06젖은 도로에 길게 번지는 신호등 빛 반사

<main class="stage">
<div class="sc is-demo" id="scRoot">
  <canvas class="sc__canvas" id="scCanvas" width="480" height="300" tabindex="0" aria-label="젖은 도로에 길게 번지는 신호등 빛 반사"></canvas>
  <p class="sc__status" id="scStatus" aria-live="polite">초록불 — 진행</p>
  <button class="sc__btn" id="scBtn" type="button">멈춤</button>
  <p class="sc__caption">젖은 도로에 길게 번지는 신호등 빛 반사</p>
</div>
</main>

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

.sc {
  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;
}

.sc__canvas {
  display: block;
  width: 100%;
  height: 100%;
  touch-action: none;
}

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

.sc__status {
  position: absolute;
  left: $sp-3;
  top: $sp-3;
  max-width: 62%;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(255, 255, 255, .85);
  color: $subject-ink;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.4;
  pointer-events: none;
}

.sc__btn {
  position: absolute;
  right: $sp-3;
  bottom: $sp-3;
  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;
}

.sc__btn:focus-visible {
  outline: 2px solid #ffffff;
  outline-offset: 2px;
}

.sc__caption {
  position: absolute;
  left: $sp-3;
  bottom: $sp-3;
  max-width: 68%;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(255, 255, 255, .85);
  color: $subject-ink;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

@media (max-width: 340px) {
  .sc__caption, .sc__btn { font-size: 10px; padding: $sp-1 $sp-2; }
  .sc__status { font-size: 10px; }
}

@media (prefers-reduced-motion: reduce) {
  .sc { 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);
}

.sc {
  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;
}

.sc__canvas {
  display: block;
  width: 100%;
  height: 100%;
  touch-action: none;
}

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

.sc__status {
  position: absolute;
  left: 12px;
  top: 12px;
  max-width: 62%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.85);
  color: #17141a;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.4;
  pointer-events: none;
}

.sc__btn {
  position: absolute;
  right: 12px;
  bottom: 12px;
  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;
}

.sc__btn:focus-visible {
  outline: 2px solid #ffffff;
  outline-offset: 2px;
}

.sc__caption {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: 68%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.85);
  color: #17141a;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

@media (max-width: 340px) {
  .sc__caption, .sc__btn {
    font-size: 10px;
    padding: 4px 8px;
  }
  .sc__status {
    font-size: 10px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .sc {
    cursor: default;
  }
}

