...

lib/models/game_level.dart

@@ -0,0 +1,94 @@
+// lib/models/game_level.dart
+
+// 11단계 레벨의 모든 속성을 정의하는 클래스
+class GameLevel {
+  final int levelIndex; // 1-11
+  final String name; // "입문 (4x4)"
+  final int blockSize; // 2, 3, 4
+  final int generatorLevel; // 서버에 요청할 생성기 난이도 (1~5)
+  final String contextId; // 랭킹 ID "SUDOKU_4x4_L1"
+  
+  // 🔽 [신규] 테마 정책
+  final bool isSequentialNumbers; // L1, L4, L9 (숫자 고정)
+  final bool isSequentialLetters; // L2, L5, L10 (문자 고정)
+  // (둘 다 false이면 HomeScreen에서 선택한 랜덤 테마 사용)
+
+  const GameLevel({
+    required this.levelIndex,
+    required this.name,
+    required this.blockSize,
+    required this.generatorLevel,
+    required this.contextId,
+    this.isSequentialNumbers = false,
+    this.isSequentialLetters = false,
+  });
+}
+
+// 앱 전역에서 사용할 11단계 레벨 정의
+class AppLevels {
+  static final List<GameLevel> allLevels = [
+    // --- 2x2 (blockSize = 2) ---
+    const GameLevel(
+      levelIndex: 1, name: "입문 (4x4)", blockSize: 2, generatorLevel: 1, 
+      contextId: "SUDOKU_4x4_L1", isSequentialNumbers: true // 👈 순차 숫자
+    ),
+    const GameLevel(
+      levelIndex: 2, name: "초급 (4x4)", blockSize: 2, generatorLevel: 3, 
+      contextId: "SUDOKU_4x4_L3", isSequentialLetters: true // 👈 순차 문자
+    ),
+    const GameLevel(
+      levelIndex: 3, name: "숙련 (4x4)", blockSize: 2, generatorLevel: 5, 
+      contextId: "SUDOKU_4x4_L5" // 👈 랜덤 테마
+    ),
+    
+    // --- 3x3 (blockSize = 3) ---
+    const GameLevel(
+      levelIndex: 4, name: "쉬움 (9x9)", blockSize: 3, generatorLevel: 1, 
+      contextId: "SUDOKU_9x9_L1", isSequentialNumbers: true // 👈 순차 숫자
+    ),
+    const GameLevel(
+      levelIndex: 5, name: "중급 (9x9)", blockSize: 3, generatorLevel: 2, 
+      contextId: "SUDOKU_9x9_L2", isSequentialLetters: true // 👈 순차 문자
+    ),
+    const GameLevel(
+      levelIndex: 6, name: "상급 (9x9)", blockSize: 3, generatorLevel: 3, 
+      contextId: "SUDOKU_9x9_L3" // 👈 랜덤 테마
+    ),
+    const GameLevel(
+      levelIndex: 7, name: "어려움 (9x9)", blockSize: 3, generatorLevel: 4, 
+      contextId: "SUDOKU_9x9_L4" // 👈 랜덤 테마
+    ),
+    const GameLevel(
+      levelIndex: 8, name: "최상급 (9x9)", blockSize: 3, generatorLevel: 5, 
+      contextId: "SUDOKU_9x9_L5" // 👈 랜덤 테마
+    ),
+
+    // --- 4x4 (blockSize = 4) ---
+    const GameLevel(
+      levelIndex: 9, name: "전문가 (16x16)", blockSize: 4, generatorLevel: 1, 
+      contextId: "SUDOKU_16x16_L1", isSequentialNumbers: true // 👈 순차 숫자
+    ),
+    const GameLevel(
+      levelIndex: 10, name: "마스터 (16x16)", blockSize: 4, generatorLevel: 3, 
+      contextId: "SUDOKU_16x16_L3", isSequentialLetters: true // 👈 순차 문자
+    ),
+    const GameLevel(
+      levelIndex: 11, name: "지옥 (16x16)", blockSize: 4, generatorLevel: 5, 
+      contextId: "SUDOKU_16x16_L5" // 👈 랜덤 테마
+    ),
+  ];
+
+  // 인덱스(1-11)로 레벨 정보 찾기
+  static GameLevel getLevel(int levelIndex) {
+    if (levelIndex < 1) levelIndex = 1;
+    if (levelIndex > allLevels.length) levelIndex = allLevels.length;
+    return allLevels.firstWhere((level) => level.levelIndex == levelIndex,
+        orElse: () => allLevels[0] // 못찾으면 L1 반환
+    );
+  }
+
+  // 랭킹 화면용 맵 (ContextId -> 이름)
+  static Map<String, String> get contextIdToNameMap {
+    return { for (var level in allLevels) level.contextId : level.name };
+  }
+}

lib/models/sudoku_theme.dart

@@ -84,29 +84,34 @@ class AppThemes {
   };
 
   // --- 4. [핵심] 게임 시작 시 호출될 테마 '빌더' 함수 ---
-  static SudokuTheme buildGameTheme(String themeName, int gridSize) {
+  static SudokuTheme buildGameTheme(String themeName, int gridSize, {bool isEasyMode = false}) { // 👈 [수정]
     String effectiveThemeName = themeName;
     
