.youtube-short-container {
    position: relative;
    padding-top: 88.89%; /* 1080 / 1920 = 0.5625, so 1 / 0.5625 = 1.778 */
    height: 0;
    overflow: hidden;
}

.youtube-short-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}