08区間値の分だけ浮き上がる影のカード

<main class="stage">
<div class="sld is-demo" id="sldRoot">
  <div class="sld__badge" id="sldBadge">通過区間 0%~100%</div>
  <button class="sld__ctrl" id="sldCtrl" type="button">一時停止</button>
  <div class="sld__view" id="sldView">
    <div class="sld__track" id="sldTrack">
      <div class="sld__spacer sld__spacer--top"></div>
      <div class="sld__card" id="sldCard">
        <span class="sld__label">カード</span>
      </div>
      <div class="sld__spacer sld__spacer--bottom"></div>
    </div>
  </div>
</div>
</main>

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

// 핵심: animation-timeline: view() + animation-range: cover 로 요소가 뷰포트를
// 통과하는 전체 구간 값(0~1)에 그림자 번짐 거리·흐림 값과 들어올림 정도를 함께
// 묶는다. 미지원 환경은 스크롤 위치로 같은 통과 진행 값을 계산해 같은 그림자를 그린다.

$duration: $dur-loop;
$easing: linear;
$color: $subject-blue-deep;

@include stage($stage-paper);

.sld {
  position: relative;
  width: min(100%, 280px);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
}

.sld__badge {
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(20, 45, 120, .08);
  color: $subject-blue-deep;
  font-weight: 700;
  font-size: 11px;
  font-variant-numeric: tabular-nums;
}

.sld__ctrl {
  position: absolute;
  top: 0;
  right: 0;
  border: 0;
  border-radius: $r-xs;
  padding: $sp-1 $sp-2;
  background: rgba(20, 45, 120, .10);
  color: $subject-blue-deep;
  font-weight: 600;
  font-size: 10px;
  line-height: 1.4;
  cursor: pointer;
}
.sld__ctrl:focus-visible { outline: 2px solid $subject-blue-deep; outline-offset: 2px; }

.sld__view {
  box-sizing: border-box;
  width: 100%;
  height: 176px;
  overflow-y: auto;
  overflow-x: hidden;
  border-radius: $r-card;
  background: rgba(20, 45, 120, .05);
  scrollbar-width: thin;
}

.sld__track {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.sld__spacer--top { height: 200px; flex: 0 0 auto; }
.sld__spacer--bottom { height: 200px; flex: 0 0 auto; }

.sld__card {
  flex: 0 0 auto;
  box-sizing: border-box;
  width: 188px;
  height: 76px;
  display: grid;
  place-items: center;
  border-radius: $r-card;
  background: $color;
  box-shadow: 0 6px 10px 0px rgba(23, 20, 26, .35);
  transform: translateY(0px);
}

.sld__label {
  color: $subject-cream;
  font-weight: 700;
  font-size: 14px;
}

.supports-vt .sld__card {
  animation-name: sldLift;
  animation-duration: 1s;
  animation-timing-function: linear;
  animation-fill-mode: both;
  animation-timeline: view();
  animation-range: cover;
}
@keyframes sldLift {
  0%   { box-shadow: 0 6px 10px 0px rgba(23, 20, 26, .35); transform: translateY(0px); }
  100% {
    box-shadow: 0 calc(6px + var(--shadow-spread, 24px) * .3) calc(10px + var(--shadow-spread, 24px) * .6) var(--shadow-spread, 24px) rgba(23, 20, 26, .35);
    transform: translateY(-14px);
  }
}

@media (max-width: 340px) {
  .sld { gap: $sp-2; }
  .sld__view { height: 130px; }
  .sld__spacer--top { height: 150px; }
  .sld__spacer--bottom { height: 150px; }
  .sld__card { width: 160px; height: 64px; }
}

@media (prefers-reduced-motion: reduce) {
  .sld__card {
    animation: none !important;
    box-shadow: 0 calc(6px + var(--shadow-spread, 24px) * .3) calc(10px + var(--shadow-spread, 24px) * .6) var(--shadow-spread, 24px) rgba(23, 20, 26, .35) !important;
    transform: translateY(-14px) !important;
  }
}

