SemanSemantic-UItic-UI/build/minified/modules/video.min.css

.ui.video {
  position: relative;
  max-width: 100%;
}

.ui.video .placeholder {
  background-color: #333;
}

.ui.video .play {
  cursor: pointer;
  position: absolute;
  top: 0;
  left: 0;
  z-index: 10;
  width: 100%;
  height: 100%;
  -ms-filter: "alpha(Opacity=60)";
  filter: alpha(opacity=60);
  opacity: .6;
  -webkit-transition: opacity .3s;
  transition: opacity .3s;
}

.ui.video .play.icon:before {
  position: absolute;
  top: 50%;
  left: 50%;
  z-index: 11;
  font-size: 6rem;
  margin: -3rem 0 0 -3rem;
  color: #FFF;
  text-shadow: 0 3px 3px rgba(0,0,0,.4);
}

.ui.video .placeholder {
  display: block;
  width: 100%;
  height: 100%;
}

.ui.video .embed {
  display: none;
}

.ui.video .play:hover {
  opacity: 1;
}

.ui.video.active .play,
.ui.video.active .placeholder {
  display: none;
}

.ui.video.active .embed {
  display: block;
}