07熱が当たった所だけ濃くなり、時間とともにノイズマップに沿ってまだらに褪せる感熱紙の文字

<main class="stage">
<div class="rc is-demo" id="rc">
  <canvas class="rc__canvas" data-role="canvas" width="480" height="300" aria-label="感熱紙の文字がノイズの地図に従って場所ごとに違う速さで褪せて消える場面"></canvas>
  <p class="rc__status" data-role="status" aria-live="polite">印字中</p>
  <div class="rc__tools">
    <button class="rc__btn" data-role="btn" type="button">もう一度印字</button>
    <button class="rc__btn" data-role="sun" type="button" aria-pressed="false">日光に当てる</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;
}

@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;
}

@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 HEAT_GAIN = 1;
    const FADE_RATE = 0.4;
    const NOISE_SCALE = 30;
    const CUTOFF = 0.25;
    const SPREAD = 2.4;
    const PRINT_MS = 700;
    const CYCLE_MS = 2800;
    const HALO = 0.24;
    const SUN_X = 3;
    const PW = 280;
    const PX = (W - PW) / 2;
    const TXT_PRINT = '印字中';
    const TXT_FADE = '褪せている';
    const TXT_GONE = 'すっかり褪せた';
    const TXT_LINES = ['つきあかり商店', '牛乳', '食パン', 'りんご', '卵', 'みかん', '合計', 'ありがとうございました'];
    const TXT_PRICES = ['', '1,200', '2,800', '3,500', '4,100', '1,900', '13,500', ''];
    const againBtn = root.querySelector('[data-role="btn"]');
    const sunBtn = root.querySelector('[data-role="sun"]');
    const off = document.createElement('canvas');
    off.width = PW;
    off.height = H;
    const offCtxRaw = off.getContext('2d');
    if (!offCtxRaw) {
        return;
    }
    const offCtx = offCtxRaw;
    const img = offCtx.createImageData(PW, H);
    const mask = new Float32Array(PW * H);
    const heat = new Float32Array(PW * H);
    const rate = new Float32Array(PW * H);
    let front = 0;
    let phaseT = 0;
    let phase = 'print';
    let sun = false;
    let clock = 0;
    function hash2(x, y) {
        let h = (Math.imul(x | 0, 374761393) + Math.imul(y | 0, 668265263) + 1442695041) | 0;
        h = Math.imul(h ^ (h >>> 13), 1274126177);
        h ^= h >>> 16;
        return (h >>> 0) / 4294967296;
    }
    // 값 노이즈 — 격자점 해시 네 개를 부드럽게 섞는다
    function noise2(x, y) {
        const xi = Math.floor(x);
        const yi = Math.floor(y);
        const fx = smooth(x - xi);
        const fy = smooth(y - yi);
        const a = hash2(xi, yi);
        const b = hash2(xi + 1, yi);
        const c = hash2(xi, yi + 1);
        const d = hash2(xi + 1, yi + 1);
        return lerp(lerp(a, b, fx), lerp(c, d, fx), fy);
    }
    // 한 자리의 바램 속도(초당 열 감소량) — 지도 값 n(0~1)이 클수록 빨리 바랜다
    function decayAt(n) {
        return FADE_RATE * (1 + SPREAD * n);
    }
    // 바램 속도 지도 — 위치마다 다른 값 (큰 덩이 + 잔 무늬)
    function buildRate() {
        for (let y = 0; y < H; y += 1) {
            for (let x = 0; x < PW; x += 1) {
                const n = 0.7 * noise2(x / NOISE_SCALE, y / NOISE_SCALE) + 0.3 * noise2(x / (NOISE_SCALE * 0.35) + 9, y / (NOISE_SCALE * 0.35) + 4);
                rate[y * PW + x] = n;
            }
        }
    }
    // 글자 마스크 — 한 번만 그려서 읽는다 (한 번뿐이라 틱마다 읽지 않는다)
    function buildMask() {
        offCtx.clearRect(0, 0, PW, H);
        offCtx.fillStyle = '#ffffff';
        offCtx.font = '700 17px "Noto Sans KR", ui-monospace, monospace';
        offCtx.textBaseline = 'middle';
        for (let i = 0; i < TXT_LINES.length; i += 1) {
            const y = 28 + i * 34;
