index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/normalize/8.0.1/normalize.min.css" integrity="sha512-NhSC1YmyruXifcj/KFRWoC561YpHpc5Jtzgvbuzx5VozKpWvQ+4nXhPdFgmx8xqexRcpAglTj9sIBWINXa8x5w==" crossorigin="anonymous" referrerpolicy="no-referrer" >
    <link rel="stylesheet" href="styles.css" />
    <title>Aim Training</title>
  </head>
  <body>
    <div class="screen ">
      <h1 class="title-games">Aim Training</h1>
      <p class="about-games"></p>
      <a href="#" class="start" id="start" >Начать игру</a>
    </div>

    <div class="screen ">
      <h1 class="title-times"></h1>
      <ul class="time-list" id="time-list">
        <li>
          <button class="time-btn" data-time="10">
            10 сек
          </button>
        </li>
        <li>
          <button class="time-btn" data-time="20">
            20 сек
          </button>
        </li>
        <li>
          <button class="time-btn" data-time="30">
            30 сек
          </button>
        </li>
        <li>
          <button class="time-btn" data-time="50">
            50 сек
          </button>
        </li>
      </ul>
    </div>

    <div class="screen">
      <h3 class="times">Осталось <span id="time">00:00</span></h3>
      <div class="board" id="board"></div>
    </div>
    <footer>

    </footer>
    <script src="app.js"></script>
    <script src="parser.js"></script>
  </body>
</html>