07Sensor-angle morph — one angle value turns coral into blood vessels

<main class="stage">
<div class="sm is-demo" id="smRoot">
  <p class="sm__hint">
    <span>Move two sliders — sensor spread angle and distance — and the same rule draws dense coral, sparse vessels, or a grid-like city network</span>
  </p>
  <div class="sm__field" id="smField" role="application" aria-label="Sensor-Angle Morph Slime Demo" tabindex="0">
    <canvas class="sm__cv" id="smCv"></canvas>
  </div>
  <div class="sm__bar">
    <label class="sm__ctl">
      <span class="sm__lab" id="smAngLab">Spread 29°</span>
      <input class="sm__rng" id="smAng" type="range" min="10" max="90" step="1" value="29" aria-label="Sensor spread angle">
    </label>
    <label class="sm__ctl">
      <span class="sm__lab" id="smDistLab">Distance 15</span>
      <input class="sm__rng" id="smDist" type="range" min="4" max="30" step="1" value="15" aria-label="Sensor distance">
    </label>
  </div>
</div>
</main>

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

// 센서 각도 모프(07). @keyframes 를 두지 않는다 —
// 움직임은 전부 캔버스 rAF 루프(슬라이더 파라미터 + 3센서 감지 → 회전 → 트레일 → 확산·증발)가 만든다.
// 무대는 종이(paper) — 일곱 번째 순환(01밤·02종이·03밀짚·04노을·05먹·06남색). 파라미터 실험판에는
// 밝은 종이가 계기판처럼 어울린다.

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

// ── 이 항목만의 파스텔 팔레트(밝은 계열, L 0.85 이상 — BD26 안전) ──
$sm-stage: #f4f7f2;   // 연한 이끼 종이 무대

@include stage($sm-stage);

$sm-floor: #f4f7f2;   // 필드 바닥 — 무대와 같은 톤
$sm-trail: #cfe3c8;   // 트레일 — 파스텔 세이지
$sm-acct:  #f6cfd4;   // 파라미터 표시기 — 파스텔 로즈
$sm-text:  #2c3326;   // 종이 위 — 짙은 이끼 글자(대비)

.sm {
  --sm-floor: #{$sm-floor};
  --sm-trail: #{$sm-trail};
  --sm-acct:  #{$sm-acct};

  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-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; flex-wrap: wrap;
}

.sm__ctl {
  display: flex; align-items: center; gap: $sp-1;
  min-width: 0;
}

.sm__lab {
  font-size: 10px; font-weight: 700; line-height: 1;
  color: rgba($sm-text, .72); white-space: nowrap;
}

.sm__rng {
  appearance: none; -webkit-appearance: none;
  width: clamp(64px, 20vw, 108px); height: 16px;
  background: transparent; border: 0; padding: 0; margin: 0;
  cursor: pointer;
}
.sm__rng::-webkit-slider-runnable-track {
  height: 4px; border-radius: $r-pill;
  background: rgba($sm-text, .22);
}
.sm__rng::-webkit-slider-thumb {
  appearance: none; -webkit-appearance: none;
  width: 12px; height: 12px; margin-top: -4px;
  border-radius: 50%; border: 0;
  background: $sm-trail;
  box-shadow: 0 0 0 2px rgba($sm-text, .35);
}
.sm__rng::-moz-range-track {
  height: 4px; border-radius: $r-pill;
  background: rgba($sm-text, .22);
}
.sm__rng::-moz-range-thumb {
  width: 12px; height: 12px; border-radius: 50%; border: 0;
  background: $sm-trail;
  box-shadow: 0 0 0 2px rgba($sm-text, .35);
}
.sm__rng:focus-visible { outline: 2px solid $sm-text; outline-offset: 2px; }

@media (max-width: 340px) {
  .sm { gap: $sp-1; }
  .sm__field { height: 82px; }
  .sm__bar { flex-direction: column; align-items: stretch; gap: $sp-1; }
  .sm__ctl { justify-content: space-between; }
  .sm__rng { flex: 0 0 auto; }
}

// reduce — rAF 를 돌리지 않고 혈관 모양 파라미터로 자란 한 장만 남는다.
@media (prefers-reduced-motion: reduce) {
  .sm.is-still .sm__rng { pointer-events: auto; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #f4f7f2;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.sm {
  --sm-floor: #f4f7f2;
  --sm-trail: #cfe3c8;
  --sm-acct: #f6cfd4;
  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: #2c3326;
}

.sm__field {
  position: relative;
  height: 180px;
  border-radius: 16px;
  overflow: hidden;
  background: #f4f7f2;
  box-shadow: inset 0 0 0 1px rgba(44, 51, 38, 0.18);
}

.sm__field:focus-visible {
  outline: 2px solid #2c3326;
  outline-offset: 2px;
}

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

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

.sm__ctl {
  display: flex;
  align-items: center;
  gap: 4px;
  min-width: 0;
}

.sm__lab {
  font-size: 10px;
  font-weight: 700;
  line-height: 1;
  color: rgba(44, 51, 38, 0.72);
  white-space: nowrap;
}

.sm__rng {
  appearance: none;
  -webkit-appearance: none;
  width: clamp(64px, 20vw, 108px);
  height: 16px;
  background: transparent;
  border: 0;
  padding: 0;
  margin: 0;
  cursor: pointer;
}

.sm__rng::-webkit-slider-runnable-track {
  height: 4px;
  border-radius: 999px;
  background: rgba(44, 51, 38, 0.22);
}

