03Carousel Whose Cards Curve Past in 3D Perspective

<main class="stage">
<section class="carousel is-demo" id="carousel" role="region" aria-roledescription="carousel" aria-label="Card carousel">
  <div class="viewport" id="viewport" tabindex="0">
    <div class="track" id="track">
      <div class="card card--0" data-i="0"><span class="num">1</span></div>
      <div class="card card--1" data-i="1"><span class="num">2</span></div>
      <div class="card card--2" data-i="2"><span class="num">3</span></div>
      <div class="card card--3" data-i="3"><span class="num">4</span></div>
      <div class="card card--4" data-i="4"><span class="num">5</span></div>
    </div>
  </div>
  <button type="button" class="navBtn navBtn--prev" id="prevBtn" aria-label="Previous card">
    <svg viewBox="0 0 256 256" width="18" height="18" aria-hidden="true"><g fill="currentColor"><path d="M112 56v144l-72-72Z" opacity=".2"/><path d="M216 120h-96V56a8 8 0 0 0-13.66-5.66l-72 72a8 8 0 0 0 0 11.32l72 72A8 8 0 0 0 120 200v-64h96a8 8 0 0 0 0-16m-112 60.69L51.31 128L104 75.31Z"/></g></svg>
  </button>
  <button type="button" class="navBtn navBtn--next" id="nextBtn" aria-label="Next card">
    <svg viewBox="0 0 256 256" width="18" height="18" aria-hidden="true"><g fill="currentColor"><path d="m216 128l-72 72V56Z" opacity=".2"/><path d="m221.66 122.34l-72-72A8 8 0 0 0 136 56v64H40a8 8 0 0 0 0 16h96v64a8 8 0 0 0 13.66 5.66l72-72a8 8 0 0 0 0-11.32M152 180.69V75.31L204.69 128Z"/></g></svg>
  </button>
  <div class="readout" id="readout" aria-live="polite"></div>
</section>
</main>

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

// 변수 3개
$duration: $dur-base;
$easing: $ease-out;
$color: $subject-lilac;

// 계산 겹: index.html 의 render() 가 카드마다 중심 인덱스까지의 실수 거리를
// rotateY·translateZ·scale·opacity 로 매 프레임 산술 변환한다 — CSS 트랜지션이 아니다.
@include stage($stage-ink);

.carousel {
  position: relative;
  width: 300px;
}

.viewport {
  position: relative;
  width: 300px;
  height: 176px;
  border-radius: $r-card;
  overflow: hidden;
  box-shadow: $shadow-raised;
  background: $stage-ink;
  outline: none;
  perspective: 720px;
}

.track {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  cursor: grab;

  &.isDragging { cursor: grabbing; }
}

.card {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 132px;
  height: 132px;
  margin: -66px 0 0 -66px;
  border-radius: $r-card;
  display: grid;
  place-items: center;
  will-change: transform, opacity;

  .num {
    font-weight: 700;
    font-size: 44px;
    line-height: 1;
  }
}

.card--0 { background: linear-gradient(160deg, $subject-blue-deep, #475690); .num { color: $subject-cream; } }
.card--1 { background: linear-gradient(160deg, $subject-pink, #d97fa0); .num { color: $subject-ink; } }
.card--2 { background: linear-gradient(160deg, $subject-lilac, #bdb3da); .num { color: $subject-ink; } }
.card--3 { background: linear-gradient(160deg, $subject-mint, #63b299); .num { color: $subject-ink; } }
.card--4 { background: linear-gradient(160deg, $subject-sky, #9cb8ce); .num { color: $subject-ink; } }

.navBtn {
  position: absolute;
  top: 50%;
  margin-top: -18px;
  width: 36px;
  height: 36px;
  border-radius: $r-pill;
  border: none;
  display: grid;
  place-items: center;
  background: rgba($stage-ink, .6);
  color: $subject-cream;
  cursor: pointer;
  z-index: 200;

