.embed-responsive {
position: relative;
display: block;
height: 0;
padding: 0;
overflow: hidden;
margin: 2em auto;
}
.embed-responsive .embed-responsive-item,
.embed-responsive iframe {
position: absolute;
top: 0;
bottom: 0;
left: 0;
width: 100%;
height: 100%;
border: 0;
}
.embed-responsive-16by9 {
padding-bottom: 56.25%;
}