hehe.org/user/plugins/vimeo/css/vimeo.css

.grav-vimeo {
  position: relative;
  overflow: hidden;
  height: 0;
  padding-top: 25px;
  padding-bottom: 50%;
  margin-bottom: 10px;
  max-width: 1920px;
  max-height: 1080px; }

.grav-vimeo iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%; }