-    // 1. "랜덤"이 선택된 경우
     if (themeName == random) {
-      // "랜덤"을 제외한 실제 테마 이름 리스트에서 무작위로 하나 선택
       final actualThemes = _themePools.keys.toList();
       effectiveThemeName = (actualThemes..shuffle()).first;
     }
 
-    // 2. 해당 테마의 '거대 풀'을 가져옴 (없으면 숫자로 대체)
     final List<String> pool = _themePools[effectiveThemeName] ?? _numberPool;
 
-    // 3. 거대 풀을 섞은 뒤, 게임에 필요한 만큼(gridSize)만 뽑음
     if (pool.length < gridSize) {
       throw Exception("$effectiveThemeName 테마의 상징이 ${pool.length}개뿐입니다. $gridSize개가 필요합니다.");
     }
-    final List<String> selectedSymbols = (pool.toList()..shuffle()).sublist(0, gridSize);
     
-    // 4. 이 게임만을 위한 '일회용' SudokuTheme 객체를 생성하여 반환
+    List<String> selectedSymbols;
+    
+    // 🔽 [수정] 'isEasyMode'가 true이면 섞지 않고 순서대로 뽑음
+    if (isEasyMode) {
+      // (예: 4x4 Easy -> 1,2,3,4 또는 A,B,C,D)
+      selectedSymbols = pool.sublist(0, gridSize);
+    } else {
+      // 그 외: 거대 풀을 섞은 뒤, gridSize만큼 뽑음
+      selectedSymbols = (pool.toList()..shuffle()).sublist(0, gridSize);
+    }
+    
     return SudokuTheme(
-      name: effectiveThemeName, // 실제 사용된 테마 이름 (예: "과일")
-      symbols: selectedSymbols,  // 무작위로 뽑힌 기호 리스트
+      name: effectiveThemeName,
+      symbols: selectedSymbols,
     );
   }
 }

lib/models/unified_rank_dto.dart

@@ -1,7 +1,7 @@
 // lib/models/unified_rank_dto.dart
 
 class UnifiedRankDto {
-  final String userId; // 👈 [추가] 앱-고유 ID
+  final String userId; // 👈 [수정] 앱-고유 ID
   final String gameType;
   final String? contextId;
   final String playerName;
@@ -9,7 +9,7 @@ class UnifiedRankDto {
   final int? secondaryScore;
 
   UnifiedRankDto({
-    required this.userId, // 👈 [추가] 생성자에 추가
+    required this.userId, // 👈 [수정] 생성자에 추가
     required this.gameType,
     this.contextId,
     required this.playerName,
@@ -20,7 +20,7 @@ class UnifiedRankDto {
   // Dart 객체를 JSON으로 변환 (서버 전송용)
   Map<String, dynamic> toJson() {
     return {
-      'userId': userId, // 👈 [추가]
+      'userId': userId, // 👈 [수정]
       'gameType': gameType,
       'contextId': contextId,
       'playerName': playerName,

lib/screens/game_screen.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 import 'dart:developer';
 import 'package:flutter/material.dart';
+import 'package:sudoku_app/models/game_level.dart'; // 👈 [추가] 레벨 모델 임포트
 import 'package:sudoku_app/models/sudoku_game_dto.dart';
 import 'package:sudoku_app/models/sudoku_theme.dart';
 import 'package:sudoku_app/models/unified_rank_dto.dart';
@@ -19,6 +20,7 @@ class GameScreen extends StatefulWidget {
   final String themeName;
   final String userId;
   final String? userName;
+  final int levelIndex; // 👈 HomeScreen에서 전달받은 현재 레벨
 
   const GameScreen({
     super.key,
@@ -26,6 +28,7 @@ class GameScreen extends StatefulWidget {
     required this.themeName,
     required this.userId,
     required this.userName,
+    required this.levelIndex,
   });
 
   @override
@@ -36,10 +39,12 @@ class _GameScreenState extends State<GameScreen> {
   final PuzzleService _puzzleService = PuzzleService();
   final IdentityService _identityService = IdentityService();
   
+  late final GameLevel currentLevel; // 👈 현재 레벨 정보
   late final int blockSize;
   late final int gridSize;
-  late final SudokuTheme activeTheme;
+  late final SudokuTheme activeTheme; // 👈 이번 게임의 '동적' 테마
 
+  // 모든 내부 로직은 'int'로 관리
   late List<int> puzzleCells;
   late List<int> solutionCells;
   late List<int> originalCells;
@@ -80,10 +85,31 @@ class _GameScreenState extends State<GameScreen> {
   @override
   void initState() {
     super.initState();
-    blockSize = widget.gameData.blockSize;
-    gridSize = widget.gameData.gridSize;
-    activeTheme = AppThemes.buildGameTheme(widget.themeName, gridSize);
+    // 1. HomeScreen에서 받은 levelIndex로 현재 레벨 정보 로드
+    currentLevel = AppLevels.getLevel(widget.levelIndex);
+    blockSize = currentLevel.blockSize;
+    gridSize = blockSize * blockSize;
+    
+    // 2. 🔽 [수정] 테마 정책 적용
+    String themeForThisGame = widget.themeName;
+    
+    // 🔽 [수정] 'isEasyMode' 변수를 'GameLevel'의 속성들로 조합
+    bool isEasyMode = currentLevel.isSequentialNumbers || currentLevel.isSequentialLetters;
 
