09A Launch Countdown Scene Where a Shockwave Spreads at Every Number and Ignition Fires at Zero

<main class="stage">
  <div class="cd is-demo" id="cd" data-demo="1">
    <div class="cd__view cd__view--scene">
      <canvas class="cd__cv" data-r="cv" role="img" aria-label="A launch countdown where the stars speed up at 0"></canvas>
      <p class="cd__read cd__read--corner" role="timer"><b data-r="num">1.4</b><span>s</span></p>
    </div>
    <div class="cd__bar">
      <button class="cd__btn" type="button" data-r="toggle">Pause</button>
      <button class="cd__btn" type="button" data-r="reset">Reset</button>
    </div>
    <p class="cd__sr" aria-live="polite" data-r="status"></p>
  </div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 핵심: 남은 시간 하나(경과는 rAF 타임스탬프 누적)에서 모양을 계산해 그린다. CSS 는 모양과 색만 맡는다.

$bg: $stage-ink;
$fg: $subject-cream;
$btn: rgba($subject-cream, .14);
@include stage($bg);
.cd {
  --view-h: min(calc(100vh - 2 * clamp(8px, 4vw, 24px) - 48px), 196px);
  position: relative;
  box-sizing: border-box;
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-2;
  color: $fg;
  font-size: 14px;
  line-height: 20px;
  font-weight: 600;
}
.cd__view { position: relative; }
.cd__view--scene { width: 100%; height: var(--view-h); overflow: hidden; border-radius: $r-card; background: mix($stage-ink, $subject-lilac, 88%); }
.cd__cv { display: block; width: 100%; height: 100%; }
.cd__read { margin: 0; display: flex; align-items: baseline; gap: $sp-1; font-variant-numeric: tabular-nums; }
.cd__read b { font-size: 28px; line-height: 32px; font-weight: 800; }
.cd__read--center { position: absolute; left: 50%; top: 50%; transform: translate(-50%, -50%); }
.cd__read--corner { position: absolute; left: $sp-2; top: $sp-2; }
.cd__bar { display: flex; gap: $sp-2; }
.cd__btn {
  box-sizing: border-box;
  height: 36px;
  padding: 0 $sp-4;
  border: 0;
  border-radius: $r-control;
  background: $btn;
  color: $fg;
  font-size: 14px;
  line-height: 20px;
  font-weight: 700;
  cursor: pointer;
}
.cd__btn:focus-visible { outline: 2px solid $subject-lilac; outline-offset: 2px; }
.cd__sr { position: absolute; width: 1px; height: 1px; margin: 0; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
@media (prefers-reduced-motion: reduce) {
  .cd__strip { filter: none !important; }
  .cd__leaf { display: none !important; }
}
.cd {
  --star: #{$subject-cream};
  --ring: #{$subject-sky};
  --flame: #{$subject-pink};
  --warm: #{mix($stage-yellow, $subject-cream, 60%)};
}

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);
}

.cd {
  --view-h: min(calc(100vh - 2 * clamp(8px, 4vw, 24px) - 48px), 196px);
  position: relative;
  box-sizing: border-box;
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  color: #fff7e6;
  font-size: 14px;
  line-height: 20px;
  font-weight: 600;
}

.cd__view {
  position: relative;
}

.cd__view--scene {
  width: 100%;
  height: var(--view-h);
  overflow: hidden;
  border-radius: 16px;
  background: rgb(16.6431372549%, 14.431372549%, 20.9725490196%);
}

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

.cd__read {
  margin: 0;
  display: flex;
  align-items: baseline;
  gap: 4px;
  font-variant-numeric: tabular-nums;
}

.cd__read b {
  font-size: 28px;
  line-height: 32px;
  font-weight: 800;
}

.cd__read--center {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
}

.cd__read--corner {
  position: absolute;
  left: 8px;
  top: 8px;
}

.cd__bar {
  display: flex;
  gap: 8px;
}

.cd__btn {
  box-sizing: border-box;
  height: 36px;
  padding: 0 16px;
  border: 0;
  border-radius: 12px;
  background: rgba(255, 247, 230, 0.14);
  color: #fff7e6;
  font-size: 14px;
  line-height: 20px;
  font-weight: 700;
  cursor: pointer;
}

