01Plan cards — a card row that recomputes its price on every billing switch

<main class="stage">
<section class="panel" id="panel">
  <p class="hint" id="hint">Every time the yearly/monthly switch flips, the discount is reapplied to recompute the displayed price.</p>
  <div class="switchRow">
    <span class="switchLabel" id="switchLabel">Annual billing</span>
    <button class="switchCtl" id="billingSwitch" type="button" role="switch" aria-checked="false" aria-label="Switch to annual billing">
      <span class="knob" aria-hidden="true"></span>
    </button>
  </div>
  <div class="cards" id="cardsRow">
    <article class="card">
      <h3 class="planName">Basic</h3>
      <p class="price"><span class="priceNum" id="price0">12</span><span class="priceUnit" id="unit0"> / mo</span></p>
      <p class="badge" id="badge0" hidden></p>
    </article>
    <article class="card card--mid">
      <h3 class="planName">Pro</h3>
      <p class="price"><span class="priceNum" id="price1">29</span><span class="priceUnit" id="unit1"> / mo</span></p>
      <p class="badge" id="badge1" hidden></p>
    </article>
    <article class="card">
      <h3 class="planName">Team</h3>
      <p class="price"><span class="priceNum" id="price2">59</span><span class="priceUnit" id="unit2"> / mo</span></p>
      <p class="badge" id="badge2" hidden></p>
    </article>
  </div>
</section>
</main>

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

$duration: $dur-enter;
$easing: $ease-spring;
$color: $subject-blue-deep;

@include stage($stage-ink);

.panel {
  width: 100%;
  max-width: 440px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
}

.hint {
  margin: 0;
  padding: 0 $sp-2;
  text-align: center;
  font-weight: 400;
  font-size: 11px;
  line-height: 1.4;
  color: rgba($subject-cream, .72);
}

.switchRow {
  display: flex;
  align-items: center;
  gap: $sp-2;
}

.switchLabel {
  font-weight: 500;
  font-size: 12px;
  color: $subject-cream;
}

.switchCtl {
  position: relative;
  width: 40px;
  height: 22px;
  border: 0;
  border-radius: $r-pill;
  background: rgba($subject-cream, .24);
  padding: 0;
  cursor: pointer;
  transition: background $duration $easing;
}

.switchCtl[aria-checked="true"] {
  background: $color;
}

.knob {
  position: absolute;
  top: 2px;
  left: 2px;
  width: 18px;
  height: 18px;
  border-radius: $r-pill;
  background: $subject-cream;
  box-shadow: $shadow-press;
  transform: translateX(0);
  transition: transform $duration $easing;
}

.switchCtl[aria-checked="true"] .knob {
  transform: translateX(18px);
}

.cards {
  display: flex;
  gap: $sp-3;
  width: 100%;
}

.card {
  flex: 1 1 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-1;
  padding: $sp-4 $sp-2;
  border-radius: $r-card;
  background: rgba($subject-cream, .08);
  text-align: center;
}

.card--mid {
  background: rgba($color, .30);
}

.planName {
  margin: 0;
  font-weight: 700;
  font-size: 13px;
  color: $subject-cream;
}

.price {
  margin: 0;
  display: flex;
  align-items: baseline;
}

.priceNum {
  font-weight: 700;
  font-size: 26px;
  color: $subject-cream;
}

.priceUnit {
  font-weight: 400;
  font-size: 11px;
  color: rgba($subject-cream, .72);
}

.badge {
  margin: 0;
  padding: $sp-1 $sp-2;
  border-radius: $r-xs;
  background: $subject-orange-deep;
  color: $subject-cream;
  font-weight: 700;
  font-size: 9px;
  opacity: 0;
  transform: scale(.6);
  transform-origin: center;
  transition: opacity $dur-quick $ease-out, transform $dur-quick $ease-pop;
}

.badge:not([hidden]) {
  opacity: 1;
  transform: scale(1);
}

@media (max-width: 340px) {
  .panel { max-width: 300px; gap: $sp-2; }
  .hint { font-size: 9px; }
  .cards { gap: $sp-1; }
  .card { padding: $sp-1 $sp-1; }
  .planName { font-size: 11px; }
  .priceNum { font-size: 17px; }
  .priceUnit { font-size: 9px; }
}

@media (prefers-reduced-motion: reduce) {
  .switchCtl,
  .knob,
  .badge {
    transition: none;
  }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.panel {
  width: 100%;
  max-width: 440px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.hint {
  margin: 0;
  padding: 0 8px;
  text-align: center;
  font-weight: 400;
  font-size: 11px;
  line-height: 1.4;
  color: rgba(255, 247, 230, 0.72);
}

