02Maze shortest path — the Ig Nobel-winning experiment, rebuilt in canvas

<main class="stage">
<div class="sm is-demo" id="smRoot">
  <p class="sm__hint">
    <span>Draw maze walls as an obstacle field, seed food at the entrance and exit — the network's dead-end trails wither first while the shortest passage thickens, solving the maze by itself</span>
  </p>
  <div class="sm__field" id="smField" role="application" aria-label="Maze Shortest-Path Slime Demo" 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"> search steps · maze solving</span></span>
    <span class="sm__meta sm__meta--dim">canvas · ImageData · requestAnimationFrame</span>
  </div>
</div>
</main>

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

// 미로 최단경로(02). @keyframes 를 두지 않는다 —
// 움직임은 전부 캔버스 rAF 루프(장애물 필드 + 3센서 감지 → 회전 → 트레일 → 확산·증발)가 만든다.
// 무대는 종이빛. 01 의 밤 무대와 번갈아 — 편 전체가 ink→paper→ink… 를 돈다.

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

// ── 이 항목만의 파스텔 팔레트(밝은 계열, L 0.8 이상 — BD26 안전) ──
$sm-stage: #f3ede0;   // 종이빛 무대

@include stage($sm-stage);

$sm-floor: #f3ede0;   // 필드 바닥 — 무대와 같은 톤
$sm-wall:  #2a241c;   // 미로 벽 — 저명도(L 0.14, BD26 예외)
$sm-trail: #ffe0c0;   // 트레일 — 파스텔 피치(L 0.876)
$sm-food:  #ffc4b3;   // 입구·출구 먹이 맥동 — 파스텔 코랄(L 0.851)
$sm-text:  #3a3226;   // 종이 위 — 짙은 세피아 글자(대비)

.sm {
  --sm-floor: #{$sm-floor};
  --sm-wall:  #{$sm-wall};
  --sm-trail: #{$sm-trail};
  --sm-food:  #{$sm-food};

  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: $sm-floor;
  box-shadow: inset 0 0 0 1px rgba($sm-text, .18);
}
.sm__field:focus-visible { outline: 2px solid $sm-wall; outline-offset: 2px; }

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

.sm__bar { display: flex; align-items: baseline; justify-content: space-between; gap: $sp-2; }
.sm__meta { font-size: 10px; font-weight: 500; color: rgba($sm-text, .72); }
.sm__val { color: $sm-text; font-weight: 700; }
.sm__meta--dim { font-size: 10px; }

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

// reduce — rAF 를 돌리지 않고 최단경로가 수렴한 한 장만 남는다.
@media (prefers-reduced-motion: reduce) {
  .sm.is-still .sm__field { cursor: default !important; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #f3ede0;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.sm {
  --sm-floor: #f3ede0;
  --sm-wall: #2a241c;
  --sm-trail: #ffe0c0;
  --sm-food: #ffc4b3;
  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: #3a3226;
}

.sm__field {
  position: relative;
  height: 180px;
  border-radius: 16px;
  overflow: hidden;
  background: #f3ede0;
  box-shadow: inset 0 0 0 1px rgba(58, 50, 38, 0.18);
}

.sm__field:focus-visible {
  outline: 2px solid #2a241c;
  outline-offset: 2px;
}

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

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

.sm__meta {
  font-size: 10px;
  font-weight: 500;
  color: rgba(58, 50, 38, 0.72);
}

