game.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <link rel="stylesheet" href="game.css" />
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Javascript Memory Game</title>
  </head>
  <body>
    <main>
      <button data-turnable="true" data-number="0" id="1"></button>
      <button data-turnable="true" data-number="0" id="2"></button>
      <button data-turnable="true" data-number="0" id="3"></button>
      <button data-turnable="true" data-number="0" id="4"></button>
      <button data-turnable="true" data-number="0" id="5"></button>
      <button data-turnable="true" data-number="0" id="6"></button>
      <button data-turnable="true" data-number="0" id="7"></button>
      <button data-turnable="true" data-number="0" id="8"></button>
      <button data-turnable="true" data-number="0" id="9"></button>
      <button data-turnable="true" data-number="0" id="10"></button>
      <button data-turnable="true" data-number="0" id="11"></button>
      <button data-turnable="true" data-number="0" id="12"></button>
      <button data-turnable="true" data-number="0" id="13"></button>
      <button data-turnable="true" data-number="0" id="14"></button>
      <button data-turnable="true" data-number="0" id="15"></button>
      <button data-turnable="true" data-number="0" id="16"></button>
    </main>
  </body>
  <script src="game.js"></script>
</html>