.sns-embed-yt {
    position: relative;
    width: 100%;
    max-width: 640px;
    margin: 10px 0;
    padding-bottom: 56.25%; /* 16:9 aspect ratio */
    height: 0;
    overflow: hidden;
    background: #000;
    border-radius: 4px;
}
.sns-embed-yt iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: 0;
}
@media (max-width: 768px) {
    .sns-embed-yt {
        max-width: 100%;
    }
}