07Required-error shake toggle — when a submit attempt hits an empty required box, its horizontal-position value shakes briefly side to side

<main class="stage">
<div class="cbe is-demo" id="cbe">
  <label class="cbe__row" id="cbeRow">
    <input type="checkbox" class="cbe__input" id="cbeInput" required>
    <span class="cbe__box" id="cbeBox" aria-hidden="true">
      <svg viewBox="0 0 20 20" width="14" height="14"><path d="M4 10.5l3.5 3.5L16 5.5" fill="none" stroke="currentColor" stroke-width="2.6" stroke-linecap="round" stroke-linejoin="round"/></svg>
    </span>
    <span class="cbe__text">I agree to the required terms</span>
  </label>
  <p class="cbe__hint" id="cbeHint">Check this box to continue</p>
  <button type="button" class="cbe__submit" id="cbeSubmit">Submit</button>
</div>
</main>

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

// 계산 겹: index.html shakeOffset() 이 감쇠 사인 진동(exp(-ZETA·t)·sin(FREQ·t))을 직접 계산해
// translateX 값으로 삼는다 — 트윈 하나로 끝내지 않고 매 프레임 진폭이 줄어드는 물리량을 적분한다.
@include stage($stage-paper);

.cbe {
  display: grid;
  gap: $sp-3;
  width: 100%;
  max-width: 260px;
}

.cbe__row {
  display: flex;
  align-items: center;
  gap: $sp-3;
  padding: $sp-3;
  border-radius: $r-sm;
  border: 2px solid transparent;
  cursor: pointer;
  user-select: none;
  transition: border-color $dur-quick $ease-out, background-color $dur-quick $ease-out;
}

.cbe__row--error {
  border-color: $error;
  background: $error-soft;
}

.cbe__input {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
  pointer-events: none;
}

.cbe__box {
  flex: 0 0 auto;
  width: 22px;
  height: 22px;
  border-radius: $r-sm;
  border: 2px solid rgba($subject-ink, .32);
  color: $subject-cream;
  display: grid;
  place-items: center;
  box-sizing: border-box;
  transition: background-color $dur-quick $ease-out, border-color $dur-quick $ease-out;

  svg { opacity: 0; transition: opacity $dur-quick $ease-out; }
}

.cbe__input:checked + .cbe__box {
  background: $subject-blue;
  border-color: $subject-blue;

  svg { opacity: 1; }
}

.cbe__input:focus-visible + .cbe__box {
  outline: 2px solid $subject-blue-light;
  outline-offset: 2px;
}

.cbe__text {
  color: $subject-ink;
  font-size: 14px;
  font-weight: 600;
}

.cbe__hint {
  margin: 0;
  padding-left: $sp-3;
  color: rgba($subject-ink, .55);
  font-size: 12px;
  transition: color $dur-quick $ease-out, opacity $dur-quick $ease-out;
}

.cbe__hint--error {
  color: $error;
  opacity: 1;
}

.cbe__submit {
  justify-self: start;
  padding: $sp-2 $sp-5;
  border: none;
  border-radius: $r-sm;
  background: $subject-blue-deep;
  color: $subject-cream;
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
}

@media (max-width: 340px) {
  .cbe { max-width: 100%; }
  .cbe__text { font-size: 13px; }
}

@media (prefers-reduced-motion: reduce) {
  .cbe__row, .cbe__box, .cbe__box svg, .cbe__hint { 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);
}

.cbe {
  display: grid;
  gap: 12px;
  width: 100%;
  max-width: 260px;
}

.cbe__row {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px;
  border-radius: 8px;
  border: 2px solid transparent;
  cursor: pointer;
  user-select: none;
  transition: border-color 220ms ease-out, background-color 220ms ease-out;
}

.cbe__row--error {
  border-color: #c2361a;
  background: #ffe0d8;
}

.cbe__input {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
  pointer-events: none;
}

.cbe__box {
  flex: 0 0 auto;
  width: 22px;
  height: 22px;
  border-radius: 8px;
  border: 2px solid rgba(23, 20, 26, 0.32);
  color: #fff7e6;
  display: grid;
  place-items: center;
  box-sizing: border-box;
  transition: background-color 220ms ease-out, border-color 220ms ease-out;
}
.cbe__box svg {
  opacity: 0;
  transition: opacity 220ms ease-out;
}

