01월·연 전환에 숫자가 굴러간다

<main class="stage">
  <div class="bt is-demo" data-period="month">
    <p class="bt__plan">프로 플랜</p>
    <div class="bt__price" aria-live="polite">
      <span class="bt__cur">$</span>
      <span class="bt__num"></span>
      <span class="bt__unit">/ 월</span>
    </div>
    <div class="bt__badgerow">
      <span class="bt__badge">20% 절약</span>
    </div>
    <div class="bt__switch" role="group" aria-label="결제 주기">
      <span class="bt__lab" data-side="m">월간</span>
      <button class="bt__pill" type="button" role="switch" aria-checked="false" aria-label="결제 주기" id="bt-sw">
        <span class="bt__knob" aria-hidden="true"></span>
      </button>
      <span class="bt__lab" data-side="y">연간</span>
    </div>
  </div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 가격 숫자를 굴리는 핵심 — 등록하지 않은 커스텀 속성은 보간되지 않는다.
// <integer> 로 등록해야 29 → 23 사이가 한 자리씩 채워진다
@property --n {
  syntax: "<integer>";
  initial-value: 29;
  inherits: false;
}

$duration: $dur-quick;
$easing: $ease-spring;
$color: $subject-blue;
$roll: 520ms;            // 숫자가 굴러가는 시간 — 자리가 넘어가는 게 눈에 보이는 길이

@include stage($stage-paper);

.bt {
  --travel: 24px;        // 손잡이가 미끄러지는 거리 — 알약 안폭(48) - 손잡이(20) - 양옆 2
  box-sizing: border-box;
  width: min(300px, 86vw);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-2;
  padding: $sp-4;
  border: 2px solid $subject-ink;
  border-radius: $r-card;
  background: $stage-paper;
  box-shadow: $shadow-raised;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: $subject-ink;
}

.bt__plan {
  margin: 0;
  font-size: 13px;
  line-height: 18px;
  font-weight: 700;
  letter-spacing: .04em;
}

.bt__price {
  display: flex;
  align-items: baseline;
  gap: $sp-1;
  color: $color;
}
.bt__cur {
  font-size: 20px;
  line-height: 28px;
  font-weight: 800;
}
// 숫자는 텍스트 노드가 아니라 카운터로 그린다 — --n 이 보간되는 동안 그 정수가 그대로 글자가 된다
.bt__num {
  --n: 29;
  counter-reset: n var(--n);
  font-size: 40px;
  line-height: 46px;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
}
.bt__num::after { content: counter(n); }
.bt__unit {
  font-size: 13px;
  line-height: 18px;
  font-weight: 700;
  color: $subject-ink;
}

.bt__badgerow {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 22px;
}
.bt__badge {
  padding: $sp-1 $sp-2;
  border-radius: $r-pill;
  background: $color;
  color: $stage-paper;
  font-size: 11px;
  line-height: 14px;
  font-weight: 800;
  opacity: 0;
  transform: scale(.7) translateY(6px);
}

.bt__switch {
  display: flex;
  align-items: center;
  gap: $sp-2;
}
.bt__lab {
  font-size: 12px;
  line-height: 16px;
  font-weight: 700;
  opacity: .45;
}
.bt__pill {
  position: relative;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  flex: 0 0 auto;
  width: 52px;
  height: 28px;
  border: 2px solid $subject-ink;
  border-radius: $r-pill;
  background: $stage-paper;
  cursor: pointer;
}
.bt__pill:focus-visible { outline: 2px solid $color; outline-offset: 2px; }
.bt__knob {
  position: absolute;
  left: 2px;
  top: 2px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: $subject-ink;
}

// ── 사람이 만진 뒤(정적 경로) — 상태는 aria-checked 와 data-period 에만 들어 있다 ──
.bt__pill[aria-checked="true"] {
  background: $color;
  border-color: $color;
}
.bt__pill[aria-checked="true"] .bt__knob {
  transform: translateX(var(--travel));
  background: $stage-paper;
}
.bt[data-period="month"] .bt__lab[data-side="m"],
.bt[data-period="year"] .bt__lab[data-side="y"] { opacity: 1; }
.bt[data-period="year"] .bt__num { --n: 23; }
.bt[data-period="year"] .bt__badge {
  opacity: 1;
  transform: scale(1) translateY(0);
}