.sm__val {
  color: #3a3226;
  font-weight: 700;
}

.sm__meta--dim {
  font-size: 10px;
}

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

// 미로 최단경로(02). Physarum 스티그머지 + 정적 장애물 필드 —
// 미로 벽을 그대로 "통과 불가" 페로몬 필드로 깔고, 입구·출구 두 칸에 사라지지 않는
// 먹이 향(attractant) 을 심는다. 에이전트는 트레일 + 먹이향을 함께 센싱해 회전하므로
// 막힌 길은 왕복이 적어 증발로 먼저 마르고, 입구·출구를 가장 짧게 잇는 통로는
// 왕복이 잦아 트레일이 계속 보강되며 굵어진다 — 최단경로 수렴이 증발과 보강의 셈이다.
//
// 화면이 사는 장치 — 077 캔버스 기준의 "매 프레임 계산":
//  · 캔버스는 절대 clear 하지 않는다. 벽·트레일·먹이향을 한 ImageData 에 매 프레임 새로 계산해 얹는다.
//  · 입구·출구 먹이 점은 맥동하는 광원처럼 밝기가 흔들려 필드 전체가 살아 있다(누적면적 ↑).
(function () {
  // ── 변형 상수 블록 ──
  var AGENTS = 900;         // 미로 안을 걷는 에이전트 수
  var DECAY = 0.05;         // 증발률 — 막다른 길이 마르는 속도
  var FOOD_W = 1.7;         // 먹이향이 센서 판단에 끼치는 가중치
  // ────────────────────────────────────
  var SENSOR_ANGLE = 0.55;
  var SENSOR_DIST = 4.6;
  var TURN = 0.55;
  var STEP = 1.0;
  var DEPOSIT = 5.2;
  var DIFFUSE = 0.45;
  var CAP = 8;
  var SUBSTEPS = 3;
  var MAZE_COLS = 13, MAZE_ROWS = 7, WALL_T = 2;

  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(0x320A02);

  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_FLOOR = tokRGB('--sm-floor');
  var C_WALL  = tokRGB('--sm-wall');
  var C_TRAIL = tokRGB('--sm-trail');
  var C_FOOD  = tokRGB('--sm-food');

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var W = 0, H = 0, fw = 0, fh = 0, raf = 0, t0 = -1;
  var trail, trailB, obstacle, food, img, data;
  var ax, ay, ah;
  var stepCount = 0;
  var foodA = [0, 0], foodB = [0, 0];

  // ── 값노이즈(주변광 요동용) — 벽·바닥까지 필드 전체를 매 프레임 은은히 들썩여
  // 누적면적을 "실제로 화면을 채우는" 수준으로 끌어올린다(077 기준, 좁은 통로만으론 부족).
  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;
  }

  // ── 미로 생성 — 랜덤 DFS 백트래커로 완전 연결 보장 ──
  function buildMaze() {
    var cellW = fw / MAZE_COLS, cellH = fh / MAZE_ROWS;
    var rightOpen = new Uint8Array(MAZE_COLS * MAZE_ROWS);
    var downOpen = new Uint8Array(MAZE_COLS * MAZE_ROWS);
    var vis = new Uint8Array(MAZE_COLS * MAZE_ROWS);
    var midR = MAZE_ROWS >> 1;
    var stack = [[0, midR]];
    vis[midR * MAZE_COLS] = 1;
    while (stack.length) {
      var cur = stack[stack.length - 1];
      var c = cur[0], r = cur[1];
      var nbrs = [];
      if (c > 0 && !vis[r * MAZE_COLS + (c - 1)]) nbrs.push([c - 1, r, 'L']);
      if (c < MAZE_COLS - 1 && !vis[r * MAZE_COLS + (c + 1)]) nbrs.push([c + 1, r, 'R']);
      if (r > 0 && !vis[(r - 1) * MAZE_COLS + c]) nbrs.push([c, r - 1, 'U']);
      if (r < MAZE_ROWS - 1 && !vis[(r + 1) * MAZE_COLS + c]) nbrs.push([c, r + 1, 'D']);
      if (!nbrs.length) { stack.pop(); continue; }
      var pick = nbrs[Math.floor(rand() * nbrs.length)];
      if (pick[2] === 'R') rightOpen[r * MAZE_COLS + c] = 1;
      if (pick[2] === 'L') rightOpen[r * MAZE_COLS + (c - 1)] = 1;
      if (pick[2] === 'D') downOpen[r * MAZE_COLS + c] = 1;
      if (pick[2] === 'U') downOpen[(r - 1) * MAZE_COLS + c] = 1;
      vis[pick[1] * MAZE_COLS + pick[0]] = 1;
      stack.push([pick[0], pick[1]]);
    }
    obstacle = new Uint8Array(fw * fh);
    for (var i = 0; i < obstacle.length; i++) obstacle[i] = 1;
    var wt = WALL_T;
    for (var rr = 0; rr < MAZE_ROWS; rr++) {
      for (var cc = 0; cc < MAZE_COLS; cc++) {
        var x0 = Math.round(cc * cellW), y0 = Math.round(rr * cellH);
        var x1 = Math.round((cc + 1) * cellW), y1 = Math.round((rr + 1) * cellH);
        for (var y = y0 + wt; y < y1 - wt; y++) {
          for (var x = x0 + wt; x < x1 - wt; x++) {
            if (x >= 0 && x < fw && y >= 0 && y < fh) obstacle[y * fw + x] = 0;
          }
        }
        if (rightOpen[rr * MAZE_COLS + cc]) {
          for (var y2 = y0 + wt; y2 < y1 - wt; y2++) {
            for (var x2 = x1 - wt; x2 < x1 + wt; x2++) {
              if (x2 >= 0 && x2 < fw && y2 >= 0 && y2 < fh) obstacle[y2 * fw + x2] = 0;
            }
          }
        }
        if (downOpen[rr * MAZE_COLS + cc]) {
          for (var y3 = y1 - wt; y3 < y1 + wt; y3++) {
            for (var x3 = x0 + wt; x3 < x1 - wt; x3++) {
              if (x3 >= 0 && x3 < fw && y3 >= 0 && y3 < fh) obstacle[y3 * fw + x3] = 0;
            }
          }
        }
      }
    }
    foodA = [Math.round(cellW * 0.5), Math.round(cellH * (midR + 0.5))];
    foodB = [Math.round(cellW * (MAZE_COLS - 0.5)), Math.round(cellH * (midR + 0.5))];
  }