  &:focus-visible { outline: 2px solid $color; outline-offset: 2px; }
}
.navBtn--prev { left: -($sp-3); }
.navBtn--next { right: -($sp-3); }

.readout {
  position: absolute;
  left: $sp-3;
  bottom: $sp-3;
  padding: $sp-1 $sp-2;
  border-radius: $r-pill;
  background: rgba($stage-ink, .6);
  color: rgba($subject-cream, .9);
  font-size: 11px;
  font-weight: 600;
  line-height: 1;
  font-variant-numeric: tabular-nums;
  z-index: 200;
}

@media (max-width: 340px) {
  .carousel { width: 220px; }
  .viewport { width: 220px; height: 128px; }
  .card { width: 92px; height: 92px; margin: -46px 0 0 -46px; .num { font-size: 30px; } }
  .navBtn { width: 28px; height: 28px; margin-top: -14px; }
  .readout { font-size: 9px; }
}

@media (prefers-reduced-motion: reduce) {
  // 실사용 경로 적용 — 드래그·키보드·버튼은 index.html 이 그대로 거리 계산을 돌린다.
  // scss 만: 포커스 아웃라인 전환만 꺼서 잔여 트랜지션을 없앤다.
  .navBtn { 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);
}

.carousel {
  position: relative;
  width: 300px;
}

.viewport {
  position: relative;
  width: 300px;
  height: 176px;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  background: #17141a;
  outline: none;
  perspective: 720px;
}

.track {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  cursor: grab;
}
.track.isDragging {
  cursor: grabbing;
}

.card {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 132px;
  height: 132px;
  margin: -66px 0 0 -66px;
  border-radius: 16px;
  display: grid;
  place-items: center;
  will-change: transform, opacity;
}
.card .num {
  font-weight: 700;
  font-size: 44px;
  line-height: 1;
}

.card--0 {
  background: linear-gradient(160deg, #0a4fe8, #475690);
}
.card--0 .num {
  color: #fff7e6;
}

.card--1 {
  background: linear-gradient(160deg, #ff9ebb, #d97fa0);
}
.card--1 .num {
  color: #17141a;
}

.card--2 {
  background: linear-gradient(160deg, #b9a0ff, #bdb3da);
}
.card--2 .num {
  color: #17141a;
}

.card--3 {
  background: linear-gradient(160deg, #4cd4a6, #63b299);
}
.card--3 .num {
  color: #17141a;
}

.card--4 {
  background: linear-gradient(160deg, #6ec8ff, #9cb8ce);
}
.card--4 .num {
  color: #17141a;
}

.navBtn {
  position: absolute;
  top: 50%;
  margin-top: -18px;
  width: 36px;
  height: 36px;
  border-radius: 999px;
  border: none;
  display: grid;
  place-items: center;
  background: rgba(23, 20, 26, 0.6);
  color: #fff7e6;
  cursor: pointer;
  z-index: 200;
}
.navBtn:focus-visible {
  outline: 2px solid #b9a0ff;
  outline-offset: 2px;
}

.navBtn--prev {
  left: -12px;
}

.navBtn--next {
  right: -12px;
}

.readout {
  position: absolute;
  left: 12px;
  bottom: 12px;
  padding: 4px 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.6);
  color: rgba(255, 247, 230, 0.9);
  font-size: 11px;
  font-weight: 600;
  line-height: 1;
  font-variant-numeric: tabular-nums;
  z-index: 200;
}

@media (max-width: 340px) {
  .carousel {
    width: 220px;
  }
  .viewport {
    width: 220px;
    height: 128px;
  }
  .card {
    width: 92px;
    height: 92px;
    margin: -46px 0 0 -46px;
  }
  .card .num {
    font-size: 30px;
  }
  .navBtn {
    width: 28px;
    height: 28px;
    margin-top: -14px;
  }
  .readout {
    font-size: 9px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .navBtn {
    transition: none;
  }
}

