koel/resources/assets/css/partials/skeleton.pcss

.skeleton {
  .pulse, &.pulse {
    @apply bg-white/5;
    animation: skeleton-pulse 2s infinite;
  }

  @keyframes skeleton-pulse {
    0%, 100% {
      @apply opacity-0;
    }
    50% {
      @apply opacity-100;
    }
  }
}