.cd__btn:focus-visible {
  outline: 2px solid #b9a0ff;
  outline-offset: 2px;
}

.cd__sr {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

@media (prefers-reduced-motion: reduce) {
  .cd__strip {
    filter: none !important;
  }
  .cd__leaf {
    display: none !important;
  }
}
.cd {
  --star: #fff7e6;
  --ring: #6ec8ff;
  --flame: #ff9ebb;
  --warm: rgb(100%, 88.1568627451%, 50.9019607843%);
}

(function () {
    const root = document.getElementById("cd");
    if (!root) return;
    function cx(s) {
        return s;
    }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo = !reduce;
    let running = demo;
    let elapsed = 0;
    let lastTs = -1;
    let lastDraw = -1e9;
    let raf = 0;
    const hooks = { stop: () => { } };
    const offs = [];
    const COUNT_FROM = 3;
    const DEMO_SECOND_MS = 450;
    const SECOND_MS = 1000;
    const HOLD_MS = 450;
    const WAVE_R = 120;
    const WAVE_MS = 420;
    const SHAKE_AMP = 5;
    const STAR_BOOST = 3;
    const STAR_N = 90;
    let secondMs = demo ? DEMO_SECOND_MS : SECOND_MS;
    let totalMs = COUNT_FROM * secondMs;
    const cv = q('[data-r="cv"]');
    const ctx2d = cv.getContext("2d");
    if (!ctx2d)
        return () => { };
    const g = ctx2d;
    let cw = 1;
    let ch = 1;
    let dpr = 1;
    // 캔버스 안쪽 해상도를 화면 크기와 devicePixelRatio 에 맞춘다. 리사이즈마다 Reset 호출된다
    function fitCanvas() {
        const r = cv.getBoundingClientRect();
        dpr = Math.min(2, window.devicePixelRatio || 1);
        cw = Math.max(1, Math.round(r.width));
        ch = Math.max(1, Math.round(r.height));
        cv.width = Math.round(cw * dpr);
        cv.height = Math.round(ch * dpr);
        g.setTransform(dpr, 0, 0, dpr, 0, 0);
    }
    function cssVar(name) {
        return getComputedStyle(root).getPropertyValue(name).trim();
    }
    function parseColor(h) {
        // CSS 변수 값은 #rrggbb 로도, rgb(r, g, b) 로도, rgb(100%, 50%, 0%) 로도 나올 수 있다
        const m6 = /^#([0-9a-f]{6})$/i.exec(h);
        if (m6) {
            const n = parseInt(m6[1], 16);
            return [(n >> 16) & 255, (n >> 8) & 255, n & 255];
        }
        const m = /([0-9.]+)(%?)[ ,]+([0-9.]+)(%?)[ ,]+([0-9.]+)(%?)/.exec(h);
        if (!m)
            return [255, 255, 255];
        const ch = (v, pct) => Math.round(pct ? (Number(v) * 255) / 100 : Number(v));
        return [ch(m[1], m[2]), ch(m[3], m[4]), ch(m[5], m[6])];
    }
    function rgba(c, a) {
        return "rgba(" + c[0] + "," + c[1] + "," + c[2] + "," + a.toFixed(3) + ")";
    }
    function q(sel) {
        return root.querySelector(sel);
    }
    function on(el, type, fn) {
        el.addEventListener(type, fn);
        offs.push(() => el.removeEventListener(type, fn));
    }
    function clamp(v, lo, hi) {
        return Math.max(lo, Math.min(hi, v));
    }
    // 지수 접근: 프레임률이 달라도 같은 속도가 되도록 dt 를 60fps 프레임 수로 환산해 쓴다
    function approach(x, target, per, dt) {
        return x + (target - x) * (1 - Math.pow(1 - per, dt * 60));
    }
    const toggle = q('[data-r="toggle"]');
    const resetBtn = q('[data-r="reset"]');
    const status = q('[data-r="status"]');
    // 남은 시간. 경과는 rAF 타임스탬프 차이를 누적한 값이라 시계를 따로 읽지 않는다
    function remainMs() {
        return clamp(totalMs - elapsed, 0, totalMs);
    }
    function syncButtons() {
        toggle.textContent = running ? "Pause" : "Start";
