.embed-responsive-21x9 iframe{aspect-ratio:21/9;height:auto;width:100%}.embed-responsive-16x9 iframe{aspect-ratio:16/9;height:auto;width:100%}.embed-responsive-4x3 iframe{aspect-ratio:4/3;height:auto;width:100%}.embed-responsive-1x1 iframe{aspect-ratio:1/1;height:auto;width:100%}