#overlay {
  display: none;
  position: fixed;
  top: 0; left: 0; width: 100%; height: 100%;
  background: rgba(255,255,255,0.7);
  z-index: 9999;
  align-items: center;
  justify-content: center;
  flex-direction: column;
}
.loader {
  border: 6px solid #f3f3f3;
  border-top: 6px solid #3498db;
  border-radius: 50%;
  width: 48px;
  height: 48px;
  animation: spin 1s linear infinite;
}
@keyframes spin {
  0%   { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}