.bt:not(.is-demo) .bt__num {
  transition-property: --n;
  transition-duration: $roll;
  transition-timing-function: $easing;
}
.bt:not(.is-demo) .bt__knob {
  transition-property: transform, background-color;
  transition-duration: $duration;
  transition-timing-function: $easing;
}
.bt:not(.is-demo) .bt__badge {
  transition-property: transform, opacity;
  transition-duration: $duration;
  transition-timing-function: $ease-pop;
}

// ── 자동 루프(2초) — 월간 29 → 연간 23 → 다시 월간. 복귀는 88% 에 끝난다 ──
.bt.is-demo .bt__num {
  animation-name: bt-roll;
  animation-duration: $dur-loop;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}
@keyframes bt-roll {
  0%   { --n: 29; }
  12%  { --n: 29; }
  36%  { --n: 23; }
  64%  { --n: 23; }
  88%  { --n: 29; }
  100% { --n: 29; }
}

// 손잡이는 미끄러지고(부드럽게), 손잡이 색은 컷으로 바뀐다
.bt.is-demo .bt__knob {
  animation-name: bt-knob, bt-knobc;
  animation-duration: $dur-loop, $dur-loop;
  animation-timing-function: $easing, steps(1, end);
  animation-iteration-count: infinite, infinite;
}
@keyframes bt-knob {
  0%, 12%   { transform: translateX(0); }
  36%, 64%  { transform: translateX(var(--travel)); }
  88%, 100% { transform: translateX(0); }
}
@keyframes bt-knobc {
  0%   { background-color: $subject-ink; }
  24%  { background-color: $stage-paper; }
  76%  { background-color: $stage-paper; }
  88%  { background-color: $subject-ink; }
  100% { background-color: $subject-ink; }
}

.bt.is-demo .bt__pill {
  animation-name: bt-pill;
  animation-duration: $dur-loop;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
@keyframes bt-pill {
  0%   { background-color: $stage-paper; border-color: $subject-ink; }
  24%  { background-color: $color; border-color: $color; }
  76%  { background-color: $color; border-color: $color; }
  88%  { background-color: $stage-paper; border-color: $subject-ink; }
  100% { background-color: $stage-paper; border-color: $subject-ink; }
}

// 라벨 강조도 같은 시계로 — 손잡이만 움직이면 어느 쪽이 켜졌는지 어긋나 보인다
.bt.is-demo .bt__lab {
  animation-duration: $dur-loop;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.bt.is-demo .bt__lab[data-side="m"] { animation-name: bt-lab-m; }
.bt.is-demo .bt__lab[data-side="y"] { animation-name: bt-lab-y; }
@keyframes bt-lab-m {
  0%   { opacity: 1; }
  24%  { opacity: .45; }
  82%  { opacity: 1; }
  100% { opacity: 1; }
}
@keyframes bt-lab-y {
  0%   { opacity: .45; }
  24%  { opacity: 1; }
  82%  { opacity: .45; }
  100% { opacity: .45; }
}

// 배지는 나타남만 컷, 튀어오름은 $ease-pop 으로 — 두 축을 따로 돌린다
.bt.is-demo .bt__badge {
  animation-name: bt-badge-face, bt-badge-pop;
  animation-duration: $dur-loop, $dur-loop;
  animation-timing-function: steps(1, end), $ease-pop;
  animation-iteration-count: infinite, infinite;
}
@keyframes bt-badge-face {
  0%   { opacity: 0; }
  30%  { opacity: 1; }
  82%  { opacity: 0; }
  100% { opacity: 0; }
}
@keyframes bt-badge-pop {
  0%, 30%   { transform: scale(.7) translateY(6px); }
  44%       { transform: scale(1.06) translateY(0); }
  54%, 100% { transform: scale(1) translateY(0); }
}

