Fade in/out - CSS only

thing.css

.thing {
  transform: scale(0);  
  opacity: 0;
  
  /* closing: delay transform scale by the duration of opacity fade */
  transition: opacity 0.2s ease-in-out, transform 0s 0.2s; 
}

.thing-show {
  transform: none;
  opacity: 1;
  
  /* opening: transform scale immediately, then opacity fade */
  transition: opacity 0.2s ease-in-out, transform 0s; 
}