03Security-code focus value toggle — when the security-code field's focus value turns on, the view switches to a value showing the card's back

<main class="stage">
<div class="cv is-demo" id="cv">
  <div class="cv__scene">
    <div class="cv__card" id="cvCard">
      <div class="cv__face cv__face--front">
        <span class="cv__chipIcon"></span>
        <span class="cv__num">9999 99•• •••• 9995</span>
        <span class="cv__exp">12/29</span>
      </div>
      <div class="cv__face cv__face--back">
        <span class="cv__strip"></span>
        <span class="cv__cvcRow"><span class="cv__cvcBox" id="cvBox">•••</span></span>
      </div>
    </div>
  </div>
  <label class="cv__field">
    <input class="cv__input" id="cvInput" type="text" inputmode="numeric" autocomplete="off" spellcheck="false" maxlength="3" placeholder="CVC">
  </label>
</div>
</main>

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

// 계산 겹: 초점 값 on/off → 3D 회전 각 값이 스프링 곡선을 타고 넘겼다가 정착한다(index.html).
@include stage($stage-orange);

.cv {
  width: 100%;
  max-width: 300px;
  display: grid;
  gap: $sp-4;
  justify-items: center;
}

.cv__scene {
  width: 220px;
  height: 132px;
  perspective: 800px;
}

.cv__card {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transform: rotateY(0deg);
  transition: transform $dur-enter $ease-lerp-settle;
}

.cv__card--flipped { transform: rotateY(180deg); }

.cv__face {
  position: absolute;
  inset: 0;
  box-sizing: border-box;
  border-radius: $r-card;
  backface-visibility: hidden;
  padding: $sp-4;
  display: grid;
  color: $subject-cream;
}

.cv__face--front {
  background: $subject-ink;
  align-content: space-between;
}

.cv__face--back {
  background: $subject-ink;
  transform: rotateY(180deg);
  align-content: start;
  gap: $sp-3;
}

.cv__chipIcon {
  width: 28px;
  height: 20px;
  border-radius: $r-xs;
  background: rgba($subject-cream, .7);
}

.cv__num {
  font-family: "SFMono-Regular", Consolas, monospace;
  font-weight: 600;
  font-size: 15px;
  letter-spacing: .05em;
}

.cv__exp {
  font-family: "SFMono-Regular", Consolas, monospace;
  font-weight: 600;
  font-size: 12px;
  color: rgba($subject-cream, .7);
}

.cv__strip {
  display: block;
  width: 100%;
  height: 28px;
  margin-top: $sp-2;
  background: rgba(0, 0, 0, .55);
  border-radius: $r-xs;
}

.cv__cvcRow { display: flex; justify-content: flex-end; }

.cv__cvcBox {
  min-width: 44px;
  box-sizing: border-box;
  padding: $sp-1 $sp-2;
  border-radius: $r-xs;
  background: $subject-cream;
  color: $subject-ink;
  font-family: "SFMono-Regular", Consolas, monospace;
  font-weight: 700;
  font-size: 13px;
  text-align: center;
}

.cv__field { width: 100%; max-width: 160px; }

.cv__input {
  width: 100%;
  box-sizing: border-box;
  padding: $sp-2 $sp-3;
  border-radius: $r-sm;
  border: 0;
  background: $subject-cream;
  color: $subject-ink;
  font-weight: 600;
  font-size: 14px;
  text-align: center;

  &::placeholder { color: rgba($subject-ink, .45); }
  &:focus, &.cv__input--focus { outline: 2px solid $subject-ink; outline-offset: 2px; }
}

@media (max-width: 340px) {
  .cv__scene { width: 190px; height: 114px; }
}

@media (prefers-reduced-motion: reduce) {
  .cv__card { transition: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.cv {
  width: 100%;
  max-width: 300px;
  display: grid;
  gap: 16px;
  justify-items: center;
}

.cv__scene {
  width: 220px;
  height: 132px;
  perspective: 800px;
}

.cv__card {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transform: rotateY(0deg);
  transition: transform 600ms linear(0, 0.051, 0.176, 0.341, 0.518, 0.685, 0.831, 0.947, 1.032, 1.087, 1.117, 1.126, 1.121, 1.105, 1.085, 1.062, 1.041, 1.022, 1.008, 0.997, 1);
}

.cv__card--flipped {
  transform: rotateY(180deg);
}

.cv__face {
  position: absolute;
  inset: 0;
  box-sizing: border-box;
  border-radius: 16px;
  backface-visibility: hidden;
  padding: 16px;
  display: grid;
  color: #fff7e6;
}

.cv__face--front {
  background: #17141a;
  align-content: space-between;
}

.cv__face--back {
  background: #17141a;
  transform: rotateY(180deg);
  align-content: start;
  gap: 12px;
}

.cv__chipIcon {
  width: 28px;
  height: 20px;
  border-radius: 4px;
  background: rgba(255, 247, 230, 0.7);
}

.cv__num {
  font-family: "SFMono-Regular", Consolas, monospace;
  font-weight: 600;
  font-size: 15px;
  letter-spacing: 0.05em;
}

.cv__exp {
  font-family: "SFMono-Regular", Consolas, monospace;
  font-weight: 600;
  font-size: 12px;
  color: rgba(255, 247, 230, 0.7);
}

.cv__strip {
  display: block;
  width: 100%;
  height: 28px;
  margin-top: 8px;
  background: rgba(0, 0, 0, 0.55);
  border-radius: 4px;
}