(function () {
    const W = 480;
    const H = 300;
    const PI2 = Math.PI * 2;
    const FIXED_DT = 16;
    const REDUCE_STEP_MS = 900;
    const REDUCE_START_MS = 1200;
    const KEY_STEP = 12;
    const FONT = '-apple-system, "Segoe UI", "Noto Sans KR", sans-serif';
    const SIG_GREEN = 0;
    const SIG_YELLOW = 1;
    const SIG_RED = 2;
    const GREEN_RGB = [61, 214, 140];
    const YELLOW_RGB = [255, 200, 64];
    const RED_RGB = [255, 92, 102];
    const SIGNAL_RGBS = [GREEN_RGB, YELLOW_RGB, RED_RGB];
    const SKY_RGB = [226, 238, 252];
    const GRASS_RGB = [206, 236, 214];
    const ROAD_RGB = [188, 192, 212];
    const ROAD_EDGE_RGB = [162, 166, 192];
    const MARK_RGB = [250, 250, 255];
    const INK_RGB = [58, 52, 84];
    const CAR_RGBS = [[255, 184, 196], [170, 208, 255], [196, 176, 255], [158, 232, 200], [255, 222, 150], [255, 196, 224]];
    const TXT_GO = '초록불 — 진행';
    const TXT_READY = '노란불 — 정지 준비';
    const TXT_STOP = '빨간불 — 정지';
    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]) + ',' + a.toFixed(3) + ')';
    }
    // 시드 고정 난수 — 같은 시드면 언제나 같은 수열
    function mulberry32(seed) {
        let s = seed >>> 0;
        return function () {
            s = (s + 0x6D2B79F5) >>> 0;
            let t = s;
            t = Math.imul(t ^ (t >>> 15), t | 1);
            t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
            return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
        };
    }
    // 격자 점의 값 — 정수 두 개를 섞어 0..1 로 (같은 입력은 언제나 같은 값)
    function hash2(ix, iy) {
        let h = Math.imul(ix | 0, 374761393) + Math.imul(iy | 0, 668265263);
        h = Math.imul(h ^ (h >>> 13), 1274126177);
        return ((h ^ (h >>> 16)) >>> 0) / 4294967296;
    }
    // 2차원 값 잡음 — 네 격자 점을 부드럽게 보간
    function vnoise(x, y) {
        const ix = Math.floor(x);
        const iy = Math.floor(y);
        const fx = smooth(x - ix);
        const fy = smooth(y - iy);
        return lerp(lerp(hash2(ix, iy), hash2(ix + 1, iy), fx), lerp(hash2(ix, iy + 1), hash2(ix + 1, iy + 1), fx), fy);
    }
    function glow(ctx, x, y, r, c, a) {
        const g = ctx.createRadialGradient(x, y, 0, x, y, r);
        g.addColorStop(0, rgba(c, a));
        g.addColorStop(1, rgba(c, 0));
        ctx.fillStyle = g;
        ctx.fillRect(x - r, y - r, r * 2, r * 2);
    }
    function rrect(ctx, x, y, w, h, r) {
        const rr = Math.min(r, w / 2, h / 2);
        ctx.beginPath();
        ctx.moveTo(x + rr, y);
        ctx.arcTo(x + w, y, x + w, y + h, rr);
        ctx.arcTo(x + w, y + h, x, y + h, rr);
        ctx.arcTo(x, y + h, x, y, rr);
        ctx.arcTo(x, y, x + w, y, rr);
        ctx.closePath();
    }
    // 주기 [초록, 노랑, 빨강] 프레임 수에서 프레임 f 의 신호 상태
    function phaseAt(f, g, y, r) {
        const total = g + y + r;
        const m = ((f % total) + total) % total;
        return m < g ? SIG_GREEN : (m < g + y ? SIG_YELLOW : SIG_RED);
    }
    function stateText(state) {
        return state === SIG_GREEN ? TXT_GO : (state === SIG_YELLOW ? TXT_READY : TXT_STOP);
    }
    // 신호 상태 -> 빨강·노랑·초록 렌즈 밝기 (위에서 아래)
    function litOf(state) {
        return [state === SIG_RED ? 1 : 0, state === SIG_YELLOW ? 1 : 0, state === SIG_GREEN ? 1 : 0];
    }
    const LENS_RGBS = [RED_RGB, YELLOW_RGB, GREEN_RGB];
    // 세로 신호등 머리 — 렌즈 세 개와 켜진 렌즈의 빛 번짐
    function drawHead(ctx, cx, cy, r, lit) {
        const step = r * 2.5;
        rrect(ctx, cx - r * 1.45, cy - step - r * 1.45, r * 2.9, step * 2 + r * 2.9, r * 0.9);
        ctx.fillStyle = rgba(INK_RGB, 1);
        ctx.fill();
        for (let i = 0; i < 3; i += 1) {
            const ly = cy + (i - 1) * step;
            ctx.beginPath();
            ctx.arc(cx, ly, r, 0, PI2);
            ctx.fillStyle = rgba(LENS_RGBS[i], 0.2 + 0.8 * lit[i]);
            ctx.fill();
            if (lit[i] > 0.02) {
                glow(ctx, cx, ly, r * 3.2, LENS_RGBS[i], 0.55 * lit[i]);
            }
        }
    }
    // 위에서 본 차 — 앞 범퍼가 x, 가운데가 y. 제동 중이면 뒷등이 켜진다
    function drawCar(ctx, x, y, len, wid, rgb, braking) {
        const x0 = x - len;
        rrect(ctx, x0, y - wid / 2, len, wid, 6);
        ctx.fillStyle = rgba(rgb, 1);
        ctx.fill();
        rrect(ctx, x - len * 0.62, y - wid / 2 + 3, len * 0.34, wid - 6, 3);
        ctx.fillStyle = 'rgba(255,255,255,0.62)';
        ctx.fill();
        ctx.fillStyle = 'rgba(255,248,214,1)';
        ctx.fillRect(x - 3, y - wid / 2 + 2, 3, 4);
        ctx.fillRect(x - 3, y + wid / 2 - 6, 3, 4);
        ctx.fillStyle = braking ? rgba(RED_RGB, 1) : 'rgba(150,120,150,0.8)';
        ctx.fillRect(x0, y - wid / 2 + 2, 3, 4);
        ctx.fillRect(x0, y + wid / 2 - 6, 3, 4);
        if (braking) {
            glow(ctx, x0, y, 12, RED_RGB, 0.45);
        }
    }
    // 한 줄 도로 장면의 바탕 — 잔디 위에 도로띠 하나, 정지선과 횡단보도
    function drawLaneBackdrop(ctx, roadY, roadH, stopX, seedTrees) {
        ctx.fillStyle = rgba(GRASS_RGB, 1);
        ctx.fillRect(0, 0, W, H);
        const rnd = mulberry32(seedTrees);
        for (let i = 0; i < 14; i += 1) {
            const tx = 16 + rnd() * (W - 32);
            const up = rnd() < 0.5;
            const ty = up ? roadY - roadH / 2 - 22 - rnd() * 26 : roadY + roadH / 2 + 22 + rnd() * 26;
            ctx.beginPath();
            ctx.arc(tx, ty, 9 + rnd() * 6, 0, PI2);
            ctx.fillStyle = 'rgba(160,214,184,0.9)';
            ctx.fill();
        }
        ctx.fillStyle = rgba(ROAD_RGB, 1);
        ctx.fillRect(0, roadY - roadH / 2, W, roadH);
        ctx.fillStyle = rgba(ROAD_EDGE_RGB, 1);
        ctx.fillRect(0, roadY - roadH / 2, W, 2);
        ctx.fillRect(0, roadY + roadH / 2 - 2, W, 2);
        ctx.fillStyle = rgba(MARK_RGB, 0.8);
        for (let x = 6; x < W; x += 36) {
            ctx.fillRect(x, roadY - 1, 18, 2);
        }
        for (let k = 0; k < 5; k += 1) {
            ctx.fillRect(stopX + 5, roadY - roadH / 2 + 3 + k * (roadH - 6) / 5, 12, (roadH - 6) / 5 - 3);
        }
        ctx.fillRect(stopX - 2, roadY - roadH / 2, 3, roadH);
    }
    // 한 줄 차량 흐름 — 앞차 간격(IDM)과 정지선을 같은 식으로 다룬다. 차는 앞쪽부터 0번이다
    class Lane {
        constructor(seed, p) {
            this.cars = [];
            this.nextAt = 0;
            this.made = 0;
            this.p = p;
            this.rnd = mulberry32(seed);
        }
        accelFor(v, s, vL, g0) {
            const p = this.p;
            const sStar = g0 + Math.max(0, v * p.headway + v * (v - vL) / (2 * Math.sqrt(p.accel * p.brake)));
            return p.accel * (1 - Math.pow(v / p.vmax, p.delta) - Math.pow(sStar / Math.max(s, 0.5), 2));
        }
        // f 프레임에, 뒤쪽이 비어 있고 때가 됐으면 한 대 들여보낸다
        maybeSpawn(f, minGap, maxGap, v0) {
            if (f < this.nextAt) {
                return false;
            }
            const last = this.cars.length > 0 ? this.cars[this.cars.length - 1] : null;
            if (last && last.x - last.len < this.p.gap + 10) {
                return false;
            }
            const rgb = CAR_RGBS[this.made % CAR_RGBS.length];
