.loader {
  border: 16px solid #f3f3f3;
  border-top: 16px solid #000;
  border-radius: 50%;
  width: 100px;
  height: 100px;
  animation: spin 2s linear infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

.container {
  position: absolute;
  left: 50%;
  top: 50%;
  -webkit-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
}