button:disabled {
  opacity: .7;
  cursor: not-allowed;
}

button:disabled::before {
  content: '';
  display: inline-block;
  width: .9em;
  height: .9em;
  margin-right: .5em;
  vertical-align: -0.1em;
  border: 2px solid currentColor;
  border-right-color: transparent;
  border-radius: 50%;
  animation: spin .8s linear infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}