.loader {
  position: relative;
  width: 300px;
  height: 3px;
  background: linear-gradient(to right, transparent, #28AE60, transparent);
  overflow: hidden;
}

.loader::after {
  content: '';
  position: absolute;
  translate: -200px 0;
  width: 150px;
  height: 100%;
  background: linear-gradient(to right, transparent, #212121, transparent);
  animation: slide 1s infinite;
}

@keyframes slide {
  100% {
    translate: 300px 0;
  }
}