05多種の縄張り競争 — 色の違う2つの群れが画面を分け合う

<main class="stage">
<div class="sm is-demo" id="smRoot">
  <p class="sm__hint">
    <span>種(species)ごとに自分のトレイルにだけ反応し、他種のトレイルは障害物として扱わせると、2色の群れが互いを押し合い、境界のはっきりした縄張りに画面を分けます</span>
  </p>
  <div class="sm__field" id="smField" role="application" aria-label="多種 縄張り競争 粘菌実験版" tabindex="0">
    <canvas class="sm__cv" id="smCv"></canvas>
  </div>
  <div class="sm__bar">
    <span class="sm__meta"><b class="sm__val" id="smN">0</b><span id="smUnit"> ステップ・2種の境界線</span></span>
    <span class="sm__meta sm__meta--dim">canvas · ImageData · requestAnimationFrame</span>
  </div>
</div>
</main>

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

// 다종 영역 경쟁(05). @keyframes 를 두지 않는다 —
// 움직임은 전부 캔버스 rAF 루프(두 종 각자 3센서 감지 → 회전 → 자기 트레일 → 확산·증발)가 만든다.
// 무대는 다시 먹(ink) — 01(밤)·02(종이)·03(밀짚)·04(노을) 다음 다섯 번째 순환. 어두운 바닥 위에
// 두 파스텔 종(핑크·민트)이 발광하며 영역 경계를 그린다.

$duration: $dur-loop;
$easing: $ease-spring;
$color: $subject-cream;

// ── 이 항목만의 파스텔 팔레트(어두운 무대 L0.1 미만 + 파스텔 종 L0.9 이상 — BD26 안전) ──
$sm-stage: #1a1620;   // 밤무대 먹 — 01 의 밤과 같은 계열

@include stage($sm-stage);

$sm-ink:   #1a1620;   // 필드 바닥 — 무대와 같은 톤
$sm-a:     #ffd6e0;   // 종 A — 파스텔 핑크
$sm-b:     #d6f5e3;   // 종 B — 파스텔 민트
$sm-text:  #f3ecdd;   // 먹 무대 위 — 크림 글자(대비)

.sm {
  --sm-ink: #{$sm-ink};
  --sm-a:   #{$sm-a};
  --sm-b:   #{$sm-b};

  display: flex; flex-direction: column; gap: $sp-2;
  width: 100%; max-width: 424px;
}

.sm__hint {
  display: flex; align-items: center; gap: $sp-1; margin: 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); line-height: 1.35;
  color: $sm-text;
}

.sm__field {
  position: relative; height: 180px;
  border-radius: $r-card; overflow: hidden;
  background: $sm-ink;
  box-shadow: inset 0 0 0 1px rgba($sm-text, .18);
}
.sm__field:focus-visible { outline: 2px solid $sm-text; outline-offset: 2px; }

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

.sm__bar { display: flex; align-items: center; justify-content: space-between; gap: $sp-2; }

.sm__val { color: $sm-a; }
.sm__meta { font-size: 10px; font-weight: 700; color: rgba($sm-text, .72); }
.sm__meta--dim { font-size: 10px; font-weight: 500; color: rgba($sm-text, .72); }

@media (max-width: 340px) {
  .sm { gap: $sp-1; }
  .sm__field { height: 100px; }
  .sm__meta--dim { display: none; }
}

// reduce — rAF 를 돌리지 않고 두 종이 영역을 나눈 한 장만 남는다.
@media (prefers-reduced-motion: reduce) {
  .sm.is-still { opacity: 1; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #1a1620;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.sm {
  --sm-ink: #1a1620;
  --sm-a: #ffd6e0;
  --sm-b: #d6f5e3;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 424px;
}

.sm__hint {
  display: flex;
  align-items: center;
  gap: 4px;
  margin: 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  line-height: 1.35;
  color: #f3ecdd;
}

.sm__field {
  position: relative;
  height: 180px;
  border-radius: 16px;
  overflow: hidden;
  background: #1a1620;
  box-shadow: inset 0 0 0 1px rgba(243, 236, 221, 0.18);
}

.sm__field:focus-visible {
  outline: 2px solid #f3ecdd;
  outline-offset: 2px;
}

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

.sm__bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.sm__val {
  color: #ffd6e0;
}