// 숫자가 굴러가는 동안 가격 덩어리가 한 번 눌렸다 편다 — 컷 옆에 움직인 프레임을 채운다
.bt.is-demo .bt__price {
  animation-name: bt-pop;
  animation-duration: $dur-loop;
  animation-timing-function: $ease-pop;
  animation-iteration-count: infinite;
}
@keyframes bt-pop {
  0%, 10%   { transform: scale(1); }
  22%       { transform: scale(1.06); }
  34%, 74%  { transform: scale(1); }
  84%       { transform: scale(1.05); }
  94%, 100% { transform: scale(1); }
}

@media (max-width: 340px) {
  .bt {
    width: min(260px, 90vw);
    gap: $sp-1;
    padding: $sp-3;
  }
  .bt__plan { font-size: 12px; line-height: 16px; }
  .bt__cur { font-size: 16px; line-height: 22px; }
  .bt__num { font-size: 30px; line-height: 34px; }
  .bt__badgerow { height: 20px; }
  .bt { --travel: 22px; }       // 좁은 화면에서는 알약도 손잡이도 작아진다 (46 - 4 - 16 - 4)
  .bt__pill { width: 46px; height: 24px; }
  .bt__knob { width: 16px; height: 16px; }
}

@media (prefers-reduced-motion: reduce) {
  .bt.is-demo .bt__num,
  .bt.is-demo .bt__knob,
  .bt.is-demo .bt__pill,
  .bt.is-demo .bt__lab,
  .bt.is-demo .bt__badge,
  .bt.is-demo .bt__price { animation: none !important; }
  .bt:not(.is-demo) .bt__num,
  .bt:not(.is-demo) .bt__knob,
  .bt:not(.is-demo) .bt__badge { transition: none !important; }
  .bt.is-demo .bt__lab[data-side="m"] { opacity: 1; }
}

@property --n {
  syntax: "<integer>";
  initial-value: 29;
  inherits: false;
}
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);
}

.bt {
  --travel: 24px;
  box-sizing: border-box;
  width: min(300px, 86vw);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  padding: 16px;
  border: 2px solid #17141a;
  border-radius: 16px;
  background: #ffffff;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: #17141a;
}

.bt__plan {
  margin: 0;
  font-size: 13px;
  line-height: 18px;
  font-weight: 700;
  letter-spacing: 0.04em;
}

.bt__price {
  display: flex;
  align-items: baseline;
  gap: 4px;
  color: #2f6df6;
}

.bt__cur {
  font-size: 20px;
  line-height: 28px;
  font-weight: 800;
}

.bt__num {
  --n: 29;
  counter-reset: n var(--n);
  font-size: 40px;
  line-height: 46px;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
}

.bt__num::after {
  content: counter(n);
}

.bt__unit {
  font-size: 13px;
  line-height: 18px;
  font-weight: 700;
  color: #17141a;
}

.bt__badgerow {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 22px;
}

.bt__badge {
  padding: 4px 8px;
  border-radius: 999px;
  background: #2f6df6;
  color: #ffffff;
  font-size: 11px;
  line-height: 14px;
  font-weight: 800;
  opacity: 0;
  transform: scale(0.7) translateY(6px);
}

.bt__switch {
  display: flex;
  align-items: center;
  gap: 8px;
}

.bt__lab {
  font-size: 12px;
  line-height: 16px;
  font-weight: 700;
  opacity: 0.45;
}

.bt__pill {
  position: relative;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  flex: 0 0 auto;
  width: 52px;
  height: 28px;
  border: 2px solid #17141a;
  border-radius: 999px;
  background: #ffffff;
  cursor: pointer;
}

.bt__pill:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: 2px;
}

.bt__knob {
  position: absolute;
  left: 2px;
  top: 2px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: #17141a;
}

.bt__pill[aria-checked=true] {
  background: #2f6df6;
  border-color: #2f6df6;
}

.bt__pill[aria-checked=true] .bt__knob {
  transform: translateX(var(--travel));
  background: #ffffff;
}

.bt[data-period=month] .bt__lab[data-side=m],
.bt[data-period=year] .bt__lab[data-side=y] {
  opacity: 1;
}

.bt[data-period=year] .bt__num {
  --n: 23;
}

.bt[data-period=year] .bt__badge {
  opacity: 1;
  transform: scale(1) translateY(0);
}

