.promo-video-wrapper {
        position: relative;
        padding-bottom: 56.25%; /* 16:9 */
        padding-top: 0px;
        height: 0;
}
.promo-video-wrapper iframe {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
} 

.video-wrapper-9-16 {
        position: relative;
        padding-bottom: 56.25%; 
        padding-top: 0px;
        height: 0;
}

.video-wrapper-9-16 iframe {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
} 

.video-wrapper-10-16 {
        position: relative;
        padding-bottom: 62.5%; 
        padding-top: 0px;
        height: 0;
}

.video-wrapper-10-16 iframe {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
}

.video-wrapper-iPhone6 {
  position: relative;
  padding-bottom: 178.218%;
  padding-top: 0px;
  height: 0;
}

.video-wrapper-iPhone6 iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

.video-wrapper-AndroidNexus4 {
  position: relative;
  padding-bottom: 166.667%;
  padding-top: 0px;
  height: 0;
}

.video-wrapper-AndroidNexus4 iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}