태를 유지한다.
+    } finally {
+      _isLoading = false;
+      _safeNotify();
+    }
+  }
+
+  void _restartTickerIfNeeded() {
+    _ticker?.cancel();
+    if (_isRunning) {
+      _ticker = Timer.periodic(
+        const Duration(seconds: 1),
+        (_) => _safeNotify(),
+      );
+    }
+  }
+
+  Future<(bool success, String message)> start() async {
+    _isBusy = true;
+    _safeNotify();
+    try {
+      final response = await http.post(
+        Uri.parse('$baseUrl/api/study/start'),
+        headers: {"Content-Type": "application/json"},
+        body: jsonEncode({"studentId": studentId, "studentName": studentName}),
+      );
+      final result = jsonDecode(utf8.decode(response.bodyBytes));
+      if (response.statusCode == 200 && result['status'] == 'success') {
+        _isRunning = true;
+        _startTime = DateTime.tryParse(result['startTime']);
+        _restartTickerIfNeeded();
+        return (true, '공부를 시작했습니다.');
+      }
+      return (false, '${result['message'] ?? '공부 시작 실패'}');
+    } catch (e) {
+      return (false, '네트워크 에러: $e');
+    } finally {
+      _isBusy = false;
+      _safeNotify();
+    }
+  }
+
+  Future<(bool success, String message)> stop() async {
+    _isBusy = true;
+    _safeNotify();
+    try {
+      final response = await http.post(
+        Uri.parse('$baseUrl/api/study/stop'),
+        headers: {"Content-Type": "application/json"},
+        body: jsonEncode({"studentId": studentId}),
+      );
+      final result = jsonDecode(utf8.decode(response.bodyBytes));
+      if (response.statusCode == 200 && result['status'] == 'success') {
+        _isRunning = false;
+        _startTime = null;
+        _ticker?.cancel();
+        await _fetchStatus(); // 오늘/이번주/전체 합계를 서버 값으로 다시 맞춘다.
+        final minutes =
+            ((result['durationSeconds'] as num?)?.toInt() ?? 0) ~/ 60;
+        return (true, '이번 공부 시간: $minutes분 기록 완료!');
+      }
+      return (false, '${result['message'] ?? '공부 종료 실패'}');
+    } catch (e) {
+      return (false, '네트워크 에러: $e');
+    } finally {
+      _isBusy = false;
+      _safeNotify();
+    }
+  }
+}
diff --git a/lib/main_client_app.dart b/lib/main_client_app.dart
index 8aa21e0..5c43740 100644
--- a/lib/main_client_app.dart
+++ b/lib/main_client_app.dart
@@ -107,6 +107,7 @@ class _StartupGateState extends State<_StartupGate> {
         userName: session.userName,
         role: session.role,
         isDeviceMatched: session.isDeviceMatched,
+        grade: session.grade,
       );
     }
     return const LoginScreen();
diff --git a/lib/ui/login_screen.dart b/lib/ui/login_screen.dart
index 9395d1d..259626a 100644
--- a/lib/ui/login_screen.dart
+++ b/lib/ui/login_screen.dart
@@ -78,6 +78,7 @@ class _LoginScreenState extends State<LoginScreen> {
           result.name!,
           result.role!,
           result.isDeviceMatched,
+          result.grade,
         );
         break;
       case LoginOutcome.success:
@@ -87,6 +88,7 @@ class _LoginScreenState extends State<LoginScreen> {
           result.studentId!,
           result.name!,
           result.isDeviceMatched,
+          result.grade,
         );
         break;