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

.switchLabel {
  font-weight: 500;
  font-size: 12px;
  color: #fff7e6;
}

.switchCtl {
  position: relative;
  width: 40px;
  height: 22px;
  border: 0;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.24);
  padding: 0;
  cursor: pointer;
  transition: background 600ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.switchCtl[aria-checked=true] {
  background: #0a4fe8;
}

.knob {
  position: absolute;
  top: 2px;
  left: 2px;
  width: 18px;
  height: 18px;
  border-radius: 999px;
  background: #fff7e6;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  transform: translateX(0);
  transition: transform 600ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.switchCtl[aria-checked=true] .knob {
  transform: translateX(18px);
}

.cards {
  display: flex;
  gap: 12px;
  width: 100%;
}

.card {
  flex: 1 1 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 16px 8px;
  border-radius: 16px;
  background: rgba(255, 247, 230, 0.08);
  text-align: center;
}

.card--mid {
  background: rgba(10, 79, 232, 0.3);
}

.planName {
  margin: 0;
  font-weight: 700;
  font-size: 13px;
  color: #fff7e6;
}

.price {
  margin: 0;
  display: flex;
  align-items: baseline;
}

.priceNum {
  font-weight: 700;
  font-size: 26px;
  color: #fff7e6;
}

.priceUnit {
  font-weight: 400;
  font-size: 11px;
  color: rgba(255, 247, 230, 0.72);
}

.badge {
  margin: 0;
  padding: 4px 8px;
  border-radius: 4px;
  background: #c93000;
  color: #fff7e6;
  font-weight: 700;
  font-size: 9px;
  opacity: 0;
  transform: scale(0.6);
  transform-origin: center;
  transition: opacity 220ms ease-out, transform 220ms cubic-bezier(0.2, 1.4, 0.4, 1);
}

.badge:not([hidden]) {
  opacity: 1;
  transform: scale(1);
}

@media (max-width: 340px) {
  .panel {
    max-width: 300px;
    gap: 8px;
  }
  .hint {
    font-size: 9px;
  }
  .cards {
    gap: 4px;
  }
  .card {
    padding: 4px 4px;
  }
  .planName {
    font-size: 11px;
  }
  .priceNum {
    font-size: 17px;
  }
  .priceUnit {
    font-size: 9px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .switchCtl,
  .knob,
  .badge {
    transition: none;
  }
}

// 플랜 카드(01) — 연/월 스위치가 눌릴 때마다 플랜별 할인율(discount)을 monthly 가격에 적용해
// mo 환산가를 다시 구하고, 그 값을 rAF 로 이전 숫자에서 새 숫자까지 이징 계산하며 굴린다(계산 한 겹).
// 자동 시연은 스위치를 700ms 마다 반전시켜 세 카드가 매번 다시 계산되는 것을 보여준다.
(function () {
  var switchCtl = document.getElementById('billingSwitch');
  var cardsRow = document.getElementById('cardsRow');
  if (!switchCtl || !cardsRow) return;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var PLANS = [
    { monthly: 12, discount: .15 },
    { monthly: 29, discount: .20 },
    { monthly: 59, discount: .25 }
  ];
  var ROLL_MS = 600;

  function yearlyMonthlyEq(plan) {
    return Math.round(plan.monthly * (1 - plan.discount));
  }

  function animateValue(el, from, to, duration) {
    if (!el) return;
    if (reduce || from === to) { el.textContent = String(to); return; }
    var start = null;
    function step(ts) {
      if (start === null) start = ts;
      var p = Math.min((ts - start) / duration, 1);
      var eased = 1 - Math.pow(1 - p, 3);
      el.textContent = String(Math.round(from + (to - from) * eased));
      if (p < 1) requestAnimationFrame(step);
    }
    requestAnimationFrame(step);
  }

  var current = PLANS.map(function (p) { return p.monthly; });

  function render(yearly) {
    switchCtl.setAttribute('aria-checked', yearly ? 'true' : 'false');
    PLANS.forEach(function (plan, i) {
      var next = yearly ? yearlyMonthlyEq(plan) : plan.monthly;
      var numEl = document.getElementById('price' + i);
      var badgeEl = document.getElementById('badge' + i);
      animateValue(numEl, current[i], next, ROLL_MS);
      current[i] = next;
      if (badgeEl) {
        if (yearly) {
          badgeEl.hidden = false;
          badgeEl.textContent = Math.round(plan.discount * 100) + '% off now';
        } else {
          badgeEl.hidden = true;
        }
      }
    });
  }

  render(false);

  if (!reduce) {
    var yearly = false;
    setInterval(function () {
      yearly = !yearly;
      render(yearly);
    }, 700);
  }
})();