.cbe__input:checked + .cbe__box {
  background: #2f6df6;
  border-color: #2f6df6;
}
.cbe__input:checked + .cbe__box svg {
  opacity: 1;
}

.cbe__input:focus-visible + .cbe__box {
  outline: 2px solid #5b8cf8;
  outline-offset: 2px;
}

.cbe__text {
  color: #17141a;
  font-size: 14px;
  font-weight: 600;
}

.cbe__hint {
  margin: 0;
  padding-left: 12px;
  color: rgba(23, 20, 26, 0.55);
  font-size: 12px;
  transition: color 220ms ease-out, opacity 220ms ease-out;
}

.cbe__hint--error {
  color: #c2361a;
  opacity: 1;
}

.cbe__submit {
  justify-self: start;
  padding: 8px 20px;
  border: none;
  border-radius: 8px;
  background: #0a4fe8;
  color: #fff7e6;
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
}

@media (max-width: 340px) {
  .cbe {
    max-width: 100%;
  }
  .cbe__text {
    font-size: 13px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .cbe__row, .cbe__box, .cbe__box svg, .cbe__hint {
    transition: none;
  }
}

(function () {
  var SHAKE_MS = 420; // 계산 겹 상수: 흔들림 감쇠가 끝나는 데 걸리는 실제 시간(ms)
  var SHAKE_FREQ = 2 * Math.PI * 5 / SHAKE_MS; // 흔들림 진동 주파수
  var SHAKE_ZETA = 4.2; // 감쇠 계수
  var SHAKE_AMP = 8; // px, 최대 흔들림 폭
  var CYCLE_MS = 480;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var root = document.getElementById('cbe');
  var input = document.getElementById('cbeInput');
  var box = document.getElementById('cbeBox');
  var row = document.getElementById('cbeRow');
  var hint = document.getElementById('cbeHint');
  var submit = document.getElementById('cbeSubmit');

  var isDemo = true;
  var shaking = false, shakeStart = 0;

  function human() {
    if (isDemo) { root.classList.remove('is-demo'); isDemo = false; }
  }

  function shakeOffset(t) {
    // 계산 겹: 감쇠 사인 진동 — 시간이 지날수록 진폭이 줄어드는 흔들림 값을 직접 계산
    var amp = Math.exp(-SHAKE_ZETA * (t / SHAKE_MS));
    return SHAKE_AMP * amp * Math.sin(SHAKE_FREQ * t);
  }

  function triggerError() {
    row.classList.add('cbe__row--error');
    hint.classList.add('cbe__hint--error');
    shakeStart = performance.now();
    shaking = true;
  }

  function clearError() {
    row.classList.remove('cbe__row--error');
    hint.classList.remove('cbe__hint--error');
  }

  input.addEventListener('change', function () {
    human();
    if (input.checked) clearError();
  });

  submit.addEventListener('click', function () {
    human();
    if (!input.checked) { triggerError(); } else { clearError(); }
  });

  var cycleStart = 0;
  var lastStep = -1;

  function loop(ts) {
    if (!cycleStart) cycleStart = ts;

    if (isDemo) {
      var step = Math.floor((ts - cycleStart) / CYCLE_MS) % 3;
      if (step !== lastStep) {
        lastStep = step;
        if (step === 0) { input.checked = false; clearError(); }
        else if (step === 1) { triggerError(); }
        else { input.checked = true; clearError(); }
      }
    }

    if (shaking) {
      var t = ts - shakeStart;
      if (t >= SHAKE_MS) {
        shaking = false;
        row.style.transform = '';
      } else {
        row.style.transform = 'translateX(' + shakeOffset(t).toFixed(2) + 'px)';
      }
    }

    requestAnimationFrame(loop);
  }

  if (reduce) { SHAKE_MS = 1; }
  requestAnimationFrame(loop);
})();

// ErrorShakeRequired — vanilla 판(run/368/demo/07-custom-checkbox-error-shake-required/index.html)
// 의 React 포트. 감쇠 사인 진동(exp(-SHAKE_ZETA·t)·sin(SHAKE_FREQ·t))을 직접 계산해 translateX
// 값으로 삼는다 — 트윈 하나로 끝내지 않고 매 프레임 진폭이 줄어드는 물리량을 적분한다.
import { useEffect, useRef } from "react";
import styles from "./ErrorShakeRequired.module.scss";