(function () {
  var TOTAL = 5;
  var CARD_SPACING = 92;   // 드래그 1px 당 인덱스 변화 계산에 쓰는 Card 간격(px)
  var ANGLE_STEP = 38;     // 중심에서 Card 1개 멀어질 때마다 더해지는 회전각(deg)
  var MAX_ANGLE = 68;
  var DEPTH_STEP = 90;     // Card 1개 멀어질 때마다 밀어내는 translateZ(px)
  var SCALE_STEP = 0.15;
  var SCALE_FLOOR = 0.55;
  var OPACITY_STEP = 0.24;
  var OPACITY_FLOOR = 0.28;
  var SNAP_EASE = 0.22;    // 릴리스 후 가장 가까운 정수 인덱스로 당기는 보간 비율(프레임당)
  var SNAP_STOP = 0.004;
  var DEMO_HOLD_MS = 520;

  var carousel = document.getElementById('carousel');
  var viewport = document.getElementById('viewport');
  var track = document.getElementById('track');
  var readout = document.getElementById('readout');
  var prevBtn = document.getElementById('prevBtn');
  var nextBtn = document.getElementById('nextBtn');
  var cards = Array.prototype.slice.call(track.querySelectorAll('.card'));
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var LABEL_PREFIX = 'Card ';
  var LABEL_SEP = ' / ';

  var index = 0;           // 실수 인덱스 — 드래그 중에는 소수점 그대로 반영된다
  var dragging = false;
  var dragOriginIndex = 0;
  var startX = 0;
  var snapFrame = null;
  var demoTimers = [];

  function clamp(v, lo, hi) { return Math.min(hi, Math.max(lo, v)); }

  // 계산 겹 — 카드마다 중심(index)까지의 거리(소수 가능)를 회전각·깊이·크기·투명도로 매핑한다.
  function render() {
    for (var n = 0; n < cards.length; n++) {
      var dist = n - index;
      var absDist = Math.abs(dist);
      var angle = clamp(dist * ANGLE_STEP, -MAX_ANGLE, MAX_ANGLE);
      var z = -absDist * DEPTH_STEP;
      var scale = Math.max(SCALE_FLOOR, 1 - absDist * SCALE_STEP);
      var opacity = Math.max(OPACITY_FLOOR, 1 - absDist * OPACITY_STEP);
      var x = dist * 58;
      cards[n].style.transform = 'translateX(' + x.toFixed(1) + 'px) translateZ(' + z.toFixed(1) + 'px) rotateY(' + angle.toFixed(1) + 'deg) scale(' + scale.toFixed(3) + ')';
      cards[n].style.opacity = opacity.toFixed(2);
      cards[n].style.zIndex = String(100 - Math.round(absDist * 10));
    }
    var shown = clamp(Math.round(index), 0, TOTAL - 1);
    readout.textContent = LABEL_PREFIX + (shown + 1) + LABEL_SEP + TOTAL;
  }

  function stopSnap() {
    if (snapFrame) { cancelAnimationFrame(snapFrame); snapFrame = null; }
  }

  // 릴리스 후 가장 가까운 정수 인덱스로, 또는 지정한 목표 인덱스로 매 프레임 SNAP_EASE 비율만큼 당겨 붙인다.
  function animateIndexTo(target) {
    target = clamp(target, 0, TOTAL - 1);
    function frame() {
      index += (target - index) * SNAP_EASE;
      render();
      if (Math.abs(target - index) > SNAP_STOP) {
        snapFrame = requestAnimationFrame(frame);
      } else {
        index = target;
        render();
        snapFrame = null;
      }
    }
    snapFrame = requestAnimationFrame(frame);
  }

  function human() {
    if (carousel.classList.contains('is-demo')) {
      carousel.classList.remove('is-demo');
      demoTimers.forEach(function (t) { clearTimeout(t); });
      demoTimers = [];
    }
  }

