01印字ヘッドが一行ずつ打つたびに紙が一段進んで細かく震えるレシート印字の場面

<main class="stage">
<div class="rc is-demo" id="rc">
  <canvas class="rc__canvas" data-role="canvas" width="480" height="300" aria-label="レシートが一行ずつ印字され、行ごとに紙が押し上げられて横に震える場面"></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>
  </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 PAPER_W = 260;
    const FEED_PX = 14;
    const LINE_MS = 180;
    const SHIVER_PX = 2.4;
    const FEED_MS = 140;
    const START_MS = 200;
    const HOLD_MS = 600;
    const OUT_MS = 420;
    const OUT_PX = 190;
    const DARKEN_MS = 160;
    const HEAD_Y = 236;
    const TXT_PRINTING = '印字中';
    const TXT_DONE = '印字完了 — 合計';
    const ROWS = [
        { kind: 'title', a: 'つきあかり商店', b: '' },
        { kind: 'rule', a: '', b: '' },
        { kind: 'item', a: '牛乳', b: '1,200' },
        { kind: 'item', a: '食パン', b: '2,800' },
        { kind: 'item', a: 'りんご', b: '3,500' },
        { kind: 'item', a: '卵', b: '4,100' },
        { kind: 'rule', a: '', b: '' },
        { kind: 'total', a: '合計', b: '11,600' },
        { kind: 'note', a: 'ありがとうございました', b: '' },
    ];
    const btn = root.querySelector('[data-role="btn"]');
    let phase = 'wait';
    let phaseT = 0;
    let now = 0;
    let lineIdx = 0;
    let scroll = 0;
    let feedFrom = 0;
    const printedAt = [];
    const born = [];
    function easeOut(k) { const c = clamp(k, 0, 1); return 1 - (1 - c) * (1 - c) * (1 - c); }
    // 이어서 밀리는 동안의 가로 떨림 — 시작에 크고 끝으로 갈수록 잦아든다
    function shiverAt(k) {
        return SHIVER_PX * Math.sin(k * Math.PI * 7) * (1 - k);
    }
    // 줄 하나의 세로 위치 — 찍힌 순간의 밀림값과 지금 밀림값의 차이만큼 머리에서 멀어진다
    function rowY(printedScroll, scrollNow) {
        return HEAD_Y - 9 - (scrollNow - printedScroll);
    }
    function restart() {
        lineIdx = 0;
        printedAt.length = 0;
        born.length = 0;
        phase = 'wait';
        phaseT = 0;
        status.textContent = TXT_PRINTING;
    }
    function step() {
        now += FIXED_DT;
        phaseT += FIXED_DT;
        if (phase === 'wait') {
            if (phaseT >= START_MS) {
                phase = 'print';
                phaseT = 0;
                printedAt[lineIdx] = scroll;
            }
        }
        else if (phase === 'print') {
            if (phaseT >= LINE_MS) {
                born[lineIdx] = now;
                feedFrom = scroll;
                phase = 'feed';
                phaseT = 0;
            }
        }
        else if (phase === 'feed') {
            const k = phaseT / FEED_MS;
            scroll = feedFrom + FEED_PX * easeOut(k);
            if (k >= 1) {
                scroll = feedFrom + FEED_PX;
                lineIdx += 1;
                phaseT = 0;
                if (lineIdx >= ROWS.length) {
                    phase = 'hold';
                    status.textContent = TXT_DONE + ' 11,600';
                }
                else {
                    phase = 'print';
                    printedAt[lineIdx] = scroll;
                }
            }
        }
        else if (phase === 'hold') {
            if (phaseT >= HOLD_MS) {
                phase = 'out';
                feedFrom = scroll;
                phaseT = 0;
            }
        }
        else if (phase === 'out') {
            const k = phaseT / OUT_MS;
            scroll = feedFrom + OUT_PX * smooth(k);
            if (k >= 1) {
                scroll = feedFrom + OUT_PX;
                restart();
            }
        }
    }
    // 움직임 줄이기 — 다 찍힌 영수증을 그대로 놓는다
    function settle() {
        for (let i = 0; i < ROWS.length; i += 1) {
            printedAt[i] = i * FEED_PX;
            born[i] = -9999;
        }
        lineIdx = ROWS.length;
        scroll = ROWS.length * FEED_PX;
        phase = 'hold';
        status.textContent = TXT_DONE + ' 11,600';
    }
    function shiverNow() {
        if (phase === 'feed') {
            return shiverAt(phaseT / FEED_MS);
        }
        if (phase === 'out') {
            return shiverAt((phaseT / OUT_MS) % 0.5 * 2) * 0.6;
        }
        return 0;
    }
    function draw() {
