01残り試行回数の揺れ — ログインに失敗するたびに残り試行回数の値が減り、数字が一瞬揺れる方式

<main class="stage">
<div class="acs is-demo" id="acs">
  <div class="acs__card">
    <div class="acs__row">
      <label class="acs__field"><input class="acs__input" id="acsUser" type="text" placeholder="ID" autocomplete="off" spellcheck="false"></label>
      <label class="acs__field"><input class="acs__input acs__input--pw" id="acsPass" type="text" placeholder="パスワード" autocomplete="off" spellcheck="false"></label>
    </div>
    <button class="acs__btn" id="acsBtn" type="button">ログイン</button>
    <div class="acs__readout">
      <span class="acs__label">残り試行</span>
      <span class="acs__count" id="acsCount">5</span>
    </div>
  </div>
</div>
</main>

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

// 계산 겹: 흔들림 진폭 = 기준값 + (최대시도 − 남은시도)×증가폭, 감쇠 사인 곡선(index.html 참조)
@include stage($stage-yellow);

.acs {
  width: 100%;
  max-width: 300px;
  display: grid;
  gap: $sp-3;
}

.acs__card {
  display: grid;
  gap: $sp-3;
}

.acs__row {
  display: grid;
  gap: $sp-2;
}

.acs__field { display: block; }

.acs__input {
  width: 100%;
  box-sizing: border-box;
  padding: $sp-2 $sp-3;
  border-radius: $r-sm;
  border: 0;
  background: rgba($stage-ink, .08);
  color: $stage-ink;
  font: 500 14px/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;

  &::placeholder { color: rgba($stage-ink, .48); }
  &:focus { outline: 2px solid $stage-ink; outline-offset: 2px; }
}

.acs__input--pw { -webkit-text-security: disc; }

.acs__btn {
  border: 0;
  border-radius: $r-control;
  padding: $sp-2 $sp-4;
  background: $stage-ink;
  color: $subject-cream;
  font: 700 14px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  cursor: pointer;
  transition: transform $dur-instant $ease-out;

  &:active { transform: scale(.96); }
}

.acs__readout {
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: $sp-2;
}

.acs__label {
  font: 500 12px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: rgba($stage-ink, .64);
}

.acs__count {
  display: inline-block;
  font: 800 28px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: $stage-ink;
  font-variant-numeric: tabular-nums;
}

.acs__count--low { color: $error; }

@media (max-width: 340px) {
  .acs { max-width: 220px; }
  .acs__count { font-size: 22px; }
}

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

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.acs {
  width: 100%;
  max-width: 300px;
  display: grid;
  gap: 12px;
}

.acs__card {
  display: grid;
  gap: 12px;
}

.acs__row {
  display: grid;
  gap: 8px;
}

.acs__field {
  display: block;
}

.acs__input {
  width: 100%;
  box-sizing: border-box;
  padding: 8px 12px;
  border-radius: 8px;
  border: 0;
  background: rgba(23, 20, 26, 0.08);
  color: #17141a;
  font: 500 14px/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}
.acs__input::placeholder {
  color: rgba(23, 20, 26, 0.48);
}
.acs__input:focus {
  outline: 2px solid #17141a;
  outline-offset: 2px;
}

.acs__input--pw {
  -webkit-text-security: disc;
}

.acs__btn {
  border: 0;
  border-radius: 12px;
  padding: 8px 16px;
  background: #17141a;
  color: #fff7e6;
  font: 700 14px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  cursor: pointer;
  transition: transform 140ms ease-out;
}
.acs__btn:active {
  transform: scale(0.96);
}

.acs__readout {
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: 8px;
}

.acs__label {
  font: 500 12px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: rgba(23, 20, 26, 0.64);
}

.acs__count {
  display: inline-block;
  font: 800 28px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: #17141a;
  font-variant-numeric: tabular-nums;
}

.acs__count--low {
  color: #c2361a;
}

@media (max-width: 340px) {
  .acs {
    max-width: 220px;
  }
  .acs__count {
    font-size: 22px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .acs__btn {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('acs');
  var btn = document.getElementById('acsBtn');
  var countEl = document.getElementById('acsCount');

  // 상수: 최대 시도 횟수·흔들림 진폭 기준값·진폭 증가폭·흔들림 지속시간·진동 횟수
  var MAX_TRIES = 5;
  var AMP_BASE = 3;   // px — 첫 失敗 때 흔들림 폭
  var AMP_STEP = 2;   // px — 남은 횟수가 줄 때마다 늘어나는 폭
  var SHAKE_MS = 480;
  var SHAKE_FREQ = 4; // 진동 횟수

  var remaining = MAX_TRIES;
  var shaking = false;

  function paint() {
    countEl.textContent = String(remaining);
    countEl.classList.toggle('acs__count--low', remaining <= 1);
  }

