.loader {
  position: relative;
  border: 16px solid #f3f3f3;
  border-radius: 50%;
  border-top: 16px solid #3498db;
  width: 70px;
  height: 70px;
  left: 45%;
  top: 45%;
  -webkit-animation: spin 2s linear infinite; /* Safari */
  animation: spin 2s linear infinite;
}
#overlay {
  position: absolute;
  top: 0px;
  left: 0px;
  width: 100%;
  height: 100%;
  background: black;
  opacity: 0.5;
}





/* Safari */
@-webkit-keyframes spin {
  0% {
    -webkit-transform: rotate(0deg);
  }
  100% {
    -webkit-transform: rotate(360deg);
  }
}

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