            this.cars.push({ x: -2, v: v0, len: this.p.len, rgb: rgb, go: false, decided: false, sigK: -1, brake: false, id: this.made });
            this.made += 1;
            this.nextAt = f + minGap + Math.floor(this.rnd() * (maxGap - minGap + 1));
            return true;
        }
        // 신호 목록은 x 오름차순. 한 번 호출 = 한 프레임. 정지선을 넘은 차(detect 용) id 를 돌려준다
        step(sigs, onCross, watchX) {
            const p = this.p;
            for (let i = 0; i < this.cars.length; i += 1) {
                const c = this.cars[i];
                let acc = this.accelFor(c.v, 1e6, c.v, p.gap);
                if (i > 0) {
                    const L = this.cars[i - 1];
                    acc = Math.min(acc, this.accelFor(c.v, (L.x - L.len) - c.x, L.v, p.gap));
                }
                let k = -1;
                for (let j = 0; j < sigs.length; j += 1) {
                    if (sigs[j].x >= c.x) {
                        k = j;
                        break;
                    }
                }
                let clampX = 1e9;
                if (k >= 0) {
                    const sg = sigs[k];
                    if (c.sigK !== k) {
                        c.sigK = k;
                        c.decided = false;
                        c.go = false;
                    }
                    if (sg.state === SIG_GREEN) {
                        c.decided = false;
                        c.go = false;
                    }
                    else {
                        if (!c.decided) {
                            c.decided = true;
                            c.go = c.v * c.v / (2 * p.brake) > sg.x - c.x;
                        }
                        if (!c.go) {
                            acc = Math.min(acc, this.accelFor(c.v, sg.x - c.x - 2, 0, p.lineGap));
                            clampX = sg.x - 1.5;
                        }
                    }
                }
                acc = Math.max(acc, -p.brake * 3);
                const prevX = c.x;
                c.v = Math.max(0, c.v + acc);
                c.x += c.v;
                if (c.x > clampX && prevX <= clampX) {
                    c.x = clampX;
                    c.v = 0;
                }
                c.brake = acc < -0.012 || c.v < 0.05;
                if (prevX < watchX && c.x >= watchX) {
                    onCross(c, watchX);
                }
            }
            while (this.cars.length > 0 && this.cars[0].x - this.cars[0].len > W + 20) {
                this.cars.shift();
            }
        }
        // 정지선 뒤에서 서 있는 차 수
        waiting(stopX) {
            let n = 0;
            for (let i = 0; i < this.cars.length; i += 1) {
                const c = this.cars[i];
                if (c.v < 0.25 && c.x < stopX + 2 && c.x > stopX - 260) {
                    n += 1;
                }
            }
            return n;
        }
    }
    function main(rootEl, canvas, statusEl, btnEl) {
        const ctx0 = canvas.getContext('2d');
        if (!ctx0) {
            return function () { return; };
        }
        canvas.width = W;
        canvas.height = H;
        const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
        const scene = makeScene(ctx0, reduce);
        if (reduce) {
            rootEl.classList.remove('is-demo');
        }
        let paused = false;
        let rafId = 0;
        let lastTs = null;
        let accMs = 0;
        let lastLabel = '';
        let px = W / 2;
        let py = H / 2;
        const cleaners = [];
        function listen(target, type, fn) {
            target.addEventListener(type, fn);
            cleaners.push(function () { target.removeEventListener(type, fn); });
        }
        function show() {
            scene.draw();
            const t = scene.label();
            if (t !== lastLabel) {
                lastLabel = t;
                statusEl.textContent = t;
            }
        }
        function advance(ms) {
            const n = Math.round(ms / FIXED_DT);
            for (let i = 0; i < n; i += 1) {
                scene.step();
            }
        }
        function setButton() {
            btnEl.textContent = reduce ? '다음 장면' : (paused ? '재생' : '멈춤');
        }
        function toLocal(e) {
            const r = canvas.getBoundingClientRect();
            return [clamp((e.clientX - r.left) * W / r.width, 0, W), clamp((e.clientY - r.top) * H / r.height, 0, H)];
        }
        function moved() {
            if (scene.point) {
                scene.point(px, py);
            }
            if (reduce) {
                show();
            }
        }
        function onButton() {
            if (reduce) {
                advance(REDUCE_STEP_MS);
                show();
                return;
            }
            paused = !paused;
            if (paused) {
                rootEl.classList.remove('is-demo');
            }
            else {
                rootEl.classList.add('is-demo');
            }
            setButton();
        }
        function onAction() {
            if (scene.tap) {
                scene.tap();
                if (reduce) {
                    show();
                }
                return;
            }
            onButton();
        }
        function tick(ts) {
            if (lastTs === null) {
                lastTs = ts;
            }
            const frameDt = Math.min(ts - lastTs, 160);
            lastTs = ts;
            if (!paused) {
                accMs += frameDt;
                while (accMs >= FIXED_DT) {
                    scene.step();
                    accMs -= FIXED_DT;
                }
                show();
            }
            rafId = requestAnimationFrame(tick);
        }
        listen(btnEl, 'click', function () { onButton(); });
        listen(canvas, 'pointerdown', function (e) {
            const p = toLocal(e);
            px = p[0];
            py = p[1];
            moved();
            if (scene.tap) {
                scene.tap();
                if (reduce) {
                    show();
                }
            }
        });
        listen(canvas, 'pointermove', function (e) {
            const p = toLocal(e);
            px = p[0];
            py = p[1];
            moved();
        });
        listen(canvas, 'keydown', function (e) {
            const k = e.key;
            if (k === 'Enter' || k === ' ') {
                e.preventDefault();
                onAction();
                return;
            }
            let dx = 0;
            let dy = 0;
            if (k === 'ArrowLeft') {
                dx = -KEY_STEP;
            }
            else if (k === 'ArrowRight') {
                dx = KEY_STEP;
            }
            else if (k === 'ArrowUp') {
                dy = -KEY_STEP;
            }
            else if (k === 'ArrowDown') {
                dy = KEY_STEP;
            }
            else {
                return;
            }
            e.preventDefault();
            px = clamp(px + dx, 0, W);
            py = clamp(py + dy, 0, H);