        toggle.setAttribute("aria-pressed", running ? "true" : "false");
    }
    // 스크린리더 안내는 멈출 때와 끝날 때만 갱신한다. 시연 루프 중에는 읽지 않는다
    function say(msg) {
        if (!demo)
            status.textContent = msg;
    }
    function stopDemo() {
        if (!demo)
            return;
        demo = false;
        root.classList.remove("is-demo");
        root.removeAttribute("data-demo");
        hooks.stop();
    }
    function restart() {
        elapsed = 0;
        resetState();
    }
    function update(dt) {
        tick(dt);
        draw();
    }
    function frame(ts) {
        raf = requestAnimationFrame(frame);
        const raw = lastTs < 0 ? 0 : ts - lastTs;
        lastTs = ts;
        if (running) {
            elapsed += raw;
            if (demo) {
                const cycle = totalMs + HOLD_MS;
                if (elapsed >= cycle) {
                    elapsed %= cycle;
                    resetState();
                }
            }
            else if (elapsed >= totalMs) {
                elapsed = totalMs;
                running = false;
                say("Time is up");
                syncButtons();
            }
        }
        if (reduce && ts - lastDraw < 250)
            return;
        lastDraw = ts;
        update(Math.min(raw, 50) / 1000);
    }
    on(toggle, "click", () => {
        stopDemo();
        if (!running && elapsed >= totalMs)
            restart();
        running = !running;
        say(running ? "" : "Paused");
        syncButtons();
        update(0);
    });
    on(resetBtn, "click", () => {
        stopDemo();
        running = false;
        restart();
        say("");
        syncButtons();
        update(0);
    });
    const sx = new Float32Array(STAR_N);
    const sy = new Float32Array(STAR_N);
    const sz = new Float32Array(STAR_N);
    let seed = 3;
    function rand() {
        seed = (Math.imul(seed, 1664525) + 1013904223) >>> 0;
        return seed / 4294967296;
    }
    for (let i = 0; i < STAR_N; i++) {
        sx[i] = rand();
        sy[i] = rand();
        sz[i] = 0.3 + 0.7 * rand();
    }
    let speed = 40;
    const num = q('[data-r="num"]');
    // 1차원 값 노이즈: 정수 격자마다 사인으로 만든 값을 두고 사이를 부드럽게 잇는다
    function lat(i) {
        const s = Math.sin(i * 127.1 + 311.7) * 43758.5453;
        return s - Math.floor(s);
    }
    function vnoise(x) {
        const i = Math.floor(x);
        const f = x - i;
        const u = f * f * (3 - 2 * f);
        return lat(i) * (1 - u) + lat(i + 1) * u - 0.5;
    }
    let cStar = [255, 247, 230];
    let cRing = [110, 200, 255];
    let cFlame = [255, 158, 187];
    let cWarm = [255, 233, 159];
    function resize() {
        fitCanvas();
        cStar = parseColor(cssVar("--star"));
        cRing = parseColor(cssVar("--ring"));
        cFlame = parseColor(cssVar("--flame"));
        cWarm = parseColor(cssVar("--warm"));
    }
    hooks.stop = () => {
        elapsed *= SECOND_MS / secondMs;
        secondMs = SECOND_MS;
        totalMs = COUNT_FROM * secondMs;
    };
    function shownCount() {
        return Math.ceil(remainMs() / secondMs - 1e-6);
    }
    function resetState() {
        speed = 40;
    }
    function tick(dt) {
        if (reduce)
            return;
        const ignited = shownCount() === 0;
        const target = 40 * (ignited ? STAR_BOOST : 1);
        speed = approach(speed, target, 0.12, dt);