// PricingPlanCards — vanilla 판(run/339/demo/01-pricing-plan-cards/index.html) 의 React 포트.
// 연/월 스위치가 눌릴 때마다 플랜별 할인율을 monthly 가격에 적용해 월 환산가를 다시 구하고,
// 그 값을 rAF 로 이전 숫자에서 새 숫자까지 이징 계산하며 굴린다(계산 한 겹).
import { useEffect, useRef } from "react";
import styles from "./PricingPlanCards.module.scss";

export type PricingPlanCardsProps = {
  duration?: string;
  easing?: string;
  color?: string;
};

const HINT = "연·월 전환마다 할인율을 적용해 표시 가격을 다시 계산합니다";
const SWITCH_LABEL = "연간 결제";
const SWITCH_ARIA = "연간 결제로 전환";

type Plan = { name: string; monthly: number; discount: number };

const PLANS: Plan[] = [
  { name: "Basic", monthly: 12, discount: 0.15 },
  { name: "Pro", monthly: 29, discount: 0.2 },
  { name: "Team", monthly: 59, discount: 0.25 }
];

const ROLL_MS = 600;

function yearlyMonthlyEq(plan: Plan): number {
  return Math.round(plan.monthly * (1 - plan.discount));
}

export default function PricingPlanCards({
  duration = "600ms",
  easing = "cubic-bezier(.2,.8,.2,1)",
  color = "#0a4fe8"
}: PricingPlanCardsProps) {
  const switchRef = useRef<HTMLButtonElement | null>(null);
  const priceRefs = useRef<(HTMLSpanElement | null)[]>([]);
  const badgeRefs = useRef<(HTMLParagraphElement | null)[]>([]);

  useEffect(() => {
    const switchCtl = switchRef.current;
    if (!switchCtl) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    const current = PLANS.map((p) => p.monthly);

    function animateValue(el: HTMLElement | null, from: number, to: number, dur: number): void {
      if (!el) return;
      if (reduce || from === to) {
        el.textContent = String(to);
        return;
      }
      let start: number | null = null;
      function step(ts: number): void {
        if (start === null) start = ts;
        const p = Math.min((ts - start) / dur, 1);
        const eased = 1 - Math.pow(1 - p, 3);
        el!.textContent = String(Math.round(from + (to - from) * eased));
        if (p < 1) requestAnimationFrame(step);
      }
      requestAnimationFrame(step);
    }

    function render(yearly: boolean): void {
      switchCtl!.setAttribute("aria-checked", yearly ? "true" : "false");
      PLANS.forEach((plan, i) => {
        const next = yearly ? yearlyMonthlyEq(plan) : plan.monthly;
        const numEl = priceRefs.current![i];
        const badgeEl = badgeRefs.current![i];
        animateValue(numEl, current[i], next, ROLL_MS);
        current[i] = next;
        if (badgeEl) {
          if (yearly) {
            badgeEl.hidden = false;
            badgeEl.textContent = Math.round(plan.discount * 100) + "% 할인 중";
          } else {
            badgeEl.hidden = true;
          }
        }
      });
    }

    render(false);

    let timer = 0;
    if (!reduce) {
      let yearly = false;
      timer = window.setInterval(() => {
        yearly = !yearly;
        render(yearly);
      }, 700);
    }

    return () => {
      if (timer) window.clearInterval(timer);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <main className={styles.stage}>
      <section className={styles.panel}>
        <p className={styles.hint}>{HINT}</p>
        <div className={styles.switchRow}>
          <span className={styles.switchLabel}>{SWITCH_LABEL}</span>
          <button
            className={styles.switchCtl}
            ref={switchRef}
            type="button"
            role="switch"
            aria-checked="false"
            aria-label={SWITCH_ARIA}
          >
            <span className={styles.knob} aria-hidden="true" />
          </button>
        </div>
        <div className={styles.cards}>
          {PLANS.map((plan, i) => (
            <article key={plan.name} className={i === 1 ? styles.card + " " + styles.cardMid : styles.card}>
              <h3 className={styles.planName}>{plan.name}</h3>
              <p className={styles.price}>
                <span
                  className={styles.priceNum}
                  ref={(el: HTMLSpanElement | null) => {
                    priceRefs.current![i] = el;
                  }}
                >
                  {plan.monthly}
                </span>
                <span className={styles.priceUnit}> / 월</span>
              </p>
              <p
                className={styles.badge}
                hidden
                ref={(el: HTMLParagraphElement | null) => {
                  badgeRefs.current![i] = el;
                }}
              />
            </article>
          ))}
        </div>
      </section>
    </main>
  );
}