diff --git a/src/12_RefactoringGolf/exo3/kata.ts b/src/12_RefactoringGolf/exo3/kata.ts
index b9cb6d6..fa8af1b 100644
--- a/src/12_RefactoringGolf/exo3/kata.ts
+++ b/src/12_RefactoringGolf/exo3/kata.ts
@@ -1,131 +1,139 @@
+// === Constants ===
+const EMPTY_SYMBOL = ' ';
+const PLAYER_O = 'O';
+const BOARD_SIZE = 3;
+
+// Error messages
+const ERROR_INVALID_FIRST_PLAYER = 'Invalid first player';
+const ERROR_INVALID_NEXT_PLAYER = 'Invalid next player';
+const ERROR_INVALID_POSITION = 'Invalid position';
 
-const leBonNom = ' ';
 export class Game {
-private _lastSymbol = leBonNom;
-private _board: Board = new Board();
+  private _lastSymbol = EMPTY_SYMBOL;
+  private _board: Board = new Board();
 
-public Play(symbol: string, x: number, y: number): void {
-this.validateFirstMove(symbol);
-this.validatePlayer(symbol);
-this.validatePositionIsEmpty(x, y);
+  public Play(symbol: string, x: number, y: number): void {
+    this.validateFirstMove(symbol);
+    this.validatePlayer(symbol);
+    this.validatePositionIsEmpty(x, y);
 
-this.updateLastPlayer(symbol);
-this.updateBoard(symbol, x, y);
-}
+    this.updateLastPlayer(symbol);
+    this.updateBoard(symbol, x, y);
+  }
 
-private validateFirstMove(player: string) {
-if (this._lastSymbol == ' ') {
-  if (player == 'O') {
-    throw new Error('Invalid first player');
+  private validateFirstMove(player: string) {
+    if (this._lastSymbol === EMPTY_SYMBOL) {
+      if (player === PLAYER_O) {
+        throw new Error(ERROR_INVALID_FIRST_PLAYER);
+      }
+    }
   }
-}
-}
 
-private validatePlayer(player: string) {
-if (player == this._lastSymbol) {
-  throw new Error('Invalid next player');
-}
-}
+  private validatePlayer(player: string) {
+    if (player === this._lastSymbol) {
+      throw new Error(ERROR_INVALID_NEXT_PLAYER);
+    }
+  }
 
-private validatePositionIsEmpty(x: number, y: number) {
-if (this._board.TileAt(x, y).Symbol != ' ') {
-  throw new Error('Invalid position');
-}
-}
+  private validatePositionIsEmpty(x: number, y: number) {
+    if (this._board.TileAt(x, y).Symbol !== EMPTY_SYMBOL) {
+      throw new Error(ERROR_INVALID_POSITION);
+    }
+  }
 
-private updateLastPlayer(player: string) {
-this._lastSymbol = player;
-}
+  private updateLastPlayer(player: string) {
+    this._lastSymbol = player;
+  }
 
-private updateBoard(player: string, x: number, y: number) {
-this._board.AddTileAt(player, x, y);
-}
+  private updateBoard(player: string, x: number, y: number) {
+    this._board.AddTileAt(player, x, y);
+  }
 
-public Winner(): string {
-if (this.isFirstRowFull() && this.isFirstRowFullWithSameSymbol()) {
-  return this._board.TileAt(0, 0)!.Symbol;
-}
+  public Winner(): string {
+    if (this.isFirstRowFull() && this.isFirstRowFullWithSameSymbol()) {
+      return this._board.TileAt(0, 0)!.Symbol;
+    }
 
-if (this.isSecondRowFull() && this.isSecondRowFullWithSameSymbol()) {
-  return this._board.TileAt(1, 0)!.Symbol;
-}
+    if (this.isSecondRowFull() && this.isSecondRowFullWithSameSymbol()) {
+      return this._board.TileAt(1, 0)!.Symbol;
+    }
 
-if (this.isThirdRowFull() && this.isThirdRowFullWithSameSymbol()) {
-  return this._board.TileAt(2, 0)!.Symbol;
-}
+    if (this.isThirdRowFull() && this.isThirdRowFullWithSameSymbol()) {
+      return this._board.TileAt(2, 0)!.Symbol;
+    }
 
-return ' ';
-}
+    return EMPTY_SYMBOL;
+  }
 
-private isFirstRowFull() {
-return (
-  this._board.TileAt(0, 0)!.Symbol != ' ' &&
-  this._board.TileAt(0, 1)!.Symbol != ' ' &&
-  this._board.TileAt(0, 2)!.Symbol != ' '
-);
-}
+  private isFirstRowFull() {
+    return (
+      this._board.TileAt(0, 0)!.Symbol !== EMPTY_SYMBOL &&
+      this._board.TileAt(0, 1)!.Symbol !== EMPTY_SYMBOL &&
+      this._board.TileAt(0, 2)!.Symbol !== EMPTY_SYMBOL
+    );
+  }
 
