.tabs-switch em span strong { position:relative; font-weight:normal; display:inline-block; }
.tabs-switch em span strong::after {

content: '';
  position: absolute;
  display: inline-block;
  width: 100%;
  height: 4px;
  left: -200%;
  bottom: -2px;
  background: #ffe500;
  -webkit-transition: -webkit-transform .2s ease-out;
  transition: -webkit-transform .2s ease-out;
  transition: transform .2s ease-out;
  transition: transform .2s ease-out,-webkit-transform .2s ease-out;
  transform: translateX(-200%);
}

.tabs-switch .active em span strong::after {
  left: 200%;
}