We use this for creating scalable elements (usually images / background images) that maintain a ratio.
div {
@include responsive-ratio(16,9);
}
@mixin responsive-ratio($x,$y, $pseudo: false) {
$padding: unquote( ( $y / $x ) * 100 + '%' );
@if $pseudo {
&:before {
@include pseudo($pos: relative);
width: 100%;
padding-top: $padding;
}
} @else {
padding-top: $padding;
}
}