body
{
}

body#index
{
 color: red;
 
 

}

iframe-wrapper
{
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
  overflow: hidden; 
 
}
iframe-wrapper iframe
{
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;}


}

 
 
@media screen and (max-width: 768px) {
  .box_youtube{
    position: relative;
    width: 100%;
    padding: calc(315 / 560 * 100%) 0 0;
  }
  .box_youtube iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
  }
}