+    if (currentLevel.isSequentialNumbers) {
+      themeForThisGame = AppThemes.numbers; // 👈 숫자 테마 강제
+    } else if (currentLevel.isSequentialLetters) {
+      themeForThisGame = AppThemes.letters; // 👈 알파벳 테마 강제
+    }
+
+    // 3. '이번 게임'의 테마 객체 생성
+    activeTheme = AppThemes.buildGameTheme(
+      themeForThisGame, 
+      gridSize,
+      isEasyMode: isEasyMode, // 👈 [수정] 조합된 bool 값 전달
+    );
+
+    // 4. 서버 데이터(String)를 내부 로직(int)으로 변환
     puzzleCells = widget.gameData.question.split('').map(_charToInt).toList();
     solutionCells = widget.gameData.solution.split('').map(_charToInt).toList();
     originalCells = widget.gameData.question.split('').map(_charToInt).toList();
@@ -107,21 +133,21 @@ class _GameScreenState extends State<GameScreen> {
 
   void onCellTapped(int index) {
     if (originalCells[index] == 0) {
+      
+      if (incorrectCells.isNotEmpty && !incorrectCells.contains(index)) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(
+            content: Text('틀린 값을 먼저 수정해주세요. (되돌리기 ↩)'),
+            duration: Duration(seconds: 1),
+          ),
+        );
+        return;
+      }
+      
       setState(() {
         selectedIndex = index;
         
         if (selectedNumberPad != null) {
-          
-          if (incorrectCells.isNotEmpty && !incorrectCells.contains(index)) {
-            ScaffoldMessenger.of(context).showSnackBar(
-              const SnackBar(
-                content: Text('틀린 값을 먼저 수정해주세요. (되돌리기 ↩)'),
-                duration: Duration(seconds: 1),
-              ),
-            );
-            return;
-          }
-          
           final int numberValue = selectedNumberPad!;
           puzzleCells[index] = numberValue;
 
@@ -159,12 +185,19 @@ class _GameScreenState extends State<GameScreen> {
   }
 
   void onUndoTapped() {
-    setState(() {
-      if (selectedIndex != null && originalCells[selectedIndex!] == 0) {
+    if (incorrectCells.isNotEmpty) {
+      int errorIndex = incorrectCells.first;
+      setState(() {
+        puzzleCells[errorIndex] = 0;
+        incorrectCells.remove(errorIndex);
+        selectedIndex = errorIndex;
+      });
+    } 
+    else if (selectedIndex != null && originalCells[selectedIndex!] == 0) {
+      setState(() {
         puzzleCells[selectedIndex!] = 0;
-        incorrectCells.remove(selectedIndex);
-      }
-    });
+      });
+    }
   }
 
   void onHintTapped() {
@@ -192,6 +225,7 @@ class _GameScreenState extends State<GameScreen> {
   }
 
 
+  // 정답 확인 API 호출
   Future<void> _validateGame() async {
     if (isValidating) return;
     setState(() { isValidating = true; });
@@ -229,18 +263,17 @@ class _GameScreenState extends State<GameScreen> {
     }
   }
 
-  // 랭킹 등록 팝업 (2단계 UI)
+  // 랭킹 등록 팝업 (2단계 UI + 레벨 잠금 해제)
   void _showRankingDialog() {
     final nameController = TextEditingController(text: widget.userName);
     bool isSubmitting = false;
-    final bool hasExistingName = widget.userName != null;
+    String? dialogErrorMessage;
     
     _rankStep = _RankSubmissionStep.enterName;
     _rankingList = [];
     _submittedPlayerName = "";
-    String? dialogErrorMessage; // 👈 [신규] 팝업 내부 에러 메시지
     
-    final String contextId = "SUDOKU_${gridSize}x${gridSize}_L${_difficultyLevel(widget.gameData.question)}";
+    final String contextId = currentLevel.contextId;
 
     showDialog(
       context: context,
@@ -290,12 +323,11 @@ class _GameScreenState extends State<GameScreen> {
                 const SizedBox(height: 20),
                 TextField(
                   controller: nameController,
-                  readOnly: hasExistingName,
+                  readOnly: false,
                   decoration: InputDecoration(
-                    labelText: hasExistingName ? '등록된 이름' : '이름 (10자 이내)',
+                    labelText: '이름 (10자 이내)',
                     border: const OutlineInputBorder(),
-                    // 🔽 [신규] 에러 메시지가 있으면 TextField에 에러 스타일 적용
-                    errorText: dialogErrorMessage, 
+                    errorText: dialogErrorMessage,
                   ),
                   maxLength: 10,
                 ),
@@ -306,7 +338,6 @@ class _GameScreenState extends State<GameScreen> {
               onPressed: () async {
                 final playerName = nameController.text.trim();
                 if (playerName.isEmpty) {
-                  // SnackBar 대신 팝업 내부 에러로 변경
                   setDialogState(() {
                     dialogErrorMessage = "이름을 입력해주세요.";
                   });
@@ -316,7 +347,7 @@ class _GameScreenState extends State<GameScreen> {
                 setDialogState(() {
                   _rankStep = _RankSubmissionStep.submitting;
                   _submittedPlayerName = playerName;
-                  dialogErrorMessage = null; // 👈 [신규] 에러 메시지 초기화
+                  dialogErrorMessage = null;
                 });
 