     }
@@ -98,6 +100,7 @@ class _LoginScreenState extends State<LoginScreen> {
     String name,
     String role,
     bool isDeviceMatched,
+    int? grade,
   ) {
     final TextEditingController newPwController = TextEditingController();
 
@@ -168,6 +171,7 @@ class _LoginScreenState extends State<LoginScreen> {
                               studentId,
                               name,
                               isDeviceMatched,
+                              grade,
                             );
                           } else {
                             AppNotice.show(context, message);
@@ -189,6 +193,7 @@ class _LoginScreenState extends State<LoginScreen> {
     String studentId,
     String name,
     bool isDeviceMatched,
+    int? grade,
   ) async {
     if (_keepLoggedIn) {
       await SessionStore.save(
@@ -197,6 +202,7 @@ class _LoginScreenState extends State<LoginScreen> {
           userName: name,
           role: role,
           isDeviceMatched: isDeviceMatched,
+          grade: grade,
         ),
       );
     } else {
@@ -211,6 +217,7 @@ class _LoginScreenState extends State<LoginScreen> {
           userName: name,
           role: role,
           isDeviceMatched: isDeviceMatched,
+          grade: grade,
         ),
       ),
     );
diff --git a/lib/ui/main_dashboard.dart b/lib/ui/main_dashboard.dart
index 31037f2..2673e2f 100644
--- a/lib/ui/main_dashboard.dart
+++ b/lib/ui/main_dashboard.dart
@@ -19,6 +19,7 @@ import 'launchpad_transition.dart';
 import 'login_screen.dart';
 import 'nfc_poccket_checkin_screen.dart';
 import 'nfc_tag_writer_screen.dart';
+import 'study_timer_screen.dart';
 import 'teacher_attendance_page.dart';
 import 'teacher_student_management_page.dart';
 
@@ -27,6 +28,7 @@ class MainDashboard extends StatefulWidget {
   final String? userName;
   final String role; // 'student' | 'teacher' | 'admin'
   final bool isDeviceMatched;
+  final int? grade; // 🎓 공부 타이머 학년별 랭킹에서 본인 학년을 기본값으로 쓰기 위함.
 
   const MainDashboard({
     super.key,
@@ -34,6 +36,7 @@ class MainDashboard extends StatefulWidget {
     this.userName,
     required this.role,
     this.isDeviceMatched = true,
+    this.grade,
   });
 
   @override
@@ -312,6 +315,23 @@ class _MainDashboardState extends State<MainDashboard> {
           ),
         ),
       ));
+      tiles.add((
+        id: 'study_timer',
+        child: _buildModernCard(
+          icon: Icons.timer_rounded,
+          title: '공부 타이머',
+          subtitle: '열품타 | 학년별 공부 랭킹',
+          color: AppPalette.ink,
+          onTap: () => pushLaunchpad(
+            context,
+            (context) => StudyTimerScreen(
+              studentId: _displayId,
+              studentName: _displayName,
+              grade: widget.grade,
+            ),
+          ),
+        ),
+      ));
     }
 
     if (_isTeacherOrAbove) {
diff --git a/lib/ui/study_ranking_screen.dart b/lib/ui/study_ranking_screen.dart
new file mode 100644
index 0000000..c8bc434
--- /dev/null
+++ b/lib/ui/study_ranking_screen.dart
@@ -0,0 +1,193 @@
+// 🏆 학년별 공부시간 랭킹 화면 (UI 전용).
+// 서버 통신/상태는 lib/function/study_ranking_controller.dart가 담당한다.
