<!DOCTYPE html>
<html>
<head>
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
  <title>Checkers</title>
  <link rel="stylesheet" type="text/css" href="css/application.css">
  <script src="js/application.js"></script>

</head>
<body>
  <div class="tabuleiro">
    <img id="image-board" src="images/tabuleiro.png" alt="Tabuleiro">
  </div>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
  <title>Checkers</title>
  <link rel="stylesheet" type="text/css" href="css/application.css">
  <script src="js/application.js"></script>
  <script src="js/game.js"></script>
  <script src="js/board.js"></script>

</head>
<body>
  <div class="board">
    <img id="image-board" src="images/tabuleiro.png" alt="Tabuleiro">
  </div>
</body>
</html>

Add script for board and game and change tabuleiro class name to board
Add script for board and game and change tabuleiro class name to board
