03ギザギザの縁と反り上がった角に列ごとに違う影がかかる紙の質感の場面

<main class="stage">
<div class="rc is-demo" id="rc">
  <canvas class="rc__canvas" data-role="canvas" width="480" height="300" tabindex="0" aria-label="ギザギザの縁と反った角のある紙の上を、光の角度が動き続けて列ごとに違う影が通る場面"></canvas>
  <p class="rc__status" data-role="status" aria-live="polite">光が動いている</p>
  <div class="rc__tools">
    <button class="rc__btn" data-role="btn" type="button" aria-pressed="false">光を固定</button>
  </div>
</div>
</main>

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

.rc {
  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;
  background: $subject-ink;
}

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

.rc__canvas:focus-visible {
  outline: 2px solid rgba(255, 255, 255, .85);
  outline-offset: -6px;
}

.rc__status {
  position: absolute;
  left: $sp-3;
  bottom: $sp-3;
  max-width: 46%;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-control;
  background: rgba(255, 255, 255, .85);
  color: $subject-ink;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.4;
  pointer-events: none;
}

.rc__tools {
  position: absolute;
  right: $sp-3;
  bottom: $sp-3;
  display: flex;
  gap: $sp-2;
}

.rc__btn {
  margin: 0;
  padding: $sp-1 $sp-3;
  border: 0;
  border-radius: $r-pill;
  background: rgba(255, 255, 255, .85);
  color: $subject-ink;
  font: inherit;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  cursor: pointer;
}

.rc__btn[aria-pressed="true"] {
  background: $subject-mint;
}

.rc__btn:focus-visible {
  outline: 2px solid rgba(255, 255, 255, .95);
  outline-offset: 2px;
}

.rc__canvas { touch-action: none; }

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

@media (prefers-reduced-motion: reduce) {
  .rc { cursor: default; }
  .rc__chip { cursor: default; }
}

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);
}

.rc {
  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);
  background: #17141a;
}

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

.rc__canvas:focus-visible {
  outline: 2px solid rgba(255, 255, 255, 0.85);
  outline-offset: -6px;
}

.rc__status {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: 46%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.85);
  color: #17141a;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.4;
  pointer-events: none;
}

.rc__tools {
  position: absolute;
  right: 12px;
  bottom: 12px;
  display: flex;
  gap: 8px;
}

.rc__btn {
  margin: 0;
  padding: 4px 12px;
  border: 0;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.85);
  color: #17141a;
  font: inherit;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  cursor: pointer;
}

.rc__btn[aria-pressed=true] {
  background: #4cd4a6;
}

.rc__btn:focus-visible {
  outline: 2px solid rgba(255, 255, 255, 0.95);
  outline-offset: 2px;
}

.rc__canvas {
  touch-action: none;
}

@media (max-width: 340px) {
  .rc__btn {
    font-size: 10px;
    padding: 4px 8px;
  }
  .rc__status {
    font-size: 10px;
    padding: 4px 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .rc {
    cursor: default;
  }
  .rc__chip {
    cursor: default;
  }
}

