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

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

.btn {
  position: relative;
  display: grid;
  place-items: center;
  min-width: clamp(150px, 40vw, 200px);
  border: 0;
  border-radius: 12px;
  padding: clamp(14px, 4vw, 22px) clamp(24px, 6vw, 40px);
  font-weight: 700;
  font-size: clamp(15px, 4vw, 20px);
  line-height: 1;
  font-family: inherit;
  color: #fff7e6;
  background: #2f6df6;
  cursor: pointer;
}
.btn__label, .btn__spin {
  grid-area: 1/1;
  transition: opacity 220ms, transform 220ms;
}
.btn__spin {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 3px solid rgba(255, 247, 230, 0.35);
  border-top-color: #fff7e6;
  opacity: 0;
  transform: scale(0.6);
  animation: spin 0.8s linear infinite;
}
.btn.is-loading .btn__label {
  opacity: 0;
  transform: translateY(6px);
}
.btn.is-loading .btn__spin {
  opacity: 1;
  transform: scale(1);
}
.btn.is-demo .btn__label {
  animation: label-loop 2s ease infinite;
}
.btn.is-demo .btn__spin {
  animation: spin 0.8s linear infinite, spin-loop 2s ease infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}
@keyframes label-loop {
  0%, 30% {
    opacity: 1;
    transform: none;
  }
  45%, 80% {
    opacity: 0;
    transform: translateY(6px);
  }
  95%, 100% {
    opacity: 1;
    transform: none;
  }
}
@keyframes spin-loop {
  0%, 30% {
    opacity: 0;
  }
  45%, 80% {
    opacity: 1;
  }
  95%, 100% {
    opacity: 0;
  }
}
@media (prefers-reduced-motion: reduce) {
  .btn__label, .btn__spin {
    transition: none;
    animation: none !important;
  }
  .btn.is-loading .btn__spin {
    opacity: 1;
    transform: none;
    border-top-color: rgba(255, 247, 230, 0.35);
  }
}