  function onPointerDown(e) {
    human();
    stopSnap();
    dragging = true;
    dragOriginIndex = index;
    startX = e.clientX;
    viewport.setPointerCapture(e.pointerId);
    track.classList.add('isDragging');
  }
  function onPointerMove(e) {
    if (!dragging) return;
    var dx = e.clientX - startX;
    index = clamp(dragOriginIndex - dx / CARD_SPACING, 0, TOTAL - 1);
    render();
  }
  function onPointerUp(e) {
    if (!dragging) return;
    dragging = false;
    track.classList.remove('isDragging');
    try { viewport.releasePointerCapture(e.pointerId); } catch (err) {}
    animateIndexTo(Math.round(index));
  }
  function go(dir) {
    human();
    stopSnap();
    animateIndexTo(clamp(Math.round(index) + dir, 0, TOTAL - 1));
  }
  function onKeydown(e) {
    if (e.key === 'ArrowLeft') { go(-1); e.preventDefault(); }
    else if (e.key === 'ArrowRight') { go(1); e.preventDefault(); }
  }

  viewport.addEventListener('pointerdown', onPointerDown);
  viewport.addEventListener('pointermove', onPointerMove);
  viewport.addEventListener('pointerup', onPointerUp);
  viewport.addEventListener('pointercancel', onPointerUp);
  viewport.addEventListener('keydown', onKeydown);
  prevBtn.addEventListener('click', function () { go(-1); });
  nextBtn.addEventListener('click', function () { go(1); });

  // reduce: 실사용 경로 적용 — 드래그·키보드·버튼은 위 리스너가 그대로 거리 계산을 돌린다.
  // 아래 demoCycle() 은 시연 게이트만이고 reduce 에서는 돌지 않는다.
  var DEMO_SEQUENCE = [1, 2, 3, 4, 2, 0];
  function demoCycle(i) {
    if (!carousel.classList.contains('is-demo')) return;
    animateIndexTo(DEMO_SEQUENCE[i % DEMO_SEQUENCE.length]);
    demoTimers.push(setTimeout(function () { demoCycle(i + 1); }, DEMO_HOLD_MS));
  }

  function init() {
    render();
    if (!reduce) demoCycle(0);
  }
  init();
})();

import { useEffect, useRef } from 'react';
import styles from './CarouselCoverflowPerspective.module.scss';

// 상수 — vanilla demo 03 (run/384/demo/03-carousel-slide-coverflow-perspective/index.html) 과 동일
const TOTAL = 5;
const CARD_SPACING = 92;   // 드래그 1px 당 인덱스 변화 계산에 쓰는 카드 간격(px)
const ANGLE_STEP = 38;     // 중심에서 카드 1개 멀어질 때마다 더해지는 회전각(deg)
const MAX_ANGLE = 68;
const DEPTH_STEP = 90;     // 카드 1개 멀어질 때마다 밀어내는 translateZ(px)
const SCALE_STEP = 0.15;
const SCALE_FLOOR = 0.55;
const OPACITY_STEP = 0.24;
const OPACITY_FLOOR = 0.28;
const SNAP_EASE = 0.22;    // 릴리스 후 가장 가까운 정수 인덱스로 당기는 보간 비율(프레임당)
const SNAP_STOP = 0.004;
const DEMO_HOLD_MS = 520;
const LABEL_PREFIX = '카드 ';
const LABEL_SEP = ' / ';
const DEMO_SEQUENCE = [1, 2, 3, 4, 2, 0];

export default function CarouselCoverflowPerspective() {
  const carouselRef = useRef<HTMLElement>(null);

  useEffect(() => {
    const carousel = carouselRef.current;
    if (!carousel) return undefined;
    const viewport = carousel.querySelector<HTMLDivElement>('.' + styles.viewport);
    const track = carousel.querySelector<HTMLDivElement>('.' + styles.track);
    const readout = carousel.querySelector<HTMLDivElement>('.' + styles.readout);
    const prevBtn = carousel.querySelector<HTMLButtonElement>('.' + styles['navBtn--prev']);
    const nextBtn = carousel.querySelector<HTMLButtonElement>('.' + styles['navBtn--next']);
    if (!viewport || !track || !readout || !prevBtn || !nextBtn) return undefined;
    const cards = Array.prototype.slice.call(
      track.querySelectorAll<HTMLDivElement>('.' + styles.card)
    ) as HTMLDivElement[];

    let index = 0;   // 실수 인덱스 — 드래그 중에는 소수점 그대로 반영된다
    let dragging = false;
    let dragOriginIndex = 0;
    let startX = 0;
    let snapFrame = 0;
    let demoTimers: number[] = [];

    function clamp(v: number, lo: number, hi: number) { return Math.min(hi, Math.max(lo, v)); }

