body {
  background-color: black;
}
.center {
  margin: auto;
  text-align: center;
  align-items:center;
  justify-content:center;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
iframe {
  width: 100%;
  height: 100%;
}
.warning {
  color: red;
}

#iframe, #videoarea, #imagearea {
  z-index: 2;
  position: absolute;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  object-fit: contain;
}

#audioarea {
  position: absolute;
  top: 0;
  left: 0;
  width: 0;
  height: 0;
  z-index: 9;
}