#fullscreen {
  position: fixed;
  top: 12px;
  right: 12px;
  z-index: 10000;
  padding: 9px 14px;
  border: 1px solid #ffffff55;
  border-radius: 6px;
  background: #172013;
  color: white;
  font: 14px system-ui, sans-serif;
  cursor: pointer;
}
:fullscreen #fullscreen { opacity: 0; }
:fullscreen #fullscreen:hover, :fullscreen #fullscreen:focus-visible { opacity: 1; }
#presentation-error {
  position: fixed;
  top: 48px;
  right: 12px;
  max-width: 360px;
  z-index: 10000;
  background: #172013;
  color: white;
  font: 14px system-ui, sans-serif;
}
#presentation-error:empty { display: none; }