.wrap{
width: 400px;
margin: auto;
border: 5px solid greenyellow;
}
.iframe-container{
height: 0;
padding-bottom: 97.6%;
position: relative;
}
.iframe-container iframe{
position: absolute;
left: 0;
top: 0;
width: 100%;
height: 100%;
}
@media screen and (max-width: 400px) {
.wrap{
width: 300px;
}
}