.sm__meta {
  font-size: 10px;
  font-weight: 700;
  color: rgba(243, 236, 221, 0.72);
}

.sm__meta--dim {
  font-size: 10px;
  font-weight: 500;
  color: rgba(243, 236, 221, 0.72);
}

@media (max-width: 340px) {
  .sm {
    gap: 4px;
  }
  .sm__field {
    height: 100px;
  }
  .sm__meta--dim {
    display: none;
  }
}
@media (prefers-reduced-motion: reduce) {
  .sm.is-still {
    opacity: 1;
  }
}

// 다종 영역 경쟁(05). Physarum 스티그머지 + 두 페로몬 필드 상호 기피 —
// 종 A·B 는 각자의 트레일 필드만 따로 갖는다. 센싱 값은 "내 종 트레일 - 남의 종 트레일 × 기피가중"
// 이라 자기 흔적은 강화되고 상대 흔적은 장애물처럼 밀어낸다. 두 군집이 중앙에서 만나 서로
// 밀고 밀리며 화면이 뚜렷한 경계선을 가진 두 영역으로 갈라진다.
//
// 화면이 사는 장치 — 077 캔버스 기준의 "매 프레임 계산":
//  · 캔버스는 절대 clear 하지 않는다. 두 필드를 합성해 매 프레임 새로 계산해 얹는다.
//  · 앰비언트 글로우 레이어(두 옥타브 값노이즈)가 전면을 확산 구조로 흔들어 누적면적을 채운다.
(function () {
  // ── 변형 상수 블록 ──
  var AGENTS_A = 700, AGENTS_B = 700;   // 종마다 개체 수
  var DECAY = 0.048;                     // 증발률
  var REPEL_W = 1.7;                     // 상대 종 트레일 기피 가중치
  // ────────────────────────────────────
  var SENSOR_ANGLE = 0.5;
  var SENSOR_DIST = 5.0;
  var TURN = 0.5;
  var STEP = 1.05;
  var DEPOSIT = 4.2;
  var DIFFUSE = 0.5;
  var CAP = 7;
  var SUBSTEPS = 3;

  var root = document.getElementById('smRoot');
  var field = document.getElementById('smField');
  var cv = document.getElementById('smCv');
  var ctx = cv.getContext('2d', { alpha: false });
  var nOut = document.getElementById('smN');

  function makeRand(seed) {
    var st = seed >>> 0;
    return function () {
      st = (st + 0x6D2B79F5) >>> 0;
      var t = st;
      t = Math.imul(t ^ (t >>> 15), t | 1);
      t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
      return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
    };
  }
  var rand = makeRand(0x320A05);

  var css = getComputedStyle(root);
  function tokRGB(name) {
    var s = css.getPropertyValue(name).trim();
    var hx = s.length === 4
      ? s.charAt(1) + s.charAt(1) + s.charAt(2) + s.charAt(2) + s.charAt(3) + s.charAt(3)
      : s.slice(1);
    return [parseInt(hx.slice(0, 2), 16), parseInt(hx.slice(2, 4), 16), parseInt(hx.slice(4, 6), 16)];
  }
  var C_INK = tokRGB('--sm-ink');
  var C_A   = tokRGB('--sm-a');
  var C_B   = tokRGB('--sm-b');

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var W = 0, H = 0, fw = 0, fh = 0, raf = 0, t0 = -1;
  var trailA, trailAB, trailB, trailBB, img, data;
  var axA, ayA, ahA, axB, ayB, ahB;
  var stepCount = 0;

  // ── 값노이즈(앰비언트 글로우용) ──
  var perm = new Uint8Array(512);
  (function () {
    var p = [];
    for (var i = 0; i < 256; i++) p.push(i);
    for (var i2 = 255; i2 > 0; i2--) {
      var k2 = Math.floor(rand() * (i2 + 1));
      var tmp = p[i2]; p[i2] = p[k2]; p[k2] = tmp;
    }
    for (var i3 = 0; i3 < 512; i3++) perm[i3] = p[i3 & 255];
  })();
  function fade(k) { return k * k * (3 - 2 * k); }
  function vnoise(x, y) {
    var xi = Math.floor(x), yi = Math.floor(y);
    var xf = x - xi, yf = y - yi;
    var a2 = perm[(perm[xi & 255] + yi) & 255];
    var b2 = perm[(perm[(xi + 1) & 255] + yi) & 255];
    var c2 = perm[(perm[xi & 255] + yi + 1) & 255];
    var d2 = perm[(perm[(xi + 1) & 255] + yi + 1) & 255];
    var u = fade(xf), v = fade(yf);
    return (a2 + (b2 - a2) * u + (c2 - a2) * v + (a2 - b2 - c2 + d2) * u * v) / 255;
  }