        for (let i = 0; i < STAR_N; i++) {
            sy[i] += (speed * sz[i] * dt) / 100;
            if (sy[i] > 1.05) {
                sy[i] -= 1.1;
                sx[i] = rand();
            }
        }
    }
    function draw() {
        const n = shownCount();
        const ignited = n === 0;
        // 흔들림: 숫자가 바뀐 직후의 한 방 + 0 에 가까울수록 커지는 바닥 진동
        let amp = 0;
        if (!reduce) {
            const since = elapsed - (COUNT_FROM - n) * secondMs;
            const base = Math.pow(1 - n / COUNT_FROM, 2) * 0.45;
            amp = SHAKE_AMP * (ignited ? 1 : base + 0.8 * Math.exp(-Math.max(0, since) / 70));
        }
        g.clearRect(0, 0, cw, ch);
        g.save();
        if (amp > 0)
            g.translate(vnoise(elapsed * 0.07) * 2 * amp, vnoise(elapsed * 0.07 + 40) * 2 * amp);
        // 별: 속도에 비례해 길어지는 줄
        const trail = reduce ? 0 : speed / 70;
        for (let i = 0; i < STAR_N; i++) {
            const x = sx[i] * cw;
            const y = sy[i] * ch;
            g.strokeStyle = rgba(cStar, 0.35 + 0.55 * sz[i]);
            g.lineWidth = 1 + sz[i];
            g.beginPath();
            g.moveTo(x, y);
            g.lineTo(x, y - trail * sz[i] * 14);
            g.stroke();
            if (reduce) {
                g.fillStyle = rgba(cStar, 0.6);
                g.fillRect(x, y, 1.6, 1.6);
            }
        }
        // 점화 불꽃(아래쪽)
        if (ignited) {
            const fx = cw / 2;
            const fy = ch;
            const pulse = reduce ? 1 : 1 + 0.12 * Math.sin(elapsed * 0.09);
            const fg = g.createRadialGradient(fx, fy, 0, fx, fy, ch * 0.9 * pulse);
            fg.addColorStop(0, rgba(cWarm, 0.9));
            fg.addColorStop(0.45, rgba(cFlame, 0.45));
            fg.addColorStop(1, rgba(cFlame, 0));
            g.fillStyle = fg;
            g.fillRect(0, 0, cw, ch);
        }
        // 충격파 링: 숫자가 바뀐 시각마다 한 개씩, 시간에서 바로 계산한다
        if (!reduce) {
            const k = Math.min(COUNT_FROM, Math.floor(elapsed / secondMs + 1e-6));
            for (let j = Math.max(0, k - 1); j <= k; j++) {
                const age = elapsed - j * secondMs;
                if (age < 0 || age >= WAVE_MS)
                    continue;
                const u = age / WAVE_MS;
                const big = j === COUNT_FROM ? 1.7 : 1;
                g.strokeStyle = rgba(j === COUNT_FROM ? cFlame : cRing, Math.pow(1 - u, 1.5) * 0.9);
                g.lineWidth = 3 + 5 * (1 - u);
                g.beginPath();
                g.arc(cw / 2, ch / 2, WAVE_R * big * (1 - Math.pow(1 - u, 3)) * Math.min(1, ch / 200), 0, Math.PI * 2);
                g.stroke();
            }
        }
        // 큰 숫자
        g.fillStyle = rgba(ignited ? cFlame : cStar, 1);
        g.font = "800 " + Math.round(ch * 0.5) + "px -apple-system, Segoe UI, sans-serif";
        g.textAlign = "center";
        g.textBaseline = "middle";
        g.fillText(String(n), cw / 2, ch / 2);
        g.restore();
        num.textContent = (remainMs() / 1000).toFixed(1);
    }
    const ro = new ResizeObserver(() => {
        resize();
        draw();
    });
    ro.observe(root);
    offs.push(() => ro.disconnect());
    resize();
    resetState();
    syncButtons();
    update(0);
    raf = requestAnimationFrame(frame);
    return () => {
        cancelAnimationFrame(raf);
        offs.forEach((f) => f());
    };
})();

