.videoContainer {
  position: absolute;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

iframe {
  /* optional */
  width: 100%;
  height: 100%; 
}