  function idx(x, y) {
    x = x % fw; if (x < 0) x += fw;
    y = y % fh; if (y < 0) y += fh;
    return (y * fw + x) | 0;
  }
  function clampIdx(x, y) {
    x = Math.max(0, Math.min(fw - 1, Math.round(x)));
    y = Math.max(0, Math.min(fh - 1, Math.round(y)));
    return y * fw + x;
  }

  function senseFrom(own, other, x, y) {
    var i = clampIdx(x, y);
    return own[i] - other[i] * REPEL_W;
  }

  function initSpecies(count, cx0) {
    var ax = new Float32Array(count), ay = new Float32Array(count), ah = new Float32Array(count);
    var cx = fw * cx0, cy = fh / 2, r = Math.min(fw, fh) * 0.13;
    for (var i = 0; i < count; i++) {
      var a = rand() * Math.PI * 2, rr = rand() * r;
      ax[i] = cx + Math.cos(a) * rr;
      ay[i] = cy + Math.sin(a) * rr;
      ah[i] = rand() * Math.PI * 2;
    }
    return [ax, ay, ah];
  }

  function stepSpecies(ax, ay, ah, count, own, other) {
    for (var i = 0; i < count; i++) {
      var x = ax[i], y = ay[i], h = ah[i];
      var sf = senseFrom(own, other, x + Math.cos(h) * SENSOR_DIST, y + Math.sin(h) * SENSOR_DIST);
      var sl = senseFrom(own, other, x + Math.cos(h + SENSOR_ANGLE) * SENSOR_DIST, y + Math.sin(h + SENSOR_ANGLE) * SENSOR_DIST);
      var sr = senseFrom(own, other, x + Math.cos(h - SENSOR_ANGLE) * SENSOR_DIST, y + Math.sin(h - SENSOR_ANGLE) * SENSOR_DIST);
      if (sf >= sl && sf >= sr) {
        // 직진
      } else if (sl > sr) {
        h += TURN;
      } else if (sr > sl) {
        h -= TURN;
      } else {
        h += (rand() < 0.5 ? 1 : -1) * TURN;
      }
      h += (rand() - 0.5) * 0.14;
      var nx = x + Math.cos(h) * STEP, ny = y + Math.sin(h) * STEP;
      nx = ((nx % fw) + fw) % fw; ny = ((ny % fh) + fh) % fh;
      ax[i] = nx; ay[i] = ny; ah[i] = h;
      var ii = idx(Math.round(nx), Math.round(ny));
      own[ii] = Math.min(CAP, own[ii] + DEPOSIT);
    }
  }

  function diffuseEvapOne(field0, field1) {
    for (var y = 0; y < fh; y++) {
      var ym = y === 0 ? fh - 1 : y - 1, yp = y === fh - 1 ? 0 : y + 1;
      var rowY = y * fw, rowYm = ym * fw, rowYp = yp * fw;
      for (var x = 0; x < fw; x++) {
        var xm = x === 0 ? fw - 1 : x - 1, xp = x === fw - 1 ? 0 : x + 1;
        var i = rowY + x;
        var avg = (field0[rowY + xm] + field0[rowY + xp] + field0[rowYm + x] + field0[rowYp + x]) * 0.25;
        field1[i] = (field0[i] * (1 - DIFFUSE) + avg * DIFFUSE) * (1 - DECAY);
      }
    }
  }

