body {
  text-align: center;
}
video, iframe {
  position: absolute;
  transform: translateX(-50%) translateY(-50%);
  top: 50%;
  max-width: 100%;
  max-height: 100%;
}
iframe {
  position: absolute;
  transform: translateX(-50%) translateY(-50%);
  top: 50%;
  max-width: 100%;
  max-height: 100%;
}
img {
  width: 250px;
  position: absolute;
  left: 0;
  right: 0;
  margin: 30px auto;
}
@media (max-width: 1000px) {
  iframe {
    max-width: 100%;
    max-height: 100vw;
  }
}