.iframe-centered {
    margin: 0 auto;
    display: block;
}
.aspect-ratio {
    padding-bottom: 20;
}
.aspect-ratio iframe {
    max-width: 100%;
}
@media only screen and (max-width: 768px) {
    .aspect-ratio {
        position: relative;
        padding-bottom: 56.25%; /* The height of the item will now be 56.25% of the width. */
    }
    .aspect-ratio iframe {
        position: absolute;
        width: 100%;
        height: 100%;
    }
}