            offCtx.textAlign = i === 0 || i === TXT_LINES.length - 1 ? 'center' : 'left';
            offCtx.fillText(TXT_LINES[i], i === 0 || i === TXT_LINES.length - 1 ? PW / 2 : 22, y);
            if (TXT_PRICES[i]) {
                offCtx.textAlign = 'right';
                offCtx.fillText(TXT_PRICES[i], PW - 22, y);
            }
        }
        offCtx.fillRect(18, 28 + 6 * 34 - 17, PW - 36, 2);
        const d = offCtx.getImageData(0, 0, PW, H).data;
        for (let i = 0; i < PW * H; i += 1) {
            mask[i] = d[i * 4 + 3] / 255;
        }
    }
    function restart() {
        heat.fill(0);
        front = 0;
        phase = 'print';
        phaseT = 0;
        status.textContent = TXT_PRINT;
    }
    function step() {
        clock += FIXED_DT;
        phaseT += FIXED_DT;
        const dt = FIXED_DT / 1000;
        // 인쇄 머리가 위에서 아래로 지나가며 열을 쌓는다
        if (phase === 'print') {
            const nf = Math.min(H, Math.round((phaseT / PRINT_MS) * H));
            for (let y = front; y < nf; y += 1) {
                for (let x = 0; x < PW; x += 1) {
                    const m = mask[y * PW + x];
                    heat[y * PW + x] = m > 0.05 ? Math.min(1.2, HEAT_GAIN * m) : HALO;
                }
            }
            front = nf;
            if (phaseT >= PRINT_MS) {
                phase = 'fade';
                status.textContent = TXT_FADE;
            }
        }
        const mul = (sun ? SUN_X : 1) * dt;
        let alive = 0;
        for (let i = 0; i < PW * H; i += 1) {
            const h = heat[i];
            if (h <= 0) {
                continue;
            }
            const nh = h - mul * decayAt(rate[i]);
            heat[i] = nh > 0 ? nh : 0;
            if (nh > CUTOFF) {
                alive += 1;
            }
        }
        if (phase === 'fade' && alive === 0 && !gone) {
            gone = true;
            status.textContent = TXT_GONE;
        }
        if (phaseT >= CYCLE_MS) {
            gone = false;
            restart();
        }
    }
    let gone = false;
    function settle() {
        for (let i = 0; i < PW * H; i += 1) {
            heat[i] = mask[i];
        }
        phase = 'fade';
        status.textContent = TXT_FADE;
    }
    function paint() {
        const d = img.data;
        for (let y = 0; y < H; y += 1) {
            for (let x = 0; x < PW; x += 1) {
                const i = y * PW + x;
                const h = heat[i];
                // 종이 바탕에도 지도가 옅게 비친다
                const base = mix(PAPER, PEACH, rate[i] * 0.16);
                let r = base[0];
                let g = base[1];
                let b = base[2];
                if (h > 0 && h <= CUTOFF) {
                    // 글자가 없는 자리도 옅게 달아올랐다 식는다 — 바램 지도가 색으로 드러난다
                    const w = (h / CUTOFF) * 0.55;
                    r = lerp(r, 238, w);
                    g = lerp(g, 186, w);
                    b = lerp(b, 150, w);
                }
                else if (h > CUTOFF) {
                    const a = smooth((h - CUTOFF) / 0.55);
                    const warm = a;
                    const k2 = a * a;
                    r = lerp(r, 205, warm * 0.8);
                    g = lerp(g, 150, warm * 0.8);
                    b = lerp(b, 135, warm * 0.8);
                    r = lerp(r, INK[0], k2);
