09Reduced-motion instant update — under a reduced-motion setting, the value jumps straight to its next state with no movement

<main class="stage">
<div class="arm is-demo" id="arm">
  <div class="arm__panel">
    <span class="arm__tag">Normal motion</span>
    <span class="arm__count" id="armCountA">5</span>
  </div>
  <div class="arm__panel">
    <span class="arm__tag">Reduced motion</span>
    <span class="arm__count arm__count--static" id="armCountB">5</span>
  </div>
</div>
</main>

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

// 계산 겹: 일반 판은 감쇠 사인 흔들림, 모션 감소 판은 같은 값을 트윈 없이 즉시 반영 — index.html 참조
@include stage($stage-paper);

.arm {
  display: flex;
  gap: $sp-6;
  cursor: pointer;
}

.arm__panel {
  display: grid;
  justify-items: center;
  gap: $sp-2;
  padding: $sp-5 $sp-6;
  border-radius: $r-card;
  background: $subject-cream;
}

.arm__tag {
  font: 600 11px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: rgba($stage-ink, .6);
  text-transform: uppercase;
  letter-spacing: .04em;
}

.arm__count {
  font: 800 40px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: $stage-ink;
  font-variant-numeric: tabular-nums;
}

@media (max-width: 340px) {
  .arm { gap: $sp-3; }
  .arm__panel { padding: $sp-3 $sp-4; }
  .arm__count { font-size: 28px; }
}

@media (prefers-reduced-motion: reduce) {
  // 모션 감소 판의 값 갱신은 원래 트윈이 없다 — OS 설정이 켜지면 일반 판도 흔들림 계산을 건너뛴다(index.html)
  .arm__count { transition: none; }
}

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);
}

.arm {
  display: flex;
  gap: 24px;
  cursor: pointer;
}

.arm__panel {
  display: grid;
  justify-items: center;
  gap: 8px;
  padding: 20px 24px;
  border-radius: 16px;
  background: #fff7e6;
}

.arm__tag {
  font: 600 11px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: rgba(23, 20, 26, 0.6);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.arm__count {
  font: 800 40px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: #17141a;
  font-variant-numeric: tabular-nums;
}

@media (max-width: 340px) {
  .arm {
    gap: 12px;
  }
  .arm__panel {
    padding: 12px 16px;
  }
  .arm__count {
    font-size: 28px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .arm__count {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('arm');
  var a = document.getElementById('armCountA');
  var b = document.getElementById('armCountB');

  // 상수: 최대 시도 횟수 · Normal motion 흔들림 진폭·지속시간
  var MAX_TRIES = 5;
  var AMP = 6;
  var SHAKE_MS = 300;

  var remaining = MAX_TRIES;

  // 계산 겹: 일반 판은 감쇠 사인으로 흔들며 값을 바꾸고, Reduced motion 판은 같은 값을 애니메이션 없이 즉시 반영한다
  function shakeA() {
    var start = null;
    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 * 3) * (1 - t);
      a.style.transform = 'translateX(' + x.toFixed(2) + 'px)';
      if (t < 1) requestAnimationFrame(frame);
      else a.style.transform = 'translateX(0)';
    }
    requestAnimationFrame(frame);
  }

  function step() {
    remaining = remaining > 0 ? remaining - 1 : MAX_TRIES;
    a.textContent = String(remaining);
    shakeA();
    // Reduced motion 판: 같은 값이 트윈 없이 그 자리에서 바로 바뀐다
    b.textContent = String(remaining);
  }

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

  var autoTimer = null;
  function stopAutoplay() { if (autoTimer) { clearInterval(autoTimer); autoTimer = null; } }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) { autoTimer = setInterval(step, 420); }
  else { autoTimer = setInterval(function () { remaining = remaining > 0 ? remaining - 1 : MAX_TRIES; a.textContent = b.textContent = String(remaining); }, 420); }
})();

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

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

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

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

    // 상수: 최대 시도 횟수 · 일반 모션 흔들림 진폭·지속시간
    const MAX_TRIES = 5;
    const AMP = 6;
    const SHAKE_MS = 300;

    let remaining = MAX_TRIES;

    // 계산 겹: 일반 판은 감쇠 사인으로 흔들며 값을 바꾸고, 모션 감소 판은 같은 값을 애니메이션 없이 즉시 반영한다
    function shakeA() {
      let start: number | null = null;
      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 * 3) * (1 - t);
        a!.style.transform = "translateX(" + x.toFixed(2) + "px)";
        if (t < 1) requestAnimationFrame(frame);
        else a!.style.transform = "translateX(0)";
      }
      requestAnimationFrame(frame);
    }

    function step() {
      remaining = remaining > 0 ? remaining - 1 : MAX_TRIES;
      a!.textContent = String(remaining);
      shakeA();
      // 모션 감소 판: 같은 값이 트윈 없이 그 자리에서 바로 바뀐다
      b!.textContent = String(remaining);
    }

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

    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(step, 420);
    } else {
      autoTimer = window.setInterval(() => {
        remaining = remaining > 0 ? remaining - 1 : MAX_TRIES;
        a!.textContent = b!.textContent = String(remaining);
      }, 420);
    }

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

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.arm} ${styles["is-demo"]}`}>
      <div className={styles.panel}>
        <span className={styles.tag}>일반 모션</span>
        <span className={`${styles.count} ${styles.a}`}>5</span>
      </div>
      <div className={styles.panel}>
        <span className={styles.tag}>모션 감소</span>
        <span className={`${styles.count} ${styles["count--static"]} ${styles.b}`}>5</span>
      </div>
    </div>
  );
}