.cv__cvcRow {
  display: flex;
  justify-content: flex-end;
}

.cv__cvcBox {
  min-width: 44px;
  box-sizing: border-box;
  padding: 4px 8px;
  border-radius: 4px;
  background: #fff7e6;
  color: #17141a;
  font-family: "SFMono-Regular", Consolas, monospace;
  font-weight: 700;
  font-size: 13px;
  text-align: center;
}

.cv__field {
  width: 100%;
  max-width: 160px;
}

.cv__input {
  width: 100%;
  box-sizing: border-box;
  padding: 8px 12px;
  border-radius: 8px;
  border: 0;
  background: #fff7e6;
  color: #17141a;
  font-weight: 600;
  font-size: 14px;
  text-align: center;
}
.cv__input::placeholder {
  color: rgba(23, 20, 26, 0.45);
}
.cv__input:focus, .cv__input.cv__input--focus {
  outline: 2px solid #17141a;
  outline-offset: 2px;
}

@media (max-width: 340px) {
  .cv__scene {
    width: 190px;
    height: 114px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .cv__card {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('cv');
  var input = document.getElementById('cvInput');
  var card = document.getElementById('cvCard');
  var box = document.getElementById('cvBox');

  // 계산 겹: 초점 값 on/off 에 따라 카드의 3D 회전 각 값이 스프링 곡선($ease-lerp-settle)을
  // 타고 180deg 를 넘겼다가 되돌아와 정착한다 — 등속 회전이 아니라 관성 있는 회전.
  function setFlipped(on) { card.classList.toggle('cv__card--flipped', on); }

  input.addEventListener('focus', function () { root.classList.remove('is-demo'); stopAutoplay(); setFlipped(true); });
  input.addEventListener('blur', function () { setFlipped(false); });
  input.addEventListener('input', function () {
    box.textContent = (input.value.replace(/\D/g, '').slice(0, 3) || '').padEnd(3, '•');
  });

  // 자동 루프: 초점 on/off 를 시드 간격으로 오간다.
  var SEQ = [true, true, false, false];
  var si = 0;
  var autoTimer = null;
  function autoTick() {
    var on = SEQ[si];
    setFlipped(on);
    input.classList.toggle('cv__input--focus', on);
    si = (si + 1) % SEQ.length;
  }
  function stopAutoplay() { if (autoTimer) { clearInterval(autoTimer); autoTimer = null; } }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) { autoTimer = setInterval(autoTick, 900); autoTick(); }
})();

import { useEffect, useRef } from "react";
import styles from "./CvcFlipReveal.module.scss";

type Box<T> = { current: T };

export default function CvcFlipReveal() {
  const rootRef = useRef(null) as unknown as Box<HTMLDivElement | null>;

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const input = root.querySelector(`.${styles.input}`) as HTMLInputElement | null;
    const card = root.querySelector(`.${styles.card}`) as HTMLElement | null;
    const box = root.querySelector(`.${styles.cvcBox}`) as HTMLElement | null;
    if (!input || !card || !box) return;

    // 계산 겹: 초점 값 on/off 에 따라 카드의 3D 회전 각 값이 스프링 곡선($ease-lerp-settle)을
    // 타고 180deg 를 넘겼다가 되돌아와 정착한다 — 등속 회전이 아니라 관성 있는 회전.
    function setFlipped(on: boolean) { card!.classList.toggle(styles["card--flipped"], on); }

    function onFocus() { root!.classList.remove(styles["is-demo"]); stopAutoplay(); setFlipped(true); }
    function onBlur() { setFlipped(false); }
    function onInput() {
      box!.textContent = (input!.value.replace(/\D/g, "").slice(0, 3) || "").padEnd(3, "•");
    }
    input.addEventListener("focus", onFocus);
    input.addEventListener("blur", onBlur);
    input.addEventListener("input", onInput);

    // 자동 루프: 초점 on/off 를 시드 간격으로 오간다.
    const SEQ = [true, true, false, false];
    let si = 0;
    let autoTimer: number | null = null;
    function autoTick() {
      const on = SEQ[si];
      setFlipped(on);
      input!.classList.toggle(styles["input--focus"], on);
      si = (si + 1) % SEQ.length;
    }
    function stopAutoplay() {
      if (autoTimer !== null) { window.clearInterval(autoTimer); autoTimer = null; }
    }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (!reduce) { autoTimer = window.setInterval(autoTick, 900); autoTick(); }

    return () => {
      stopAutoplay();
      input.removeEventListener("focus", onFocus);
      input.removeEventListener("blur", onBlur);
      input.removeEventListener("input", onInput);
    };
  }, []);

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.cv} ${styles["is-demo"]}`}>
      <div className={styles.scene}>
        <div className={styles.card}>
          <div className={`${styles.face} ${styles["face--front"]}`}>
            <span className={styles.chipIcon} />
            <span className={styles.num}>9999 99•• •••• 9995</span>
            <span className={styles.exp}>12/29</span>
          </div>
          <div className={`${styles.face} ${styles["face--back"]}`}>
            <span className={styles.strip} />
            <span className={styles.cvcRow}><span className={styles.cvcBox}>•••</span></span>
          </div>
        </div>
      </div>
      <label className={styles.field}>
        <input className={styles.input} type="text" inputMode="numeric" autoComplete="off" spellCheck={false} maxLength={3} placeholder="CVC" />
      </label>
    </div>
  );
}