diff --git a/lib/domain/game/game_engine.dart b/lib/domain/game/game_engine.dart
new file mode 100644
index 0000000..3f16add
--- /dev/null
+++ b/lib/domain/game/game_engine.dart
@@ -0,0 +1,97 @@
+import '../../core/config/app_constants.dart';
+import '../entities/pokemon.dart';
+import 'game_state.dart';
+
+/// Règles du jeu, pures (aucune IO, aucun widget). Entièrement testable.
+class GameEngine {
+  const GameEngine();
+
+  /// Nouvelle partie : réinitialise tout sauf le bestScore.
+  GameState newGame(GameState s) {
+    return s.copyWith(
+      lives: AppConstants.startingLives,
+      skips: AppConstants.startingSkips,
+      hints: AppConstants.startingHints,
+      sessionCorrectCount: 0,
+      currentScore: 0,
+      status: GameStatus.loading,
+      isHintUsed: false,
+    );
+  }
+
+  /// Démarre une manche avec un nouveau Pokémon.
+  GameState startRound(GameState s, Pokemon p, {required bool isShiny}) {
+    return s.copyWith(
+      currentPokemon: p,
+      isShiny: isShiny,
+      isHintUsed: false,
+      status: GameStatus.playing,
+    );
+  }
+
+  /// Soumet une réponse. Renvoie le nouvel état + la nature du résultat.
+  GuessOutcome submitGuess(GameState s, String guess) {
+    final pokemon = s.currentPokemon;
+    if (pokemon == null || s.status != GameStatus.playing) {
+      return GuessOutcome(s, GuessResult.invalid);
+    }
+
+    final normalizedGuess = _normalize(guess.trim().toLowerCase());
+    final normalizedActual = _normalize(pokemon.name.toLowerCase());
+
+    if (normalizedGuess == normalizedActual) {
+      final newSession = s.sessionCorrectCount + 1;
+      final gained = s.isShiny ? AppConstants.pointsShiny : AppConstants.pointsNormal;
+      final newScore = s.currentScore + gained;
+      final hintBonus =
+          newSession % AppConstants.hintBonusEvery == 0 ? 1 : 0;
+      final skipBonus =
+          newSession % AppConstants.skipBonusEvery == 0 ? 1 : 0;
+
+      final newState = s.copyWith(
+        currentPokemon: pokemon.copyWith(isCaught: true, isSeen: true),
+        currentScore: newScore,
+        bestScore: newScore > s.bestScore ? newScore : s.bestScore,
+        sessionCorrectCount: newSession,
+        hints: s.hints + hintBonus,
+        skips: s.skips + skipBonus,
+        status: GameStatus.roundWon,
+      );
+      return GuessOutcome(newState, GuessResult.correct);
+    }
+
+    final remainingLives = s.lives - 1;
+    if (remainingLives <= 0) {
+      return GuessOutcome(
+        s.copyWith(lives: 0, status: GameStatus.gameOver),
+        GuessResult.gameOver,
+      );
+    }
+    return GuessOutcome(
+      s.copyWith(lives: remainingLives),
+      GuessResult.wrong,
+    );
+  }
+
+  /// Consomme un indice si disponible et non déjà utilisé.
+  GameState useHint(GameState s) {
+    if (s.isHintUsed || s.hints <= 0) return s;
+    return s.copyWith(isHintUsed: true, hints: s.hints - 1);
+  }
+
+  /// Consomme un skip si disponible.