(function () {
    const root = document.getElementById("rc");
    if (!root) return;
    const W = 480;
    const H = 300;
    const FIXED_DT = 16;
    // 파스텔 팔레트 — 어두운 무대 위에 밝은 종이를 얹어 명도 차로 읽힌다
    const BG = [29, 26, 44];
    const PAPER = [255, 248, 234];
    const INK = [58, 48, 76];
    const MINT = [126, 226, 192];
    const SKY = [124, 196, 255];
    const LILAC = [190, 164, 255];
    const PINK = [255, 160, 190];
    const PEACH = [255, 208, 168];
    function clamp(v, lo, hi) { return v < lo ? lo : (v > hi ? hi : v); }
    function lerp(a, b, k) { return a + (b - a) * k; }
    function smooth(x) { const c = clamp(x, 0, 1); return c * c * (3 - 2 * c); }
    function rgba(c, a) {
        return 'rgba(' + Math.round(c[0]) + ',' + Math.round(c[1]) + ',' + Math.round(c[2]) + ',' + clamp(a, 0, 1).toFixed(3) + ')';
    }
    function mix(a, b, k) { return [lerp(a[0], b[0], k), lerp(a[1], b[1], k), lerp(a[2], b[2], k)]; }
    // 시드 고정 난수 — 같은 시드면 언제나 같은 수열 (선형 합동 방식)
    function lcg(seed) {
        let s = seed >>> 0;
        return function () {
            s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
            return s / 4294967296;
        };
    }
    const canvasEl = root.querySelector('[data-role="canvas"]');
    const statusEl = root.querySelector('[data-role="status"]');
    const ctxRaw = canvasEl ? canvasEl.getContext('2d') : null;
    if (!canvasEl || !ctxRaw || !statusEl) {
        return;
    }
    const cv = canvasEl;
    const ctx = ctxRaw;
    const status = statusEl;
    const reduceQuery = window.matchMedia('(prefers-reduced-motion: reduce)');
    function fitCanvas() {
        const dpr = window.devicePixelRatio || 1;
        cv.width = Math.round(W * dpr);
        cv.height = Math.round(H * dpr);
        ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    }
    function onResize() {
        fitCanvas();
        if (reduceQuery.matches) {
            draw();
        }
    }
    fitCanvas();
    window.addEventListener('resize', onResize);
    // 화면 좌표(CSS px) → 장면 좌표(480x300). 리사이즈 뒤에도 늘 현재 크기로 다시 잰다
    function toScene(ev) {
        const r = cv.getBoundingClientRect();
        return [((ev.clientX - r.left) / r.width) * W, ((ev.clientY - r.top) / r.height) * H];
    }
    const TOOTH_N = 18;
    const CURL_PX = 74;
    const LIGHT_DEG = 38;
    const SHADE_MAX = 0.46;
    const SWAY_DEG = 46;
    const SWAY_MS = 2400;
    const SHEET_W = 300;
    const SHEET_T = 22;
    const SHEET_B = 262;
    const TXT_AUTO = '光が動いている';
    const TXT_HOLD = '光の角度を固定';
    const LINES = ['つきあかり商店', '牛乳', '食パン', 'りんご'];
    const PRICES = ['', '1,200', '2,800', '3,500'];
    const holdBtn = root.querySelector('[data-role="btn"]');
    let clock = 0;
    let manual = false;
    let manualDeg = LIGHT_DEG;
    let dragging = false;
    const sheetX = (W - SHEET_W) / 2;
    // 지금 빛이 오는 각도(도) — 자동이면 기준 각도를 중심으로 계속 흔든다
    function lightDeg() {
        if (manual) {
            return manualDeg;
        }
        return LIGHT_DEG + SWAY_DEG * Math.sin((clock / SWAY_MS) * Math.PI * 2);
    }
    // 가로 열 하나의 음영 세기 — 종이를 부드럽게 말린 곡면으로 보고 법선과 빛 방향의 내적을 쓴다
    function shadeAt(col, deg) {
        const u = col / SHEET_W * 2 - 1;
        const slope = u * 0.62;
        const nx = -slope;
        const nz = Math.sqrt(1 - Math.min(0.99, slope * slope));
        const rad = deg * Math.PI / 180;
        const lx = Math.sin(rad);
        const lz = Math.cos(rad);
        const dot = clamp(nx * lx + nz * lz, 0, 1);
        return (1 - dot) * SHADE_MAX;
    }
    function edgeY(i, top) {
        const amp = 7;
        const y = top ? SHEET_T : SHEET_B;
        const up = (i % 2 === 0) === top;
        return y + (up ? -amp * 0.4 : amp * 0.8);
    }
    function step() {
        clock += FIXED_DT;
    }
    function settle() {
        clock = SWAY_MS * 0.16;
    }
    function outline(ctx2, dx, dy) {
        ctx2.beginPath();
        const n = TOOTH_N;
        ctx2.moveTo(sheetX + dx, edgeY(0, true) + dy);
        for (let i = 1; i <= n; i += 1) {
            ctx2.lineTo(sheetX + dx + (SHEET_W * i) / n, edgeY(i, true) + dy);
        }
        // 오른쪽 아래 모서리는 말려 올라간 만큼 잘라 낸다
        ctx2.lineTo(sheetX + dx + SHEET_W, SHEET_B - CURL_PX + dy);
        ctx2.lineTo(sheetX + dx + SHEET_W - CURL_PX, SHEET_B + dy);
        for (let i = n - 1; i >= 0; i -= 1) {
            ctx2.lineTo(sheetX + dx + (SHEET_W * i) / n, edgeY(i, false) + dy);
        }
        ctx2.closePath();
    }
    function draw() {
        const deg = lightDeg();
        ctx.fillStyle = rgba(BG, 1);
        ctx.fillRect(0, 0, W, H);
        // 바닥 그림자 — 빛 반대쪽으로 밀려 나간다
        const rad = deg * Math.PI / 180;
        const sx = -Math.sin(rad) * 14;
        ctx.fillStyle = rgba([10, 8, 22], 0.45);
        outline(ctx, sx + 4, 10);
