03Book Stack Where Multiple Pages Flip in Sequence

<main class="stage">
<div class="vd is-demo" id="vdRoot">
  <canvas class="vd__canvas" id="vdCanvas" width="480" height="300"></canvas>
  <p class="vd__caption">A Book Stack Flip Where Sheets Turn One After Another</p>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;
@include stage($stage-orange);

.vd {
  position: relative;
  width: min(92vw, calc(160vh - 12.8vw));
  aspect-ratio: 480 / 300;
  margin: 0 auto;
  border-radius: $r-card;
  overflow: hidden;
  box-shadow: $shadow-raised;
  cursor: pointer;
}

.vd__canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.vd__caption {
  position: absolute;
  left: $sp-3;
  bottom: $sp-3;
  max-width: 72%;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(255, 247, 230, .85);
  color: $subject-ink;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

@media (max-width: 340px) {
  .vd__caption { font-size: 10px; padding: $sp-1 $sp-2; }
}

@media (prefers-reduced-motion: reduce) {
  .vd { cursor: pointer; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.vd {
  position: relative;
  width: min(92vw, 160vh - 12.8vw);
  aspect-ratio: 480/300;
  margin: 0 auto;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  cursor: pointer;
}

.vd__canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.vd__caption {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: 72%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.85);
  color: #17141a;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

@media (max-width: 340px) {
  .vd__caption {
    font-size: 10px;
    padding: 4px 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .vd {
    cursor: pointer;
  }
}

(function () {
  var root = document.getElementById('vdRoot');
  var canvas = document.getElementById('vdCanvas');
  var ctx = canvas.getContext('2d');
  var wrap = canvas.parentElement;

  var LW = 320, LH = 200;
  var BOOK_L = 96, BOOK_T = 24, BOOK_R = 250, BOOK_B = 176;
  var FOLD_X = BOOK_L;
  var STACK_TOTAL = 5;
  var SCENE_BG = '#17141a';
  var PAGE_COLORS = ['#fff7e6', '#f6eede', '#efe4cd', '#e7dcc2'];
  var PAGE_BACK = '#caa96b';

  function seedRand(seed) {
    var s = seed >>> 0;
    return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
  }
  var rand = seedRand(41303);

  function clamp(v, a, b) { return v < a ? a : (v > b ? b : v); }

  var remaining = STACK_TOTAL;                          // 아직 안 넘긴 페이지 수
  var flipping = false;
  var angle = 0;
  var FLIP_MS = 460;
  var flipT = 0;

  function stackThickness(n) { return clamp(n, 0, STACK_TOTAL) * 2.2; }

  function startFlip() {
    if (flipping || remaining <= 0) return;
    flipping = true; flipT = 0;
  }
  function nextPage() {
    if (flipping || remaining <= 0) { remaining = STACK_TOTAL; return; }
    startFlip();
  }

  function stepFlip(dt) {
    if (!flipping) return;
    flipT += dt * 1000;
    var p = clamp(flipT / FLIP_MS, 0, 1);
    angle = p * Math.PI;
    if (p >= 1) {
      flipping = false; angle = 0;
      remaining -= 1;
      if (remaining <= 0) remaining = STACK_TOTAL;      // 다 넘기면 처음부터
    }
  }

  var AUTO_PERIOD = 620;
  var autoTimer = 0;
  function autoplay(dt) {
    if (pointerActive || reduce) return;
    autoTimer += dt * 1000;
    if (autoTimer >= AUTO_PERIOD) { autoTimer = 0; nextPage(); }
  }

  function drawStackShadow() {
    var th = stackThickness(remaining - (flipping ? 1 : 0));
    ctx.fillStyle = 'rgba(23,20,26,.5)';
    ctx.fillRect(BOOK_L + th, BOOK_T + th, BOOK_R - BOOK_L, BOOK_B - BOOK_T);
  }

  function drawLines(x, y, w, h) {
    ctx.strokeStyle = 'rgba(23,20,26,.24)';
    ctx.lineWidth = 1.4;
    for (var i = 0; i < 4; i += 1) {
      var ly = y + h * (0.2 + i * 0.18);
      ctx.beginPath(); ctx.moveTo(x + w * 0.1, ly); ctx.lineTo(x + w * 0.9, ly); ctx.stroke();
    }
  }

  function pageAt(color) {
    var w = BOOK_R - BOOK_L, h = BOOK_B - BOOK_T;
    ctx.fillStyle = color;
    ctx.fillRect(BOOK_L, BOOK_T, w, h);
    drawLines(BOOK_L, BOOK_T, w, h);
  }

  function draw() {
    ctx.fillStyle = SCENE_BG;
    ctx.fillRect(0, 0, LW, LH);
    drawStackShadow();
    var w = BOOK_R - BOOK_L, h = BOOK_B - BOOK_T;
    var belowIdx = Math.max(0, STACK_TOTAL - remaining) % PAGE_COLORS.length;
    pageAt(PAGE_COLORS[(belowIdx + 1) % PAGE_COLORS.length]);

