a.fancylink {
  border-bottom: 3px solid red;
  font-size: 1em;
  transition: all 0.25s linear;
  position: relative;
  color: white;
  text-decoration: none;
  cursor: pointer;
}

a.fancylink:before {
  content: "";
  display: block;
  width: 100%;
  height: 3px;
  background-color: white;
  position: absolute;
  left: 0;
  bottom: -3px; /* this is to match where the border is */
  transform-origin: left; 
  transform: scale(0);
  transition: 0.25s linear;
/*   will-change: transform; */
}

a.fancylink:hover {
  color: red;
}
a.fancylink:hover:before {
  transform: scale(1);
}