.youtube-video-wrapper {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 */
    height: 0;
}

.youtube-video-wrapper > iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: 0 none;
}

body {
    margin: 0;
}