bigbluebutton-Github/bigbluebutton-html5/app/client/stylesheets/mixins.less

.radius(@size: 4px) {
  -moz-border-radius: @size;
  -webkit-border-radius: @size;
  border-radius: @size;
}

.linear-gradient(@color1, @color2) {
  background: -moz-linear-gradient(@color1, @color2); /* For Firefox 3.6 to 15 */
  background: -o-linear-gradient(@color1, @color2); /* For Opera 11.1 to 12.0 */
  background: -webkit-linear-gradient(@color1, @color2); /* For Safari 5.1 to 6.0 */
  background: linear-gradient(@color1, @color2); /* Standard syntax (must be last) */
}

.vertically-centered {
  position: relative;
  top: 50%;
  -webkit-transform: translateY(-50%);
  -ms-transform: translateY(-50%);
  transform: translateY(-50%);
}