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);
}

.sld {
  position: relative;
  width: min(100%, 280px);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.sld__badge {
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(20, 45, 120, 0.08);
  color: #0a4fe8;
  font-weight: 700;
  font-size: 11px;
  font-variant-numeric: tabular-nums;
}

.sld__ctrl {
  position: absolute;
  top: 0;
  right: 0;
  border: 0;
  border-radius: 4px;
  padding: 4px 8px;
  background: rgba(20, 45, 120, 0.1);
  color: #0a4fe8;
  font-weight: 600;
  font-size: 10px;
  line-height: 1.4;
  cursor: pointer;
}

.sld__ctrl:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

.sld__view {
  box-sizing: border-box;
  width: 100%;
  height: 176px;
  overflow-y: auto;
  overflow-x: hidden;
  border-radius: 16px;
  background: rgba(20, 45, 120, 0.05);
  scrollbar-width: thin;
}

.sld__track {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.sld__spacer--top {
  height: 200px;
  flex: 0 0 auto;
}

.sld__spacer--bottom {
  height: 200px;
  flex: 0 0 auto;
}

.sld__card {
  flex: 0 0 auto;
  box-sizing: border-box;
  width: 188px;
  height: 76px;
  display: grid;
  place-items: center;
  border-radius: 16px;
  background: #0a4fe8;
  box-shadow: 0 6px 10px 0px rgba(23, 20, 26, 0.35);
  transform: translateY(0px);
}

.sld__label {
  color: #fff7e6;
  font-weight: 700;
  font-size: 14px;
}

.supports-vt .sld__card {
  animation-name: sldLift;
  animation-duration: 1s;
  animation-timing-function: linear;
  animation-fill-mode: both;
  animation-timeline: view();
  animation-range: cover;
}

@keyframes sldLift {
  0% {
    box-shadow: 0 6px 10px 0px rgba(23, 20, 26, 0.35);
    transform: translateY(0px);
  }
  100% {
    box-shadow: 0 calc(6px + var(--shadow-spread, 24px) * 0.3) calc(10px + var(--shadow-spread, 24px) * 0.6) var(--shadow-spread, 24px) rgba(23, 20, 26, 0.35);
    transform: translateY(-14px);
  }
}
@media (max-width: 340px) {
  .sld {
    gap: 8px;
  }
  .sld__view {
    height: 130px;
  }
  .sld__spacer--top {
    height: 150px;
  }
  .sld__spacer--bottom {
    height: 150px;
  }
  .sld__card {
    width: 160px;
    height: 64px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .sld__card {
    animation: none !important;
    box-shadow: 0 calc(6px + var(--shadow-spread, 24px) * 0.3) calc(10px + var(--shadow-spread, 24px) * 0.6) var(--shadow-spread, 24px) rgba(23, 20, 26, 0.35) !important;
    transform: translateY(-14px) !important;
  }
}

(function () {
  // VIEWTL_SHADOW_SPREAD_PX — 변형 3: 24 → 48 로 늘리면 그림자가 멀리 번져 카드가 훨씬 높이 떠 보인다.
  var VIEWTL_SHADOW_SPREAD_PX = 24;
  document.documentElement.style.setProperty('--shadow-spread', VIEWTL_SHADOW_SPREAD_PX + 'px');

  var supportsVt = CSS.supports('animation-timeline: view()');
  var root = document.getElementById('sldRoot');
  var view = document.getElementById('sldView');
  var card = document.getElementById('sldCard');
  var badge = document.getElementById('sldBadge');
  var ctrl = document.getElementById('sldCtrl');
  root.classList.add(supportsVt ? 'supports-vt' : 'no-vt');