// LaunchSequenceShockwaveHero - vanilla 판(09-cd-launch-sequence-shockwave-hero) 의 React 포트. 같은 계산을 useEffect 안에서 돌린다.
import { useEffect, useRef } from "react";
import styles from "./LaunchSequenceShockwaveHero.module.scss";

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

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

  useEffect(() => {
    const rootEl = rootRef.current;
    if (!rootEl) return;
    const root: HTMLElement = rootEl;
    const reduce: boolean = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo: boolean = !reduce;
    let running: boolean = demo;
    let elapsed = 0;
    let lastTs = -1;
    let lastDraw = -1e9;
    let raf = 0;
    const hooks: { stop: () => void } = { stop: () => {} };
    const offs: Array<() => void> = [];
    const COUNT_FROM = 3;
    const DEMO_SECOND_MS = 450;
    const SECOND_MS = 1000;
    const HOLD_MS = 450;
    const WAVE_R = 120;
    const WAVE_MS = 420;
    const SHAKE_AMP = 5;
    const STAR_BOOST = 3;
    const STAR_N = 90;
    let secondMs = demo ? DEMO_SECOND_MS : SECOND_MS;
    let totalMs = COUNT_FROM * secondMs;
    const cv = q<HTMLCanvasElement>('[data-r="cv"]');
    const ctx2d = cv.getContext("2d");
    if (!ctx2d) return () => {};
    const g: CanvasRenderingContext2D = ctx2d;
    let cw = 1;
    let ch = 1;
    let dpr = 1;
    // 캔버스 안쪽 해상도를 화면 크기와 devicePixelRatio 에 맞춘다. 리사이즈마다 다시 호출된다
    function fitCanvas(): void {
        const r = cv.getBoundingClientRect();
        dpr = Math.min(2, window.devicePixelRatio || 1);
        cw = Math.max(1, Math.round(r.width));
        ch = Math.max(1, Math.round(r.height));
        cv.width = Math.round(cw * dpr);
        cv.height = Math.round(ch * dpr);
        g.setTransform(dpr, 0, 0, dpr, 0, 0);
    }
    function cssVar(name: string): string {
        return getComputedStyle(root).getPropertyValue(name).trim();
    }
    function parseColor(h: string): number[] {
        // CSS 변수 값은 #rrggbb 로도, rgb(r, g, b) 로도, rgb(100%, 50%, 0%) 로도 나올 수 있다
        const m6 = /^#([0-9a-f]{6})$/i.exec(h);
        if (m6) {
            const n = parseInt(m6[1], 16);
            return [(n >> 16) & 255, (n >> 8) & 255, n & 255];
        }
        const m = /([0-9.]+)(%?)[ ,]+([0-9.]+)(%?)[ ,]+([0-9.]+)(%?)/.exec(h);
        if (!m) return [255, 255, 255];
        const ch = (v: string, pct: string): number => Math.round(pct ? (Number(v) * 255) / 100 : Number(v));
        return [ch(m[1], m[2]), ch(m[3], m[4]), ch(m[5], m[6])];
    }
    function rgba(c: number[], a: number): string {
        return "rgba(" + c[0] + "," + c[1] + "," + c[2] + "," + a.toFixed(3) + ")";
    }
    function q<T extends Element>(sel: string): T {
        return root.querySelector(sel) as T;
    }
    function on(el: EventTarget, type: string, fn: (e: Event) => void): void {
        el.addEventListener(type, fn);
        offs.push(() => el.removeEventListener(type, fn));
    }
    function clamp(v: number, lo: number, hi: number): number {
        return Math.max(lo, Math.min(hi, v));
    }
    // 지수 접근: 프레임률이 달라도 같은 속도가 되도록 dt 를 60fps 프레임 수로 환산해 쓴다
    function approach(x: number, target: number, per: number, dt: number): number {
        return x + (target - x) * (1 - Math.pow(1 - per, dt * 60));
    }
    const toggle = q<HTMLButtonElement>('[data-r="toggle"]');
    const resetBtn = q<HTMLButtonElement>('[data-r="reset"]');
    const status = q<HTMLElement>('[data-r="status"]');
    // 남은 시간. 경과는 rAF 타임스탬프 차이를 누적한 값이라 시계를 따로 읽지 않는다
    function remainMs(): number {
        return clamp(totalMs - elapsed, 0, totalMs);
    }
    function syncButtons(): void {
        toggle.textContent = running ? "멈춤" : "시작";
        toggle.setAttribute("aria-pressed", running ? "true" : "false");