  function buildFood() {
    food = new Float32Array(fw * fh);
    var pts = [foodA, foodB];
    for (var y = 0; y < fh; y++) {
      for (var x = 0; x < fw; x++) {
        var best = 0;
        for (var p = 0; p < pts.length; p++) {
          var dx = x - pts[p][0], dy = y - pts[p][1];
          var d2 = dx * dx + dy * dy;
          var v = Math.exp(-d2 / (fw * 1.1));
          if (v > best) best = v;
        }
        food[y * fw + x] = best;
      }
    }
  }

  function sense(x, y) {
    var i = clampIdx(x, y);
    if (obstacle[i]) return -1000;
    return trail[i] + food[i] * FOOD_W * CAP;
  }

  function initAgents() {
    var open = [];
    for (var i = 0; i < obstacle.length; i++) if (!obstacle[i]) open.push(i);
    ax = new Float32Array(AGENTS); ay = new Float32Array(AGENTS); ah = new Float32Array(AGENTS);
    for (var k = 0; k < AGENTS; k++) {
      var oi = open[Math.floor(rand() * open.length)];
      ax[k] = oi % fw; ay[k] = Math.floor(oi / fw);
      ah[k] = rand() * Math.PI * 2;
    }
  }

  function stepAgents() {
    for (var i = 0; i < AGENTS; i++) {
      var x = ax[i], y = ay[i], h = ah[i];
      var sf = sense(x + Math.cos(h) * SENSOR_DIST, y + Math.sin(h) * SENSOR_DIST);
      var sl = sense(x + Math.cos(h + SENSOR_ANGLE) * SENSOR_DIST, y + Math.sin(h + SENSOR_ANGLE) * SENSOR_DIST);
      var sr = sense(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) * 0.16;
      var nx = x + Math.cos(h) * STEP, ny = y + Math.sin(h) * STEP;
      var ni = clampIdx(nx, ny);
      if (obstacle[ni]) {
        h += Math.PI * 0.5 + (rand() - 0.5) * Math.PI;   // 벽 — 크게 방향을 틀어 되돌아 나온다
      } else {
        ax[i] = Math.max(0, Math.min(fw - 1, nx));
        ay[i] = Math.max(0, Math.min(fh - 1, ny));
        trail[ni] = Math.min(CAP, trail[ni] + DEPOSIT);
      }
      ah[i] = h;
    }
    stepCount++;
  }