  // 계산 한 겹: 요소가 뷰포트를 통과하는 구간(cover) 진행 값을 요소 높이·뷰포트
  // 높이·스크롤 위치로 직접 계산한다.
  function coverProgress() {
    var elTop = card.offsetTop;
    var elH = card.offsetHeight;
    var viewH = view.clientHeight;
    var raw = (view.scrollTop - elTop + viewH) / (elH + viewH);
    return Math.min(1, Math.max(0, raw));
  }

  function render(cov) {
    var spread = VIEWTL_SHADOW_SPREAD_PX * cov;
    if (!supportsVt) {
      var y = (6 + spread * 0.3).toFixed(1);
      var blur = (10 + spread * 0.6).toFixed(1);
      card.style.boxShadow = '0 ' + y + 'px ' + blur + 'px ' + spread.toFixed(1) + 'px rgba(23, 20, 26, .35)';
      card.style.transform = 'translateY(' + (-14 * cov).toFixed(1) + 'px)';
    }
    badge.textContent = '通過進行 ' + Math.round(cov * 100) + '% · にじみ ' + spread.toFixed(1) + 'px';
  }

  view.addEventListener('scroll', function () {
    render(coverProgress());
  }, { passive: true });
  render(coverProgress());

  var playing = true;
  var frame = 0;
  var PERIOD = 80;
  function tick() {
    if (playing) {
      frame += 1;
      var max = view.scrollHeight - view.clientHeight;
      var t = frame % (PERIOD * 2);
      var f = t < PERIOD ? (t / PERIOD) : ((PERIOD * 2 - t) / PERIOD);
      view.scrollTop = f * max;
      render(coverProgress());
    }
    requestAnimationFrame(tick);
  }
  requestAnimationFrame(tick);

  function stopAuto() {
    if (root.classList.contains('is-demo')) { root.classList.remove('is-demo'); }
    playing = false;
    ctrl.textContent = '再生';
  }
  view.addEventListener('wheel', stopAuto, { passive: true });
  view.addEventListener('touchstart', stopAuto, { passive: true });

  ctrl.addEventListener('click', function () {
    playing = !playing;
    ctrl.textContent = playing ? '一時停止' : '再生';
    if (playing) { root.classList.add('is-demo'); }
    render(coverProgress());
  });
  ctrl.addEventListener('keydown', function (e) {
    if (e.key === 'r' || e.key === 'R') {
      frame = 0;
      view.scrollTop = 0;
      playing = true;
      root.classList.add('is-demo');
      ctrl.textContent = '一時停止';
      render(coverProgress());
    }
  });

  window.addEventListener('resize', function () {
    render(coverProgress());
  });

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (reduce) {
    playing = false;
    root.classList.remove('is-demo');
    render(1);
    badge.textContent = '通過進行 100% · にじみ ' + VIEWTL_SHADOW_SPREAD_PX.toFixed(1) + 'px';
  }
})();

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

// 핵심: animation-timeline: view() + animation-range: cover 로 요소가 뷰포트를
// 통과하는 전체 구간 값(0~1)에 그림자 번짐 거리·흐림 값과 들어올림 정도를 함께
// 묶는다. 미지원 환경은 스크롤 위치로 같은 통과 진행 값을 계산해 같은 그림자를 그린다.
// VIEWTL_SHADOW_SPREAD_PX — 변형 3: 24 → 48 로 늘리면 그림자가 더 멀리 번져 보인다.
const VIEWTL_SHADOW_SPREAD_PX = 24;

export default function ShadowLiftDepth() {
  const rootRef = useRef<HTMLDivElement>(null);
  const viewRef = useRef<HTMLDivElement>(null);
  const cardRef = useRef<HTMLDivElement>(null);
  const [badge, setBadge] = useState("통과 구간 0%~100%");
  const [demo, setDemo] = useState(true);
  const [supportsVt, setSupportsVt] = useState(false);

  useEffect(() => {
    const view = viewRef.current;
    const card = cardRef.current;
    const root = rootRef.current;
    if (!view || !card || !root) { return; }

    card.style.setProperty("--shadow-spread", VIEWTL_SHADOW_SPREAD_PX + "px");
    const vt = CSS.supports("animation-timeline: view()");
    setSupportsVt(vt);