.bt:not(.is-demo) .bt__num {
  transition-property: --n;
  transition-duration: 520ms;
  transition-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
}

.bt:not(.is-demo) .bt__knob {
  transition-property: transform, background-color;
  transition-duration: 220ms;
  transition-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
}

.bt:not(.is-demo) .bt__badge {
  transition-property: transform, opacity;
  transition-duration: 220ms;
  transition-timing-function: cubic-bezier(0.2, 1.4, 0.4, 1);
}

.bt.is-demo .bt__num {
  animation-name: bt-roll;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1);
  animation-iteration-count: infinite;
}

@keyframes bt-roll {
  0% {
    --n: 29;
  }
  12% {
    --n: 29;
  }
  36% {
    --n: 23;
  }
  64% {
    --n: 23;
  }
  88% {
    --n: 29;
  }
  100% {
    --n: 29;
  }
}
.bt.is-demo .bt__knob {
  animation-name: bt-knob, bt-knobc;
  animation-duration: 2s, 2s;
  animation-timing-function: cubic-bezier(0.2, 0.8, 0.2, 1), steps(1, end);
  animation-iteration-count: infinite, infinite;
}

@keyframes bt-knob {
  0%, 12% {
    transform: translateX(0);
  }
  36%, 64% {
    transform: translateX(var(--travel));
  }
  88%, 100% {
    transform: translateX(0);
  }
}
@keyframes bt-knobc {
  0% {
    background-color: #17141a;
  }
  24% {
    background-color: #ffffff;
  }
  76% {
    background-color: #ffffff;
  }
  88% {
    background-color: #17141a;
  }
  100% {
    background-color: #17141a;
  }
}
.bt.is-demo .bt__pill {
  animation-name: bt-pill;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

@keyframes bt-pill {
  0% {
    background-color: #ffffff;
    border-color: #17141a;
  }
  24% {
    background-color: #2f6df6;
    border-color: #2f6df6;
  }
  76% {
    background-color: #2f6df6;
    border-color: #2f6df6;
  }
  88% {
    background-color: #ffffff;
    border-color: #17141a;
  }
  100% {
    background-color: #ffffff;
    border-color: #17141a;
  }
}
.bt.is-demo .bt__lab {
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

.bt.is-demo .bt__lab[data-side=m] {
  animation-name: bt-lab-m;
}

.bt.is-demo .bt__lab[data-side=y] {
  animation-name: bt-lab-y;
}

@keyframes bt-lab-m {
  0% {
    opacity: 1;
  }
  24% {
    opacity: 0.45;
  }
  82% {
    opacity: 1;
  }
  100% {
    opacity: 1;
  }
}
@keyframes bt-lab-y {
  0% {
    opacity: 0.45;
  }
  24% {
    opacity: 1;
  }
  82% {
    opacity: 0.45;
  }
  100% {
    opacity: 0.45;
  }
}
.bt.is-demo .bt__badge {
  animation-name: bt-badge-face, bt-badge-pop;
  animation-duration: 2s, 2s;
  animation-timing-function: steps(1, end), cubic-bezier(0.2, 1.4, 0.4, 1);
  animation-iteration-count: infinite, infinite;
}

@keyframes bt-badge-face {
  0% {
    opacity: 0;
  }
  30% {
    opacity: 1;
  }
  82% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}
@keyframes bt-badge-pop {
  0%, 30% {
    transform: scale(0.7) translateY(6px);
  }
  44% {
    transform: scale(1.06) translateY(0);
  }
  54%, 100% {
    transform: scale(1) translateY(0);
  }
}
.bt.is-demo .bt__price {
  animation-name: bt-pop;
  animation-duration: 2s;
  animation-timing-function: cubic-bezier(0.2, 1.4, 0.4, 1);
  animation-iteration-count: infinite;
}