    if (flipping) {
      var c = Math.cos(angle);
      var frontFacing = c >= 0;
      ctx.save();
      ctx.translate(FOLD_X, 0);
      ctx.scale(c === 0 ? 0.001 : c, 1);
      ctx.fillStyle = frontFacing ? PAGE_COLORS[belowIdx] : PAGE_BACK;
      ctx.fillRect(0, BOOK_T, w, h);
      if (frontFacing) drawLines(6, BOOK_T, w - 12, h);
      ctx.restore();
      var shadowA = 0.06 + Math.abs(Math.sin(angle)) * 0.3;
      ctx.fillStyle = 'rgba(0,0,0,' + shadowA + ')';
      ctx.fillRect(FOLD_X, BOOK_T, 36, h);
    } else if (remaining > 0) {
      pageAt(PAGE_COLORS[belowIdx]);
    }

    ctx.fillStyle = 'rgba(255,247,230,.9)';
    ctx.font = '11px sans-serif';
    ctx.fillText(String(remaining) + ' / ' + String(STACK_TOTAL), BOOK_R - 34, BOOK_T - 8);
  }

  var pointerActive = false;
  var pointerCooldown = 0;
  function update(dt, tMs) {
    stepFlip(dt);
    if (pointerCooldown > 0) { pointerCooldown -= dt * 1000; if (pointerCooldown <= 0) pointerActive = false; }
    autoplay(dt);
  }

  var cw = 480, ch = 300, sx = 1, sy = 1;
  function fit() {
    var r = wrap.getBoundingClientRect();
    cw = Math.max(1, Math.round(r.width));
    ch = Math.max(1, Math.round(r.height));
    canvas.width = cw; canvas.height = ch;
    sx = cw / LW; sy = ch / LH;
    render();
  }
  function render() {
    ctx.setTransform(1, 0, 0, 1, 0, 0);
    ctx.clearRect(0, 0, cw, ch);
    ctx.save();
    ctx.scale(sx, sy);
    draw();
    ctx.restore();
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var playing = !reduce;
  if (reduce) { root.classList.remove('is-demo'); remaining = 3; }

  function onClick() {
    pointerActive = true; pointerCooldown = 1400;
    nextPage();
    if (reduce) render();
  }
  wrap.addEventListener('click', onClick);
  wrap.setAttribute('tabindex', '0');
  wrap.addEventListener('keydown', function (e) {
    if (e.key === 'Enter' || e.key === ' ' || e.key === 'ArrowRight') { e.preventDefault(); onClick(); }
  });

  var lastTs = null;
  function tick(ts) {
    if (lastTs === null) lastTs = ts;
    var dt = Math.min((ts - lastTs) / 1000, 0.05);
    lastTs = ts;
    if (playing) update(dt, ts);
    render();
    requestAnimationFrame(tick);
  }
  fit();
  window.addEventListener('resize', fit);
  render();
  if (playing) requestAnimationFrame(tick);
})();

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

export default function PaperStackMultipageFlip() {
  const rootRef = useRef<HTMLDivElement>(null);
  const canvasRef = useRef<HTMLCanvasElement>(null);

  useEffect(() => {
    const root = rootRef.current;
    const canvas = canvasRef.current;
    if (!root || !canvas) return;
    const ctx = canvas.getContext("2d");
    if (!ctx) return;
    const wrap = canvas.parentElement as HTMLElement;

    const LW = 320, LH = 200;
    const BOOK_L = 96, BOOK_T = 24, BOOK_R = 250, BOOK_B = 176;
    const FOLD_X = BOOK_L;
    const STACK_TOTAL = 5;
    const SCENE_BG = "#17141a";
    const PAGE_COLORS = ["#fff7e6", "#f6eede", "#efe4cd", "#e7dcc2"];
    const PAGE_BACK = "#caa96b";

    function seedRand(seed: number) {
      let s = seed >>> 0;
      return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
    }
    const rand = seedRand(41303);

    function clamp(v: number, a: number, b: number): number { return v < a ? a : (v > b ? b : v); }

    let remaining = STACK_TOTAL;
    let flipping = false;
    let angle = 0;
    const FLIP_MS = 460;
    let flipT = 0;

    function stackThickness(n: number): number { return clamp(n, 0, STACK_TOTAL) * 2.2; }

    function startFlip(): void {
      if (flipping || remaining <= 0) return;
      flipping = true; flipT = 0;
    }
    function nextPage(): void {
      if (flipping || remaining <= 0) { remaining = STACK_TOTAL; return; }
      startFlip();
    }

    function stepFlip(dt: number): void {
      if (!flipping) return;
      flipT += dt * 1000;
      const p = clamp(flipT / FLIP_MS, 0, 1);
      angle = p * Math.PI;
      if (p >= 1) {
        flipping = false; angle = 0;
        remaining -= 1;
        if (remaining <= 0) remaining = STACK_TOTAL;
      }
    }

    const AUTO_PERIOD = 620;
    let autoTimer = 0;
    function autoplay(dt: number): void {
      if (pointerActive || reduce) return;
      autoTimer += dt * 1000;
      if (autoTimer >= AUTO_PERIOD) { autoTimer = 0; nextPage(); }
    }