  function render(t) {
    for (var y = 0; y < fh; y++) {
      for (var x = 0; x < fw; x++) {
        var i = y * fw + x;
        var j = i * 4;
        var va = trailA[i] / CAP; if (va > 1) va = 1;
        var vb = trailB[i] / CAP; if (vb > 1) vb = 1;
        var ka = va * va * (3 - 2 * va);
        var kb = vb * vb * (3 - 2 * vb);
        var rr = C_INK[0] + (C_A[0] - C_INK[0]) * ka + (C_B[0] - C_INK[0]) * kb;
        var gg = C_INK[1] + (C_A[1] - C_INK[1]) * ka + (C_B[1] - C_INK[1]) * kb;
        var bb = C_INK[2] + (C_A[2] - C_INK[2]) * ka + (C_B[2] - C_INK[2]) * kb;
        var n1 = vnoise(x * 0.09, y * 0.09 + t * 0.9);
        var n2 = vnoise(x * 0.03 + 40, y * 0.03 + t * 0.6);
        var sh = (n1 - 0.5) * 22 + (n2 - 0.5) * 14;
        rr += sh; gg += sh; bb += sh;
        data[j] = rr; data[j + 1] = gg; data[j + 2] = bb; data[j + 3] = 255;
      }
    }
    ctx.putImageData(img, 0, 0);
  }

  function fit() {
    var r = field.getBoundingClientRect();
    W = Math.round(r.width); H = Math.round(r.height);
    fw = Math.max(96, Math.min(200, Math.round(W / 3)));
    fh = Math.max(52, Math.min(120, Math.round(H / 3)));
    cv.width = fw; cv.height = fh;
    cv.style.width = '100%'; cv.style.height = '100%';
    ctx = cv.getContext('2d', { alpha: false });
    img = ctx.createImageData(fw, fh); data = img.data;
    trailA = new Float32Array(fw * fh); trailAB = new Float32Array(fw * fh);
    trailB = new Float32Array(fw * fh); trailBB = new Float32Array(fw * fh);
    stepCount = 0;
    var sa = initSpecies(AGENTS_A, 0.3); axA = sa[0]; ayA = sa[1]; ahA = sa[2];
    var sb = initSpecies(AGENTS_B, 0.7); axB = sb[0]; ayB = sb[1]; ahB = sb[2];
  }

  function stepAll() {
    stepSpecies(axA, ayA, ahA, AGENTS_A, trailA, trailB);
    stepSpecies(axB, ayB, ahB, AGENTS_B, trailB, trailA);
    diffuseEvapOne(trailA, trailAB);
    diffuseEvapOne(trailB, trailBB);
    var ta = trailA; trailA = trailAB; trailAB = ta;
    var tb = trailB; trailB = trailBB; trailBB = tb;
    stepCount++;
  }

  function stillFrame() {
    for (var k = 0; k < 260; k++) stepAll();
    render(2.6);
  }

  function frame(now) {
    if (t0 < 0) t0 = now;
    var t = (now - t0) / 1000;
    for (var s = 0; s < SUBSTEPS; s++) stepAll();
    render(t);
    if (nOut) nOut.textContent = String(stepCount);
    raf = requestAnimationFrame(frame);
  }

  window.addEventListener('resize', function () {
    fit();
    if (reduce) stillFrame();
  });

  fit();
  if (reduce) {
    stillFrame();
    root.classList.add('is-still');
  } else {
    raf = requestAnimationFrame(frame);
  }
})();

// MultiSpeciesTerritory — vanilla 판(run/320/demo/05-slime-multi-species-territory/index.html) 의 React 포트.
// 다종 영역 경쟁. 두 종(A·B) 이 각자의 트레일 필드만 갖고, 센싱값은 "내 종 - 남의 종 × 기피가중"
// 이라 자기 흔적은 강화되고 상대 흔적은 장애물처럼 밀어낸다 — 화면이 뚜렷한 경계선을 가진 두
// 영역으로 갈라진다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./MultiSpeciesTerritory.module.scss";

export type MultiSpeciesTerritoryProps = {
  duration?: string;
  easing?: string;
  color?: string;
  agentsA?: number;
  agentsB?: number;
  decay?: number;
  repelWeight?: number;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Box<T> = { current: T };
type RGB = [number, number, number];

const FIELD_LABEL = "다종 영역 경쟁 점균 실험판";
const SENSOR_ANGLE = 0.5;
const SENSOR_DIST = 5.0;
const TURN = 0.5;
const STEP = 1.05;
const DEPOSIT = 4.2;
const DIFFUSE = 0.5;
const CAP = 7;
const SUBSTEPS = 3;

function makePRNG(seed: number): () => number {
  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;
  };
}

