07完了値のひらめき表示 — ダウンロードが終わる瞬間に完了値が1に変わり、一定時間後に0へ戻って消える方式

<main class="stage">
<div class="dcf is-demo" id="dcf">
  <div class="dcf__badge" id="dcfBadge">
    <span class="dcf__sweep" id="dcfSweep"></span>
    <span class="dcf__text">完了</span>
  </div>
  <button class="dcf__btn" id="dcfBtn" type="button">もう一度見る</button>
</div>
</main>

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

// 계산 겹: 광택 sweep 세기 = 초기값 × 0.55^회차(지수 감쇠) — index.html sweepOpacity() 참조
@include stage($stage-ink);

.dcf {
  width: 100%;
  max-width: 220px;
  display: grid;
  justify-items: center;
  gap: $sp-4;
}

.dcf__badge {
  position: relative;
  overflow: hidden;
  width: 140px;
  height: 56px;
  border-radius: $r-card;
  background: $subject-mint;
  display: grid;
  place-items: center;
  opacity: 0;
  transform: scale(.7);
  transition: opacity $dur-quick $ease-out, transform $dur-quick $ease-pop;
}

.dcf--on .dcf__badge {
  opacity: 1;
  transform: scale(1);
}

.dcf__sweep {
  position: absolute;
  top: -20%;
  left: 0;
  width: 40%;
  height: 140%;
  background: linear-gradient(90deg, rgba($subject-cream, 0), rgba($subject-cream, .8), rgba($subject-cream, 0));
  opacity: 0;
  pointer-events: none;
}

.dcf__text {
  font: 700 15px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: $stage-ink;
}

.dcf__btn {
  width: 100%;
  border: 0;
  border-radius: $r-control;
  padding: $sp-2 $sp-4;
  background: $subject-cream;
  color: $stage-ink;
  font: 700 12px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  cursor: pointer;
  transition: transform $dur-instant $ease-out;

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

@media (max-width: 340px) {
  .dcf { max-width: 180px; }
  .dcf__badge { width: 120px; height: 48px; }
}

@media (prefers-reduced-motion: reduce) {
  .dcf__badge, .dcf__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: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.dcf {
  width: 100%;
  max-width: 220px;
  display: grid;
  justify-items: center;
  gap: 16px;
}

.dcf__badge {
  position: relative;
  overflow: hidden;
  width: 140px;
  height: 56px;
  border-radius: 16px;
  background: #4cd4a6;
  display: grid;
  place-items: center;
  opacity: 0;
  transform: scale(0.7);
  transition: opacity 220ms ease-out, transform 220ms cubic-bezier(0.2, 1.4, 0.4, 1);
}

.dcf--on .dcf__badge {
  opacity: 1;
  transform: scale(1);
}

.dcf__sweep {
  position: absolute;
  top: -20%;
  left: 0;
  width: 40%;
  height: 140%;
  background: linear-gradient(90deg, rgba(255, 247, 230, 0), rgba(255, 247, 230, 0.8), rgba(255, 247, 230, 0));
  opacity: 0;
  pointer-events: none;
}

.dcf__text {
  font: 700 15px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: #17141a;
}

.dcf__btn {
  width: 100%;
  border: 0;
  border-radius: 12px;
  padding: 8px 16px;
  background: #fff7e6;
  color: #17141a;
  font: 700 12px/1 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  cursor: pointer;
  transition: transform 140ms ease-out;
}
.dcf__btn:active {
  transform: scale(0.96);
}

@media (max-width: 340px) {
  .dcf {
    max-width: 180px;
  }
  .dcf__badge {
    width: 120px;
    height: 48px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .dcf__badge, .dcf__btn {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('dcf');
  var badge = document.getElementById('dcfBadge');
  var sweep = document.getElementById('dcfSweep');
  var btn = document.getElementById('dcfBtn');

  // 상수: 完了 표시 유지 시간(ms) · 광택 sweep 1회 길이(ms) · 반복 횟수 · 감쇠율
  var VISIBLE_MS = 1500;
  var SWEEP_MS = 420;
  var SWEEP_COUNT = 3;
  var DECAY = 0.55; // 회차마다 강도(불투명도)가 이 비율로 줄어든다
  var CYCLE_MS = 2400;

  var start = performance.now();
  var raf = null;

  // 계산 겹: 광택 sweep 의 세기 = 초기값 × DECAY^회차(지수 감쇠) — 매 회차 옅어지다 사라진다
  function sweepOpacity(passIndex) {
    return Math.pow(DECAY, passIndex);
  }

  function frame(now) {
    var e = (now - start) % CYCLE_MS;
    var on = e < VISIBLE_MS;
    root.classList.toggle('dcf--on', on);
    if (on) {
      var passLen = SWEEP_MS;
      var passIdx = Math.floor(e / passLen);
      var passT = (e % passLen) / passLen;
      if (passIdx < SWEEP_COUNT) {
        var x = -30 + passT * 160; // %
        sweep.style.transform = 'translateX(' + x.toFixed(1) + '%) skewX(-18deg)';
        sweep.style.opacity = sweepOpacity(passIdx).toFixed(3);
      } else {
        sweep.style.opacity = '0';
      }
    }
    raf = requestAnimationFrame(frame);
  }
  raf = requestAnimationFrame(frame);

  btn.addEventListener('click', function () {
    root.classList.remove('is-demo');
    start = performance.now();
    root.classList.add('dcf--on');
  });
})();

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

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

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

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

    // 상수: 완료 표시 유지 시간(ms) · 광택 sweep 1회 길이(ms) · 반복 횟수 · 감쇠율
    const VISIBLE_MS = 1500;
    const SWEEP_MS = 420;
    const SWEEP_COUNT = 3;
    const DECAY = 0.55;
    const CYCLE_MS = 2400;

    let start = performance.now();
    let rafId = 0;
    let stopped = false;

    // 계산 겹: 광택 sweep 의 세기 = 초기값 × DECAY^회차(지수 감쇠) — 매 회차 옅어지다 사라진다
    function sweepOpacity(passIndex: number) {
      return Math.pow(DECAY, passIndex);
    }

    function frame(now: number) {
      if (stopped) return;
      const e = (now - start) % CYCLE_MS;
      const on = e < VISIBLE_MS;
      root!.classList.toggle(styles["dcf--on"], on);
      if (on) {
        const passLen = SWEEP_MS;
        const passIdx = Math.floor(e / passLen);
        const passT = (e % passLen) / passLen;
        if (passIdx < SWEEP_COUNT) {
          const x = -30 + passT * 160;
          sweep!.style.transform = "translateX(" + x.toFixed(1) + "%) skewX(-18deg)";
          sweep!.style.opacity = sweepOpacity(passIdx).toFixed(3);
        } else {
          sweep!.style.opacity = "0";
        }
      }
      rafId = requestAnimationFrame(frame);
    }
    rafId = requestAnimationFrame(frame);

    function onClick() {
      root!.classList.remove(styles["is-demo"]);
      start = performance.now();
      root!.classList.add(styles["dcf--on"]);
    }
    btn.addEventListener("click", onClick);

    return () => {
      stopped = true;
      cancelAnimationFrame(rafId);
      btn.removeEventListener("click", onClick);
    };
  }, []);

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.dcf} ${styles["is-demo"]}`}>
      <div className={styles.badge}>
        <span className={styles.sweep} />
        <span className={styles.text}>완료</span>
      </div>
      <button className={styles.btn} type="button">다시 보기</button>
    </div>
  );
}