html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.link {
  position: relative;
  display: inline-block;
  padding: 8px 4px 12px;
  color: #17141a;
  text-decoration: none;
  font-weight: 700;
  font-size: clamp(18px, 5vw, 26px);
  line-height: 1.2;
}
.link::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 10px;
  background-image: radial-gradient(circle at 10px -5px, transparent 12px, currentColor 13px, currentColor 14px, transparent 15px), radial-gradient(circle at 30px 5px, transparent 12px, currentColor 13px, currentColor 14px, transparent 15px);
  background-repeat: repeat-x;
  background-size: 40px 10px;
  background-position: 0 0, 0 0;
  opacity: 0;
  transition: opacity 220ms ease-out;
}
.link:hover::after, .link:focus-visible::after {
  opacity: 1;
  animation: wave-flow 1.2s linear infinite;
}
.link.is-demo::after {
  animation: wave-loop 2s ease-out infinite;
}

@keyframes wave-flow {
  0% {
    background-position: 0 0, 0 0;
  }
  100% {
    background-position: -40px 0, -40px 0;
  }
}
@keyframes wave-loop {
  0% {
    opacity: 0;
    background-position: 0 0, 0 0;
  }
  15% {
    opacity: 1;
    background-position: 0 0, 0 0;
  }
  85% {
    opacity: 1;
    background-position: -40px 0, -40px 0;
  }
  100% {
    opacity: 0;
    background-position: -40px 0, -40px 0;
  }
}
@media (prefers-reduced-motion: reduce) {
  .link::after, .link.is-demo::after {
    transition: none;
    animation: none;
  }
  .link:hover::after, .link:focus-visible::after {
    opacity: 1;
  }
}