    }
    // 스크린리더 안내는 멈출 때와 끝날 때만 갱신한다. 시연 루프 중에는 읽지 않는다
    function say(msg: string): void {
        if (!demo) status.textContent = msg;
    }
    function stopDemo(): void {
        if (!demo) return;
        demo = false;
        root.classList.remove("is-demo");
        root.removeAttribute("data-demo");
        hooks.stop();
    }
    function restart(): void {
        elapsed = 0;
        resetState();
    }
    function update(dt: number): void {
        tick(dt);
        draw();
    }
    function frame(ts: number): void {
        raf = requestAnimationFrame(frame);
        const raw = lastTs < 0 ? 0 : ts - lastTs;
        lastTs = ts;
        if (running) {
            elapsed += raw;
            if (demo) {
                const cycle = totalMs + HOLD_MS;
                if (elapsed >= cycle) {
                    elapsed %= cycle;
                    resetState();
                }
            } else if (elapsed >= totalMs) {
                elapsed = totalMs;
                running = false;
                say("시간이 다 됐습니다");
                syncButtons();
            }
        }
        if (reduce && ts - lastDraw < 250) return;
        lastDraw = ts;
        update(Math.min(raw, 50) / 1000);
    }
    on(toggle, "click", () => {
        stopDemo();
        if (!running && elapsed >= totalMs) restart();
        running = !running;
        say(running ? "" : "멈췄습니다");
        syncButtons();
        update(0);
    });
    on(resetBtn, "click", () => {
        stopDemo();
        running = false;
        restart();
        say("");
        syncButtons();
        update(0);
    });
    const sx = new Float32Array(STAR_N);
    const sy = new Float32Array(STAR_N);
    const sz = new Float32Array(STAR_N);
    let seed = 3;
    function rand(): number {
        seed = (Math.imul(seed, 1664525) + 1013904223) >>> 0;
        return seed / 4294967296;
    }
    for (let i = 0; i < STAR_N; i++) {
        sx[i] = rand();
        sy[i] = rand();
        sz[i] = 0.3 + 0.7 * rand();
    }
    let speed = 40;
    const num = q<HTMLElement>('[data-r="num"]');
    // 1차원 값 노이즈: 정수 격자마다 사인으로 만든 값을 두고 사이를 부드럽게 잇는다
    function lat(i: number): number {
        const s = Math.sin(i * 127.1 + 311.7) * 43758.5453;
        return s - Math.floor(s);
    }
    function vnoise(x: number): number {
        const i = Math.floor(x);
        const f = x - i;
        const u = f * f * (3 - 2 * f);
        return lat(i) * (1 - u) + lat(i + 1) * u - 0.5;
    }
    let cStar = [255, 247, 230];
    let cRing = [110, 200, 255];
    let cFlame = [255, 158, 187];
    let cWarm = [255, 233, 159];
    function resize(): void {
        fitCanvas();
        cStar = parseColor(cssVar("--star"));
        cRing = parseColor(cssVar("--ring"));
        cFlame = parseColor(cssVar("--flame"));
        cWarm = parseColor(cssVar("--warm"));
    }
    hooks.stop = () => {
        elapsed *= SECOND_MS / secondMs;
        secondMs = SECOND_MS;
        totalMs = COUNT_FROM * secondMs;
    };
    function shownCount(): number {
        return Math.ceil(remainMs() / secondMs - 1e-6);
    }
    function resetState(): void {
        speed = 40;
    }
    function tick(dt: number): void {
        if (reduce) return;
        const ignited = shownCount() === 0;
        const target = 40 * (ignited ? STAR_BOOST : 1);
        speed = approach(speed, target, 0.12, dt);
        for (let i = 0; i < STAR_N; i++) {
            sy[i] += (speed * sz[i] * dt) / 100;
            if (sy[i] > 1.05) {
                sy[i] -= 1.1;
                sx[i] = rand();
            }
        }
    }
    function draw(): void {
        const n = shownCount();
        const ignited = n === 0;
