.button-spinner {
  border: 2px solid #f3f3f3;
  border-top: 2px solid #3498db;
  border-radius: 50%;
  width: 16px;
  height: 16px;
  animation: spin 1s linear infinite;
  display: inline-block;
  vertical-align: middle;
  margin-left: 5px;
}

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