                 final rankDto = UnifiedRankDto(
@@ -330,9 +361,18 @@ class _GameScreenState extends State<GameScreen> {
 
                 try {
                   await _puzzleService.submitRank(rankDto);
-                  
-                  if (!hasExistingName) {
-                    await _identityService.saveUserName(playerName);
+                  await _identityService.saveUserName(playerName);
+
+                  final int currentMaxLevel = await _identityService.getMaxUnlockedLevel();
+                  if (currentMaxLevel < 99) {
+                    if (widget.levelIndex >= currentMaxLevel) {
+                      int nextLevel = widget.levelIndex + 1;
+                      if (nextLevel > AppLevels.allLevels.length) {
+                        await _identityService.saveMaxUnlockedLevel(99);
+                      } else {
+                        await _identityService.saveMaxUnlockedLevel(nextLevel);
+                      }
+                    }
                   }
                   
                   final ranks = await _puzzleService.fetchRanks('SUDOKU', contextId);
@@ -343,15 +383,11 @@ class _GameScreenState extends State<GameScreen> {
                   });
 
                 } catch (e) {
-                  // 🔽 [수정] 랭킹 등록 실패 시 (이름 중복 등)
                   log("!!! 랭킹 등록 실패 !!!", error: e);
-                  
                   setDialogState(() {
-                    _rankStep = _RankSubmissionStep.enterName; // 1단계(이름 입력)로 복귀
-                    // 👈 [신규] 서버 에러 메시지를 팝업에 표시
-                    dialogErrorMessage = e.toString().replaceFirst("Exception: ", ""); 
+                    _rankStep = _RankSubmissionStep.enterName;
+                    dialogErrorMessage = e.toString().replaceFirst("Exception: ", "");
                   });
-                  // ❌ SnackBar 제거
                 }
               },
               child: const Text('랭킹 등록'),
@@ -399,6 +435,7 @@ class _GameScreenState extends State<GameScreen> {
     );
   }
   
+  // 랭킹 ID 생성을 위해, 원본 문제의 빈칸 비율로 레벨(1~5)을 역산
   int _difficultyLevel(String question) {
     int holes = question.split('').where((c) => c == '0').length;
     double holeRatio = holes / (gridSize * gridSize);

lib/screens/home_screen.dart

@@ -1,10 +1,11 @@
 import 'package:flutter/material.dart';
+import 'package:sudoku_app/models/game_level.dart'; // 👈 [추가]
 import 'package:sudoku_app/models/sudoku_game_dto.dart';
 import 'package:sudoku_app/models/sudoku_theme.dart';
 import 'package:sudoku_app/screens/game_screen.dart';
 import 'package:sudoku_app/screens/ranking_screen.dart';
 import 'package:sudoku_app/services/puzzle_service.dart';
-import 'package:sudoku_app/services/identity_service.dart'; // 👈 ID 서비스 임포트
+import 'package:sudoku_app/services/identity_service.dart';
 import 'package:sudoku_app/widgets/ad_banner_widget.dart';
 
 class HomeScreen extends StatefulWidget {
@@ -15,51 +16,61 @@ class HomeScreen extends StatefulWidget {
 }
 
 class _HomeScreenState extends State<HomeScreen> {
-  // 8단계 난이도
-  double _difficultyLevel = 4.0; // 1.0 ~ 8.0 (기본값 Level 4: 중급 9x9)
-  final List<String> levelLabels = [
-    "입문 (4x4)", "초급 (4x4)", 
-    "쉬움 (9x9)", "중급 (9x9)", "어려움 (9x9)",
-    "전문가 (16x16)", "마스터 (16x16)", "지옥 (16x16)"
-  ];
-  
+  // '최대 잠금 해제 레벨' 상태
+  int _maxUnlockedLevel = 1; 
   late String _selectedThemeName;
-  bool isLoading = false;
+  bool _isLoading = false;
+  
   final PuzzleService _puzzleService = PuzzleService();
-  final IdentityService _identityService = IdentityService(); // 👈 ID 서비스 초기화
+  final IdentityService _identityService = IdentityService();
 
   @override
   void initState() {
     super.initState();
-    _selectedThemeName = AppThemes.random; // 기본 테마 '랜덤'
+    _selectedThemeName = AppThemes.random;
+    _loadProgress(); // 👈 저장된 진행 상황 로드
   }
 
-  Future<void> _startGame() async {
-    setState(() { isLoading = true; });
+  // 로컬 저장소에서 클리어 레벨 불러오기
+  Future<void> _loadProgress() async {
+    final maxLevel = await _identityService.getMaxUnlockedLevel();
+    if (mounted) {
+      setState(() {
+        _maxUnlockedLevel = maxLevel;
+      });
+    }
+  }
+
+  // 게임 시작 로직
+  Future<void> _startGame(GameLevel level) async {
+    setState(() { _isLoading = true; });
 
     try {
-      // 1. 난이도 값(String) 전달
-      final String difficulty = _difficultyLevel.round().toString();
+      // 1. 선택한 레벨의 '인덱스'(1-11)를 문자열로 전달
+      final String difficulty = level.levelIndex.toString();
       
