html, body {
      height: 100%;
      margin: 0;
      font-family: Roboto, sans-serif;
    }

    .center-wrapper {
      height: 100vh;
      display: flex;
      align-items: center;      /* vertical */
      justify-content: center;  /* horizontal */
      background: #f5f6fa;      /* optional */
    }

    .login-box {
      background: #fff;
      padding: 20px;
      border-radius: 8px;
      box-shadow: 0 10px 30px rgba(0,0,0,.15);
    }