            moved();
        });
        advance(REDUCE_START_MS);
        setButton();
        show();
        if (!reduce) {
            rafId = requestAnimationFrame(tick);
        }
        function destroy() {
            cancelAnimationFrame(rafId);
            for (let i = 0; i < cleaners.length; i += 1) {
                cleaners[i]();
            }
        }
        return destroy;
    }
    const REFLECT_STRETCH = 1.7;
    const RIPPLE_AMP = 7;
    const FADE_RATE = 0.9;
    const NOISE_SCALE = 0.05;
    const HORIZON = 120;
    const SEG_W = 20;
    const ROW_STEP = 2;
    const GREEN_LEN = 90;
    const YELLOW_LEN = 24;
    const RED_LEN = 110;
    const RIPPLE_COUNT = 7;
    const SEED = 446;
    function makeScene(ctx, reduce) {
        const src = document.createElement('canvas');
        src.width = W;
        src.height = HORIZON;
        const sc = src.getContext('2d');
        if (!sc) {
            return { step: function () { return; }, draw: function () { return; }, label: function () { return TXT_STOP; } };
        }
        const rnd = mulberry32(SEED);
        const buildings = [];
        let bx = -10;
        while (bx < W) {
            const bw = 30 + Math.floor(rnd() * 34);
            const bh = 46 + Math.floor(rnd() * 56);
            buildings.push([bx, bw, bh, Math.floor(rnd() * 1000)]);
            bx += bw + 3;
        }
        const ripples = [];
        for (let i = 0; i < RIPPLE_COUNT; i += 1) {
            ripples.push({ x: 30 + rnd() * 420, y: HORIZON + 24 + rnd() * 110, period: 80 + Math.floor(rnd() * 60), off: Math.floor(rnd() * 120) });
        }
        let f = 40;
        let carX = -60;
        function stateA() { return phaseAt(f, GREEN_LEN, YELLOW_LEN, RED_LEN); }
        function stateB() { return phaseAt(f + 110, GREEN_LEN, YELLOW_LEN, RED_LEN); }
        function drawSource() {
            const g = sc.createLinearGradient(0, 0, 0, HORIZON);
            g.addColorStop(0, 'rgba(255,224,214,1)');
            g.addColorStop(1, 'rgba(214,204,246,1)');
            sc.fillStyle = g;
            sc.fillRect(0, 0, W, HORIZON);
            for (let i = 0; i < buildings.length; i += 1) {
                const b = buildings[i];
                sc.fillStyle = 'rgba(150,140,190,1)';
                sc.fillRect(b[0], HORIZON - b[2] - 8, b[1], b[2] + 8);
                for (let wy = HORIZON - b[2]; wy < HORIZON - 14; wy += 12) {
                    for (let wx = b[0] + 5; wx < b[0] + b[1] - 8; wx += 10) {
                        if (hash2(wx + b[3], wy) < 0.34) {
                            sc.fillStyle = 'rgba(255,236,176,1)';
                            sc.fillRect(wx, wy, 5, 6);
                        }
                    }
                }
            }
            sc.fillStyle = 'rgba(120,112,164,1)';
            sc.fillRect(0, HORIZON - 9, W, 9);
            // 신호 두 대 — 한쪽이 초록이면 다른 쪽은 빨강
            const heads = [[140, 8, stateA()], [352, 11, stateB()]];
            for (let h = 0; h < heads.length; h += 1) {
                const hx = heads[h][0];
                const hr = heads[h][1];
                const st = heads[h][2];
                sc.fillStyle = rgba(INK_RGB, 1);
                sc.fillRect(hx - 2, 66, 4, HORIZON - 66);
                drawHead(sc, hx, 52, hr, litOf(st));
            }
            // 가로등
            sc.fillStyle = rgba(INK_RGB, 1);
            sc.fillRect(432, 70, 3, HORIZON - 70);
            glow(sc, 434, 68, 46, [255, 226, 160], 0.9);
            sc.beginPath();
            sc.arc(434, 68, 5, 0, PI2);
            sc.fillStyle = 'rgba(255,248,214,1)';
            sc.fill();
            // 지나가는 차 — 앞 등이 반사의 가장 밝은 줄이 된다
            if (carX > -50 && carX < W + 20) {
                rrect(sc, carX - 38, HORIZON - 24, 38, 14, 5);
                sc.fillStyle = 'rgba(206,176,214,1)';
                sc.fill();
                sc.fillStyle = 'rgba(88,80,128,1)';
                sc.fillRect(carX - 28, HORIZON - 28, 20, 6);
                sc.beginPath();
                sc.arc(carX - 28, HORIZON - 9, 4, 0, PI2);
                sc.arc(carX - 9, HORIZON - 9, 4, 0, PI2);
                sc.fill();
                glow(sc, carX + 2, HORIZON - 16, 34, [255, 240, 190], 0.95);
                sc.fillStyle = 'rgba(255,252,230,1)';
                sc.fillRect(carX - 3, HORIZON - 19, 4, 5);
            }
        }
        const scene = {
            step: function () {
                f += 1;
                carX += 2.1;
                if (carX > W + 40) {
                    carX = -60 - (f % 140);
                }
            },
            label: function () { return stateText(stateA()); },
            draw: function () {
                drawSource();
                ctx.drawImage(src, 0, 0);
                // 젖은 도로 바탕
                const road = ctx.createLinearGradient(0, HORIZON, 0, H);
                road.addColorStop(0, 'rgba(92,84,128,1)');
                road.addColorStop(1, 'rgba(56,50,88,1)');
                ctx.fillStyle = road;
                ctx.fillRect(0, HORIZON, W, H - HORIZON);
                // 반사 — 도로 행마다 원본의 거꾸로 된 행을 가져오고, 잡음으로 가로로 흔들고, 멀수록 흐려진다
                const depth = H - HORIZON;
                const t = reduce ? 0 : f * 0.06;
                for (let dy = 0; dy < depth; dy += ROW_STEP) {
                    const sy = HORIZON - 1 - dy / REFLECT_STRETCH;
                    if (sy < 0) {
                        break;
                    }
                    const near = dy / depth;
                    const alpha = Math.max(0, 0.82 - near * FADE_RATE * 0.8);
                    if (alpha <= 0.02) {
                        continue;
                    }
                    ctx.globalAlpha = alpha;
                    for (let sx = 0; sx < W; sx += SEG_W) {
                        const n = vnoise(sx * 0.031 + t * 0.7, dy * NOISE_SCALE + t) * 2 - 1;
                        const dx = n * RIPPLE_AMP * (0.35 + near * 1.1);
                        ctx.drawImage(src, sx, Math.floor(sy), SEG_W, 1, sx + dx, HORIZON + dy, SEG_W, ROW_STEP + 0.6);
                    }
                }
                ctx.globalAlpha = 1;
                // 빗방울 파문
                for (let i = 0; i < ripples.length; i += 1) {
                    const r = ripples[i];
                    const ph = (((f + r.off) % r.period) / r.period);
                    const rad = 4 + 30 * ph * (0.6 + (r.y - HORIZON) / 200);
                    ctx.beginPath();
                    ctx.ellipse(r.x, r.y, rad, rad * 0.28, 0, 0, PI2);
                    ctx.lineWidth = 1.6;
                    ctx.strokeStyle = 'rgba(236,232,255,' + (0.7 * (1 - ph)).toFixed(3) + ')';
                    ctx.stroke();
                }
            }
        };
        for (let i = 0; i < 60; i += 1) {
            scene.step();
        }
        return scene;
    }
    main(document.getElementById('scRoot'), document.getElementById('scCanvas'), document.getElementById('scStatus'), document.getElementById('scBtn'));
})();

