style.scss

.blocks-embed {
	margin: 0;
	clear: both;	// necessary because we use responsive trickery to set width/height, and therefore the video doesn't intrinsically clear floats like an img does
}

.blocks-embed .iframe-overlay {
	position: relative;
	width: 100%;
	height: 0;
	padding-bottom: 56.25%; /* 16:9 */
}

.blocks-embed iframe {
	position: absolute;
	top: 0;
	left: 0;
	width: 100%;
	height: 100%;
}