        ctx.fillStyle = rgba(BG, 1);
        ctx.fillRect(0, 0, W, H);
        // 인쇄기 몸체
        const body = ctx.createLinearGradient(0, HEAD_Y, 0, H);
        body.addColorStop(0, rgba(mix(BG, LILAC, 0.34), 1));
        body.addColorStop(1, rgba(mix(BG, LILAC, 0.1), 1));
        ctx.fillStyle = body;
        ctx.fillRect(0, HEAD_Y, W, H - HEAD_Y);
        const px = (W - PAPER_W) / 2 + shiverNow();
        // 종이 — 가장자리 음영과 가로 결이 밀리는 만큼 같이 움직인다
        ctx.fillStyle = rgba(BG, 0.5);
        ctx.fillRect(px + 6, 0, PAPER_W, HEAD_Y);
        const sheet = ctx.createLinearGradient(px, 0, px + PAPER_W, 0);
        sheet.addColorStop(0, rgba(mix(PAPER, INK, 0.14), 1));
        sheet.addColorStop(0.12, rgba(PAPER, 1));
        sheet.addColorStop(0.88, rgba(PAPER, 1));
        sheet.addColorStop(1, rgba(mix(PAPER, INK, 0.14), 1));
        ctx.fillStyle = sheet;
        ctx.fillRect(px, 0, PAPER_W, HEAD_Y);
        const off = ((scroll % 8) + 8) % 8;
        ctx.fillStyle = rgba(INK, 0.1);
        for (let y = off - 8; y < HEAD_Y; y += 8) {
            ctx.fillRect(px, y, PAPER_W, 1);
        }
        // 줄들
        ctx.font = '600 12px "Noto Sans KR", ui-monospace, monospace';
        ctx.textBaseline = 'alphabetic';
        for (let i = 0; i < ROWS.length; i += 1) {
            if (printedAt[i] === undefined) {
                continue;
            }
            const y = rowY(printedAt[i], scroll);
            if (y < -4 || y > HEAD_Y) {
                continue;
            }
            const done = born[i] !== undefined;
            let alpha = 0.3;
            if (done) {
                alpha = 0.3 + 0.7 * smooth((now - born[i]) / DARKEN_MS);
            }
            let reveal = 1;
            if (!done && i === lineIdx && phase === 'print') {
                reveal = clamp(phaseT / LINE_MS, 0, 1);
            }
            ctx.save();
            ctx.beginPath();
            ctx.rect(px, y - 14, PAPER_W * reveal, 20);
            ctx.clip();
            ctx.fillStyle = rgba(INK, alpha);
            const r = ROWS[i];
            if (r.kind === 'rule') {
                ctx.fillRect(px + 18, y - 4, PAPER_W - 36, 1);
            }
            else if (r.kind === 'title') {
                ctx.textAlign = 'center';
                ctx.font = '700 14px "Noto Sans KR", ui-monospace, monospace';
                ctx.fillText(r.a, px + PAPER_W / 2, y);
            }
            else if (r.kind === 'note') {
                ctx.textAlign = 'center';
                ctx.font = '600 12px "Noto Sans KR", ui-monospace, monospace';
                ctx.fillText(r.a, px + PAPER_W / 2, y);
            }
            else {
                ctx.font = (r.kind === 'total' ? '700 13px' : '600 12px') + ' "Noto Sans KR", ui-monospace, monospace';
                ctx.textAlign = 'left';
                ctx.fillText(r.a, px + 18, y);
                ctx.textAlign = 'right';
                ctx.fillText(r.b, px + PAPER_W - 18, y);
            }
            ctx.restore();
        }
        // 인쇄 머리 — 찍는 동안 한 줄이 달아오른다
        ctx.fillStyle = rgba(mix(BG, LILAC, 0.5), 1);
        ctx.fillRect(px - 14, HEAD_Y - 2, PAPER_W + 28, 12);
        const heat = phase === 'print' ? 0.55 + 0.45 * Math.sin(now / 24) : 0.12;
        const glow = ctx.createLinearGradient(0, HEAD_Y - 14, 0, HEAD_Y + 4);
        glow.addColorStop(0, rgba(PEACH, 0));
        glow.addColorStop(0.7, rgba(PEACH, 0.5 * heat));
        glow.addColorStop(1, rgba(PINK, 0.9 * heat));
        ctx.fillStyle = glow;
        ctx.fillRect(px, HEAD_Y - 14, PAPER_W, 18);
        // 종이 나오는 틈
        ctx.fillStyle = rgba(BG, 0.9);
        ctx.fillRect(px - 14, HEAD_Y + 10, PAPER_W + 28, 4);
    }
    if (btn) {
        btn.addEventListener('click', function () {
            if (reduceQuery.matches) {
                settle();
                draw();
                return;
            }
            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);
    };
})();

// RecThermalHeadLineFeedJitter - vanilla 판(01-rec-thermal-head-line-feed-jitter) 의 React 포트. 같은 계산을 useEffect 안에서 돌린다.