+import 'package:flutter/material.dart';
+import '../function/study_ranking_controller.dart';
+import '../theme/app_palette.dart';
+import 'title_pill.dart';
+
+class StudyRankingScreen extends StatefulWidget {
+  final int grade;
+  final String myStudentId;
+
+  const StudyRankingScreen({
+    super.key,
+    required this.grade,
+    required this.myStudentId,
+  });
+
+  @override
+  State<StudyRankingScreen> createState() => _StudyRankingScreenState();
+}
+
+class _StudyRankingScreenState extends State<StudyRankingScreen> {
+  late final StudyRankingController _controller;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller = StudyRankingController(grade: widget.grade);
+    _controller.init();
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
+  String _formatHM(int totalSeconds) {
+    final h = totalSeconds ~/ 3600;
+    final m = (totalSeconds % 3600) ~/ 60;
+    if (h > 0) return '$h시간 $m분';
+    return '$m분';
+  }
+
+  Color? _rankColor(int rank) {
+    switch (rank) {
+      case 1:
+        return const Color(0xFFC9A227); // 금
+      case 2:
+        return const Color(0xFF9AA0A6); // 은
+      case 3:
+        return const Color(0xFFB07A4B); // 동
+      default:
+        return null;
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return ListenableBuilder(
+      listenable: _controller,
+      builder: (context, _) {
+        final ranking = _controller.ranking;
+        return Scaffold(
+          backgroundColor: AppPalette.mist,
+          appBar: AppBar(
+            backgroundColor: Colors.transparent,
+            foregroundColor: AppPalette.ink,
+            elevation: 0,
+            centerTitle: true,
+            title: TitlePill('${widget.grade}학년 공부 랭킹'),
+          ),
+          body: Column(
+            children: [
+              Padding(
+                padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
+                child: Row(
+                  children: [
+                    _periodChip('today', '오늘'),
+                    const SizedBox(width: 8),
+                    _periodChip('week', '이번주'),
+                    const SizedBox(width: 8),
+                    _periodChip('total', '전체'),
+                  ],
+                ),
+              ),
+              Expanded(
+                child: _controller.isLoading
+                    ? const Center(child: CircularProgressIndicator())
+                    : ranking.isEmpty
+                    ? const Center(
+                        child: Text(
+                          '아직 기록이 없어요.\n공부 타이머를 눌러 1등에 도전해보세요.',
+                          textAlign: TextAlign.center,
+                          style: TextStyle(color: Colors.grey),
+                        ),
+                      )
+                    : ListView.builder(
+                        padding: const EdgeInsets.symmetric(
+                          horizontal: 16,
+                          vertical: 8,
+                        ),
+                        itemCount: ranking.length,
+                        itemBuilder: (context, index) {
+                          final r = ranking[index];
+                          final bool isMe =
+                              r['studentId'] == widget.myStudentId;
+                          final int rank = (r['rank'] as num).toInt();
+                          final medalColor = _rankColor(rank);
+
+                          return Container(
+                            margin: const EdgeInsets.only(bottom: 8),
+                            padding: const EdgeInsets.symmetric(
+                              horizontal: 16,
+                              vertical: 12,
+                            ),
+                            decoration: BoxDecoration(
+                              color: isMe ? AppPalette.ink : AppPalette.paper,
+                              borderRadius: BorderRadius.circular(14),
+                              border: Border.all(
+                                color: isMe ? AppPalette.ink : AppPalette.sage,
+                              ),
+                            ),
+                            child: Row(
+                              children: [
+                                SizedBox(
+                                  width: 32,
+                                  child: medalColor != null
+                                      ? Icon(
+                                          Icons.emoji_events_rounded,
+                                          color: medalColor,
+                                          size: 22,
+                                        )
+                                      : Text(
+                                          '$rank',
+                                          style: TextStyle(
+                                            fontWeight: FontWeight.bold,
+                                            color: isMe
+                                                ? Colors.white
+                                                : AppPalette.ink,
+                                          ),
+                                        ),
+                                ),
+                                const SizedBox(width: 8),
+                                Expanded(
+                                  child: Text(
+                                    r['name'] ?? '',
+                                    maxLines: 1,
+                                    overflow: TextOverflow.ellipsis,
+                                    style: TextStyle(
+                                      fontWeight: FontWeight.bold,
+                                      color: isMe
+                                          ? Colors.white
+                                          : AppPalette.ink,
+                                    ),
+                                  ),
+                                ),
+                                Text(
+                                  _formatHM((r['totalSeconds'] as num).toInt()),
+                                  style: TextStyle(
+                                    fontWeight: FontWeight.bold,
+                                    color: isMe ? Colors.white : AppPalette.ink,
+                                  ),
+                                ),
+                              ],
+                            ),
+                          );
+                        },
+                      ),
+              ),
+            ],
+          ),
+        );
+      },
+    );
+  }
+
+  Widget _periodChip(String value, String label) {
+    final bool selected = _controller.period == value;
+    return Expanded(
+      child: ChoiceChip(
+        label: Center(child: Text(label)),
+        selected: selected,
+        onSelected: (_) => _controller.setPeriod(value),
+        selectedColor: AppPalette.ink,
+        labelStyle: TextStyle(
+          color: selected ? Colors.white : AppPalette.ink,
+          fontWeight: FontWeight.bold,
+        ),
+      ),
+    );
+  }
+}
diff --git a/lib/ui/study_timer_screen.dart b/lib/ui/study_timer_screen.dart
new file mode 100644
index 0000000..3c9f48a
--- /dev/null
+++ b/lib/ui/study_timer_screen.dart
@@ -0,0 +1,233 @@
+// ⏱️ 우리 학교 전용 "열품타" 공부 타이머 화면 (UI 전용).