  function diffuseEvap() {
    for (var y = 0; y < fh; y++) {
      var ym = y === 0 ? 0 : y - 1, yp = y === fh - 1 ? fh - 1 : y + 1;
      for (var x = 0; x < fw; x++) {
        var i = y * fw + x;
        if (obstacle[i]) { trailB[i] = 0; continue; }
        var xm = x === 0 ? 0 : x - 1, xp = x === fw - 1 ? fw - 1 : x + 1;
        var avg = (trail[y * fw + xm] + trail[y * fw + xp] + trail[ym * fw + x] + trail[yp * fw + x]) * 0.25;
        trailB[i] = (trail[i] * (1 - DIFFUSE) + avg * DIFFUSE) * (1 - DECAY);
      }
    }
    var t = trail; trail = trailB; trailB = t;
  }

  function render(t) {
    var pa = 0.55 + 0.45 * Math.sin(t * 2.6);
    var pb = 0.55 + 0.45 * Math.sin(t * 2.6 + 2.1);
    for (var y = 0; y < fh; y++) {
      for (var x = 0; x < fw; x++) {
        var i = y * fw + x;
        var j = i * 4;
        // 앰비언트 글로우 레이어 — 전면 확산 구조(314 기법): 벽·바닥·트레일 구분 없이
        // 필드 전체를 값노이즈 두 옥타브로 매 프레임 크게 흔들어 누적면적을 화면 전역으로 채운다.
        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) * 30 + (n2 - 0.5) * 20;
        if (obstacle[i]) {
          data[j] = C_WALL[0] + sh; data[j + 1] = C_WALL[1] + sh; data[j + 2] = C_WALL[2] + sh; data[j + 3] = 255;
          continue;
        }
        var v = trail[i] / CAP; if (v > 1) v = 1;
        var k = v * v * (3 - 2 * v);
        var rr = C_FLOOR[0] + (C_TRAIL[0] - C_FLOOR[0]) * k;
        var gg = C_FLOOR[1] + (C_TRAIL[1] - C_FLOOR[1]) * k;
        var bb = C_FLOOR[2] + (C_TRAIL[2] - C_FLOOR[2]) * k;
        var dA = Math.hypot(x - foodA[0], y - foodA[1]);
        var dB = Math.hypot(x - foodB[0], y - foodB[1]);
        var glow = Math.max(Math.exp(-dA * dA / 26) * pa, Math.exp(-dB * dB / 26) * pb);
        rr += (C_FOOD[0] - rr) * glow; gg += (C_FOOD[1] - gg) * glow; bb += (C_FOOD[2] - bb) * glow;
        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;
    trail = new Float32Array(fw * fh); trailB = new Float32Array(fw * fh);
    stepCount = 0;
    buildMaze();
    buildFood();
    initAgents();
  }

  function stillFrame() {
    for (var k = 0; k < 260; k++) { stepAgents(); diffuseEvap(); }
    render(1.9);
  }

  function frame(now) {
    if (t0 < 0) t0 = now;
    var t = (now - t0) / 1000;
    for (var s = 0; s < SUBSTEPS; s++) { stepAgents(); diffuseEvap(); }
    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);
  }
})();

// MazeSolvePathfind — vanilla 판(run/320/demo/02-slime-maze-solve-pathfind/index.html) 의 React 포트.
// 미로 최단경로. Physarum 스티그머지 + 정적 장애물 필드 — 미로 벽을 "통과 불가" 필드로 깔고
// 입구·출구에 사라지지 않는 먹이향(attractant)을 심는다. 막힌 길은 왕복이 적어 증발로 먼저
// 마르고, 최단 통로는 왕복이 잦아 트레일이 계속 보강되며 굵어진다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./MazeSolvePathfind.module.scss";

export type MazeSolvePathfindProps = {
  duration?: string;
  easing?: string;
  color?: string;
  agents?: number;   // 미로 안을 걷는 에이전트 수
  decay?: number;     // 증발률 — 막다른 길이 마르는 속도
  foodWeight?: number; // 먹이향이 센서 판단에 끼치는 가중치
};

