.kdgm-responsive-player {
 position: relative;
 padding-bottom: 56.25%; /* 75% voor 4:3 video */
 height: 0;
 overflow: hidden;
}
.kdgm-responsive-player iframe {
 position: absolute;
 top:0;
 left: 0;
 width: 100%;
 height: 100%;
}