.loader {
  width: 60px;
  height: 14px;
  margin: 0 auto;
  margin-top: 14px;
  display: none;
  aspect-ratio: 4;
  --c:#808080 90%,#0000;
  background: 
    radial-gradient(circle closest-side at left  6px top 50%,var(--c)),
    radial-gradient(circle closest-side                     ,var(--c)),
    radial-gradient(circle closest-side at right 6px top 50%,var(--c));
  background-size: 100% 100%;
  background-repeat: no-repeat;
  animation: l4 1s infinite alternate;
}

@keyframes l4 {
  to {width: 25px; aspect-ratio: 1}
}