+// 서버 통신/상태는 lib/function/study_timer_controller.dart가 담당한다.
+import 'package:flutter/material.dart';
+import '../function/study_timer_controller.dart';
+import '../theme/app_palette.dart';
+import 'app_notice.dart';
+import 'launchpad_transition.dart';
+import 'study_ranking_screen.dart';
+import 'title_pill.dart';
+
+class StudyTimerScreen extends StatefulWidget {
+  final String studentId;
+  final String studentName;
+  final int? grade;
+
+  const StudyTimerScreen({
+    super.key,
+    required this.studentId,
+    required this.studentName,
+    this.grade,
+  });
+
+  @override
+  State<StudyTimerScreen> createState() => _StudyTimerScreenState();
+}
+
+class _StudyTimerScreenState extends State<StudyTimerScreen> {
+  late final StudyTimerController _controller;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller = StudyTimerController(
+      studentId: widget.studentId,
+      studentName: widget.studentName,
+    );
+    _controller.init();
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
+  String _formatHMS(int totalSeconds) {
+    final h = totalSeconds ~/ 3600;
+    final m = (totalSeconds % 3600) ~/ 60;
+    final s = totalSeconds % 60;
+    final hh = h.toString().padLeft(2, '0');
+    final mm = m.toString().padLeft(2, '0');
+    final ss = s.toString().padLeft(2, '0');
+    return '$hh:$mm:$ss';
+  }
+
+  String _formatHM(int totalSeconds) {
+    final h = totalSeconds ~/ 3600;
+    final m = (totalSeconds % 3600) ~/ 60;
+    if (h > 0) return '$h시간 $m분';
+    return '$m분';
+  }
+
+  Future<void> _toggle() async {
+    final (success, message) = _controller.isRunning
+        ? await _controller.stop()
+        : await _controller.start();
+    if (!mounted) return;
+    AppNotice.show(
+      context,
+      message,
+      icon: success ? Icons.check_circle_rounded : Icons.error_outline_rounded,
+    );
+  }
+
+  void _openRanking() {
+    if (widget.grade == null) {
+      AppNotice.show(context, '학년 정보가 없어 랭킹을 볼 수 없어요.');
+      return;
+    }
+    pushLaunchpad(
+      context,
+      (context) => StudyRankingScreen(
+        grade: widget.grade!,
+        myStudentId: widget.studentId,
+      ),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return ListenableBuilder(
+      listenable: _controller,
+      builder: (context, _) {
+        final bool isRunning = _controller.isRunning;
+        return Scaffold(
+          backgroundColor: AppPalette.mist,
+          appBar: AppBar(
+            backgroundColor: Colors.transparent,
+            foregroundColor: AppPalette.ink,
+            elevation: 0,
+            centerTitle: true,
+            title: const TitlePill('공부 타이머'),
+            actions: [
+              IconButton(
+                icon: const Icon(Icons.leaderboard_rounded),
+                tooltip: '학년 랭킹',
+                onPressed: _openRanking,
+              ),
+            ],
+          ),
+          body: _controller.isLoading
+              ? const Center(child: CircularProgressIndicator())
+              : Center(
+                  child: SingleChildScrollView(
+                    padding: const EdgeInsets.all(24),
+                    child: Column(
+                      mainAxisSize: MainAxisSize.min,
+                      children: [
+                        Text(
+                          isRunning ? '지금 공부 중이에요' : '공부를 시작해볼까요?',
+                          style: const TextStyle(
+                            fontSize: 15,
+                            color: Colors.grey,
+                          ),
+                        ),
+                        const SizedBox(height: 12),
+                        Text(
+                          _formatHMS(_controller.liveElapsedSeconds),
+                          style: const TextStyle(
+                            fontSize: 52,
+                            fontWeight: FontWeight.bold,
+                            color: AppPalette.ink,
+                          ),
+                        ),
+                        const SizedBox(height: 36),
+                        GestureDetector(