export default function MultiSpeciesTerritory({
  duration = "2s",
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#f3ecdd",
  agentsA = 700,
  agentsB = 700,
  decay = 0.048,
  repelWeight = 1.7,
}: MultiSpeciesTerritoryProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const fieldRef = useRef<HTMLDivElement | null>(null);
  const cvRef = useRef<HTMLCanvasElement | null>(null);
  const ctxRef = useRef<CanvasRenderingContext2D | null>(null);
  const colRef = useRef<{ ink: RGB; a: RGB; b: RGB } | null>(null);
  const agentsARef = useRef(agentsA) as Box<number>;
  const agentsBRef = useRef(agentsB) as Box<number>;
  const decayRef = useRef(decay) as Box<number>;
  const repelRef = useRef(repelWeight) as Box<number>;
  const randRef = useRef(makePRNG(0x320a05)) as Box<() => number>;
  const fwRef = useRef(0) as Box<number>;
  const fhRef = useRef(0) as Box<number>;
  const trailARef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const trailABRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const trailBRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const trailBBRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const axARef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const ayARef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const ahARef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const axBRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const ayBRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const ahBRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const imgRef = useRef<ImageData | null>(null) as Box<ImageData | null>;
  const permRef = useRef<Uint8Array>(new Uint8Array(512)) as Box<Uint8Array>;
  const stepCountRef = useRef(0) as Box<number>;
  const rafRef = useRef(0) as Box<number>;
  const [n, setN] = useState("0");
  const [still, setStill] = useState(false);
  const vars: Vars = { "--duration": duration, "--easing": easing, "--color": color };

  function reduced(): boolean {
    return window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  }

  function tokRGB(root: HTMLDivElement, name: string): RGB {
    const s = getComputedStyle(root).getPropertyValue(name).trim();
    const hx = s.length === 4
      ? s.charAt(1) + s.charAt(1) + s.charAt(2) + s.charAt(2) + s.charAt(3) + s.charAt(3)
      : s.slice(1);
    return [parseInt(hx.slice(0, 2), 16), parseInt(hx.slice(2, 4), 16), parseInt(hx.slice(4, 6), 16)];
  }

  function buildPerm(): void {
    const rand = randRef.current;
    const p: number[] = [];
    for (let i = 0; i < 256; i++) p.push(i);
    for (let i2 = 255; i2 > 0; i2--) {
      const k2 = Math.floor(rand() * (i2 + 1));
      const tmp = p[i2]; p[i2] = p[k2]; p[k2] = tmp;
    }
    const perm = new Uint8Array(512);
    for (let i3 = 0; i3 < 512; i3++) perm[i3] = p[i3 & 255];
    permRef.current = perm;
  }
  function fade(k: number): number { return k * k * (3 - 2 * k); }
  function vnoise(x: number, y: number): number {
    const perm = permRef.current;
    const xi = Math.floor(x), yi = Math.floor(y);
    const xf = x - xi, yf = y - yi;
    const a2 = perm[(perm[xi & 255] + yi) & 255];
    const b2 = perm[(perm[(xi + 1) & 255] + yi) & 255];
    const c2 = perm[(perm[xi & 255] + yi + 1) & 255];
    const d2 = perm[(perm[(xi + 1) & 255] + yi + 1) & 255];
    const u = fade(xf), v = fade(yf);
    return (a2 + (b2 - a2) * u + (c2 - a2) * v + (a2 - b2 - c2 + d2) * u * v) / 255;
  }

  function idx(x: number, y: number): number {
    const fw = fwRef.current, fh = fhRef.current;
    let xx = x % fw; if (xx < 0) xx += fw;
    let yy = y % fh; if (yy < 0) yy += fh;
    return (yy * fw + xx) | 0;
  }
  function clampIdx(x: number, y: number): number {
    const fw = fwRef.current, fh = fhRef.current;
    const xx = Math.max(0, Math.min(fw - 1, Math.round(x)));
    const yy = Math.max(0, Math.min(fh - 1, Math.round(y)));
    return yy * fw + xx;
  }

  function senseFrom(own: Float32Array, other: Float32Array, x: number, y: number): number {
    const i = clampIdx(x, y);
    return own[i] - other[i] * repelRef.current;
  }

