.loading-bar {
  display: inline-block;
  width: 4px;
  height: 20px;
  border-radius: 4px;
  animation: loading 1s ease-in-out infinite;
  margin-right: 2px;
}

.loading-bar:nth-child(1) {
 background-color: #3498db;
 animation-delay: 0;
}

.loading-bar:nth-child(2) {
 background-color: #c0392b;
 animation-delay: 0.09s;
}

.loading-bar:nth-child(3) {
 background-color: #f1c40f;
 animation-delay: .18s;
}

.loading-bar:nth-child(4) {
 background-color: #27ae60;
 animation-delay: .27s;
}

@keyframes loading {
 0% {
   transform: scale(1);
 }

 20% {
   transform: scale(1, 2.2);
 }

 40% {
   transform: scale(1);
 }
}