#modal {
  position: fixed;
  top: 0px;
  bottom: 0px;
  left: 0px;
  right: 0px;
  background-color: rgba(0, 0, 0, 0.5);
  z-index: 1000; /* Flexbox centers the .modal-content vertically and horizontally */
  display: flex;
  flex-direction: column;
  align-items: center;
}

#modal > .modal-underlay {
  /* underlay takes up the entire viewport. This is only required if you want to click to dismiss the popup */
  position: absolute;
  z-index: -1;
  top: 0px;
  bottom: 0px;
  left: 0px;
  right: 0px;
}

#modal > .modal-content {
  /* Position visible dialog near the top of the window */
  margin-top: 10vh; /* Sizing for visible dialog */
  width: 80%;
  max-width: 600px; /* Display properties for visible dialog*/
  border: solid 1px #999;
  border-radius: 8px;
  box-shadow: 0px 0px 20px 0px rgba(0, 0, 0, 0.3);
  background-color: white;
  padding: 20px;
}