#rotate-warning {
  display: none;
  position: fixed;
  z-index: 9999;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background: #111;
  color: white;
  text-align: center;
  padding-top: 40vh;
  font-size: 1.5rem;
}

/* Hide main content by default for landscape mobile */
@media screen and (orientation: landscape) and (max-width: 1024px) {
  body {
    overflow: hidden;
  }

  #main-content {
    display: none;
  }

  #rotate-warning {
    display: block;
  }
}