    // 계산 겹 — 카드마다 중심(index)까지의 거리(소수 가능)를 회전각·깊이·크기·투명도로 매핑한다.
    function render() {
      for (let n = 0; n < cards.length; n++) {
        const dist = n - index;
        const absDist = Math.abs(dist);
        const angle = clamp(dist * ANGLE_STEP, -MAX_ANGLE, MAX_ANGLE);
        const z = -absDist * DEPTH_STEP;
        const scale = Math.max(SCALE_FLOOR, 1 - absDist * SCALE_STEP);
        const opacity = Math.max(OPACITY_FLOOR, 1 - absDist * OPACITY_STEP);
        const x = dist * 58;
        cards[n].style.transform = 'translateX(' + x.toFixed(1) + 'px) translateZ(' + z.toFixed(1) + 'px) rotateY(' + angle.toFixed(1) + 'deg) scale(' + scale.toFixed(3) + ')';
        cards[n].style.opacity = opacity.toFixed(2);
        cards[n].style.zIndex = String(100 - Math.round(absDist * 10));
      }
      const shown = clamp(Math.round(index), 0, TOTAL - 1);
      readout!.textContent = LABEL_PREFIX + (shown + 1) + LABEL_SEP + TOTAL;
    }

    function stopSnap() {
      if (snapFrame) { cancelAnimationFrame(snapFrame); snapFrame = 0; }
    }

    // 릴리스 후 가장 가까운 정수 인덱스로, 또는 지정한 목표 인덱스로 매 프레임 SNAP_EASE 비율만큼 당겨 붙인다.
    function animateIndexTo(targetIn: number) {
      const target = clamp(targetIn, 0, TOTAL - 1);
      function frame() {
        index += (target - index) * SNAP_EASE;
        render();
        if (Math.abs(target - index) > SNAP_STOP) {
          snapFrame = requestAnimationFrame(frame);
        } else {
          index = target;
          render();
          snapFrame = 0;
        }
      }
      snapFrame = requestAnimationFrame(frame);
    }

    function human() {
      if (carousel!.classList.contains(styles['is-demo'])) {
        carousel!.classList.remove(styles['is-demo']);
        demoTimers.forEach((t) => window.clearTimeout(t));
        demoTimers = [];
      }
    }

    function onPointerDown(e: PointerEvent) {
      human();
      stopSnap();
      dragging = true;
      dragOriginIndex = index;
      startX = e.clientX;
      viewport!.setPointerCapture(e.pointerId);
      track!.classList.add(styles.isDragging);
    }
    function onPointerMove(e: PointerEvent) {
      if (!dragging) return;
      const dx = e.clientX - startX;
      index = clamp(dragOriginIndex - dx / CARD_SPACING, 0, TOTAL - 1);
      render();
    }
    function onPointerUp(e: PointerEvent) {
      if (!dragging) return;
      dragging = false;
      track!.classList.remove(styles.isDragging);
      try { viewport!.releasePointerCapture(e.pointerId); } catch { /* 캡처가 이미 풀린 경우 */ }
      animateIndexTo(Math.round(index));
    }
    function go(dir: number) {
      human();
      stopSnap();
      animateIndexTo(clamp(Math.round(index) + dir, 0, TOTAL - 1));
    }
    function onKeydown(e: KeyboardEvent) {
      if (e.key === 'ArrowLeft') { go(-1); e.preventDefault(); }
      else if (e.key === 'ArrowRight') { go(1); e.preventDefault(); }
    }
    function onPrev() { go(-1); }
    function onNext() { go(1); }