    function coverProgress() {
      const elTop = card!.offsetTop;
      const elH = card!.offsetHeight;
      const viewH = view!.clientHeight;
      const raw = (view!.scrollTop - elTop + viewH) / (elH + viewH);
      return Math.min(1, Math.max(0, raw));
    }

    function render(cov: number) {
      const spread = VIEWTL_SHADOW_SPREAD_PX * cov;
      if (!vt) {
        const y = (6 + spread * 0.3).toFixed(1);
        const blur = (10 + spread * 0.6).toFixed(1);
        card!.style.boxShadow = "0 " + y + "px " + blur + "px " + spread.toFixed(1) + "px rgba(23, 20, 26, .35)";
        card!.style.transform = "translateY(" + (-14 * cov).toFixed(1) + "px)";
      }
      setBadge("통과 진행 " + Math.round(cov * 100) + "% · 번짐 " + spread.toFixed(1) + "px");
    }

    function onScroll() { render(coverProgress()); }
    view.addEventListener("scroll", onScroll, { passive: true });
    render(coverProgress());

    let playing = true;
    let frame = 0;
    const PERIOD = 80;
    let rafId = 0;
    function tick() {
      if (playing) {
        frame += 1;
        const max = view!.scrollHeight - view!.clientHeight;
        const t = frame % (PERIOD * 2);
        const f = t < PERIOD ? (t / PERIOD) : ((PERIOD * 2 - t) / PERIOD);
        view!.scrollTop = f * max;
        render(coverProgress());
      }
      rafId = requestAnimationFrame(tick);
    }
    rafId = requestAnimationFrame(tick);

    function stopAuto() {
      setDemo(false);
      playing = false;
    }
    view.addEventListener("wheel", stopAuto, { passive: true });
    view.addEventListener("touchstart", stopAuto, { passive: true });

    function onClick() {
      playing = !playing;
      setDemo(playing);
      render(coverProgress());
    }
    function onKeyDown(e: KeyboardEvent) {
      if (e.key === "r" || e.key === "R") {
        frame = 0;
        view!.scrollTop = 0;
        playing = true;
        setDemo(true);
        render(coverProgress());
      }
    }
    root.addEventListener("keydown", onKeyDown);

    function onResize() { render(coverProgress()); }
    window.addEventListener("resize", onResize);

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (reduce) {
      playing = false;
      setDemo(false);
      render(1);
      setBadge("통과 진행 100% · 번짐 " + VIEWTL_SHADOW_SPREAD_PX.toFixed(1) + "px");
    }

    const ctrl = root.querySelector("button");
    ctrl?.addEventListener("click", onClick);

    return () => {
      cancelAnimationFrame(rafId);
      view.removeEventListener("scroll", onScroll);
      view.removeEventListener("wheel", stopAuto);
      view.removeEventListener("touchstart", stopAuto);
      root.removeEventListener("keydown", onKeyDown);
      window.removeEventListener("resize", onResize);
      ctrl?.removeEventListener("click", onClick);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <main className={styles.stage}>
      <div ref={rootRef} className={`${styles.sld} ${demo ? styles["is-demo"] : ""} ${supportsVt ? styles["supports-vt"] : styles["no-vt"]}`}>
        <div className={styles["sld__badge"]}>{badge}</div>
        <button className={styles["sld__ctrl"]} type="button">{demo ? "일시정지" : "재생"}</button>
        <div ref={viewRef} className={styles["sld__view"]}>
          <div className={styles["sld__track"]}>
            <div className={`${styles["sld__spacer"]} ${styles["sld__spacer--top"]}`} />
            <div ref={cardRef} className={styles["sld__card"]}>
              <span className={styles["sld__label"]}>카드</span>
            </div>
            <div className={`${styles["sld__spacer"]} ${styles["sld__spacer--bottom"]}`} />
          </div>
        </div>
      </div>
    </main>
  );
}