  function initSpecies(count: number, cx0: number): [Float32Array, Float32Array, Float32Array] {
    const rand = randRef.current;
    const fw = fwRef.current, fh = fhRef.current;
    const ax = new Float32Array(count), ay = new Float32Array(count), ah = new Float32Array(count);
    const cx = fw * cx0, cy = fh / 2, r = Math.min(fw, fh) * 0.13;
    for (let i = 0; i < count; i++) {
      const a = rand() * Math.PI * 2, rr = rand() * r;
      ax[i] = cx + Math.cos(a) * rr;
      ay[i] = cy + Math.sin(a) * rr;
      ah[i] = rand() * Math.PI * 2;
    }
    return [ax, ay, ah];
  }

  function stepSpecies(
    ax: Float32Array, ay: Float32Array, ah: Float32Array, count: number,
    own: Float32Array, other: Float32Array,
  ): void {
    const rand = randRef.current;
    const fw = fwRef.current, fh = fhRef.current;
    for (let i = 0; i < count; i++) {
      const x = ax[i], y = ay[i];
      let h = ah[i];
      const sf = senseFrom(own, other, x + Math.cos(h) * SENSOR_DIST, y + Math.sin(h) * SENSOR_DIST);
      const sl = senseFrom(own, other, x + Math.cos(h + SENSOR_ANGLE) * SENSOR_DIST, y + Math.sin(h + SENSOR_ANGLE) * SENSOR_DIST);
      const sr = senseFrom(own, other, x + Math.cos(h - SENSOR_ANGLE) * SENSOR_DIST, y + Math.sin(h - SENSOR_ANGLE) * SENSOR_DIST);
      if (sf >= sl && sf >= sr) {
        // 직진
      } else if (sl > sr) {
        h += TURN;
      } else if (sr > sl) {
        h -= TURN;
      } else {
        h += (rand() < 0.5 ? 1 : -1) * TURN;
      }
      h += (rand() - 0.5) * 0.14;
      let nx = x + Math.cos(h) * STEP, ny = y + Math.sin(h) * STEP;
      nx = ((nx % fw) + fw) % fw; ny = ((ny % fh) + fh) % fh;
      ax[i] = nx; ay[i] = ny; ah[i] = h;
      const ii = idx(Math.round(nx), Math.round(ny));
      own[ii] = Math.min(CAP, own[ii] + DEPOSIT);
    }
  }

  function diffuseEvapOne(field0: Float32Array, field1: Float32Array): void {
    const fw = fwRef.current, fh = fhRef.current;
    const dc = decayRef.current;
    for (let y = 0; y < fh; y++) {
      const ym = y === 0 ? fh - 1 : y - 1, yp = y === fh - 1 ? 0 : y + 1;
      const rowY = y * fw, rowYm = ym * fw, rowYp = yp * fw;
      for (let x = 0; x < fw; x++) {
        const xm = x === 0 ? fw - 1 : x - 1, xp = x === fw - 1 ? 0 : x + 1;
        const i = rowY + x;
        const avg = (field0[rowY + xm] + field0[rowY + xp] + field0[rowYm + x] + field0[rowYp + x]) * 0.25;
        field1[i] = (field0[i] * (1 - DIFFUSE) + avg * DIFFUSE) * (1 - dc);
      }
    }
  }

  function stepAll(): void {
    stepSpecies(axARef.current, ayARef.current, ahARef.current, agentsARef.current, trailARef.current, trailBRef.current);
    stepSpecies(axBRef.current, ayBRef.current, ahBRef.current, agentsBRef.current, trailBRef.current, trailARef.current);
    diffuseEvapOne(trailARef.current, trailABRef.current);
    diffuseEvapOne(trailBRef.current, trailBBRef.current);
    const ta = trailARef.current; trailARef.current = trailABRef.current; trailABRef.current = ta;
    const tb = trailBRef.current; trailBRef.current = trailBBRef.current; trailBBRef.current = tb;
    stepCountRef.current++;
  }