-      // 2. 서버에서 게임 데이터 가져오기
       final SudokuGameDto gameData = await _puzzleService.startGame(difficulty);
       
-      // 3. 로컬에서 앱-고유 ID와 저장된 이름 가져오기
       final String userId = await _identityService.getOrCreateUserId();
       final String? userName = await _identityService.getSavedUserName();
 
       if (mounted) {
-        Navigator.push(
+        // 2. GameScreen으로 이동 (게임 클리어 후 돌아오면 _loadProgress() 호출)
+        await Navigator.push(
           context,
           MaterialPageRoute(
             builder: (context) => GameScreen(
               gameData: gameData,
-              themeName: _selectedThemeName,
-              userId: userId,     // 👈 ID 전달
-              userName: userName, // 👈 이름 전달
+              themeName: _selectedThemeName, // 👈 '랜덤' 또는 '과일' 등
+              userId: userId,
+              userName: userName,
+              levelIndex: level.levelIndex, // 👈 1~11
             ),
           ),
         );
+        
+        // 3. GameScreen에서 돌아왔을 때, 진행 상황(클리어)을 다시 로드
+        _loadProgress();
       }
     } catch (e) {
       if (mounted) {
@@ -69,107 +80,109 @@ class _HomeScreenState extends State<HomeScreen> {
       }
     } finally {
       if (mounted) {
-        setState(() { isLoading = false; });
+        setState(() { _isLoading = false; });
       }
     }
   }
 
   @override
   Widget build(BuildContext context) {
+    // 99 = 모든 레벨 클리어
+    final bool allLevelsUnlocked = _maxUnlockedLevel >= 99;
+    
     return Scaffold(
       appBar: AppBar(title: const Text('스도쿠 게임')),
-      body: LayoutBuilder( // 비율 기반 레이아웃
+      body: LayoutBuilder(
         builder: (context, constraints) {
-          // 너비/높이 비율 변수 (0.6 = 너비가 높이의 60%를 넘지 않도록 함)
           const double maxContentRatio = 0.6;
-          final double constrainedWidth = constraints.maxHeight * maxContentRatio;
+          // 🔽 [수정] 태블릿 등에서 너무 커지는 것을 방지 (최대 500px)
+          final double constrainedWidth = (constraints.maxHeight * maxContentRatio) > 500
+                                          ? 500 : (constraints.maxHeight * maxContentRatio);
 