                    g = lerp(g, INK[1], k2);
                    b = lerp(b, INK[2], k2);
                }
                // 가장자리 음영
                const e = Math.min(x, PW - 1 - x);
                const sh = e < 10 ? 0.9 + 0.1 * (e / 10) : 1;
                d[i * 4] = r * sh;
                d[i * 4 + 1] = g * sh;
                d[i * 4 + 2] = b * sh;
                d[i * 4 + 3] = 255;
            }
        }
        offCtx.putImageData(img, 0, 0);
    }
    function draw() {
        ctx.fillStyle = rgba(BG, 1);
        ctx.fillRect(0, 0, W, H);
        ctx.fillStyle = rgba([10, 8, 22], 0.45);
        ctx.fillRect(PX + 7, 0, PW, H);
        paint();
        ctx.imageSmoothingEnabled = false;
        ctx.drawImage(off, PX, 0);
        ctx.fillStyle = rgba(mix(BG, LILAC, 0.14), 1);
        ctx.fillRect(0, H - 28, W, 28);
        // 인쇄 머리 선
        if (phase === 'print') {
            ctx.fillStyle = rgba(PINK, 0.9);
            ctx.fillRect(PX - 16, front - 1, PW + 32, 3);
        }
    }
    buildRate();
    buildMask();
    if (againBtn) {
        againBtn.addEventListener('click', function () {
            gone = false;
            restart();
            if (reduceQuery.matches) {
                settle();
                draw();
            }
        });
    }
    if (sunBtn) {
        sunBtn.addEventListener('click', function () {
            sun = !sun;
            sunBtn.setAttribute('aria-pressed', sun ? 'true' : 'false');
            if (reduceQuery.matches) {
                draw();
            }
        });
    }
    restart();
    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);
    };
})();

// RecThermalFadeNoiseBurnMap - vanilla 판(07-rec-thermal-fade-noise-burn-map) 의 React 포트. 같은 계산을 useEffect 안에서 돌린다.
import { useEffect, useRef } from "react";
import styles from "./RecThermalFadeNoiseBurnMap.module.scss";

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

export default function RecThermalFadeNoiseBurnMap() {
  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 HEAT_GAIN = 1;
    const FADE_RATE = 0.4;
    const NOISE_SCALE = 30;
    const CUTOFF = 0.25;
    const SPREAD = 2.4;
    const PRINT_MS = 700;
    const CYCLE_MS = 2800;
    const HALO = 0.24;
    const SUN_X = 3;
    const PW = 280;
    const PX = (W - PW) / 2;
    const TXT_PRINT = '인쇄 중';
    const TXT_FADE = '바래는 중';
    const TXT_GONE = '다 바램';
    const TXT_LINES: string[] = ['달빛 상점', '우유', '식빵', '사과', '달걀', '귤', '합계', '감사합니다'];
    const TXT_PRICES: string[] = ['', '1,200', '2,800', '3,500', '4,100', '1,900', '13,500', ''];
    const againBtn = root.querySelector('[data-role="btn"]') as HTMLButtonElement | null;
    const sunBtn = root.querySelector('[data-role="sun"]') as HTMLButtonElement | null;
    const off = document.createElement('canvas');
    off.width = PW;
    off.height = H;
    const offCtxRaw = off.getContext('2d');
    if (!offCtxRaw) { return; }
    const offCtx: CanvasRenderingContext2D = offCtxRaw;
    const img = offCtx.createImageData(PW, H);
    const mask = new Float32Array(PW * H);
    const heat = new Float32Array(PW * H);
    const rate = new Float32Array(PW * H);
    let front = 0;
    let phaseT = 0;
    let phase = 'print';
    let sun = false;
    let clock = 0;
    function hash2(x: number, y: number): number {
