053D Card Whose Range Value Becomes an Angle Value

<main class="stage">
<div class="r3f is-demo" id="r3fRoot">
  <div class="r3f__badge" id="r3fBadge">cover range 0%~100%</div>
  <button class="r3f__ctrl" id="r3fCtrl" type="button">Pause</button>
  <div class="r3f__view" id="r3fView">
    <div class="r3f__track" id="r3fTrack">
      <div class="r3f__spacer r3f__spacer--top"></div>
      <div class="r3f__flip">
        <div class="r3f__inner" id="r3fInner">
          <div class="r3f__face r3f__face--front">Service</div>
          <div class="r3f__face r3f__face--back">Details</div>
        </div>
      </div>
      <div class="r3f__spacer r3f__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)을 그대로 각도 값(0~180deg)으로 바꿔 카드를 입체적으로
// 뒤집는다. 미지원 환경은 스크롤 위치로 같은 통과 진행 값을 계산해 같은 각도를 적용한다.

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

@include stage($stage-ink);

.r3f {
  position: relative;
  width: min(100%, 280px);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
}

.r3f__badge {
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(255, 247, 230, .08);
  color: $subject-cream;
  font-weight: 700;
  font-size: 11px;
  font-variant-numeric: tabular-nums;
}

.r3f__ctrl {
  position: absolute;
  top: 0;
  right: 0;
  border: 0;
  border-radius: $r-xs;
  padding: $sp-1 $sp-2;
  background: rgba(255, 247, 230, .12);
  color: $subject-cream;
  font-weight: 600;
  font-size: 10px;
  line-height: 1.4;
  cursor: pointer;
}
.r3f__ctrl:focus-visible { outline: 2px solid $subject-blue-light; outline-offset: 2px; }

.r3f__view {
  box-sizing: border-box;
  width: 100%;
  height: 176px;
  overflow-y: auto;
  overflow-x: hidden;
  border-radius: $r-card;
  background: rgba(255, 255, 255, .05);
  scrollbar-width: thin;
}

.r3f__track {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.r3f__spacer--top { height: 200px; flex: 0 0 auto; }
.r3f__spacer--bottom { height: 200px; flex: 0 0 auto; }

.r3f__flip {
  flex: 0 0 auto;
  width: 168px;
  height: 88px;
  perspective: 560px;
}

.r3f__inner {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transform: rotateY(0deg);
}

.r3f__face {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  border-radius: $r-card;
  box-shadow: $shadow-raised;
  backface-visibility: hidden;
  color: $subject-cream;
  font-weight: 700;
  font-size: 14px;
}
.r3f__face--front { background: $color; }
.r3f__face--back { background: $subject-orange-deep; transform: rotateY(180deg); }

.supports-vt .r3f__inner {
  animation-name: r3fFlip;
  animation-duration: 1s;
  animation-timing-function: linear;
  animation-fill-mode: both;
  animation-timeline: view();
  animation-range: cover;
}
@keyframes r3fFlip {
  0%   { transform: rotateY(0deg); }
  100% { transform: rotateY(180deg); }
}

@media (max-width: 340px) {
  .r3f { gap: $sp-2; }
  .r3f__view { height: 130px; }
  .r3f__spacer--top { height: 150px; }
  .r3f__spacer--bottom { height: 150px; }
  .r3f__flip { width: 140px; height: 72px; }
}

@media (prefers-reduced-motion: reduce) {
  .r3f__inner { animation: none !important; transform: rotateY(0deg) !important; }
}

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);
}

.r3f {
  position: relative;
  width: min(100%, 280px);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.r3f__badge {
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.08);
  color: #fff7e6;
  font-weight: 700;
  font-size: 11px;
  font-variant-numeric: tabular-nums;
}

.r3f__ctrl {
  position: absolute;
  top: 0;
  right: 0;
  border: 0;
  border-radius: 4px;
  padding: 4px 8px;
  background: rgba(255, 247, 230, 0.12);
  color: #fff7e6;
  font-weight: 600;
  font-size: 10px;
  line-height: 1.4;
  cursor: pointer;
}

.r3f__ctrl:focus-visible {
  outline: 2px solid #5b8cf8;
  outline-offset: 2px;
}

.r3f__view {
  box-sizing: border-box;
  width: 100%;
  height: 176px;
  overflow-y: auto;
  overflow-x: hidden;
  border-radius: 16px;
  background: rgba(255, 255, 255, 0.05);
  scrollbar-width: thin;
}

.r3f__track {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.r3f__spacer--top {
  height: 200px;
  flex: 0 0 auto;
}

.r3f__spacer--bottom {
  height: 200px;
  flex: 0 0 auto;
}

.r3f__flip {
  flex: 0 0 auto;
  width: 168px;
  height: 88px;
  perspective: 560px;
}

.r3f__inner {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transform: rotateY(0deg);
}

.r3f__face {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  border-radius: 16px;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  backface-visibility: hidden;
  color: #fff7e6;
  font-weight: 700;
  font-size: 14px;
}

