iframe[src*="youtube.com"] {
    width: 100% !important;
    height: auto !important;
    aspect-ratio: 16 / 9;
    display: block;
}

@supports not (aspect-ratio: 16 / 9) {
    /* fallback untuk browser lama */
    iframe[src*="youtube.com"] {
        width: 100% !important;
        height: 56.25vw !important; /* 9/16 * 100 */
    }
}