  function render(t: number): void {
    const ctx = ctxRef.current;
    const col = colRef.current;
    const img = imgRef.current;
    if (!ctx || !col || !img) return;
    const fw = fwRef.current, fh = fhRef.current;
    const trailA = trailARef.current, trailB = trailBRef.current;
    const data = img.data;
    for (let y = 0; y < fh; y++) {
      for (let x = 0; x < fw; x++) {
        const i = y * fw + x;
        const j = i * 4;
        let va = trailA[i] / CAP; if (va > 1) va = 1;
        let vb = trailB[i] / CAP; if (vb > 1) vb = 1;
        const ka = va * va * (3 - 2 * va);
        const kb = vb * vb * (3 - 2 * vb);
        let rr = col.ink[0] + (col.a[0] - col.ink[0]) * ka + (col.b[0] - col.ink[0]) * kb;
        let gg = col.ink[1] + (col.a[1] - col.ink[1]) * ka + (col.b[1] - col.ink[1]) * kb;
        let bb = col.ink[2] + (col.a[2] - col.ink[2]) * ka + (col.b[2] - col.ink[2]) * kb;
        const n1 = vnoise(x * 0.09, y * 0.09 + t * 0.9);
        const n2 = vnoise(x * 0.03 + 40, y * 0.03 + t * 0.6);
        const sh = (n1 - 0.5) * 22 + (n2 - 0.5) * 14;
        rr += sh; gg += sh; bb += sh;
        data[j] = rr; data[j + 1] = gg; data[j + 2] = bb; data[j + 3] = 255;
      }
    }
    ctx.putImageData(img, 0, 0);
  }

  function fit(): void {
    const field = fieldRef.current;
    const cv = cvRef.current;
    if (!field || !cv) return;
    const r = field.getBoundingClientRect();
    const W = Math.round(r.width), H = Math.round(r.height);
    const fw = Math.max(96, Math.min(200, Math.round(W / 3)));
    const fh = Math.max(52, Math.min(120, Math.round(H / 3)));
    fwRef.current = fw; fhRef.current = fh;
    cv.width = fw; cv.height = fh;
    cv.style.width = "100%"; cv.style.height = "100%";
    const ctx = cv.getContext("2d", { alpha: false });
    if (!ctx) return;
    ctxRef.current = ctx;
    const img = ctx.createImageData(fw, fh);
    imgRef.current = img;
    trailARef.current = new Float32Array(fw * fh);
    trailABRef.current = new Float32Array(fw * fh);
    trailBRef.current = new Float32Array(fw * fh);
    trailBBRef.current = new Float32Array(fw * fh);
    stepCountRef.current = 0;
    const sa = initSpecies(agentsARef.current, 0.3);
    axARef.current = sa[0]; ayARef.current = sa[1]; ahARef.current = sa[2];
    const sb = initSpecies(agentsBRef.current, 0.7);
    axBRef.current = sb[0]; ayBRef.current = sb[1]; ahBRef.current = sb[2];
  }

  function stillFrame(): void {
    for (let k = 0; k < 260; k++) stepAll();
    render(2.6);
  }

  let t0 = -1;
  function frame(now: number): void {
    if (t0 < 0) t0 = now;
    const t = (now - t0) / 1000;
    for (let s = 0; s < SUBSTEPS; s++) stepAll();
    render(t);
    setN(String(stepCountRef.current));
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    agentsARef.current = agentsA;
    agentsBRef.current = agentsB;
    decayRef.current = decay;
    repelRef.current = repelWeight;
    randRef.current = makePRNG(0x320a05);
    colRef.current = {
      ink: tokRGB(root, "--sm-ink"),
      a: tokRGB(root, "--sm-a"),
      b: tokRGB(root, "--sm-b"),
    };
    buildPerm();
    fit();
    function onResize(): void {
      fit();
      if (reduced()) stillFrame();
    }
    window.addEventListener("resize", onResize);
    if (reduced()) {
      stillFrame();
      setStill(true);
    } else {
      t0 = -1;
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [agentsA, agentsB, decay, repelWeight]);

  const rootCls = still ? `${styles.root} ${styles.isStill}` : styles.root;

  return (
    <main className={styles.stage}>
      <div className={rootCls} ref={rootRef} style={vars}>
        <p className={styles.hint}>
          <span>종(species)마다 자기 트레일에만 반응하고 남의 트레일은 장애물로 취급하게 하면, 두 색 군집이 서로 밀어내며 화면을 경계선 뚜렷한 영역으로 나눕니다</span>
        </p>
        <div className={styles.field} ref={fieldRef} role="application" aria-label={FIELD_LABEL} tabIndex={0}>
          <canvas className={styles.cv} ref={cvRef}></canvas>
        </div>
        <div className={styles.bar}>
          <span className={styles.meta}>
            <b className={styles.val}>{n}</b>
            <span> 스텝 · 2종 경계선</span>
          </span>
          <span className={styles.metaDim}>canvas · ImageData · requestAnimationFrame</span>
        </div>
      </div>
    </main>
  );
}