-private isFirstRowFullWithSameSymbol() {
-return (
-  this._board.TileAt(0, 0)!.Symbol == this._board.TileAt(0, 1)!.Symbol &&
-  this._board.TileAt(0, 2)!.Symbol == this._board.TileAt(0, 1)!.Symbol
-);
-}
+  private isFirstRowFullWithSameSymbol() {
+    return (
+      this._board.TileAt(0, 0)!.Symbol === this._board.TileAt(0, 1)!.Symbol &&
+      this._board.TileAt(0, 2)!.Symbol === this._board.TileAt(0, 1)!.Symbol
+    );
+  }
 
-private isSecondRowFull() {
-return (
-  this._board.TileAt(1, 0)!.Symbol != ' ' &&
-  this._board.TileAt(1, 1)!.Symbol != ' ' &&
-  this._board.TileAt(1, 2)!.Symbol != ' '
-);
-}
+  private isSecondRowFull() {
+    return (
+      this._board.TileAt(1, 0)!.Symbol !== EMPTY_SYMBOL &&
+      this._board.TileAt(1, 1)!.Symbol !== EMPTY_SYMBOL &&
+      this._board.TileAt(1, 2)!.Symbol !== EMPTY_SYMBOL
+    );
+  }
 
-private isSecondRowFullWithSameSymbol() {
-return (
-  this._board.TileAt(1, 0)!.Symbol == this._board.TileAt(1, 1)!.Symbol &&
-  this._board.TileAt(1, 2)!.Symbol == this._board.TileAt(1, 1)!.Symbol
-);
-}
+  private isSecondRowFullWithSameSymbol() {
+    return (
+      this._board.TileAt(1, 0)!.Symbol === this._board.TileAt(1, 1)!.Symbol &&
+      this._board.TileAt(1, 2)!.Symbol === this._board.TileAt(1, 1)!.Symbol
+    );
+  }
 
-private isThirdRowFull() {
-return (
-  this._board.TileAt(2, 0)!.Symbol != ' ' &&
-  this._board.TileAt(2, 1)!.Symbol != ' ' &&
-  this._board.TileAt(2, 2)!.Symbol != ' '
-);
-}
+  private isThirdRowFull() {
+    return (
+      this._board.TileAt(2, 0)!.Symbol !== EMPTY_SYMBOL &&
+      this._board.TileAt(2, 1)!.Symbol !== EMPTY_SYMBOL &&
+      this._board.TileAt(2, 2)!.Symbol !== EMPTY_SYMBOL
+    );
+  }
 
-private isThirdRowFullWithSameSymbol() {
-return (
-  this._board.TileAt(2, 0)!.Symbol == this._board.TileAt(2, 1)!.Symbol &&
-  this._board.TileAt(2, 2)!.Symbol == this._board.TileAt(2, 1)!.Symbol
-);
-}
+  private isThirdRowFullWithSameSymbol() {
+    return (
+      this._board.TileAt(2, 0)!.Symbol === this._board.TileAt(2, 1)!.Symbol &&
+      this._board.TileAt(2, 2)!.Symbol === this._board.TileAt(2, 1)!.Symbol
+    );
+  }
 }
 
 interface Tile {
-X: number;
-Y: number;
-Symbol: string;
+  X: number;
+  Y: number;
+  Symbol: string;
 }
 
 class Board {
-private _plays: Tile[] = [];
-
-constructor() {
-for (let i = 0; i < 3; i++) {
-  for (let j = 0; j < 3; j++) {
-    const tile: Tile = { X: i, Y: j, Symbol: ' ' };
-    this._plays.push(tile);
+  private _plays: Tile[] = [];
+
+  constructor() {
+    for (let i = 0; i < BOARD_SIZE; i++) {
+      for (let j = 0; j < BOARD_SIZE; j++) {
+        const tile: Tile = { X: i, Y: j, Symbol: EMPTY_SYMBOL };
+        this._plays.push(tile);
+      }
+    }
   }
-}
-}
 
-public TileAt(x: number, y: number): Tile {
-return this._plays.find((t: Tile) => t.X == x && t.Y == y)!;
-}
+  public TileAt(x: number, y: number): Tile {
+    return this._plays.find((t: Tile) => t.X === x && t.Y === y)!;
+  }
 
-public AddTileAt(symbol: string, x: number, y: number): void {
-this._plays.find((t: Tile) => t.X == x && t.Y == y)!.Symbol = symbol;
-}
-}
+  public AddTileAt(symbol: string, x: number, y: number): void {
+    this._plays.find((t: Tile) => t.X === x && t.Y === y)!.Symbol = symbol;
+  }
+}
\ No newline at end of file