@keyframes bt-pop {
  0%, 10% {
    transform: scale(1);
  }
  22% {
    transform: scale(1.06);
  }
  34%, 74% {
    transform: scale(1);
  }
  84% {
    transform: scale(1.05);
  }
  94%, 100% {
    transform: scale(1);
  }
}
@media (max-width: 340px) {
  .bt {
    width: min(260px, 90vw);
    gap: 4px;
    padding: 12px;
  }
  .bt__plan {
    font-size: 12px;
    line-height: 16px;
  }
  .bt__cur {
    font-size: 16px;
    line-height: 22px;
  }
  .bt__num {
    font-size: 30px;
    line-height: 34px;
  }
  .bt__badgerow {
    height: 20px;
  }
  .bt {
    --travel: 22px;
  }
  .bt__pill {
    width: 46px;
    height: 24px;
  }
  .bt__knob {
    width: 16px;
    height: 16px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .bt.is-demo .bt__num,
  .bt.is-demo .bt__knob,
  .bt.is-demo .bt__pill,
  .bt.is-demo .bt__lab,
  .bt.is-demo .bt__badge,
  .bt.is-demo .bt__price {
    animation: none !important;
  }
  .bt:not(.is-demo) .bt__num,
  .bt:not(.is-demo) .bt__knob,
  .bt:not(.is-demo) .bt__badge {
    transition: none !important;
  }
  .bt.is-demo .bt__lab[data-side=m] {
    opacity: 1;
  }
}

// 실제 동작: 스위치를 누르면 aria-checked 가 뒤집히고 뿌리의 data-period 가 바뀐다.
// 가격 숫자는 CSS 가 굴린다 — @property 로 등록한 --n 을 transition 이 정수로 보간하고
// counter-reset: n var(--n) + content: counter(n) 이 그 값을 글자로 그린다.
var root = document.querySelector('.bt');
var sw = document.getElementById('bt-sw');
sw.addEventListener('click', function () {
  root.classList.remove('is-demo');
  var on = sw.getAttribute('aria-checked') === 'true';
  sw.setAttribute('aria-checked', String(!on));
  root.setAttribute('data-period', on ? 'month' : 'year');
});

import { useState } from "react";
import type { CSSProperties } from "react";
import styles from "./BillingToggleRoll.module.scss";

export type BillingToggleRollProps = {
  planName?: string;
  monthLabel?: string;
  yearLabel?: string;
  groupLabel?: string;
  saveLabel?: string;
  unit?: string;
  currency?: string;
  monthly?: number;
  yearly?: number;
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & {
  "--duration"?: string;
  "--easing"?: string;
  "--color"?: string;
};
type NumVars = CSSProperties & { "--n"?: string };

export default function BillingToggleRoll({
  planName = "Pro plan",
  monthLabel = "Monthly",
  yearLabel = "Yearly",
  groupLabel = "Billing period",
  saveLabel = "Save 20%",
  unit = "/ mo",
  currency = "$",
  monthly = 29,
  yearly = 23,
  duration = 220,
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#2f6df6",
}: BillingToggleRollProps) {
  const [demo, setDemo] = useState(true);
  const [year, setYear] = useState(false);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  // --n 은 @property 로 등록된 정수라 값을 바꾸면 transition 이 한 자리씩 굴린다.
  // 자동 루프가 도는 동안에는 keyframes 가 이 인라인 값보다 우선한다(애니메이션이 캐스케이드에서 위)
  const numVars: NumVars = { "--n": String(year ? yearly : monthly) };

  function toggle() {
    setDemo(false);
    setYear((v) => !v);
  }

  return (
    <div
      className={`${styles.bt} ${demo ? styles.isDemo : ""}`}
      data-period={year ? "year" : "month"}
      style={vars}
    >
      <p className={styles.plan}>{planName}</p>
      <div className={styles.price} aria-live="polite">
        <span className={styles.cur}>{currency}</span>
        <span className={styles.num} style={numVars} />
        <span className={styles.unit}>{unit}</span>
      </div>
      <div className={styles.badgerow}>
        <span className={styles.badge}>{saveLabel}</span>
      </div>
      <div className={styles.switch} role="group" aria-label={groupLabel}>
        <span className={styles.lab} data-side="m">{monthLabel}</span>
        <button
          className={styles.pill}
          type="button"
          role="switch"
          aria-checked={year}
          aria-label={groupLabel}
          onClick={toggle}
        >
          <span className={styles.knob} aria-hidden="true" />
        </button>
        <span className={styles.lab} data-side="y">{yearLabel}</span>
      </div>
    </div>
  );
}