        ctx.fill();
        // 종이 본체
        ctx.fillStyle = rgba(PAPER, 1);
        outline(ctx, 0, 0);
        ctx.fill();
        ctx.save();
        outline(ctx, 0, 0);
        ctx.clip();
        // 열마다 다른 음영
        const colW = 3;
        for (let c = 0; c < SHEET_W; c += colW) {
            const s = shadeAt(c + colW / 2, deg);
            ctx.fillStyle = rgba(INK, s);
            ctx.fillRect(sheetX + c, 0, colW, H);
        }
        // 가로 결과 글자
        ctx.fillStyle = rgba(INK, 0.06);
        for (let y = SHEET_T; y < SHEET_B; y += 8) {
            ctx.fillRect(sheetX, y, SHEET_W, 1);
        }
        ctx.font = '600 13px "Noto Sans KR", ui-monospace, monospace';
        for (let i = 0; i < LINES.length; i += 1) {
            const y = 62 + i * 30;
            ctx.fillStyle = rgba(INK, 0.9);
            ctx.textAlign = i === 0 ? 'center' : 'left';
            ctx.fillText(LINES[i], i === 0 ? sheetX + SHEET_W / 2 : sheetX + 26, y);
            if (PRICES[i]) {
                ctx.textAlign = 'right';
                ctx.fillText(PRICES[i], sheetX + SHEET_W - 26, y);
            }
        }
        // 말린 모서리가 종이 위에 던지는 그림자 — 빛이 기울면 길이와 방향이 바뀐다
        const cx = sheetX + SHEET_W;
        const cy = SHEET_B;
        const throwX = Math.sin(rad) * 26;
        ctx.fillStyle = rgba([40, 30, 60], 0.3);
        ctx.beginPath();
        ctx.moveTo(cx - CURL_PX, cy);
        ctx.lineTo(cx, cy - CURL_PX);
        ctx.lineTo(cx - CURL_PX * 0.55 - throwX, cy - CURL_PX * 0.55 - 12);
        ctx.closePath();
        ctx.fill();
        ctx.restore();
        // 접힌 날개 — 종이 뒷면이 빛을 받아 밝게 보인다
        const flap = ctx.createLinearGradient(cx - CURL_PX, cy, cx, cy - CURL_PX);
        const lit = 0.5 + 0.5 * Math.cos(rad - 0.9);
        flap.addColorStop(0, rgba(mix(PAPER, LILAC, 0.5), 1));
        flap.addColorStop(1, rgba(mix(PAPER, [255, 255, 255], 0.5 * lit), 1));
        ctx.fillStyle = flap;
        ctx.beginPath();
        ctx.moveTo(cx - CURL_PX, cy);
        ctx.lineTo(cx, cy - CURL_PX);
        ctx.lineTo(cx - CURL_PX * 0.86, cy - CURL_PX * 0.86 + 4);
        ctx.lineTo(cx - CURL_PX - 6, cy - 6);
        ctx.closePath();
        ctx.fill();
        // 빛 방향 표시 — 위쪽 반원에서 해가 돈다
        const hx = W / 2 + Math.sin(rad) * 190;
        const hy = 18 - Math.cos(rad) * 6;
        ctx.fillStyle = rgba(PEACH, 0.95);
        ctx.beginPath();
        ctx.arc(clamp(hx, 14, W - 14), hy + 6, 7, 0, Math.PI * 2);
        ctx.fill();
    }
    function setHold(on) {
        // 고정하는 순간의 각도를 먼저 읽는다 — manual 을 먼저 바꾸면 옛 manualDeg 로 튄다
        if (on && !manual) {
            manualDeg = lightDeg();
        }
        manual = on;
        if (holdBtn) {
            holdBtn.setAttribute('aria-pressed', on ? 'true' : 'false');
        }
        status.textContent = on ? TXT_HOLD : TXT_AUTO;
        if (reduceQuery.matches) {
            draw();
        }
    }
    if (holdBtn) {
        holdBtn.addEventListener('click', function () { setHold(!manual); });
    }
    cv.addEventListener('pointerdown', function (ev) {
        dragging = true;
        cv.setPointerCapture(ev.pointerId);
        setHold(true);
        manualDeg = clamp((toScene(ev)[0] / W - 0.5) * 120, -60, 60);
        if (reduceQuery.matches) {
            draw();
        }
    });
    cv.addEventListener('pointermove', function (ev) {
        if (!dragging) {
            return;
        }
        manualDeg = clamp((toScene(ev)[0] / W - 0.5) * 120, -60, 60);
        if (reduceQuery.matches) {
            draw();
        }
    });
    cv.addEventListener('pointerup', function () { dragging = false; });
    cv.addEventListener('pointercancel', function () { dragging = false; });
    cv.addEventListener('keydown', function (ev) {
        if (ev.key === 'ArrowLeft' || ev.key === 'ArrowRight') {
            ev.preventDefault();
            if (!manual) {
                setHold(true);
            }
            manualDeg = clamp(manualDeg + (ev.key === 'ArrowLeft' ? -6 : 6), -90, 90);
            if (reduceQuery.matches) {
                draw();
            }
        }
    });
    let rafId = 0;
    let lastTs = -1;
    let acc = 0;
    function frame(ts) {
        if (lastTs < 0) {
            lastTs = ts;
        }
        acc += Math.min(ts - lastTs, 100);
        lastTs = ts;
        let n = 0;
        while (acc >= FIXED_DT && n < 6) {
            step();
            acc -= FIXED_DT;
            n += 1;
        }
        draw();
        rafId = window.requestAnimationFrame(frame);
    }
    if (reduceQuery.matches) {
        settle();
        draw();
    }
    else {
        rafId = window.requestAnimationFrame(frame);
    }
    return function () {
        window.cancelAnimationFrame(rafId);
        window.removeEventListener('resize', onResize);
    };
})();