           return Center(
             child: ConstrainedBox(
               constraints: BoxConstraints(maxWidth: constrainedWidth),
               child: Column(
                 children: [
-                  Expanded(
-                    child: Center(
-                      child: Padding(
-                        padding: const EdgeInsets.symmetric(horizontal: 20.0),
-                        child: Column(
-                          mainAxisAlignment: MainAxisAlignment.center,
-                          children: [
-                            // 1. 난이도 선택 (8단계)
-                            const Text("난이도", style: TextStyle(fontSize: 18)),
-                            Text(
-                              levelLabels[_difficultyLevel.round() - 1],
-                              style: const TextStyle(fontSize: 22, fontWeight: FontWeight.bold, color: Colors.blue),
-                            ),
-                            Slider(
-                              value: _difficultyLevel,
-                              min: 1.0, max: 8.0, divisions: 7, // 8단계
-                              label: levelLabels[_difficultyLevel.round() - 1],
-                              onChanged: (newValue) => setState(() { _difficultyLevel = newValue; }),
-                            ),
-                            
-                            const SizedBox(height: 20),
-
-                            // 2. 테마 선택 (String 기반)
-                            const Text("테마", style: TextStyle(fontSize: 18)),
-                            DropdownButton<String>(
-                              value: _selectedThemeName,
-                              items: AppThemes.selectableThemeNames.map((themeName) {
-                                return DropdownMenuItem<String>(
-                                  value: themeName,
-                                  child: Text(themeName, style: const TextStyle(fontSize: 20)),
-                                );
-                              }).toList(),
-                              onChanged: (themeName) {
-                                if (themeName != null) {
-                                  setState(() { _selectedThemeName = themeName; });
-                                }
-                              },
-                            ),
-                            
-                            const SizedBox(height: 30),
-                            
-                            if (isLoading)
-                              const CircularProgressIndicator()
-                            else
-                              ElevatedButton(
-                                onPressed: _startGame,
-                                style: ElevatedButton.styleFrom(padding: const EdgeInsets.symmetric(horizontal: 40, vertical: 15)),
-                                child: const Text('게임 시작', style: TextStyle(fontSize: 18)),
-                              ),
-                            
-                            const SizedBox(height: 10),
-
-                            // "랭킹 보기" 버튼
-                            TextButton(
-                              onPressed: () {
-                                // 현재 슬라이더의 난이도 이름(String)을 가져옴
-                                final String currentDifficultyName = levelLabels[_difficultyLevel.round() - 1];
-                                
-                                Navigator.push(
-                                  context,
-                                  MaterialPageRoute(
-                                    builder: (context) => RankingScreen(
-                                      initialDifficultyName: currentDifficultyName,
-                                    ),
-                                  ),
-                                );
-                              },
-                              child: const Text('랭킹 보기'),
-                            ),
-                          ],
+                  // 1. 테마 선택
+                  Padding(
+                    padding: const EdgeInsets.symmetric(horizontal: 20.0, vertical: 10.0),
+                    child: Row(
+                      mainAxisAlignment: MainAxisAlignment.center,
+                      children: [
+                        const Text("테마: ", style: TextStyle(fontSize: 18)),
+                        DropdownButton<String>(
+                          value: _selectedThemeName,
+                          items: AppThemes.selectableThemeNames.map((themeName) {
+                            return DropdownMenuItem<String>(
+                              value: themeName,
+                              child: Text(themeName, style: const TextStyle(fontSize: 20)),
+                            );
+                          }).toList(),
+                          onChanged: (themeName) {
+                            if (themeName != null) {
+                              setState(() { _selectedThemeName = themeName; });
+                            }
+                          },
                         ),
-                      ),
+                      ],
                     ),
                   ),
-                  const AdBannerWidget(),
+                  
+                  // 2. 🔽 [수정] 레벨 선택 리스트 (Slider 대체)
+                  Expanded(
+                    child: ListView.builder(
+                      itemCount: AppLevels.allLevels.length,
+                      itemBuilder: (context, index) {
+                        final GameLevel level = AppLevels.allLevels[index];
+                        // 3. 잠금 해제 로직
+                        final bool isUnlocked = allLevelsUnlocked || level.levelIndex <= _maxUnlockedLevel;
+
+                        return Card(
+                          margin: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 4.0),
+                          child: ListTile(
+                            leading: Icon(
+                              isUnlocked ? Icons.lock_open_rounded : Icons.lock_rounded,
+                              color: isUnlocked ? Colors.blue : Colors.grey,
+                            ),
+                            title: Text(level.name, style: TextStyle(
+                              fontSize: 18,
+                              fontWeight: isUnlocked ? FontWeight.bold : FontWeight.normal,
+                              color: isUnlocked ? Colors.black : Colors.grey,
+                            )),
+                            trailing: isUnlocked ? const Icon(Icons.play_arrow_rounded) : null,
+                            onTap: isUnlocked && !_isLoading
+                                ? () => _startGame(level)
+                                : null, // 잠겼거나 로딩 중이면 탭 비활성화
+                          ),
+                        );
+                      },
+                    ),
+                  ),
+                  
+                  // 3. 랭킹 보기 버튼
+                  TextButton(
+                    onPressed: () {
+                      // 현재 최고 레벨을 랭킹 화면의 기본값으로 전달
+                      final String currentDifficultyName = AppLevels.getLevel(_maxUnlockedLevel).name;
+                      Navigator.push(
+                        context,
+                        MaterialPageRoute(
+                          builder: (context) => RankingScreen(
+                            initialDifficultyName: currentDifficultyName,
+                          ),
+                        ),
+                      );
+                    },
+                    child: const Text('전체 랭킹 보기'),
+                  ),
                 ],
               ),
             ),
           );
         },
       ),
+      bottomNavigationBar: const AdBannerWidget(), // 👈 [수정] body -> bottomNavigationBar
     );
   }
 }

lib/screens/ranking_screen.dart

@@ -1,14 +1,15 @@
 import 'package:flutter/material.dart';
+import 'package:sudoku_app/models/game_level.dart';
 import 'package:sudoku_app/models/game_rank_dto.dart';
 import 'package:sudoku_app/services/puzzle_service.dart';
 
 class RankingScreen extends StatefulWidget {
-  // 🔽 [추가] 홈 화면에서 전달받을 초기 난이도 이름
+  // 🔽 [수정] 홈 화면에서 전달받을 초기 난이도 이름
   final String? initialDifficultyName;
 
   const RankingScreen({
     super.key,
-    this.initialDifficultyName, // 👈 생성자에 추가
+    this.initialDifficultyName, // 👈 [수정] 생성자에 이 파라미터 추가
   });
 
   @override
@@ -19,39 +20,28 @@ class _RankingScreenState extends State<RankingScreen> {
   final PuzzleService _puzzleService = PuzzleService();
   late Future<List<GameRankDto>> _rankingFuture;
 
-  // 8단계 난이도에 맞는 Context ID 맵
+  // 9단계 난이도에 맞는 (이름 -> ContextId) 맵
   final Map<String, String> difficultyContexts = {
-    "입문 (4x4)": "SUDOKU_4x4_L1",
-    "초급 (4x4)": "SUDOKU_4x4_L2",
-    "쉬움 (9x9)": "SUDOKU_9x9_L3",
-    "중급 (9x9)": "SUDOKU_9x9_L4",
-    "어려움 (9x9)": "SUDOKU_9x9_L5",
-    "전문가 (16x16)": "SUDOKU_16x16_L6",
-    "마스터 (16x16)": "SUDOKU_16x16_L7",
-    "지옥 (16x16)": "SUDOKU_16x16_L8",
+    for (var level in AppLevels.allLevels) level.name : level.contextId
   };
-  late String _selectedDifficulty;
+  late String _selectedDifficultyName;
 
   @override
   void initState() {
     super.initState();
-    // 🔽 [수정]
-    // 1. HomeScreen에서 전달받은 값이 있는지 확인
     String defaultDifficulty = widget.initialDifficultyName ?? "중급 (9x9)";
 
