#modal {
          position: fixed;
          top: 50%; left: 50%;
          transform: translate(-50%, -50%);
          background-color: #ccc;
          padding: 20px;
          box-sizing: border-box;
          z-index: 101;
          width: 80%;
          max-width: 600px;
        }
        .hidden {
          display: none;
        }