03톱니 모양 가장자리와 위로 말린 모서리에 열마다 다른 그림자가 지나가는 종이 질감 장면

<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="톱니 가장자리와 말린 모서리가 있는 종이 위로 빛 각도가 계속 움직이며 열마다 다른 그림자가 지나가는 장면"></canvas>
  <p class="rc__status" data-role="status" aria-live="polite">빛이 움직이는 중</p>
  <div class="rc__tools">
    <button class="rc__btn" data-role="btn" type="button" aria-pressed="false">빛 고정</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 = '빛이 움직이는 중';
    const TXT_HOLD = '빛 각도 고정';
    const LINES = ['달빛 상점', '우유', '식빵', '사과'];
    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>
  );
}