        let h = (Math.imul(x | 0, 374761393) + Math.imul(y | 0, 668265263) + 1442695041) | 0;
        h = Math.imul(h ^ (h >>> 13), 1274126177);
        h ^= h >>> 16;
        return (h >>> 0) / 4294967296;
    }
    // 값 노이즈 — 격자점 해시 네 개를 부드럽게 섞는다
    function noise2(x: number, y: number): number {
        const xi = Math.floor(x);
        const yi = Math.floor(y);
        const fx = smooth(x - xi);
        const fy = smooth(y - yi);
        const a = hash2(xi, yi);
        const b = hash2(xi + 1, yi);
        const c = hash2(xi, yi + 1);
        const d = hash2(xi + 1, yi + 1);
        return lerp(lerp(a, b, fx), lerp(c, d, fx), fy);
    }
    // 한 자리의 바램 속도(초당 열 감소량) — 지도 값 n(0~1)이 클수록 빨리 바랜다
    function decayAt(n: number): number {
        return FADE_RATE * (1 + SPREAD * n);
    }
    // 바램 속도 지도 — 위치마다 다른 값 (큰 덩이 + 잔 무늬)
    function buildRate(): void {
        for (let y = 0; y < H; y += 1) {
            for (let x = 0; x < PW; x += 1) {
                const n = 0.7 * noise2(x / NOISE_SCALE, y / NOISE_SCALE) + 0.3 * noise2(x / (NOISE_SCALE * 0.35) + 9, y / (NOISE_SCALE * 0.35) + 4);
                rate[y * PW + x] = n;
            }
        }
    }
    // 글자 마스크 — 한 번만 그려서 읽는다 (한 번뿐이라 틱마다 읽지 않는다)
    function buildMask(): void {
        offCtx.clearRect(0, 0, PW, H);
        offCtx.fillStyle = '#ffffff';
        offCtx.font = '700 17px "Noto Sans KR", ui-monospace, monospace';
        offCtx.textBaseline = 'middle';
        for (let i = 0; i < TXT_LINES.length; i += 1) {
            const y = 28 + i * 34;
            offCtx.textAlign = i === 0 || i === TXT_LINES.length - 1 ? 'center' : 'left';
            offCtx.fillText(TXT_LINES[i], i === 0 || i === TXT_LINES.length - 1 ? PW / 2 : 22, y);
            if (TXT_PRICES[i]) {
                offCtx.textAlign = 'right';
                offCtx.fillText(TXT_PRICES[i], PW - 22, y);
            }
        }
        offCtx.fillRect(18, 28 + 6 * 34 - 17, PW - 36, 2);
        const d = offCtx.getImageData(0, 0, PW, H).data;
        for (let i = 0; i < PW * H; i += 1) { mask[i] = d[i * 4 + 3] / 255; }
    }
    function restart(): void {
        heat.fill(0);
        front = 0;
        phase = 'print';
        phaseT = 0;
        status.textContent = TXT_PRINT;
    }
    function step(): void {
        clock += FIXED_DT;
        phaseT += FIXED_DT;
        const dt = FIXED_DT / 1000;
        // 인쇄 머리가 위에서 아래로 지나가며 열을 쌓는다
        if (phase === 'print') {
            const nf = Math.min(H, Math.round((phaseT / PRINT_MS) * H));
            for (let y = front; y < nf; y += 1) {
                for (let x = 0; x < PW; x += 1) {
                    const m = mask[y * PW + x];
                    heat[y * PW + x] = m > 0.05 ? Math.min(1.2, HEAT_GAIN * m) : HALO;
                }
            }
            front = nf;
            if (phaseT >= PRINT_MS) { phase = 'fade'; status.textContent = TXT_FADE; }
        }
        const mul = (sun ? SUN_X : 1) * dt;
        let alive = 0;
        for (let i = 0; i < PW * H; i += 1) {
            const h = heat[i];
            if (h <= 0) { continue; }
            const nh = h - mul * decayAt(rate[i]);
            heat[i] = nh > 0 ? nh : 0;
            if (nh > CUTOFF) { alive += 1; }
        }
        if (phase === 'fade' && alive === 0 && !gone) {
            gone = true;
            status.textContent = TXT_GONE;
        }