-    // 2. (안전장치) 전달받은 값이 맵에 없으면(예: 향후 변경) 기본값 사용
     if (!difficultyContexts.containsKey(defaultDifficulty)) {
       defaultDifficulty = "중급 (9x9)";
     }
     
-    // 3. 랭킹 조회
     _fetchRanksForDifficulty(defaultDifficulty);
   }
 
   void _fetchRanksForDifficulty(String difficultyName) {
     setState(() {
-      _selectedDifficulty = difficultyName;
-      _rankingFuture = _puzzleService.fetchRanks('SUDOKU', difficultyContexts[_selectedDifficulty]);
+      _selectedDifficultyName = difficultyName;
+      _rankingFuture = _puzzleService.fetchRanks('SUDOKU', difficultyContexts[_selectedDifficultyName]);
     });
   }
 
@@ -78,12 +68,12 @@ class _RankingScreenState extends State<RankingScreen> {
           Padding(
             padding: const EdgeInsets.all(16.0),
             child: DropdownButton<String>(
-              value: _selectedDifficulty, // 👈 initState에서 설정된 값으로 시작
+              value: _selectedDifficultyName,
               isExpanded: true,
-              items: difficultyContexts.keys.map((String difficultyName) {
+              items: AppLevels.allLevels.map((level) {
                 return DropdownMenuItem<String>(
-                  value: difficultyName,
-                  child: Text(difficultyName),
+                  value: level.name,
+                  child: Text(level.name),
                 );
               }).toList(),
               onChanged: (String? newValue) {

lib/services/identity_service.dart

@@ -1,12 +1,11 @@
-// lib/services/identity_service.dart
-
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:uuid/uuid.dart';
 
-// 앱-고유 ID와 사용자 이름을 관리하는 서비스
+// 앱-고유 ID와 사용자 이름, 레벨 진행 상황을 관리하는 서비스
 class IdentityService {
   static const String _userIdKey = 'app_user_id';
   static const String _userNameKey = 'app_user_name';
+  static const String _maxLevelKey = 'max_unlocked_level'; // 👈 [추가]
 
   // 1. 앱-고유 ID 가져오기 (없으면 생성)
   Future<String> getOrCreateUserId() async {
@@ -32,4 +31,17 @@ class IdentityService {
     final prefs = await SharedPreferences.getInstance();
     await prefs.setString(_userNameKey, name);
   }
+
+  // 4. 🔽 [추가] 현재 잠금 해제된 최고 레벨 가져오기
+  Future<int> getMaxUnlockedLevel() async {
+    final prefs = await SharedPreferences.getInstance();
+    // 최초 실행 시 1 (L1) 반환, 9레벨 클리어 시 99 반환
+    return prefs.getInt(_maxLevelKey) ?? 1; 
+  }
+
+  // 5. 🔽 [추가] 새 레벨 잠금 해제
+  Future<void> saveMaxUnlockedLevel(int level) async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setInt(_maxLevelKey, level);
+  }
 }

lib/services/puzzle_service.dart

@@ -1,5 +1,5 @@
 import 'dart:convert';
-import 'dart:developer'; // 👈 [추가] log 함수를 위한 임포트
+import 'dart:developer';
 import 'package:http/http.dart' as http;
 import 'package:sudoku_app/models/sudoku_game_dto.dart';
 import 'package:sudoku_app/models/unified_rank_dto.dart';
@@ -8,11 +8,13 @@ import 'package:sudoku_app/models/game_rank_dto.dart';
 class PuzzleService {
   final String _baseUrl = "https://lunaticbum.kr"; 
 
-  // ... (startGame 함수는 동일) ...
+  // 🔽 [수정] 'difficulty' 파라미터 1개만 받음 (1~11)
   Future<SudokuGameDto> startGame(String difficulty) async {
     final response = await http.get(
+      // 🔽 [수정] 'difficulty' 파라미터만 전달
       Uri.parse('$_baseUrl/puzzle/sudoku/start?difficulty=$difficulty'),
     );
+
     if (response.statusCode == 200) {
       final data = jsonDecode(utf8.decode(response.bodyBytes));
       return SudokuGameDto.fromJson(data);
@@ -21,7 +23,7 @@ class PuzzleService {
     }
   }
 
-  // ... (validateSolution 함수는 동일) ...
+  // 'puzzleId'를 받아 검증 (서버 DTO와 일치)
   Future<bool> validateSolution(int puzzleId, String answer) async {
     final response = await http.post(
       Uri.parse('$_baseUrl/puzzle/sudoku/validate'),
@@ -31,6 +33,7 @@ class PuzzleService {
         'answer': answer,
       }),
     );
+
     if (response.statusCode == 200) {
       return jsonDecode(response.body)['correct'] ?? false;
     } else {
@@ -40,12 +43,10 @@ class PuzzleService {
     }
   }
 
