_sass/core/includes/video-content-band.scss

.video-content-band {
  .video-container {
      position: relative;
      width: 100%;
      height: 0;
      padding-bottom: 56.25%;
  }
  .video-container iframe {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
  }
}