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);
}

.bf {
  width: min(260px, 86vw);
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.bf__field {
  position: relative;
}

.bf__input {
  box-sizing: border-box;
  width: 100%;
  padding: 8px 12px;
  border-radius: 8px;
  border: 2px solid rgba(23, 20, 26, 0.18);
  background: #fff;
  color: #17141a;
  font-weight: 400;
  font-size: 14px;
  line-height: 1;
  font-family: inherit;
}

.bf__ring {
  position: absolute;
  inset: -4px;
  border: 2px solid #c2361a;
  border-radius: 8px;
  opacity: 0;
  pointer-events: none;
}

.bf__msg {
  margin: 0;
  color: #c2361a;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.3;
  font-family: inherit;
}

@keyframes bf-flash {
  0%, 100% {
    opacity: 0;
  }
  15% {
    opacity: 1;
  }
  30% {
    opacity: 0;
  }
  45% {
    opacity: 1;
  }
  60% {
    opacity: 0;
  }
}
.bf__ring.bf--flash {
  animation: bf-flash 500ms ease-in-out;
}

.bf.is-demo .bf__ring {
  animation: bf-flash 500ms ease-in-out infinite;
}

@media (prefers-reduced-motion: reduce) {
  .bf__ring.bf--flash,
  .bf.is-demo .bf__ring {
    animation: none !important;
  }
}