/* estado normal */
#top-loader{
  position: fixed;
  top: 0; left: 0;
  width: 100%;
  height: 3px;
  z-index: 99999;

  background: rgba(255,255,255,.9);

  transform-origin: left;
  transform: scaleX(0);
  opacity: 0;

  transition:
    transform .35s ease,
    opacity .25s ease;
}

/* visible mientras carga */
body.is-loading #top-loader{
  opacity: 1;
}

/* salida elegante */
body.is-loaded #top-loader{
  opacity: 0;
  transform: scaleX(1);
}