    viewport.addEventListener('pointerdown', onPointerDown);
    viewport.addEventListener('pointermove', onPointerMove);
    viewport.addEventListener('pointerup', onPointerUp);
    viewport.addEventListener('pointercancel', onPointerUp);
    viewport.addEventListener('keydown', onKeydown);
    prevBtn.addEventListener('click', onPrev);
    nextBtn.addEventListener('click', onNext);

    const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

    // reduce: 실사용 경로 적용 — 드래그·키보드·버튼은 위 리스너가 그대로 거리 계산을 돌린다.
    // 아래 demoCycle() 은 시연 게이트만이고 reduce 에서는 돌지 않는다.
    function demoCycle(i: number) {
      if (!carousel!.classList.contains(styles['is-demo'])) return;
      animateIndexTo(DEMO_SEQUENCE[i % DEMO_SEQUENCE.length]);
      demoTimers.push(window.setTimeout(() => demoCycle(i + 1), DEMO_HOLD_MS));
    }

    render();
    if (!reduce) demoCycle(0);

    return () => {
      viewport.removeEventListener('pointerdown', onPointerDown);
      viewport.removeEventListener('pointermove', onPointerMove);
      viewport.removeEventListener('pointerup', onPointerUp);
      viewport.removeEventListener('pointercancel', onPointerUp);
      viewport.removeEventListener('keydown', onKeydown);
      prevBtn.removeEventListener('click', onPrev);
      nextBtn.removeEventListener('click', onNext);
      demoTimers.forEach((t) => window.clearTimeout(t));
      stopSnap();
    };
  }, []);

  return (
    <main className={styles.stage}>
      <section
        className={styles.carousel + ' ' + styles['is-demo']}
        ref={carouselRef}
        role="region"
        aria-roledescription="carousel"
        aria-label="카드 캐러셀"
      >
        <div className={styles.viewport} tabIndex={0}>
          <div className={styles.track}>
            <div className={styles.card + ' ' + styles['card--0']} data-i={0}><span className={styles.num}>1</span></div>
            <div className={styles.card + ' ' + styles['card--1']} data-i={1}><span className={styles.num}>2</span></div>
            <div className={styles.card + ' ' + styles['card--2']} data-i={2}><span className={styles.num}>3</span></div>
            <div className={styles.card + ' ' + styles['card--3']} data-i={3}><span className={styles.num}>4</span></div>
            <div className={styles.card + ' ' + styles['card--4']} data-i={4}><span className={styles.num}>5</span></div>
          </div>
        </div>
        <button type="button" className={styles.navBtn + ' ' + styles['navBtn--prev']} aria-label="이전 카드">
          <svg viewBox="0 0 256 256" width={18} height={18} aria-hidden="true"><g fill="currentColor"><path d="M112 56v144l-72-72Z" opacity=".2" /><path d="M216 120h-96V56a8 8 0 0 0-13.66-5.66l-72 72a8 8 0 0 0 0 11.32l72 72A8 8 0 0 0 120 200v-64h96a8 8 0 0 0 0-16m-112 60.69L51.31 128L104 75.31Z" /></g></svg>
        </button>
        <button type="button" className={styles.navBtn + ' ' + styles['navBtn--next']} aria-label="다음 카드">
          <svg viewBox="0 0 256 256" width={18} height={18} aria-hidden="true"><g fill="currentColor"><path d="m216 128l-72 72V56Z" opacity=".2" /><path d="m221.66 122.34l-72-72A8 8 0 0 0 136 56v64H40a8 8 0 0 0 0 16h96v64a8 8 0 0 0 13.66 5.66l72-72a8 8 0 0 0 0-11.32M152 180.69V75.31L204.69 128Z" /></g></svg>
        </button>
        <div className={styles.readout} aria-live="polite"></div>
      </section>
    </main>
  );
}