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

export default function ErrorShakeRequired() {
  const rootRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const inputRef = useRef(null) as unknown as Box<HTMLInputElement>;
  const rowRef = useRef(null) as unknown as Box<HTMLLabelElement>;
  const hintRef = useRef(null) as unknown as Box<HTMLParagraphElement>;
  const submitRef = useRef(null) as unknown as Box<HTMLButtonElement>;
  const rafRef = useRef(0) as unknown as Box<number>;

  useEffect(() => {
    let SHAKE_MS = 420; // 계산 겹 상수: 흔들림 감쇠가 끝나는 데 걸리는 실제 시간(ms)
    const SHAKE_FREQ = (2 * Math.PI * 5) / SHAKE_MS; // 흔들림 진동 주파수
    const SHAKE_ZETA = 4.2; // 감쇠 계수
    const SHAKE_AMP = 8; // px, 최대 흔들림 폭
    const CYCLE_MS = 480;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

    const root = rootRef.current;
    const input = inputRef.current;
    const row = rowRef.current;
    const hint = hintRef.current;
    const submit = submitRef.current;
    if (!root || !input || !row || !hint || !submit) return;

    let isDemo = true;
    let shaking = false, shakeStart = 0;

    function human() {
      if (isDemo) { root!.classList.remove(styles.isDemo); isDemo = false; }
    }

    function shakeOffset(t: number) {
      // 계산 겹: 감쇠 사인 진동 — 시간이 지날수록 진폭이 줄어드는 흔들림 값을 직접 계산
      const amp = Math.exp(-SHAKE_ZETA * (t / SHAKE_MS));
      return SHAKE_AMP * amp * Math.sin(SHAKE_FREQ * t);
    }

    function triggerError() {
      row!.classList.add(styles.rowError);
      hint!.classList.add(styles.hintError);
      shakeStart = performance.now();
      shaking = true;
    }

    function clearError() {
      row!.classList.remove(styles.rowError);
      hint!.classList.remove(styles.hintError);
    }

    function onInputChange() { human(); if (input!.checked) clearError(); }
    input.addEventListener("change", onInputChange);

    function onSubmitClick() {
      human();
      if (!input!.checked) { triggerError(); } else { clearError(); }
    }
    submit.addEventListener("click", onSubmitClick);

    let cycleStart = 0;
    let lastStep = -1;

    function loop(ts: number) {
      if (!cycleStart) cycleStart = ts;

      if (isDemo) {
        const step = Math.floor((ts - cycleStart) / CYCLE_MS) % 3;
        if (step !== lastStep) {
          lastStep = step;
          if (step === 0) { input!.checked = false; clearError(); }
          else if (step === 1) { triggerError(); }
          else { input!.checked = true; clearError(); }
        }
      }

      if (shaking) {
        const t = ts - shakeStart;
        if (t >= SHAKE_MS) {
          shaking = false;
          row!.style.transform = "";
        } else {
          row!.style.transform = "translateX(" + shakeOffset(t).toFixed(2) + "px)";
        }
      }

      rafRef.current = requestAnimationFrame(loop);
    }

    if (reduce) { SHAKE_MS = 1; }
    rafRef.current = requestAnimationFrame(loop);

    return () => {
      input.removeEventListener("change", onInputChange);
      submit.removeEventListener("click", onSubmitClick);
      cancelAnimationFrame(rafRef.current);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.cbe + " " + styles.isDemo} ref={rootRef}>
        <label className={styles.cbeRow} ref={rowRef}>
          <input type="checkbox" className={styles.cbeInput} ref={inputRef} required />
          <span className={styles.cbeBox} aria-hidden="true">
            <svg viewBox="0 0 20 20" width={14} height={14}>
              <path d="M4 10.5l3.5 3.5L16 5.5" fill="none" stroke="currentColor" strokeWidth={2.6} strokeLinecap="round" strokeLinejoin="round" />
            </svg>
          </span>
          <span className={styles.cbeText}>필수 약관에 동의합니다</span>
        </label>
        <p className={styles.cbeHint} ref={hintRef}>체크해야 다음으로 진행됩니다</p>
        <button type="button" className={styles.cbeSubmit} ref={submitRef}>제출</button>
      </div>
    </main>
  );
}