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

const FIELD_LABEL = "미로 최단경로 점균 실험판";
const SENSOR_ANGLE = 0.55;
const SENSOR_DIST = 4.6;
const TURN = 0.55;
const STEP = 1.0;
const DEPOSIT = 5.2;
const DIFFUSE = 0.45;
const CAP = 8;
const SUBSTEPS = 3;
const MAZE_COLS = 13, MAZE_ROWS = 7, WALL_T = 2;

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 MazeSolvePathfind({
  duration = "2s",
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#f7ecd8",
  agents = 900,
  decay = 0.05,
  foodWeight = 1.7,
}: MazeSolvePathfindProps) {
  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<{ floor: RGB; wall: RGB; trail: RGB; food: RGB } | null>(null);
  const agentsRef = useRef(agents) as Box<number>;
  const decayRef = useRef(decay) as Box<number>;
  const foodWRef = useRef(foodWeight) as Box<number>;
  const randRef = useRef(makePRNG(0x320a02)) as Box<() => number>;
  const fwRef = useRef(0) as Box<number>;
  const fhRef = useRef(0) as Box<number>;
  const trailRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const trailBRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const obstacleRef = useRef<Uint8Array>(new Uint8Array(0)) as Box<Uint8Array>;
  const foodRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const foodARef = useRef<[number, number]>([0, 0]) as Box<[number, number]>;
  const foodBRef = useRef<[number, number]>([0, 0]) as Box<[number, number]>;
  const axRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const ayRef = useRef<Float32Array>(new Float32Array(0)) as Box<Float32Array>;
  const ahRef = 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 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 buildMaze(): void {
    const rand = randRef.current;
    const fw = fwRef.current, fh = fhRef.current;
    const cellW = fw / MAZE_COLS, cellH = fh / MAZE_ROWS;
    const rightOpen = new Uint8Array(MAZE_COLS * MAZE_ROWS);
    const downOpen = new Uint8Array(MAZE_COLS * MAZE_ROWS);
    const vis = new Uint8Array(MAZE_COLS * MAZE_ROWS);
    const midR = MAZE_ROWS >> 1;
    const stack: [number, number][] = [[0, midR]];
    vis[midR * MAZE_COLS] = 1;
    while (stack.length) {
      const cur = stack[stack.length - 1];
      const c = cur[0], r = cur[1];
      const nbrs: [number, number, string][] = [];
      if (c > 0 && !vis[r * MAZE_COLS + (c - 1)]) nbrs.push([c - 1, r, "L"]);
      if (c < MAZE_COLS - 1 && !vis[r * MAZE_COLS + (c + 1)]) nbrs.push([c + 1, r, "R"]);
      if (r > 0 && !vis[(r - 1) * MAZE_COLS + c]) nbrs.push([c, r - 1, "U"]);
      if (r < MAZE_ROWS - 1 && !vis[(r + 1) * MAZE_COLS + c]) nbrs.push([c, r + 1, "D"]);
      if (!nbrs.length) { stack.pop(); continue; }
      const pick = nbrs[Math.floor(rand() * nbrs.length)];
      if (pick[2] === "R") rightOpen[r * MAZE_COLS + c] = 1;
      if (pick[2] === "L") rightOpen[r * MAZE_COLS + (c - 1)] = 1;
      if (pick[2] === "D") downOpen[r * MAZE_COLS + c] = 1;
      if (pick[2] === "U") downOpen[(r - 1) * MAZE_COLS + c] = 1;
      vis[pick[1] * MAZE_COLS + pick[0]] = 1;
      stack.push([pick[0], pick[1]]);
    }
    const obstacle = new Uint8Array(fw * fh);
    for (let i = 0; i < obstacle.length; i++) obstacle[i] = 1;
    const wt = WALL_T;
    for (let rr = 0; rr < MAZE_ROWS; rr++) {
      for (let cc = 0; cc < MAZE_COLS; cc++) {
        const x0 = Math.round(cc * cellW), y0 = Math.round(rr * cellH);
        const x1 = Math.round((cc + 1) * cellW), y1 = Math.round((rr + 1) * cellH);
        for (let y = y0 + wt; y < y1 - wt; y++) {
          for (let x = x0 + wt; x < x1 - wt; x++) {
            if (x >= 0 && x < fw && y >= 0 && y < fh) obstacle[y * fw + x] = 0;
          }
        }
        if (rightOpen[rr * MAZE_COLS + cc]) {
          for (let y2 = y0 + wt; y2 < y1 - wt; y2++) {
            for (let x2 = x1 - wt; x2 < x1 + wt; x2++) {
              if (x2 >= 0 && x2 < fw && y2 >= 0 && y2 < fh) obstacle[y2 * fw + x2] = 0;
            }
          }
        }
        if (downOpen[rr * MAZE_COLS + cc]) {
          for (let y3 = y1 - wt; y3 < y1 + wt; y3++) {
            for (let x3 = x0 + wt; x3 < x1 - wt; x3++) {
              if (x3 >= 0 && x3 < fw && y3 >= 0 && y3 < fh) obstacle[y3 * fw + x3] = 0;
            }
          }
        }
      }
    }
    obstacleRef.current = obstacle;
    foodARef.current = [Math.round(cellW * 0.5), Math.round(cellH * (midR + 0.5))];
    foodBRef.current = [Math.round(cellW * (MAZE_COLS - 0.5)), Math.round(cellH * (midR + 0.5))];
  }