.r3f__face--front {
  background: #0a4fe8;
}

.r3f__face--back {
  background: #c93000;
  transform: rotateY(180deg);
}

.supports-vt .r3f__inner {
  animation-name: r3fFlip;
  animation-duration: 1s;
  animation-timing-function: linear;
  animation-fill-mode: both;
  animation-timeline: view();
  animation-range: cover;
}

@keyframes r3fFlip {
  0% {
    transform: rotateY(0deg);
  }
  100% {
    transform: rotateY(180deg);
  }
}
@media (max-width: 340px) {
  .r3f {
    gap: 8px;
  }
  .r3f__view {
    height: 130px;
  }
  .r3f__spacer--top {
    height: 150px;
  }
  .r3f__spacer--bottom {
    height: 150px;
  }
  .r3f__flip {
    width: 140px;
    height: 72px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .r3f__inner {
    animation: none !important;
    transform: rotateY(0deg) !important;
  }
}

(function () {
  var supportsVt = CSS.supports('animation-timeline: view()');
  var root = document.getElementById('r3fRoot');
  var view = document.getElementById('r3fView');
  var inner = document.getElementById('r3fInner');
  var badge = document.getElementById('r3fBadge');
  var ctrl = document.getElementById('r3fCtrl');
  root.classList.add(supportsVt ? 'supports-vt' : 'no-vt');

  // 계산 한 겹: 요소가 뷰포트를 통과하는 구간(cover) 진행 값을 요소 높이·뷰포트
  // 높이·스크롤 위치로 계산해, 같은 값을 각도 값으로 바꾼다.
  function coverProgress() {
    var elTop = inner.parentElement.offsetTop;
    var elH = inner.parentElement.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 angle = cov * 180;
    if (!supportsVt) {
      inner.style.transform = 'rotateY(' + angle.toFixed(1) + 'deg)';
    }
    badge.textContent = 'cover progress ' + Math.round(cov * 100) + '% · angle ' + Math.round(angle) + 'deg';
  }

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

  // 자동 시연: rAF 로 프레임을 누적해 컨테이너를 왕복 스크롤한다.
  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 = 'Play';
  }
  view.addEventListener('wheel', stopAuto, { passive: true });
  view.addEventListener('touchstart', stopAuto, { passive: true });

  ctrl.addEventListener('click', function () {
    playing = !playing;
    ctrl.textContent = playing ? 'Pause' : 'Play';
    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 = 'Pause';
      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');
    inner.style.transform = 'rotateY(0deg)';
    badge.textContent = 'cover progress 0% · angle 0deg';
  }
})();

import { useEffect, useRef, useState } from "react";
import styles from "./Rotate3dFlip.module.scss";

// 핵심: animation-timeline: view() + animation-range: cover 로 요소가 뷰포트를
// 통과하는 전체 구간 값(0~1)을 그대로 각도 값(0~180deg)으로 바꿔 카드를 입체적으로
// 뒤집는다. 미지원 환경은 스크롤 위치로 같은 통과 진행 값을 계산해 같은 각도를 적용한다.
export default function Rotate3dFlip() {
  const rootRef = useRef<HTMLDivElement>(null);
  const viewRef = useRef<HTMLDivElement>(null);
  const flipRef = useRef<HTMLDivElement>(null);
  const innerRef = 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 flip = flipRef.current;
    const inner = innerRef.current;
    const root = rootRef.current;
    if (!view || !flip || !inner || !root) { return; }

    const vt = CSS.supports("animation-timeline: view()");
    setSupportsVt(vt);

    function coverProgress() {
      const elTop = flip!.offsetTop;
      const elH = flip!.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 angle = cov * 180;
      if (!vt) {
        inner!.style.transform = "rotateY(" + angle.toFixed(1) + "deg)";
      }
      setBadge("통과 진행 " + Math.round(cov * 100) + "% · 각도 " + Math.round(angle) + "deg");
    }

    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);
      inner.style.transform = "rotateY(0deg)";
      setBadge("통과 진행 0% · 각도 0deg");
    }

    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.r3f} ${demo ? styles["is-demo"] : ""} ${supportsVt ? styles["supports-vt"] : styles["no-vt"]}`}>
        <div className={styles["r3f__badge"]}>{badge}</div>
        <button className={styles["r3f__ctrl"]} type="button">{demo ? "일시정지" : "재생"}</button>
        <div ref={viewRef} className={styles["r3f__view"]}>
          <div className={styles["r3f__track"]}>
            <div className={`${styles["r3f__spacer"]} ${styles["r3f__spacer--top"]}`} />
            <div ref={flipRef} className={styles["r3f__flip"]}>
              <div ref={innerRef} className={styles["r3f__inner"]}>
                <div className={`${styles["r3f__face"]} ${styles["r3f__face--front"]}`}>서비스</div>
                <div className={`${styles["r3f__face"]} ${styles["r3f__face--back"]}`}>자세히</div>
              </div>
            </div>
            <div className={`${styles["r3f__spacer"]} ${styles["r3f__spacer--bottom"]}`} />
          </div>
        </div>
      </div>
    </main>
  );
}