import { useEffect, useRef } from "react";
import styles from "./TlWetRoadReflectionStreak.module.scss";

const W = 480;
const H = 300;
const PI2 = Math.PI * 2;
const FIXED_DT = 16;
const REDUCE_STEP_MS = 900;
const REDUCE_START_MS = 1200;
const KEY_STEP = 12;
const FONT = '-apple-system, "Segoe UI", "Noto Sans KR", sans-serif';

const SIG_GREEN = 0;
const SIG_YELLOW = 1;
const SIG_RED = 2;
const GREEN_RGB = [61, 214, 140];
const YELLOW_RGB = [255, 200, 64];
const RED_RGB = [255, 92, 102];
const SIGNAL_RGBS = [GREEN_RGB, YELLOW_RGB, RED_RGB];
const SKY_RGB = [226, 238, 252];
const GRASS_RGB = [206, 236, 214];
const ROAD_RGB = [188, 192, 212];
const ROAD_EDGE_RGB = [162, 166, 192];
const MARK_RGB = [250, 250, 255];
const INK_RGB = [58, 52, 84];
const CAR_RGBS = [[255, 184, 196], [170, 208, 255], [196, 176, 255], [158, 232, 200], [255, 222, 150], [255, 196, 224]];

const TXT_GO = '초록불 — 진행';
const TXT_READY = '노란불 — 정지 준비';
const TXT_STOP = '빨간불 — 정지';

type Pt = [number, number];
interface Scene {
  step(): void;
  draw(): void;
  label(): string;
  point?(x: number, y: number): void;
  tap?(): void;
}

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: number[], a: number): string {
  return 'rgba(' + Math.round(c[0]) + ',' + Math.round(c[1]) + ',' + Math.round(c[2]) + ',' + a.toFixed(3) + ')';
}
// 시드 고정 난수 — 같은 시드면 언제나 같은 수열
function mulberry32(seed: number): () => number {
  let s = seed >>> 0;
  return function (): number {
    s = (s + 0x6D2B79F5) >>> 0;
    let t = s;
    t = Math.imul(t ^ (t >>> 15), t | 1);
    t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}
// 격자 점의 값 — 정수 두 개를 섞어 0..1 로 (같은 입력은 언제나 같은 값)
function hash2(ix: number, iy: number): number {
  let h = Math.imul(ix | 0, 374761393) + Math.imul(iy | 0, 668265263);
  h = Math.imul(h ^ (h >>> 13), 1274126177);
  return ((h ^ (h >>> 16)) >>> 0) / 4294967296;
}
// 2차원 값 잡음 — 네 격자 점을 부드럽게 보간
function vnoise(x: number, y: number): number {
  const ix = Math.floor(x);
  const iy = Math.floor(y);
  const fx = smooth(x - ix);
  const fy = smooth(y - iy);
  return lerp(lerp(hash2(ix, iy), hash2(ix + 1, iy), fx), lerp(hash2(ix, iy + 1), hash2(ix + 1, iy + 1), fx), fy);
}
function glow(ctx: CanvasRenderingContext2D, x: number, y: number, r: number, c: number[], a: number): void {
  const g = ctx.createRadialGradient(x, y, 0, x, y, r);
  g.addColorStop(0, rgba(c, a));
  g.addColorStop(1, rgba(c, 0));
  ctx.fillStyle = g;
  ctx.fillRect(x - r, y - r, r * 2, r * 2);
}
function rrect(ctx: CanvasRenderingContext2D, x: number, y: number, w: number, h: number, r: number): void {
  const rr = Math.min(r, w / 2, h / 2);
  ctx.beginPath();
  ctx.moveTo(x + rr, y);
  ctx.arcTo(x + w, y, x + w, y + h, rr);
  ctx.arcTo(x + w, y + h, x, y + h, rr);
  ctx.arcTo(x, y + h, x, y, rr);
  ctx.arcTo(x, y, x + w, y, rr);
  ctx.closePath();
}
// 주기 [초록, 노랑, 빨강] 프레임 수에서 프레임 f 의 신호 상태
function phaseAt(f: number, g: number, y: number, r: number): number {
  const total = g + y + r;
  const m = ((f % total) + total) % total;
  return m < g ? SIG_GREEN : (m < g + y ? SIG_YELLOW : SIG_RED);
}
function stateText(state: number): string {
  return state === SIG_GREEN ? TXT_GO : (state === SIG_YELLOW ? TXT_READY : TXT_STOP);
}
// 신호 상태 -> 빨강·노랑·초록 렌즈 밝기 (위에서 아래)
function litOf(state: number): number[] {
  return [state === SIG_RED ? 1 : 0, state === SIG_YELLOW ? 1 : 0, state === SIG_GREEN ? 1 : 0];
}
const LENS_RGBS = [RED_RGB, YELLOW_RGB, GREEN_RGB];
// 세로 신호등 머리 — 렌즈 세 개와 켜진 렌즈의 빛 번짐
function drawHead(ctx: CanvasRenderingContext2D, cx: number, cy: number, r: number, lit: number[]): void {
  const step = r * 2.5;
  rrect(ctx, cx - r * 1.45, cy - step - r * 1.45, r * 2.9, step * 2 + r * 2.9, r * 0.9);
  ctx.fillStyle = rgba(INK_RGB, 1);
  ctx.fill();
  for (let i = 0; i < 3; i += 1) {
    const ly = cy + (i - 1) * step;
    ctx.beginPath();
    ctx.arc(cx, ly, r, 0, PI2);
    ctx.fillStyle = rgba(LENS_RGBS[i], 0.2 + 0.8 * lit[i]);
    ctx.fill();
    if (lit[i] > 0.02) {
      glow(ctx, cx, ly, r * 3.2, LENS_RGBS[i], 0.55 * lit[i]);
    }
  }
}
// 위에서 본 차 — 앞 범퍼가 x, 가운데가 y. 제동 중이면 뒷등이 켜진다
function drawCar(ctx: CanvasRenderingContext2D, x: number, y: number, len: number, wid: number, rgb: number[], braking: boolean): void {
  const x0 = x - len;
  rrect(ctx, x0, y - wid / 2, len, wid, 6);
  ctx.fillStyle = rgba(rgb, 1);
  ctx.fill();
  rrect(ctx, x - len * 0.62, y - wid / 2 + 3, len * 0.34, wid - 6, 3);
  ctx.fillStyle = 'rgba(255,255,255,0.62)';
  ctx.fill();
  ctx.fillStyle = 'rgba(255,248,214,1)';
  ctx.fillRect(x - 3, y - wid / 2 + 2, 3, 4);
  ctx.fillRect(x - 3, y + wid / 2 - 6, 3, 4);
  ctx.fillStyle = braking ? rgba(RED_RGB, 1) : 'rgba(150,120,150,0.8)';
  ctx.fillRect(x0, y - wid / 2 + 2, 3, 4);
  ctx.fillRect(x0, y + wid / 2 - 6, 3, 4);
  if (braking) {
    glow(ctx, x0, y, 12, RED_RGB, 0.45);
  }
}
// 한 줄 도로 장면의 바탕 — 잔디 위에 도로띠 하나, 정지선과 횡단보도
function drawLaneBackdrop(ctx: CanvasRenderingContext2D, roadY: number, roadH: number, stopX: number, seedTrees: number): void {
  ctx.fillStyle = rgba(GRASS_RGB, 1);
  ctx.fillRect(0, 0, W, H);
  const rnd = mulberry32(seedTrees);
  for (let i = 0; i < 14; i += 1) {
    const tx = 16 + rnd() * (W - 32);
    const up = rnd() < 0.5;
    const ty = up ? roadY - roadH / 2 - 22 - rnd() * 26 : roadY + roadH / 2 + 22 + rnd() * 26;
    ctx.beginPath();
    ctx.arc(tx, ty, 9 + rnd() * 6, 0, PI2);
    ctx.fillStyle = 'rgba(160,214,184,0.9)';
    ctx.fill();
  }
  ctx.fillStyle = rgba(ROAD_RGB, 1);
  ctx.fillRect(0, roadY - roadH / 2, W, roadH);
  ctx.fillStyle = rgba(ROAD_EDGE_RGB, 1);
  ctx.fillRect(0, roadY - roadH / 2, W, 2);
  ctx.fillRect(0, roadY + roadH / 2 - 2, W, 2);
  ctx.fillStyle = rgba(MARK_RGB, 0.8);
  for (let x = 6; x < W; x += 36) {
    ctx.fillRect(x, roadY - 1, 18, 2);
  }
  for (let k = 0; k < 5; k += 1) {
    ctx.fillRect(stopX + 5, roadY - roadH / 2 + 3 + k * (roadH - 6) / 5, 12, (roadH - 6) / 5 - 3);
  }
  ctx.fillRect(stopX - 2, roadY - roadH / 2, 3, roadH);
}

