HTML - définir taille bouton

<[/contents/242-introduction-au-dynamic-html-dhtml div] class="box">
  <button>Commencez maintenant</button>
  <style>
      button{
          font-size: 10em;
          font-family: Arial, Helvetica, sans-serif;
          padding: 10px;
          border: none;
          background-color: green;
          color: white;
          border-radius: 3px;
          box-shadow: 6px 6px 20px 4px rgba(0, 0, 0, 0.3);
          cursor: pointer;
          outline: none;
          transition: 0.2s;
      }

      button:hover{
          transform: scale(1.01);
          box-shadow: 6px 6px 25px 4px rgba(0, 0, 0, 0.18);
      }
      button:active{
          transform: scale(0.98);
          box-shadow: 6px 6px 18px 2px rgba(0, 0, 0, 0.23);
      }
  </style>

</div>

width: 200px;
height: 150px;