// RecZigzagEdgePaperCurlShadow - vanilla 판(03-rec-zigzag-edge-paper-curl-shadow) 의 React 포트. 같은 계산을 useEffect 안에서 돌린다.
import { useEffect, useRef } from "react";
import styles from "./RecZigzagEdgePaperCurlShadow.module.scss";

const cx = (s: string): string => s.split(" ").map((n) => styles[n] ?? n).join(" ");

export default function RecZigzagEdgePaperCurlShadow() {
  const rootRef = useRef<HTMLDivElement | null>(null);

  useEffect(() => {
    const rootEl = rootRef.current;
    if (!rootEl) return;
    const root: HTMLElement = rootEl;
    type RGB = [number, number, number];
    const W = 480;
    const H = 300;
    const FIXED_DT = 16;
    // 파스텔 팔레트 — 어두운 무대 위에 밝은 종이를 얹어 명도 차로 읽힌다
    const BG: RGB = [29, 26, 44];
    const PAPER: RGB = [255, 248, 234];
    const INK: RGB = [58, 48, 76];
    const MINT: RGB = [126, 226, 192];
    const SKY: RGB = [124, 196, 255];
    const LILAC: RGB = [190, 164, 255];
    const PINK: RGB = [255, 160, 190];
    const PEACH: RGB = [255, 208, 168];
    function clamp(v: number, lo: number, hi: number): number { return v < lo ? lo : (v > hi ? hi : v); }
    function lerp(a: number, b: number, k: number): number { return a + (b - a) * k; }
    function smooth(x: number): number { const c = clamp(x, 0, 1); return c * c * (3 - 2 * c); }
    function rgba(c: RGB, a: number): string {
        return 'rgba(' + Math.round(c[0]) + ',' + Math.round(c[1]) + ',' + Math.round(c[2]) + ',' + clamp(a, 0, 1).toFixed(3) + ')';
    }
    function mix(a: RGB, b: RGB, k: number): RGB { return [lerp(a[0], b[0], k), lerp(a[1], b[1], k), lerp(a[2], b[2], k)]; }
    // 시드 고정 난수 — 같은 시드면 언제나 같은 수열 (선형 합동 방식)
    function lcg(seed: number): () => number {
        let s = seed >>> 0;
        return function (): number {
            s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
            return s / 4294967296;
        };
    }
    const canvasEl = root.querySelector('[data-role="canvas"]') as HTMLCanvasElement | null;
    const statusEl = root.querySelector('[data-role="status"]') as HTMLElement | null;
    const ctxRaw = canvasEl ? canvasEl.getContext('2d') : null;
    if (!canvasEl || !ctxRaw || !statusEl) { return; }
    const cv: HTMLCanvasElement = canvasEl;
    const ctx: CanvasRenderingContext2D = ctxRaw;
    const status: HTMLElement = statusEl;
    const reduceQuery = window.matchMedia('(prefers-reduced-motion: reduce)');
    function fitCanvas(): void {
        const dpr = window.devicePixelRatio || 1;
        cv.width = Math.round(W * dpr);
        cv.height = Math.round(H * dpr);
        ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    }
    function onResize(): void {
        fitCanvas();
        if (reduceQuery.matches) { draw(); }
    }
    fitCanvas();
    window.addEventListener('resize', onResize);
    // 화면 좌표(CSS px) → 장면 좌표(480x300). 리사이즈 뒤에도 늘 현재 크기로 다시 잰다
    function toScene(ev: PointerEvent): [number, number] {
        const r = cv.getBoundingClientRect();
        return [((ev.clientX - r.left) / r.width) * W, ((ev.clientY - r.top) / r.height) * H];
    }
    const TOOTH_N = 18;
    const CURL_PX = 74;
    const LIGHT_DEG = 38;
    const SHADE_MAX = 0.46;
    const SWAY_DEG = 46;
    const SWAY_MS = 2400;
    const SHEET_W = 300;