interface Car { x: number; v: number; len: number; rgb: number[]; go: boolean; decided: boolean; sigK: number; brake: boolean; id: number; }
interface Sig { x: number; state: number; }
interface LaneParams { accel: number; brake: number; gap: number; lineGap: number; vmax: number; headway: number; delta: number; len: number; }

// 한 줄 차량 흐름 — 앞차 간격(IDM)과 정지선을 같은 식으로 다룬다. 차는 앞쪽부터 0번이다
class Lane {
  cars: Car[] = [];
  p: LaneParams;
  rnd: () => number;
  nextAt = 0;
  made = 0;
  constructor(seed: number, p: LaneParams) {
    this.p = p;
    this.rnd = mulberry32(seed);
  }
  accelFor(v: number, s: number, vL: number, g0: number): number {
    const p = this.p;
    const sStar = g0 + Math.max(0, v * p.headway + v * (v - vL) / (2 * Math.sqrt(p.accel * p.brake)));
    return p.accel * (1 - Math.pow(v / p.vmax, p.delta) - Math.pow(sStar / Math.max(s, 0.5), 2));
  }
  // f 프레임에, 뒤쪽이 비어 있고 때가 됐으면 한 대 들여보낸다
  maybeSpawn(f: number, minGap: number, maxGap: number, v0: number): boolean {
    if (f < this.nextAt) { return false; }
    const last = this.cars.length > 0 ? this.cars[this.cars.length - 1] : null;
    if (last && last.x - last.len < this.p.gap + 10) { return false; }
    const rgb = CAR_RGBS[this.made % CAR_RGBS.length];
    this.cars.push({ x: -2, v: v0, len: this.p.len, rgb: rgb, go: false, decided: false, sigK: -1, brake: false, id: this.made });
    this.made += 1;
    this.nextAt = f + minGap + Math.floor(this.rnd() * (maxGap - minGap + 1));
    return true;
  }
  // 신호 목록은 x 오름차순. 한 번 호출 = 한 프레임. 정지선을 넘은 차(detect 용) id 를 돌려준다
  step(sigs: Sig[], onCross: (c: Car, x: number) => void, watchX: number): void {
    const p = this.p;
    for (let i = 0; i < this.cars.length; i += 1) {
      const c = this.cars[i];
      let acc = this.accelFor(c.v, 1e6, c.v, p.gap);
      if (i > 0) {
        const L = this.cars[i - 1];
        acc = Math.min(acc, this.accelFor(c.v, (L.x - L.len) - c.x, L.v, p.gap));
      }
      let k = -1;
      for (let j = 0; j < sigs.length; j += 1) {
        if (sigs[j].x >= c.x) { k = j; break; }
      }
      let clampX = 1e9;
      if (k >= 0) {
        const sg = sigs[k];
        if (c.sigK !== k) { c.sigK = k; c.decided = false; c.go = false; }
        if (sg.state === SIG_GREEN) {
          c.decided = false;
          c.go = false;
        } else {
          if (!c.decided) {
            c.decided = true;
            c.go = c.v * c.v / (2 * p.brake) > sg.x - c.x;
          }
          if (!c.go) {
            acc = Math.min(acc, this.accelFor(c.v, sg.x - c.x - 2, 0, p.lineGap));
            clampX = sg.x - 1.5;
          }
        }
      }
      acc = Math.max(acc, -p.brake * 3);
      const prevX = c.x;
      c.v = Math.max(0, c.v + acc);
      c.x += c.v;
      if (c.x > clampX && prevX <= clampX) {
        c.x = clampX;
        c.v = 0;
      }
      c.brake = acc < -0.012 || c.v < 0.05;
      if (prevX < watchX && c.x >= watchX) { onCross(c, watchX); }
    }
    while (this.cars.length > 0 && this.cars[0].x - this.cars[0].len > W + 20) {
      this.cars.shift();
    }
  }
  // 정지선 뒤에서 서 있는 차 수
  waiting(stopX: number): number {
    let n = 0;
    for (let i = 0; i < this.cars.length; i += 1) {
      const c = this.cars[i];
      if (c.v < 0.25 && c.x < stopX + 2 && c.x > stopX - 260) { n += 1; }
    }
    return n;
  }
}