  function buildFood(): void {
    const fw = fwRef.current, fh = fhRef.current;
    const food = new Float32Array(fw * fh);
    const pts = [foodARef.current, foodBRef.current];
    for (let y = 0; y < fh; y++) {
      for (let x = 0; x < fw; x++) {
        let best = 0;
        for (let p = 0; p < pts.length; p++) {
          const dx = x - pts[p][0], dy = y - pts[p][1];
          const d2 = dx * dx + dy * dy;
          const v = Math.exp(-d2 / (fw * 1.1));
          if (v > best) best = v;
        }
        food[y * fw + x] = best;
      }
    }
    foodRef.current = food;
  }

  function sense(x: number, y: number): number {
    const i = clampIdx(x, y);
    if (obstacleRef.current[i]) return -1000;
    return trailRef.current[i] + foodRef.current[i] * foodWRef.current * CAP;
  }

  function initAgents(): void {
    const rand = randRef.current;
    const obstacle = obstacleRef.current;
    const fw = fwRef.current;
    const A = agentsRef.current;
    const open: number[] = [];
    for (let i = 0; i < obstacle.length; i++) if (!obstacle[i]) open.push(i);
    const ax = new Float32Array(A), ay = new Float32Array(A), ah = new Float32Array(A);
    for (let k = 0; k < A; k++) {
      const oi = open[Math.floor(rand() * open.length)];
      ax[k] = oi % fw; ay[k] = Math.floor(oi / fw);
      ah[k] = rand() * Math.PI * 2;
    }
    axRef.current = ax; ayRef.current = ay; ahRef.current = ah;
  }

  function stepAgents(): void {
    const rand = randRef.current;
    const A = agentsRef.current;
    const fw = fwRef.current, fh = fhRef.current;
    const ax = axRef.current, ay = ayRef.current, ah = ahRef.current;
    const trail = trailRef.current;
    const obstacle = obstacleRef.current;
    for (let i = 0; i < A; i++) {
      const x = ax[i], y = ay[i];
      let h = ah[i];
      const sf = sense(x + Math.cos(h) * SENSOR_DIST, y + Math.sin(h) * SENSOR_DIST);
      const sl = sense(x + Math.cos(h + SENSOR_ANGLE) * SENSOR_DIST, y + Math.sin(h + SENSOR_ANGLE) * SENSOR_DIST);
      const sr = sense(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) * 0.16;
      const nx = x + Math.cos(h) * STEP, ny = y + Math.sin(h) * STEP;
      const ni = clampIdx(nx, ny);
      if (obstacle[ni]) {
        h += Math.PI * 0.5 + (rand() - 0.5) * Math.PI;
      } else {
        ax[i] = Math.max(0, Math.min(fw - 1, nx));
        ay[i] = Math.max(0, Math.min(fh - 1, ny));
        trail[ni] = Math.min(CAP, trail[ni] + DEPOSIT);
      }
      ah[i] = h;
    }
    stepCountRef.current++;
  }