+  GameState useSkip(GameState s) {
+    if (s.skips <= 0) return s;
+    return s.copyWith(skips: s.skips - 1);
+  }
+
+  static String _normalize(String input) {
+    const withDia = 'ÀÁÂÃÄÅàáâãäåÒÓÔÕÖØòóôõöøÈÉÊËèéêëÇçÌÍÎÏìíîïÙÚÛÜùúûüÿÑñ';
+    const withoutDia = 'AAAAAAaaaaaaOOOOOOooooooEEEEeeeeCcIIIIiiiiUUUUuuuuyNn';
+    var output = input;
+    for (var i = 0; i < withDia.length; i++) {
+      output = output.replaceAll(withDia[i], withoutDia[i]);
+    }
+    return output;
+  }
+}
diff --git a/test/domain/game_engine_test.dart b/test/domain/game_engine_test.dart
new file mode 100644
index 0000000..f810de2
--- /dev/null
+++ b/test/domain/game_engine_test.dart
@@ -0,0 +1,108 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pokeguess/domain/entities/pokemon.dart';
+import 'package:pokeguess/domain/game/game_engine.dart';
+import 'package:pokeguess/domain/game/game_state.dart';
+
+const _engine = GameEngine();
+
+Pokemon _poke(String name) => Pokemon(
+      name: name, id: 1, type1: PokemonType.normal,
+      hp: 1, atk: 1, def: 1, spd: 1,
+    );
+
+GameState _playing(String name, {bool shiny = false}) => _engine.startRound(
+      const GameState(), _poke(name), isShiny: shiny);
+
+void main() {
+  test('newGame réinitialise vies/score/session, garde le bestScore', () {
+    const s = GameState(
+        lives: 1, currentScore: 50, sessionCorrectCount: 7, bestScore: 99);
+    final r = _engine.newGame(s);
+    expect(r.lives, 3);
+    expect(r.currentScore, 0);
+    expect(r.sessionCorrectCount, 0);
+    expect(r.bestScore, 99);
+    expect(r.status, GameStatus.loading);
+  });
+
+  test('startRound place le Pokémon et passe en playing', () {
+    final r = _playing('pikachu', shiny: true);
+    expect(r.currentPokemon?.name, 'pikachu');
+    expect(r.isShiny, true);
+    expect(r.isHintUsed, false);
+    expect(r.status, GameStatus.playing);
+  });
+
+  test('bonne réponse: +10 points et roundWon', () {
+    final o = _engine.submitGuess(_playing('pikachu'), 'pikachu');
+    expect(o.result, GuessResult.correct);
+    expect(o.state.currentScore, 10);
+    expect(o.state.sessionCorrectCount, 1);
+    expect(o.state.status, GameStatus.roundWon);
+    expect(o.state.currentPokemon?.isCaught, true);
+  });
+
+  test('bonne réponse shiny: +20 points', () {
+    final o = _engine.submitGuess(_playing('pikachu', shiny: true), 'pikachu');
+    expect(o.state.currentScore, 20);
+  });
+
+  test('comparaison insensible aux accents et à la casse', () {
+    final o = _engine.submitGuess(_playing('Dracaufeu'), 'dracaufeu');
+    expect(o.result, GuessResult.correct);
+    final o2 = _engine.submitGuess(_playing('Électhor'), 'electhor');
+    expect(o2.result, GuessResult.correct);
+  });
+
+  test('mauvaise réponse: -1 vie, reste playing tant qu\'il reste des vies', () {
+    final o = _engine.submitGuess(_playing('pikachu'), 'salameche');
+    expect(o.result, GuessResult.wrong);
+    expect(o.state.lives, 2);
+    expect(o.state.status, GameStatus.playing);
+  });
+
+  test('mauvaise réponse à 1 vie: gameOver', () {
+    const start = GameState(lives: 1, status: GameStatus.playing);
+    final round = _engine.startRound(start, _poke('pikachu'), isShiny: false);
+    final o = _engine.submitGuess(round, 'faux');
+    expect(o.result, GuessResult.gameOver);
+    expect(o.state.lives, 0);
+    expect(o.state.status, GameStatus.gameOver);
+  });
+
+  test('le cheat "pikachu" n\'existe plus: faux nom sur un autre Pokémon = wrong', () {
+    final o = _engine.submitGuess(_playing('bulbizarre'), 'pikachu');
+    expect(o.result, GuessResult.wrong);
+  });
+
+  test('bonus: indice tous les 5, skip tous les 10', () {
+    var s = const GameState(sessionCorrectCount: 4, status: GameStatus.playing);
+    s = _engine.startRound(s, _poke('pikachu'), isShiny: false);
+    final o = _engine.submitGuess(s, 'pikachu'); // 5e bonne réponse
+    expect(o.state.sessionCorrectCount, 5);
+    expect(o.state.hints, AppConstantsHints + 1);
+  });
+
+  test('useHint consomme un indice', () {
+    final s = _playing('pikachu');
+    final r = _engine.useHint(s);
+    expect(r.isHintUsed, true);
+    expect(r.hints, 2);
+  });
+
+  test('useHint sans indice restant ne change rien', () {
+    final s = _playing('pikachu').copyWith(hints: 0);
+    final r = _engine.useHint(s);
+    expect(r.isHintUsed, false);
+    expect(r.hints, 0);
+  });
+
+  test('useSkip décrémente les skips', () {
+    final s = _playing('pikachu');
+    final r = _engine.useSkip(s);
+    expect(r.skips, 2);
+  });
+}
+
+/// Valeur attendue de hints au démarrage (miroir d'AppConstants.startingHints = 3).
+const AppConstantsHints = 3;