Ripple Touch Feedback

<button type="button" class="nuda-ripple">
  <span class="nuda-ripple__label">Tap me</span>
  <span class="nuda-ripple__wave" aria-hidden="true"></span>
</button>

/* Ripple Touch Feedback
   Material-style expanding ripple on tap.
   Customize: --ripple-color */

.nuda-ripple {
  --ripple-color: rgba(228, 255, 84, 0.35);
  position: relative;
  appearance: none;
  overflow: hidden;
  min-width: 180px;
  min-height: 48px;
  padding: 0 20px;
  border-radius: 12px;
  border: 1px solid rgba(255, 255, 255, 0.1);
  background: #111114;
  color: #fafafa;
  font: 600 13px/1 system-ui;
  cursor: pointer;
  transition: background 0.2s;
}

.nuda-ripple:hover { background: #1a1a20; }

.nuda-ripple__label {
  position: relative;
  z-index: 1;
}

.nuda-ripple__wave {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--ripple-color);
  transform: translate(-50%, -50%) scale(0);
  animation: nuda-ripple-out 1.8s ease-out infinite;
}

@keyframes nuda-ripple-out {
  0% { transform: translate(-50%, -50%) scale(0); opacity: 0.8; }
  80% { opacity: 0.1; }
  100% { transform: translate(-50%, -50%) scale(20); opacity: 0; }
}

@media (prefers-reduced-motion: reduce) {
  .nuda-ripple__wave { animation: none; opacity: 0; }
}