        // 흔들림: 숫자가 바뀐 직후의 한 방 + 0 에 가까울수록 커지는 바닥 진동
        let amp = 0;
        if (!reduce) {
            const since = elapsed - (COUNT_FROM - n) * secondMs;
            const base = Math.pow(1 - n / COUNT_FROM, 2) * 0.45;
            amp = SHAKE_AMP * (ignited ? 1 : base + 0.8 * Math.exp(-Math.max(0, since) / 70));
        }
        g.clearRect(0, 0, cw, ch);
        g.save();
        if (amp > 0) g.translate(vnoise(elapsed * 0.07) * 2 * amp, vnoise(elapsed * 0.07 + 40) * 2 * amp);
        // 별: 속도에 비례해 길어지는 줄
        const trail = reduce ? 0 : speed / 70;
        for (let i = 0; i < STAR_N; i++) {
            const x = sx[i] * cw;
            const y = sy[i] * ch;
            g.strokeStyle = rgba(cStar, 0.35 + 0.55 * sz[i]);
            g.lineWidth = 1 + sz[i];
            g.beginPath();
            g.moveTo(x, y);
            g.lineTo(x, y - trail * sz[i] * 14);
            g.stroke();
            if (reduce) {
                g.fillStyle = rgba(cStar, 0.6);
                g.fillRect(x, y, 1.6, 1.6);
            }
        }
        // 점화 불꽃(아래쪽)
        if (ignited) {
            const fx = cw / 2;
            const fy = ch;
            const pulse = reduce ? 1 : 1 + 0.12 * Math.sin(elapsed * 0.09);
            const fg = g.createRadialGradient(fx, fy, 0, fx, fy, ch * 0.9 * pulse);
            fg.addColorStop(0, rgba(cWarm, 0.9));
            fg.addColorStop(0.45, rgba(cFlame, 0.45));
            fg.addColorStop(1, rgba(cFlame, 0));
            g.fillStyle = fg;
            g.fillRect(0, 0, cw, ch);
        }
        // 충격파 링: 숫자가 바뀐 시각마다 한 개씩, 시간에서 바로 계산한다
        if (!reduce) {
            const k = Math.min(COUNT_FROM, Math.floor(elapsed / secondMs + 1e-6));
            for (let j = Math.max(0, k - 1); j <= k; j++) {
                const age = elapsed - j * secondMs;
                if (age < 0 || age >= WAVE_MS) continue;
                const u = age / WAVE_MS;
                const big = j === COUNT_FROM ? 1.7 : 1;
                g.strokeStyle = rgba(j === COUNT_FROM ? cFlame : cRing, Math.pow(1 - u, 1.5) * 0.9);
                g.lineWidth = 3 + 5 * (1 - u);
                g.beginPath();
                g.arc(cw / 2, ch / 2, WAVE_R * big * (1 - Math.pow(1 - u, 3)) * Math.min(1, ch / 200), 0, Math.PI * 2);
                g.stroke();
            }
        }
        // 큰 숫자
        g.fillStyle = rgba(ignited ? cFlame : cStar, 1);
        g.font = "800 " + Math.round(ch * 0.5) + "px -apple-system, Segoe UI, sans-serif";
        g.textAlign = "center";
        g.textBaseline = "middle";
        g.fillText(String(n), cw / 2, ch / 2);
        g.restore();
        num.textContent = (remainMs() / 1000).toFixed(1);
    }
    const ro = new ResizeObserver(() => {
        resize();
        draw();
    });
    ro.observe(root);
    offs.push(() => ro.disconnect());
    resize();
    resetState();
    syncButtons();
    update(0);
    raf = requestAnimationFrame(frame);
    return () => {
        cancelAnimationFrame(raf);
        offs.forEach((f) => f());
    };
  }, []);

  return (
    <div className={cx("cd") + " is-demo"} id="cd" data-demo="1" ref={rootRef}>
      <div className={cx("cd__view cd__view--scene")}>
      <canvas className={cx("cd__cv")} data-r="cv" role="img" aria-label="숫자가 줄다 0 에서 별이 빨라지는 발사 카운트다운"></canvas>
      <p className={cx("cd__read cd__read--corner")} role="timer"><b data-r="num">1.4</b><span>초</span></p>
      </div>
      <div className={cx("cd__bar")}>
        <button className={cx("cd__btn")} type="button" data-r="toggle">멈춤</button>
        <button className={cx("cd__btn")} type="button" data-r="reset">다시</button>
      </div>
      <p className={cx("cd__sr")} aria-live="polite" data-r="status"></p>
    </div>
  );
}