main{
  min-height: 900px;
  position: relative;
}
.loading{
  position:absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 999;
}
.loader {
  border: 6px solid #f3f3f3;
  border-top: 6px solid #3498db;
  border-radius: 50%;
  width: 30px;
  height: 30px;
  animation: spin 2s linear infinite;
}
@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}