    const SHEET_T = 22;
    const SHEET_B = 262;
    const TXT_AUTO = '빛이 움직이는 중';
    const TXT_HOLD = '빛 각도 고정';
    const LINES: string[] = ['달빛 상점', '우유', '식빵', '사과'];
    const PRICES: string[] = ['', '1,200', '2,800', '3,500'];
    const holdBtn = root.querySelector('[data-role="btn"]') as HTMLButtonElement | null;
    let clock = 0;
    let manual = false;
    let manualDeg = LIGHT_DEG;
    let dragging = false;
    const sheetX = (W - SHEET_W) / 2;
    // 지금 빛이 오는 각도(도) — 자동이면 기준 각도를 중심으로 계속 흔든다
    function lightDeg(): number {
        if (manual) { return manualDeg; }
        return LIGHT_DEG + SWAY_DEG * Math.sin((clock / SWAY_MS) * Math.PI * 2);
    }
    // 가로 열 하나의 음영 세기 — 종이를 부드럽게 말린 곡면으로 보고 법선과 빛 방향의 내적을 쓴다
    function shadeAt(col: number, deg: number): number {
        const u = col / SHEET_W * 2 - 1;
        const slope = u * 0.62;
        const nx = -slope;
        const nz = Math.sqrt(1 - Math.min(0.99, slope * slope));
        const rad = deg * Math.PI / 180;
        const lx = Math.sin(rad);
        const lz = Math.cos(rad);
        const dot = clamp(nx * lx + nz * lz, 0, 1);
        return (1 - dot) * SHADE_MAX;
    }
    function edgeY(i: number, top: boolean): number {
        const amp = 7;
        const y = top ? SHEET_T : SHEET_B;
        const up = (i % 2 === 0) === top;
        return y + (up ? -amp * 0.4 : amp * 0.8);
    }
    function step(): void {
        clock += FIXED_DT;
    }
    function settle(): void {
        clock = SWAY_MS * 0.16;
    }
    function outline(ctx2: CanvasRenderingContext2D, dx: number, dy: number): void {
        ctx2.beginPath();
        const n = TOOTH_N;
        ctx2.moveTo(sheetX + dx, edgeY(0, true) + dy);
        for (let i = 1; i <= n; i += 1) { ctx2.lineTo(sheetX + dx + (SHEET_W * i) / n, edgeY(i, true) + dy); }
        // 오른쪽 아래 모서리는 말려 올라간 만큼 잘라 낸다
        ctx2.lineTo(sheetX + dx + SHEET_W, SHEET_B - CURL_PX + dy);
        ctx2.lineTo(sheetX + dx + SHEET_W - CURL_PX, SHEET_B + dy);
        for (let i = n - 1; i >= 0; i -= 1) { ctx2.lineTo(sheetX + dx + (SHEET_W * i) / n, edgeY(i, false) + dy); }
        ctx2.closePath();
    }
    function draw(): void {
        const deg = lightDeg();
        ctx.fillStyle = rgba(BG, 1);
        ctx.fillRect(0, 0, W, H);
        // 바닥 그림자 — 빛 반대쪽으로 밀려 나간다
        const rad = deg * Math.PI / 180;
        const sx = -Math.sin(rad) * 14;
        ctx.fillStyle = rgba([10, 8, 22], 0.45);
        outline(ctx, sx + 4, 10);
        ctx.fill();
        // 종이 본체
        ctx.fillStyle = rgba(PAPER, 1);
        outline(ctx, 0, 0);
        ctx.fill();
        ctx.save();
        outline(ctx, 0, 0);
        ctx.clip();
        // 열마다 다른 음영
        const colW = 3;
        for (let c = 0; c < SHEET_W; c += colW) {
            const s = shadeAt(c + colW / 2, deg);
            ctx.fillStyle = rgba(INK, s);
            ctx.fillRect(sheetX + c, 0, colW, H);
        }
        // 가로 결과 글자
        ctx.fillStyle = rgba(INK, 0.06);
        for (let y = SHEET_T; y < SHEET_B; y += 8) { ctx.fillRect(sheetX, y, SHEET_W, 1); }
        ctx.font = '600 13px "Noto Sans KR", ui-monospace, monospace';
        for (let i = 0; i < LINES.length; i += 1) {
            const y = 62 + i * 30;
