.surface-reward {
  padding: 12px;
  border: 1px solid currentColor;
  border-radius: 8px;
}
.surface-reward.celebrate {
  animation: surface-celebration 900ms ease-out;
}
@keyframes surface-celebration {
  0% { box-shadow: 0 0 0 0 currentColor; }
  100% { box-shadow: 0 0 0 12px transparent; }
}
@media (prefers-reduced-motion: reduce) {
  .surface-reward.celebrate { animation: none; }
}