button, a.btn {
  transition: background-color 120ms ease, border-color 120ms ease, box-shadow 120ms ease;
}

button:not(:disabled):hover, a.btn:hover {
  filter: brightness(.97);
}

button:not(:disabled):active, a.btn:active {
  filter: brightness(.94);
}

button:focus-visible, a.btn:focus-visible {
  outline: 2px solid #0066f5;
  outline-offset: 3px;
}

button.is-loading {
  position: relative;
  color: transparent !important;
  text-shadow: none;
  opacity: 1 !important;
  cursor: wait;
}

button.is-loading > * {
  visibility: hidden;
}

button.is-loading::after {
  content: "";
  position: absolute;
  inset: 0;
  margin: auto;
  width: 14px;
  height: 14px;
  border: 2px solid var(--button-spinner-color, #002677);
  border-right-color: transparent;
  border-radius: 50%;
  animation: button-spinner 700ms linear infinite;
}

@keyframes button-spinner {
  to { transform: rotate(360deg); }
}

@media (prefers-reduced-motion: reduce) {
  button, a.btn { transition: none; }
  button.is-loading::after { animation: none; }
}