            ctx.fillStyle = rgba(INK, 0.9);
            ctx.textAlign = i === 0 ? 'center' : 'left';
            ctx.fillText(LINES[i], i === 0 ? sheetX + SHEET_W / 2 : sheetX + 26, y);
            if (PRICES[i]) {
                ctx.textAlign = 'right';
                ctx.fillText(PRICES[i], sheetX + SHEET_W - 26, y);
            }
        }
        // 말린 모서리가 종이 위에 던지는 그림자 — 빛이 기울면 길이와 방향이 바뀐다
        const cx = sheetX + SHEET_W;
        const cy = SHEET_B;
        const throwX = Math.sin(rad) * 26;
        ctx.fillStyle = rgba([40, 30, 60], 0.3);
        ctx.beginPath();
        ctx.moveTo(cx - CURL_PX, cy);
        ctx.lineTo(cx, cy - CURL_PX);
        ctx.lineTo(cx - CURL_PX * 0.55 - throwX, cy - CURL_PX * 0.55 - 12);
        ctx.closePath();
        ctx.fill();
        ctx.restore();
        // 접힌 날개 — 종이 뒷면이 빛을 받아 밝게 보인다
        const flap = ctx.createLinearGradient(cx - CURL_PX, cy, cx, cy - CURL_PX);
        const lit = 0.5 + 0.5 * Math.cos(rad - 0.9);
        flap.addColorStop(0, rgba(mix(PAPER, LILAC, 0.5), 1));
        flap.addColorStop(1, rgba(mix(PAPER, [255, 255, 255], 0.5 * lit), 1));
        ctx.fillStyle = flap;
        ctx.beginPath();
        ctx.moveTo(cx - CURL_PX, cy);
        ctx.lineTo(cx, cy - CURL_PX);
        ctx.lineTo(cx - CURL_PX * 0.86, cy - CURL_PX * 0.86 + 4);
        ctx.lineTo(cx - CURL_PX - 6, cy - 6);
        ctx.closePath();
        ctx.fill();
        // 빛 방향 표시 — 위쪽 반원에서 해가 돈다
        const hx = W / 2 + Math.sin(rad) * 190;
        const hy = 18 - Math.cos(rad) * 6;
        ctx.fillStyle = rgba(PEACH, 0.95);
        ctx.beginPath();
        ctx.arc(clamp(hx, 14, W - 14), hy + 6, 7, 0, Math.PI * 2);
        ctx.fill();
    }
    function setHold(on: boolean): void {
        // 고정하는 순간의 각도를 먼저 읽는다 — manual 을 먼저 바꾸면 옛 manualDeg 로 튄다
        if (on && !manual) { manualDeg = lightDeg(); }
        manual = on;
        if (holdBtn) { holdBtn.setAttribute('aria-pressed', on ? 'true' : 'false'); }
        status.textContent = on ? TXT_HOLD : TXT_AUTO;
        if (reduceQuery.matches) { draw(); }
    }
    if (holdBtn) {
        holdBtn.addEventListener('click', function (): void { setHold(!manual); });
    }
    cv.addEventListener('pointerdown', function (ev: PointerEvent): void {
        dragging = true;
        cv.setPointerCapture(ev.pointerId);
        setHold(true);
        manualDeg = clamp((toScene(ev)[0] / W - 0.5) * 120, -60, 60);
        if (reduceQuery.matches) { draw(); }
    });
    cv.addEventListener('pointermove', function (ev: PointerEvent): void {
        if (!dragging) { return; }
        manualDeg = clamp((toScene(ev)[0] / W - 0.5) * 120, -60, 60);
        if (reduceQuery.matches) { draw(); }
    });
    cv.addEventListener('pointerup', function (): void { dragging = false; });
    cv.addEventListener('pointercancel', function (): void { dragging = false; });
    cv.addEventListener('keydown', function (ev: KeyboardEvent): void {
        if (ev.key === 'ArrowLeft' || ev.key === 'ArrowRight') {
            ev.preventDefault();
            if (!manual) { setHold(true); }
            manualDeg = clamp(manualDeg + (ev.key === 'ArrowLeft' ? -6 : 6), -90, 90);
            if (reduceQuery.matches) { draw(); }
        }
    });

