/* CSS is crucial for the 16:9 aspect ratio and responsiveness */
.video-responsive-container {
    position: relative;
    /* This sets the 16:9 aspect ratio (9 / 16 * 100) */
    padding-bottom: 56.25%; 
    height: 0;
    overflow: hidden;
    max-width: 100%;
}

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