import { useEffect, useRef } from "react";
import styles from "./RecThermalHeadLineFeedJitter.module.scss";

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

export default function RecThermalHeadLineFeedJitter() {
  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 PAPER_W = 260;
    const FEED_PX = 14;
    const LINE_MS = 180;
    const SHIVER_PX = 2.4;
    const FEED_MS = 140;
    const START_MS = 200;
    const HOLD_MS = 600;
    const OUT_MS = 420;
    const OUT_PX = 190;
    const DARKEN_MS = 160;
    const HEAD_Y = 236;
    const TXT_PRINTING = '인쇄 중';
    const TXT_DONE = '인쇄 완료 — 합계';
    interface Row { kind: string; a: string; b: string; }
    const ROWS: Row[] = [
        { kind: 'title', a: '달빛 상점', b: '' },
        { kind: 'rule', a: '', b: '' },
        { kind: 'item', a: '우유', b: '1,200' },
        { kind: 'item', a: '식빵', b: '2,800' },
        { kind: 'item', a: '사과', b: '3,500' },
        { kind: 'item', a: '달걀', b: '4,100' },
        { kind: 'rule', a: '', b: '' },
        { kind: 'total', a: '합계', b: '11,600' },
        { kind: 'note', a: '감사합니다', b: '' },
    ];
    const btn = root.querySelector('[data-role="btn"]') as HTMLButtonElement | null;
    let phase = 'wait';
    let phaseT = 0;
    let now = 0;
    let lineIdx = 0;
    let scroll = 0;
    let feedFrom = 0;
    const printedAt: number[] = [];
    const born: number[] = [];
    function easeOut(k: number): number { const c = clamp(k, 0, 1); return 1 - (1 - c) * (1 - c) * (1 - c); }
    // 이어서 밀리는 동안의 가로 떨림 — 시작에 크고 끝으로 갈수록 잦아든다
    function shiverAt(k: number): number {
        return SHIVER_PX * Math.sin(k * Math.PI * 7) * (1 - k);
    }
    // 줄 하나의 세로 위치 — 찍힌 순간의 밀림값과 지금 밀림값의 차이만큼 머리에서 멀어진다
    function rowY(printedScroll: number, scrollNow: number): number {
        return HEAD_Y - 9 - (scrollNow - printedScroll);
    }
    function restart(): void {
        lineIdx = 0;
        printedAt.length = 0;
        born.length = 0;
        phase = 'wait';
        phaseT = 0;
        status.textContent = TXT_PRINTING;
    }
    function step(): void {
        now += FIXED_DT;
        phaseT += FIXED_DT;
        if (phase === 'wait') {
            if (phaseT >= START_MS) { phase = 'print'; phaseT = 0; printedAt[lineIdx] = scroll; }
        } else if (phase === 'print') {
            if (phaseT >= LINE_MS) { born[lineIdx] = now; feedFrom = scroll; phase = 'feed'; phaseT = 0; }
        } else if (phase === 'feed') {
            const k = phaseT / FEED_MS;
            scroll = feedFrom + FEED_PX * easeOut(k);
            if (k >= 1) {
                scroll = feedFrom + FEED_PX;
                lineIdx += 1;
                phaseT = 0;
                if (lineIdx >= ROWS.length) {
                    phase = 'hold';
                    status.textContent = TXT_DONE + ' 11,600';
                } else {
                    phase = 'print';
                    printedAt[lineIdx] = scroll;
                }
            }
        } else if (phase === 'hold') {
            if (phaseT >= HOLD_MS) { phase = 'out'; feedFrom = scroll; phaseT = 0; }
        } else if (phase === 'out') {
            const k = phaseT / OUT_MS;
            scroll = feedFrom + OUT_PX * smooth(k);
            if (k >= 1) { scroll = feedFrom + OUT_PX; restart(); }
        }
    }
    // 움직임 줄이기 — 다 찍힌 영수증을 그대로 놓는다
    function settle(): void {
        for (let i = 0; i < ROWS.length; i += 1) { printedAt[i] = i * FEED_PX; born[i] = -9999; }
        lineIdx = ROWS.length;
        scroll = ROWS.length * FEED_PX;
        phase = 'hold';
        status.textContent = TXT_DONE + ' 11,600';
    }
    function shiverNow(): number {
        if (phase === 'feed') { return shiverAt(phaseT / FEED_MS); }
        if (phase === 'out') { return shiverAt((phaseT / OUT_MS) % 0.5 * 2) * 0.6; }
        return 0;
    }
    function draw(): void {