    let rafId = 0;
    let lastTs = -1;
    let acc = 0;
    function frame(ts: number): void {
        if (lastTs < 0) { lastTs = ts; }
        acc += Math.min(ts - lastTs, 100);
        lastTs = ts;
        let n = 0;
        while (acc >= FIXED_DT && n < 6) {
            step();
            acc -= FIXED_DT;
            n += 1;
        }
        draw();
        rafId = window.requestAnimationFrame(frame);
    }
    if (reduceQuery.matches) {
        settle();
        draw();
    } else {
        rafId = window.requestAnimationFrame(frame);
    }
    return function (): void {
        window.cancelAnimationFrame(rafId);
        window.removeEventListener('resize', onResize);
    };

  }, []);

  return (
    <div className={cx("rc") + " is-demo"} ref={rootRef}>
        <canvas className={cx("rc__canvas")} data-role="canvas" width={480} height={300} tabIndex={0} aria-label="톱니 가장자리와 말린 모서리가 있는 종이 위로 빛 각도가 계속 움직이며 열마다 다른 그림자가 지나가는 장면"></canvas>
        <p className={cx("rc__status")} data-role="status" aria-live="polite">빛이 움직이는 중</p>
        <div className={cx("rc__tools")}>
          <button className={cx("rc__btn")} data-role="btn" type="button" aria-pressed="false">빛 고정</button>
        </div>
    </div>
  );
}