  // 계산 겹: 진폭 = 기준값 + (최대-남은)×증가폭, 감쇠 사인 = sin(t·2π·진동수)×(1-t)
  function shake() {
    var amp = AMP_BASE + (MAX_TRIES - remaining) * AMP_STEP;
    var start = null;
    shaking = true;
    function frame(ts) {
      if (start === null) start = ts;
      var t = Math.min(1, (ts - start) / SHAKE_MS);
      var x = amp * Math.sin(t * Math.PI * 2 * SHAKE_FREQ) * (1 - t);
      countEl.style.transform = 'translateX(' + x.toFixed(2) + 'px)';
      if (t < 1) requestAnimationFrame(frame);
      else { countEl.style.transform = 'translateX(0)'; shaking = false; }
    }
    requestAnimationFrame(frame);
  }

  function fail() {
    if (shaking) return;
    remaining = remaining > 0 ? remaining - 1 : MAX_TRIES;
    paint();
    shake();
  }

  btn.addEventListener('click', function () {
    root.classList.remove('is-demo');
    stopAutoplay();
    fail();
  });
  paint();

  var autoTimer = null;
  function stopAutoplay() { if (autoTimer) { clearInterval(autoTimer); autoTimer = null; } }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) { autoTimer = setInterval(fail, 420); }
})();

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

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

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

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const btn = root.querySelector(`.${styles.btn}`) as HTMLButtonElement | null;
    const countEl = root.querySelector(`.${styles.count}`) as HTMLElement | null;
    if (!btn || !countEl) return;

    // 상수: 최대 시도 횟수·흔들림 진폭 기준값·진폭 증가폭·흔들림 지속시간·진동 횟수
    const MAX_TRIES = 5;
    const AMP_BASE = 3;
    const AMP_STEP = 2;
    const SHAKE_MS = 480;
    const SHAKE_FREQ = 4;

    let remaining = MAX_TRIES;
    let shaking = false;

    function paint() {
      countEl!.textContent = String(remaining);
      countEl!.classList.toggle(styles["count--low"], remaining <= 1);
    }

    // 계산 겹: 진폭 = 기준값 + (최대-남은)×증가폭, 감쇠 사인 = sin(t·2π·진동수)×(1-t)
    function shake() {
      const amp = AMP_BASE + (MAX_TRIES - remaining) * AMP_STEP;
      let start: number | null = null;
      shaking = true;
      function frame(ts: number) {
        if (start === null) start = ts;
        const t = Math.min(1, (ts - start) / SHAKE_MS);
        const x = amp * Math.sin(t * Math.PI * 2 * SHAKE_FREQ) * (1 - t);
        countEl!.style.transform = "translateX(" + x.toFixed(2) + "px)";
        if (t < 1) requestAnimationFrame(frame);
        else { countEl!.style.transform = "translateX(0)"; shaking = false; }
      }
      requestAnimationFrame(frame);
    }

    function fail() {
      if (shaking) return;
      remaining = remaining > 0 ? remaining - 1 : MAX_TRIES;
      paint();
      shake();
    }

    function onClick() {
      root!.classList.remove(styles["is-demo"]);
      stopAutoplay();
      fail();
    }
    btn.addEventListener("click", onClick);
    paint();

    let autoTimer: number | null = null;
    function stopAutoplay() { if (autoTimer !== null) { window.clearInterval(autoTimer); autoTimer = null; } }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (!reduce) { autoTimer = window.setInterval(fail, 420); }

    return () => {
      stopAutoplay();
      btn.removeEventListener("click", onClick);
    };
  }, []);

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.acs} ${styles["is-demo"]}`}>
      <div className={styles.card}>
        <div className={styles.row}>
          <label className={styles.field}>
            <input className={styles.input} type="text" placeholder="아이디" autoComplete="off" spellCheck={false} />
          </label>
          <label className={styles.field}>
            <input className={`${styles.input} ${styles["input--pw"]}`} type="text" placeholder="비밀번호" autoComplete="off" spellCheck={false} />
          </label>
        </div>
        <button className={styles.btn} type="button">로그인</button>
        <div className={styles.readout}>
          <span className={styles.label}>남은 시도</span>
          <span className={styles.count}>5</span>
        </div>
      </div>
    </div>
  );
}