        ctx.fillStyle = rgba(BG, 1);
        ctx.fillRect(0, 0, W, H);
        // 인쇄기 몸체
        const body = ctx.createLinearGradient(0, HEAD_Y, 0, H);
        body.addColorStop(0, rgba(mix(BG, LILAC, 0.34), 1));
        body.addColorStop(1, rgba(mix(BG, LILAC, 0.1), 1));
        ctx.fillStyle = body;
        ctx.fillRect(0, HEAD_Y, W, H - HEAD_Y);
        const px = (W - PAPER_W) / 2 + shiverNow();
        // 종이 — 가장자리 음영과 가로 결이 밀리는 만큼 같이 움직인다
        ctx.fillStyle = rgba(BG, 0.5);
        ctx.fillRect(px + 6, 0, PAPER_W, HEAD_Y);
        const sheet = ctx.createLinearGradient(px, 0, px + PAPER_W, 0);
        sheet.addColorStop(0, rgba(mix(PAPER, INK, 0.14), 1));
        sheet.addColorStop(0.12, rgba(PAPER, 1));
        sheet.addColorStop(0.88, rgba(PAPER, 1));
        sheet.addColorStop(1, rgba(mix(PAPER, INK, 0.14), 1));
        ctx.fillStyle = sheet;
        ctx.fillRect(px, 0, PAPER_W, HEAD_Y);
        const off = ((scroll % 8) + 8) % 8;
        ctx.fillStyle = rgba(INK, 0.1);
        for (let y = off - 8; y < HEAD_Y; y += 8) { ctx.fillRect(px, y, PAPER_W, 1); }
        // 줄들
        ctx.font = '600 12px "Noto Sans KR", ui-monospace, monospace';
        ctx.textBaseline = 'alphabetic';
        for (let i = 0; i < ROWS.length; i += 1) {
            if (printedAt[i] === undefined) { continue; }
            const y = rowY(printedAt[i], scroll);
            if (y < -4 || y > HEAD_Y) { continue; }
            const done = born[i] !== undefined;
            let alpha = 0.3;
            if (done) { alpha = 0.3 + 0.7 * smooth((now - born[i]) / DARKEN_MS); }
            let reveal = 1;
            if (!done && i === lineIdx && phase === 'print') { reveal = clamp(phaseT / LINE_MS, 0, 1); }
            ctx.save();
            ctx.beginPath();
            ctx.rect(px, y - 14, PAPER_W * reveal, 20);
            ctx.clip();
            ctx.fillStyle = rgba(INK, alpha);
            const r = ROWS[i];
            if (r.kind === 'rule') {
                ctx.fillRect(px + 18, y - 4, PAPER_W - 36, 1);
            } else if (r.kind === 'title') {
                ctx.textAlign = 'center';
                ctx.font = '700 14px "Noto Sans KR", ui-monospace, monospace';
                ctx.fillText(r.a, px + PAPER_W / 2, y);
            } else if (r.kind === 'note') {
                ctx.textAlign = 'center';
                ctx.font = '600 12px "Noto Sans KR", ui-monospace, monospace';
                ctx.fillText(r.a, px + PAPER_W / 2, y);
            } else {
                ctx.font = (r.kind === 'total' ? '700 13px' : '600 12px') + ' "Noto Sans KR", ui-monospace, monospace';
                ctx.textAlign = 'left';
                ctx.fillText(r.a, px + 18, y);
                ctx.textAlign = 'right';
                ctx.fillText(r.b, px + PAPER_W - 18, y);
            }
            ctx.restore();
        }
        // 인쇄 머리 — 찍는 동안 한 줄이 달아오른다
        ctx.fillStyle = rgba(mix(BG, LILAC, 0.5), 1);
        ctx.fillRect(px - 14, HEAD_Y - 2, PAPER_W + 28, 12);
        const heat = phase === 'print' ? 0.55 + 0.45 * Math.sin(now / 24) : 0.12;
        const glow = ctx.createLinearGradient(0, HEAD_Y - 14, 0, HEAD_Y + 4);
        glow.addColorStop(0, rgba(PEACH, 0));
        glow.addColorStop(0.7, rgba(PEACH, 0.5 * heat));
        glow.addColorStop(1, rgba(PINK, 0.9 * heat));
        ctx.fillStyle = glow;
        ctx.fillRect(px, HEAD_Y - 14, PAPER_W, 18);
        // 종이 나오는 틈
        ctx.fillStyle = rgba(BG, 0.9);
        ctx.fillRect(px - 14, HEAD_Y + 10, PAPER_W + 28, 4);
    }
    if (btn) {
        btn.addEventListener('click', function (): void {
            if (reduceQuery.matches) { settle(); draw(); return; }
            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="영수증이 한 줄씩 인쇄되며 줄마다 종이가 밀려 올라가고 가로로 떨리는 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>
        </div>
    </div>
  );
}