        if (phaseT >= CYCLE_MS) { gone = false; restart(); }
    }
    let gone = false;
    function settle(): void {
        for (let i = 0; i < PW * H; i += 1) { heat[i] = mask[i]; }
        phase = 'fade';
        status.textContent = TXT_FADE;
    }
    function paint(): void {
        const d = img.data;
        for (let y = 0; y < H; y += 1) {
            for (let x = 0; x < PW; x += 1) {
                const i = y * PW + x;
                const h = heat[i];
                // 종이 바탕에도 지도가 옅게 비친다
                const base = mix(PAPER, PEACH, rate[i] * 0.16);
                let r = base[0];
                let g = base[1];
                let b = base[2];
                if (h > 0 && h <= CUTOFF) {
                    // 글자가 없는 자리도 옅게 달아올랐다 식는다 — 바램 지도가 색으로 드러난다
                    const w = (h / CUTOFF) * 0.55;
                    r = lerp(r, 238, w);
                    g = lerp(g, 186, w);
                    b = lerp(b, 150, w);
                } else if (h > CUTOFF) {
                    const a = smooth((h - CUTOFF) / 0.55);
                    const warm = a;
                    const k2 = a * a;
                    r = lerp(r, 205, warm * 0.8);
                    g = lerp(g, 150, warm * 0.8);
                    b = lerp(b, 135, warm * 0.8);
                    r = lerp(r, INK[0], k2);
                    g = lerp(g, INK[1], k2);
                    b = lerp(b, INK[2], k2);
                }
                // 가장자리 음영
                const e = Math.min(x, PW - 1 - x);
                const sh = e < 10 ? 0.9 + 0.1 * (e / 10) : 1;
                d[i * 4] = r * sh;
                d[i * 4 + 1] = g * sh;
                d[i * 4 + 2] = b * sh;
                d[i * 4 + 3] = 255;
            }
        }
        offCtx.putImageData(img, 0, 0);
    }
    function draw(): void {
        ctx.fillStyle = rgba(BG, 1);
        ctx.fillRect(0, 0, W, H);
        ctx.fillStyle = rgba([10, 8, 22], 0.45);
        ctx.fillRect(PX + 7, 0, PW, H);
        paint();
        ctx.imageSmoothingEnabled = false;
        ctx.drawImage(off, PX, 0);
        ctx.fillStyle = rgba(mix(BG, LILAC, 0.14), 1);
        ctx.fillRect(0, H - 28, W, 28);
        // 인쇄 머리 선
        if (phase === 'print') {
            ctx.fillStyle = rgba(PINK, 0.9);
            ctx.fillRect(PX - 16, front - 1, PW + 32, 3);
        }
    }
    buildRate();
    buildMask();
    if (againBtn) {
        againBtn.addEventListener('click', function (): void {
            gone = false;
            restart();
            if (reduceQuery.matches) { settle(); draw(); }
        });
    }
    if (sunBtn) {
        sunBtn.addEventListener('click', function (): void {
            sun = !sun;
            sunBtn.setAttribute('aria-pressed', sun ? 'true' : 'false');
            if (reduceQuery.matches) { draw(); }
        });
    }
    restart();

    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} aria-label="감열지 글자가 노이즈 지도에 따라 위치마다 다른 속도로 바래 사라지는 장면"></canvas>
        <p className={cx("rc__status")} data-role="status" aria-live="polite">인쇄 중</p>
        <div className={cx("rc__tools")}>
          <button className={cx("rc__btn")} data-role="btn" type="button">다시 인쇄</button>
          <button className={cx("rc__btn")} data-role="sun" type="button" aria-pressed="false">햇빛 쬐기</button>
        </div>
    </div>
  );
}