Simple CSS transitions in Elm?

I changed a few things around and looks like it works for variable height now, although you have to specify a max height.

.slide {
  clear: both;
  width: 100%;
  max-height: 0px;
  overflow: hidden;
  text-align: center;
  transition: max-height .4s ease;
}

.fake-checkbox:checked+.slide {
  max-height: 500px;
}