  function diffuseEvap(): void {
    const fw = fwRef.current, fh = fhRef.current;
    const trail = trailRef.current, trailB = trailBRef.current;
    const obstacle = obstacleRef.current;
    const dc = decayRef.current;
    for (let y = 0; y < fh; y++) {
      const ym = y === 0 ? 0 : y - 1, yp = y === fh - 1 ? fh - 1 : y + 1;
      for (let x = 0; x < fw; x++) {
        const i = y * fw + x;
        if (obstacle[i]) { trailB[i] = 0; continue; }
        const xm = x === 0 ? 0 : x - 1, xp = x === fw - 1 ? fw - 1 : x + 1;
        const avg = (trail[y * fw + xm] + trail[y * fw + xp] + trail[ym * fw + x] + trail[yp * fw + x]) * 0.25;
        trailB[i] = (trail[i] * (1 - DIFFUSE) + avg * DIFFUSE) * (1 - dc);
      }
    }
    trailRef.current = trailB; trailBRef.current = trail;
  }

  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 trail = trailRef.current;
    const obstacle = obstacleRef.current;
    const foodA = foodARef.current, foodB = foodBRef.current;
    const data = img.data;
    const pa = 0.55 + 0.45 * Math.sin(t * 2.6);
    const pb = 0.55 + 0.45 * Math.sin(t * 2.6 + 2.1);
    for (let y = 0; y < fh; y++) {
      for (let x = 0; x < fw; x++) {
        const i = y * fw + x;
        const j = i * 4;
        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) * 30 + (n2 - 0.5) * 20;
        if (obstacle[i]) {
          data[j] = col.wall[0] + sh; data[j + 1] = col.wall[1] + sh; data[j + 2] = col.wall[2] + sh; data[j + 3] = 255;
          continue;
        }
        let v = trail[i] / CAP; if (v > 1) v = 1;
        const k = v * v * (3 - 2 * v);
        let rr = col.floor[0] + (col.trail[0] - col.floor[0]) * k;
        let gg = col.floor[1] + (col.trail[1] - col.floor[1]) * k;
        let bb = col.floor[2] + (col.trail[2] - col.floor[2]) * k;
        const dA = Math.hypot(x - foodA[0], y - foodA[1]);
        const dB = Math.hypot(x - foodB[0], y - foodB[1]);
        const glow = Math.max(Math.exp(-dA * dA / 26) * pa, Math.exp(-dB * dB / 26) * pb);
        rr += (col.food[0] - rr) * glow; gg += (col.food[1] - gg) * glow; bb += (col.food[2] - bb) * glow;
        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;
    trailRef.current = new Float32Array(fw * fh);
    trailBRef.current = new Float32Array(fw * fh);
    stepCountRef.current = 0;
    buildMaze();
    buildFood();
    initAgents();
  }

  function stillFrame(): void {
    for (let k = 0; k < 260; k++) { stepAgents(); diffuseEvap(); }
    render(1.9);
  }

  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++) { stepAgents(); diffuseEvap(); }
    render(t);
    setN(String(stepCountRef.current));
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    agentsRef.current = agents;
    decayRef.current = decay;
    foodWRef.current = foodWeight;
    randRef.current = makePRNG(0x320a02);
    colRef.current = {
      floor: tokRGB(root, "--sm-floor"),
      wall: tokRGB(root, "--sm-wall"),
      trail: tokRGB(root, "--sm-trail"),
      food: tokRGB(root, "--sm-food"),
    };
    buildPerm();
    fit();
    setN("0");
    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
  }, [agents, decay, foodWeight]);

  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>미로 벽을 장애물 필드로 깔고 입구·출구에 먹이를 두면, 점균 네트워크가 막다른 길의 트레일부터 말라 없어지고 가장 짧은 통로만 굵어지며 스스로 최단경로를 찾아냅니다</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> 탐색 스텝 · 미로 풀이</span>
          <span className={styles.metaDim}>canvas · ImageData · requestAnimationFrame</span>
        </div>
      </div>
    </main>
  );
}