+                          onTap: _controller.isBusy ? null : _toggle,
+                          child: Container(
+                            width: 140,
+                            height: 140,
+                            decoration: BoxDecoration(
+                              shape: BoxShape.circle,
+                              color: isRunning
+                                  ? Colors.red[400]
+                                  : AppPalette.ink,
+                              boxShadow: [
+                                BoxShadow(
+                                  color:
+                                      (isRunning ? Colors.red : AppPalette.ink)
+                                          .withValues(alpha: 0.3),
+                                  blurRadius: 20,
+                                  offset: const Offset(0, 8),
+                                ),
+                              ],
+                            ),
+                            child: Center(
+                              child: _controller.isBusy
+                                  ? const CircularProgressIndicator(
+                                      color: Colors.white,
+                                    )
+                                  : Column(
+                                      mainAxisSize: MainAxisSize.min,
+                                      children: [
+                                        Icon(
+                                          isRunning
+                                              ? Icons.stop_rounded
+                                              : Icons.play_arrow_rounded,
+                                          color: Colors.white,
+                                          size: 36,
+                                        ),
+                                        Text(
+                                          isRunning ? '공부 종료' : '공부 시작',
+                                          style: const TextStyle(
+                                            color: Colors.white,
+                                            fontWeight: FontWeight.bold,
+                                          ),
+                                        ),
+                                      ],
+                                    ),
+                            ),
+                          ),
+                        ),
+                        const SizedBox(height: 40),
+                        Row(
+                          mainAxisAlignment: MainAxisAlignment.center,
+                          children: [
+                            _statBox(
+                              '오늘',
+                              _formatHM(_controller.todaySecondsLive),
+                            ),
+                            const SizedBox(width: 12),
+                            _statBox(
+                              '이번주',
+                              _formatHM(_controller.weekSecondsLive),
+                            ),
+                            const SizedBox(width: 12),
+                            _statBox(
+                              '전체',
+                              _formatHM(_controller.totalSecondsLive),
+                            ),
+                          ],
+                        ),
+                      ],
+                    ),
+                  ),
+                ),
+        );
+      },
+    );
+  }
+
+  Widget _statBox(String label, String value) {
+    return Container(
+      width: 100,
+      padding: const EdgeInsets.symmetric(vertical: 14),
+      decoration: BoxDecoration(
+        color: AppPalette.paper,
+        borderRadius: BorderRadius.circular(16),
+        border: Border.all(color: AppPalette.sage),
+      ),
+      child: Column(
+        children: [
+          Text(label, style: TextStyle(color: Colors.grey[600], fontSize: 12)),
+          const SizedBox(height: 4),
+          Text(
+            value,
+            style: const TextStyle(fontWeight: FontWeight.bold, fontSize: 15),
+          ),
+        ],
+      ),
+    );
+  }
+}