.fade {
  opacity: 0;
  -webkit-transition: opacity 0.15s linear;
          transition: opacity 0.15s linear;
}

.fade.in {
  opacity: 1;
}

.collapse {
  display: none;
}

.collapse.in {
  display: block;
}

.collapsing {
  position: relative;
  height: 0;
  overflow: hidden;
  -webkit-transition: height 0.35s ease;
          transition: height 0.35s ease;
}