    function drawStackShadow(): void {
      const th = stackThickness(remaining - (flipping ? 1 : 0));
      ctx!.fillStyle = "rgba(23,20,26,.5)";
      ctx!.fillRect(BOOK_L + th, BOOK_T + th, BOOK_R - BOOK_L, BOOK_B - BOOK_T);
    }

    function drawLines(x: number, y: number, w: number, h: number): void {
      ctx!.strokeStyle = "rgba(23,20,26,.24)";
      ctx!.lineWidth = 1.4;
      for (let i = 0; i < 4; i += 1) {
        const ly = y + h * (0.2 + i * 0.18);
        ctx!.beginPath(); ctx!.moveTo(x + w * 0.1, ly); ctx!.lineTo(x + w * 0.9, ly); ctx!.stroke();
      }
    }

    function pageAt(color: string): void {
      const w = BOOK_R - BOOK_L, h = BOOK_B - BOOK_T;
      ctx!.fillStyle = color;
      ctx!.fillRect(BOOK_L, BOOK_T, w, h);
      drawLines(BOOK_L, BOOK_T, w, h);
    }

    function draw(): void {
      ctx!.fillStyle = SCENE_BG;
      ctx!.fillRect(0, 0, LW, LH);
      drawStackShadow();
      const w = BOOK_R - BOOK_L, h = BOOK_B - BOOK_T;
      const belowIdx = Math.max(0, STACK_TOTAL - remaining) % PAGE_COLORS.length;
      pageAt(PAGE_COLORS[(belowIdx + 1) % PAGE_COLORS.length]);

      if (flipping) {
        const c = Math.cos(angle);
        const frontFacing = c >= 0;
        ctx!.save();
        ctx!.translate(FOLD_X, 0);
        ctx!.scale(c === 0 ? 0.001 : c, 1);
        ctx!.fillStyle = frontFacing ? PAGE_COLORS[belowIdx] : PAGE_BACK;
        ctx!.fillRect(0, BOOK_T, w, h);
        if (frontFacing) drawLines(6, BOOK_T, w - 12, h);
        ctx!.restore();
        const shadowA = 0.06 + Math.abs(Math.sin(angle)) * 0.3;
        ctx!.fillStyle = "rgba(0,0,0," + shadowA + ")";
        ctx!.fillRect(FOLD_X, BOOK_T, 36, h);
      } else if (remaining > 0) {
        pageAt(PAGE_COLORS[belowIdx]);
      }

      ctx!.fillStyle = "rgba(255,247,230,.9)";
      ctx!.font = "11px sans-serif";
      ctx!.fillText(String(remaining) + " / " + String(STACK_TOTAL), BOOK_R - 34, BOOK_T - 8);
    }

    let pointerActive = false;
    let pointerCooldown = 0;
    function update(dt: number, tMs: number): void {
      stepFlip(dt);
      if (pointerCooldown > 0) { pointerCooldown -= dt * 1000; if (pointerCooldown <= 0) pointerActive = false; }
      autoplay(dt);
    }

    let cw = 480, ch = 300, sx = 1, sy = 1;
    function fit(): void {
      const r = wrap.getBoundingClientRect();
      cw = Math.max(1, Math.round(r.width));
      ch = Math.max(1, Math.round(r.height));
      canvas!.width = cw; canvas!.height = ch;
      sx = cw / LW; sy = ch / LH;
      render();
    }
    function render(): void {
      ctx!.setTransform(1, 0, 0, 1, 0, 0);
      ctx!.clearRect(0, 0, cw, ch);
      ctx!.save();
      ctx!.scale(sx, sy);
      draw();
      ctx!.restore();
    }

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    const playing = !reduce;
    if (reduce) { root.classList.remove("is-demo"); remaining = 3; }

    function onClick(): void {
      pointerActive = true; pointerCooldown = 1400;
      nextPage();
      if (reduce) render();
    }
    function onKeyDown(e: KeyboardEvent): void {
      if (e.key === "Enter" || e.key === " " || e.key === "ArrowRight") { e.preventDefault(); onClick(); }
    }
    wrap.addEventListener("click", onClick);
    wrap.setAttribute("tabindex", "0");
    wrap.addEventListener("keydown", onKeyDown);

    let lastTs: number | null = null;
    let raf = 0;
    function tick(ts: number): void {
      if (lastTs === null) lastTs = ts;
      const dt = Math.min((ts - lastTs) / 1000, 0.05);
      lastTs = ts;
      if (playing) update(dt, ts);
      render();
      raf = requestAnimationFrame(tick);
    }
    fit();
    window.addEventListener("resize", fit);
    render();
    if (playing) raf = requestAnimationFrame(tick);

    return () => {
      cancelAnimationFrame(raf);
      window.removeEventListener("resize", fit);
      wrap.removeEventListener("click", onClick);
      wrap.removeEventListener("keydown", onKeyDown);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.vd} is-demo`} ref={rootRef}>
        <canvas className={styles.vd__canvas} ref={canvasRef} width={480} height={300} />
        <p className={styles.vd__caption}>여러 장이 차례로 넘어가는 책 스택 플립</p>
      </div>
    </main>
  );
}