function main(rootEl: HTMLElement, canvas: HTMLCanvasElement, statusEl: HTMLElement, btnEl: HTMLButtonElement): () => void {
  const ctx0 = canvas.getContext('2d');
  if (!ctx0) { return function (): void { return; }; }
  canvas.width = W;
  canvas.height = H;
  const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  const scene = makeScene(ctx0, reduce);
  if (reduce) { rootEl.classList.remove('is-demo'); }
  let paused = false;
  let rafId = 0;
  let lastTs: number | null = null;
  let accMs = 0;
  let lastLabel = '';
  let px = W / 2;
  let py = H / 2;
  const cleaners: Array<() => void> = [];

  function listen(target: EventTarget, type: string, fn: (e: Event) => void): void {
    target.addEventListener(type, fn);
    cleaners.push(function (): void { target.removeEventListener(type, fn); });
  }
  function show(): void {
    scene.draw();
    const t = scene.label();
    if (t !== lastLabel) {
      lastLabel = t;
      statusEl.textContent = t;
    }
  }
  function advance(ms: number): void {
    const n = Math.round(ms / FIXED_DT);
    for (let i = 0; i < n; i += 1) { scene.step(); }
  }
  function setButton(): void {
    btnEl.textContent = reduce ? '다음 장면' : (paused ? '재생' : '멈춤');
  }
  function toLocal(e: PointerEvent): Pt {
    const r = canvas.getBoundingClientRect();
    return [clamp((e.clientX - r.left) * W / r.width, 0, W), clamp((e.clientY - r.top) * H / r.height, 0, H)];
  }
  function moved(): void {
    if (scene.point) { scene.point(px, py); }
    if (reduce) { show(); }
  }
  function onButton(): void {
    if (reduce) {
      advance(REDUCE_STEP_MS);
      show();
      return;
    }
    paused = !paused;
    if (paused) { rootEl.classList.remove('is-demo'); } else { rootEl.classList.add('is-demo'); }
    setButton();
  }
  function onAction(): void {
    if (scene.tap) {
      scene.tap();
      if (reduce) { show(); }
      return;
    }
    onButton();
  }
  function tick(ts: number): void {
    if (lastTs === null) { lastTs = ts; }
    const frameDt = Math.min(ts - lastTs, 160);
    lastTs = ts;
    if (!paused) {
      accMs += frameDt;
      while (accMs >= FIXED_DT) {
        scene.step();
        accMs -= FIXED_DT;
      }
      show();
    }
    rafId = requestAnimationFrame(tick);
  }
  listen(btnEl, 'click', function (): void { onButton(); });
  listen(canvas, 'pointerdown', function (e: Event): void {
    const p = toLocal(e as PointerEvent);
    px = p[0];
    py = p[1];
    moved();
    if (scene.tap) {
      scene.tap();
      if (reduce) { show(); }
    }
  });
  listen(canvas, 'pointermove', function (e: Event): void {
    const p = toLocal(e as PointerEvent);
    px = p[0];
    py = p[1];
    moved();
  });
  listen(canvas, 'keydown', function (e: Event): void {
    const k = (e as KeyboardEvent).key;
    if (k === 'Enter' || k === ' ') {
      e.preventDefault();
      onAction();
      return;
    }
    let dx = 0;
    let dy = 0;
    if (k === 'ArrowLeft') { dx = -KEY_STEP; } else if (k === 'ArrowRight') { dx = KEY_STEP; }
    else if (k === 'ArrowUp') { dy = -KEY_STEP; } else if (k === 'ArrowDown') { dy = KEY_STEP; }
    else { return; }
    e.preventDefault();
    px = clamp(px + dx, 0, W);
    py = clamp(py + dy, 0, H);
    moved();
  });
  advance(REDUCE_START_MS);
  setButton();
  show();
  if (!reduce) {
    rafId = requestAnimationFrame(tick);
  }
  function destroy(): void {
    cancelAnimationFrame(rafId);
    for (let i = 0; i < cleaners.length; i += 1) { cleaners[i](); }
  }
  return destroy;
}

const REFLECT_STRETCH = 1.7;
const RIPPLE_AMP = 7;
const FADE_RATE = 0.9;
const NOISE_SCALE = 0.05;
const HORIZON = 120;
const SEG_W = 20;
const ROW_STEP = 2;
const GREEN_LEN = 90;
const YELLOW_LEN = 24;
const RED_LEN = 110;
const RIPPLE_COUNT = 7;
const SEED = 446;