-  // POST /api/ranks/submit
+  // 랭킹 등록
   Future<void> submitRank(UnifiedRankDto rankDto) async {
     
     final requestBody = jsonEncode(rankDto.toJson());
-    
-    // 🔽 [로그 추가] 1. 서버로 전송하는 JSON 데이터 출력
     log(">>> 랭킹 등록 요청: $requestBody");
 
     final response = await http.post(
@@ -55,22 +56,19 @@ class PuzzleService {
     );
 
     if (response.statusCode != 200) {
-      // 🔽 [로그 추가] 2. 서버가 200(OK)이 아닌 응답을 줬을 때
       log("<<< 랭킹 등록 실패: ${response.statusCode}");
       try {
         final errorBody = utf8.decode(response.bodyBytes);
-        log("<<< 서버 에러 메시지: $errorBody"); // 👈 (예: "이미 사용 중인 이름입니다.")
+        log("<<< 서버 에러 메시지: $errorBody");
         throw Exception(errorBody);
       } catch (e) {
          throw Exception('랭킹 등록 실패: ${response.reasonPhrase}');
       }
     }
-    
-    // 🔽 [로그 추가] 3. 성공 시
     log("<<< 랭킹 등록 성공: 200 OK");
   }
 
-  // ... (fetchRanks 함수는 동일) ...
+  // 랭킹 조회
   Future<List<GameRankDto>> fetchRanks(String gameType, String? contextId) async {
     final queryParams = {
       'gameType': gameType,

lib/widgets/sudoku_board.dart

@@ -1,13 +1,13 @@
 import 'package:flutter/material.dart';
-import 'package:sudoku_app/models/sudoku_theme.dart'; // 👈 테마 모델 임포트
+import 'package:sudoku_app/models/sudoku_theme.dart';
 
 class SudokuBoard extends StatelessWidget {
   final int blockSize;
-  final SudokuTheme theme; // 👈 이번 게임의 테마
-  final List<int> cells; // 👈 List<int> (0, 1, 10...)
-  final List<int> originalCells; // 👈 List<int> (0, 1, 10...)
+  final SudokuTheme theme;
+  final List<int> cells;
+  final List<int> originalCells;
   final int? selectedIndex;
-  final int? selectedNumberPad; // 10진수 숫자 (1, 10...)
+  final int? selectedNumberPad;
   final Set<int> incorrectCells;
   final Function(int) onCellTapped;
 
@@ -26,7 +26,6 @@ class SudokuBoard extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final int gridSize = blockSize * blockSize;
-    // 그리드 크기에 따라 폰트 크기 동적 조절
     final double fontSize = (gridSize > 9) ? (gridSize > 16 ? 12 : 16) : 24;
 
     return AspectRatio(
@@ -41,18 +40,19 @@ class SudokuBoard extends StatelessWidget {
           int row = index ~/ gridSize;
           int col = index % gridSize;
           
-          int cellValue = cells[index]; // 0, 1, 10...
+          int cellValue = cells[index];
           bool isEditable = (originalCells[index] == 0);
           bool isSelected = (index == selectedIndex);
 
-          // int == int 비교
+          int selectedNumAsInt = selectedNumberPad ?? -1;
+          String selectedNumAsSymbol = (selectedNumberPad != null) ? theme.getSymbol(selectedNumberPad!) : "";
+          
           bool isHighlighted = (cellValue != 0 &&
               selectedNumberPad != null &&
               cellValue == selectedNumberPad);
               
           bool isIncorrect = incorrectCells.contains(index);
 
-          // blockSize에 따른 동적 보더
           BorderSide thickBorder = const BorderSide(color: Colors.black, width: 2.0);
           BorderSide thinBorder = const BorderSide(color: Colors.grey, width: 0.5);
 
@@ -61,15 +61,14 @@ class SudokuBoard extends StatelessWidget {
             child: Container(
               alignment: Alignment.center,
               decoration: BoxDecoration(
+                // 🔽 [수정] 'isSelected' 조건 제거 (배경색 없음)
                 color: isIncorrect
-                    ? Colors.red.shade100
-                    : isSelected
-                        ? Colors.blue.shade100
-                        : isHighlighted
-                            ? Colors.blue.shade200
-                            : isEditable
-                                ? Colors.white
-                                : Colors.grey.shade200,
+                    ? Colors.red.shade100   // 1순위: 틀림
+                    : isHighlighted
+                        ? Colors.blue.shade200 // 2순위: 숫자 하이라이트
+                        : isEditable
+                            ? Colors.white
+                            : Colors.grey.shade200, // 기본
                 border: Border(
                   top: (row == 0) ? thickBorder : thinBorder,
                   left: (col == 0) ? thickBorder : thinBorder,
@@ -78,16 +77,18 @@ class SudokuBoard extends StatelessWidget {
                 ),
               ),
               child: Text(
-                // 0이면 비우고, 아니면 테마 기호("1", "A", "🍎") 표시
                 cellValue == 0 ? '' : theme.getSymbol(cellValue),
                 style: TextStyle(
                   fontSize: fontSize,
                   fontWeight: FontWeight.bold,
-                  color: isIncorrect
-                      ? Colors.red.shade900
-                      : isEditable
-                          ? Colors.blue
-                          : Colors.black,
+                  // 🔽 [수정] 'isSelected'를 최우선 순위로 추가 (텍스트 색상 변경)
+                  color: isSelected
+                      ? Colors.orange.shade700 // 1순위: 선택된 셀
+                      : isIncorrect
+                          ? Colors.red.shade900 // 2순위: 틀린 셀
+                          : isEditable
+                              ? Colors.blue     // 3순위: 수정 가능 셀
+                              : Colors.black,   // 기본 (원본 숫자)
                 ),
               ),
             ),