interface Ripple { x: number; y: number; period: number; off: number; }

function makeScene(ctx: CanvasRenderingContext2D, reduce: boolean): Scene {
  const src = document.createElement('canvas');
  src.width = W;
  src.height = HORIZON;
  const sc = src.getContext('2d');
  if (!sc) { return { step: function (): void { return; }, draw: function (): void { return; }, label: function (): string { return TXT_STOP; } }; }
  const rnd = mulberry32(SEED);
  const buildings: number[][] = [];
  let bx = -10;
  while (bx < W) {
    const bw = 30 + Math.floor(rnd() * 34);
    const bh = 46 + Math.floor(rnd() * 56);
    buildings.push([bx, bw, bh, Math.floor(rnd() * 1000)]);
    bx += bw + 3;
  }
  const ripples: Ripple[] = [];
  for (let i = 0; i < RIPPLE_COUNT; i += 1) {
    ripples.push({ x: 30 + rnd() * 420, y: HORIZON + 24 + rnd() * 110, period: 80 + Math.floor(rnd() * 60), off: Math.floor(rnd() * 120) });
  }
  let f = 40;
  let carX = -60;
  function stateA(): number { return phaseAt(f, GREEN_LEN, YELLOW_LEN, RED_LEN); }
  function stateB(): number { return phaseAt(f + 110, GREEN_LEN, YELLOW_LEN, RED_LEN); }
  function drawSource(): void {
    const g = sc!.createLinearGradient(0, 0, 0, HORIZON);
    g.addColorStop(0, 'rgba(255,224,214,1)');
    g.addColorStop(1, 'rgba(214,204,246,1)');
    sc!.fillStyle = g;
    sc!.fillRect(0, 0, W, HORIZON);
    for (let i = 0; i < buildings.length; i += 1) {
      const b = buildings[i];
      sc!.fillStyle = 'rgba(150,140,190,1)';
      sc!.fillRect(b[0], HORIZON - b[2] - 8, b[1], b[2] + 8);
      for (let wy = HORIZON - b[2]; wy < HORIZON - 14; wy += 12) {
        for (let wx = b[0] + 5; wx < b[0] + b[1] - 8; wx += 10) {
          if (hash2(wx + b[3], wy) < 0.34) {
            sc!.fillStyle = 'rgba(255,236,176,1)';
            sc!.fillRect(wx, wy, 5, 6);
          }
        }
      }
    }
    sc!.fillStyle = 'rgba(120,112,164,1)';
    sc!.fillRect(0, HORIZON - 9, W, 9);
    // 신호 두 대 — 한쪽이 초록이면 다른 쪽은 빨강
    const heads = [[140, 8, stateA()], [352, 11, stateB()]];
    for (let h = 0; h < heads.length; h += 1) {
      const hx = heads[h][0];
      const hr = heads[h][1];
      const st = heads[h][2];
      sc!.fillStyle = rgba(INK_RGB, 1);
      sc!.fillRect(hx - 2, 66, 4, HORIZON - 66);
      drawHead(sc!, hx, 52, hr, litOf(st));
    }
    // 가로등
    sc!.fillStyle = rgba(INK_RGB, 1);
    sc!.fillRect(432, 70, 3, HORIZON - 70);
    glow(sc!, 434, 68, 46, [255, 226, 160], 0.9);
    sc!.beginPath();
    sc!.arc(434, 68, 5, 0, PI2);
    sc!.fillStyle = 'rgba(255,248,214,1)';
    sc!.fill();
    // 지나가는 차 — 앞 등이 반사의 가장 밝은 줄이 된다
    if (carX > -50 && carX < W + 20) {
      rrect(sc!, carX - 38, HORIZON - 24, 38, 14, 5);
      sc!.fillStyle = 'rgba(206,176,214,1)';
      sc!.fill();
      sc!.fillStyle = 'rgba(88,80,128,1)';
      sc!.fillRect(carX - 28, HORIZON - 28, 20, 6);
      sc!.beginPath();
      sc!.arc(carX - 28, HORIZON - 9, 4, 0, PI2);
      sc!.arc(carX - 9, HORIZON - 9, 4, 0, PI2);
      sc!.fill();
      glow(sc!, carX + 2, HORIZON - 16, 34, [255, 240, 190], 0.95);
      sc!.fillStyle = 'rgba(255,252,230,1)';
      sc!.fillRect(carX - 3, HORIZON - 19, 4, 5);
    }
  }
  const scene: Scene = {
    step: function (): void {
      f += 1;
      carX += 2.1;
      if (carX > W + 40) { carX = -60 - (f % 140); }
    },
    label: function (): string { return stateText(stateA()); },
    draw: function (): void {
      drawSource();
      ctx.drawImage(src, 0, 0);
      // 젖은 도로 바탕
      const road = ctx.createLinearGradient(0, HORIZON, 0, H);
      road.addColorStop(0, 'rgba(92,84,128,1)');
      road.addColorStop(1, 'rgba(56,50,88,1)');
      ctx.fillStyle = road;
      ctx.fillRect(0, HORIZON, W, H - HORIZON);
      // 반사 — 도로 행마다 원본의 거꾸로 된 행을 가져오고, 잡음으로 가로로 흔들고, 멀수록 흐려진다
      const depth = H - HORIZON;
      const t = reduce ? 0 : f * 0.06;
      for (let dy = 0; dy < depth; dy += ROW_STEP) {
        const sy = HORIZON - 1 - dy / REFLECT_STRETCH;
        if (sy < 0) { break; }
        const near = dy / depth;
        const alpha = Math.max(0, 0.82 - near * FADE_RATE * 0.8);
        if (alpha <= 0.02) { continue; }
        ctx.globalAlpha = alpha;
        for (let sx = 0; sx < W; sx += SEG_W) {
          const n = vnoise(sx * 0.031 + t * 0.7, dy * NOISE_SCALE + t) * 2 - 1;
          const dx = n * RIPPLE_AMP * (0.35 + near * 1.1);
          ctx.drawImage(src, sx, Math.floor(sy), SEG_W, 1, sx + dx, HORIZON + dy, SEG_W, ROW_STEP + 0.6);
        }
      }
      ctx.globalAlpha = 1;
      // 빗방울 파문
      for (let i = 0; i < ripples.length; i += 1) {
        const r = ripples[i];
        const ph = (((f + r.off) % r.period) / r.period);
        const rad = 4 + 30 * ph * (0.6 + (r.y - HORIZON) / 200);
        ctx.beginPath();
        ctx.ellipse(r.x, r.y, rad, rad * 0.28, 0, 0, PI2);
        ctx.lineWidth = 1.6;
        ctx.strokeStyle = 'rgba(236,232,255,' + (0.7 * (1 - ph)).toFixed(3) + ')';
        ctx.stroke();
      }
    }
  };
  for (let i = 0; i < 60; i += 1) { scene.step(); }
  return scene;
}

export default function TlWetRoadReflectionStreak() {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const canvasRef = useRef<HTMLCanvasElement | null>(null);
  const statusRef = useRef<HTMLParagraphElement | null>(null);
  const btnRef = useRef<HTMLButtonElement | null>(null);

  useEffect(() => {
    const root = rootRef.current;
    const canvas = canvasRef.current;
    const statusEl = statusRef.current;
    const btnEl = btnRef.current;
    if (!root || !canvas || !statusEl || !btnEl) return;
    return main(root, canvas, statusEl, btnEl);
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.sc} is-demo`} ref={rootRef}>
        <canvas className={styles.sc__canvas} ref={canvasRef} width={480} height={300} tabIndex={0} aria-label="젖은 도로에 길게 번지는 신호등 빛 반사" />
        <p className={styles.sc__status} ref={statusRef} aria-live="polite">초록불 — 진행</p>
        <button className={styles.sc__btn} ref={btnRef} type="button">멈춤</button>
        <p className={styles.sc__caption}>젖은 도로에 길게 번지는 신호등 빛 반사</p>
      </div>
    </main>
  );
}