.sm__rng::-webkit-slider-thumb {
  appearance: none;
  -webkit-appearance: none;
  width: 12px;
  height: 12px;
  margin-top: -4px;
  border-radius: 50%;
  border: 0;
  background: #cfe3c8;
  box-shadow: 0 0 0 2px rgba(44, 51, 38, 0.35);
}

.sm__rng::-moz-range-track {
  height: 4px;
  border-radius: 999px;
  background: rgba(44, 51, 38, 0.22);
}

.sm__rng::-moz-range-thumb {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  border: 0;
  background: #cfe3c8;
  box-shadow: 0 0 0 2px rgba(44, 51, 38, 0.35);
}

.sm__rng:focus-visible {
  outline: 2px solid #2c3326;
  outline-offset: 2px;
}

@media (max-width: 340px) {
  .sm {
    gap: 4px;
  }
  .sm__field {
    height: 82px;
  }
  .sm__bar {
    flex-direction: column;
    align-items: stretch;
    gap: 4px;
  }
  .sm__ctl {
    justify-content: space-between;
  }
  .sm__rng {
    flex: 0 0 auto;
  }
}
@media (prefers-reduced-motion: reduce) {
  .sm.is-still .sm__rng {
    pointer-events: auto;
  }
}

// 센서 각도 모프(07). Physarum 스티그머지 + 실시간 파라미터 모프 —
// Sensor spread angle(도)과 Sensor distance 두 값을 실제 range 슬라이더로 바꾼다. 같은 3센서 규칙이라도
// 좁은 각도+짧은 거리는 촘촘한 산호, 넓은 각도+긴 거리는 성긴 혈관·격자형 도시망을 그린다.
// .is-demo 동안은 슬라이더가 사람 손 없이 스스로 움직여(자동 시연) 형태 변화를 보여주고,
// 사람이 실제로 슬라이더를 잡으면 그 즉시 같은 파라미터가 시뮬레이션에 반영된다.
//
// 화면이 사는 장치 — 077 캔버스 기준의 "매 프레임 계산":
//  · 캔버스는 절대 clear 하지 않는다. 필드 전체를 매 프레임 새로 계산해 얹는다.
//  · 앰비언트 글로우 레이어(두 옥타브 값노이즈)가 전면을 확산 구조로 흔들어 누적면적을 채운다.
(function () {
  // ── 변형 상수 블록 ──
  var AGENTS = 1500;        // 동시에 걷는 에이전트 수
  var DECAY = 0.045;        // 증발률
  // ────────────────────────────────────
  var TURN = 0.5;
  var STEP = 1.05;
  var DEPOSIT = 4.2;
  var DIFFUSE = 0.5;
  var CAP = 7;
  var SUBSTEPS = 3;

  // 파라미터(슬라이더가 실시간으로 바꾼다)
  var sensorAngleDeg = 29;   // 도(°)
  var sensorDist = 15;

  var root = document.getElementById('smRoot');
  var field = document.getElementById('smField');
  var cv = document.getElementById('smCv');
  var ctx = cv.getContext('2d', { alpha: false });
  var angRng = document.getElementById('smAng');
  var distRng = document.getElementById('smDist');
  var angLab = document.getElementById('smAngLab');
  var distLab = document.getElementById('smDistLab');

  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(0x320A07);

  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_TRAIL = tokRGB('--sm-trail');
  var C_ACCT  = tokRGB('--sm-acct');

  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, img, data;
  var ax, ay, ah;

  // ── 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 sense(x, y) {
    return trail[clampIdx(x, y)];
  }

  function initAgents() {
    ax = new Float32Array(AGENTS); ay = new Float32Array(AGENTS); ah = new Float32Array(AGENTS);
    var cx = fw / 2, cy = fh / 2, r = Math.min(fw, fh) * 0.15;
    for (var i = 0; i < AGENTS; 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;
    }
  }

  function stepAgents() {
    var sa = sensorAngleDeg * Math.PI / 180;
    var sd = sensorDist / 3;
    for (var i = 0; i < AGENTS; i++) {
      var x = ax[i], y = ay[i], h = ah[i];
      var sf = sense(x + Math.cos(h) * sd, y + Math.sin(h) * sd);
      var sl = sense(x + Math.cos(h + sa) * sd, y + Math.sin(h + sa) * sd);
      var sr = sense(x + Math.cos(h - sa) * sd, y + Math.sin(h - sa) * sd);
      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));
      trail[ii] = Math.min(CAP, trail[ii] + DEPOSIT);
    }
  }

  function diffuseEvap() {
    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 = (trail[rowY + xm] + trail[rowY + xp] + trail[rowYm + x] + trail[rowYp + x]) * 0.25;
        trailB[i] = (trail[i] * (1 - DIFFUSE) + avg * DIFFUSE) * (1 - DECAY);
      }
    }
    var t = trail; trail = trailB; trailB = t;
  }

  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 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;
        // 파라미터 표시기 — 슬라이더 값이 화면 구석에 옅게 비친다(파라미터 실험 컨셉)
        var meterX = x / fw;
        var inAng = y < 5 && meterX < sensorAngleDeg / 90;
        var inDist = y >= 6 && y < 11 && meterX < (sensorDist - 4) / 26;
        if (inAng || inDist) {
          rr += (C_ACCT[0] - rr) * 0.5; gg += (C_ACCT[1] - gg) * 0.5; bb += (C_ACCT[2] - bb) * 0.5;
        }
        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) * 28 + (n2 - 0.5) * 18;
        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);
    initAgents();
  }

  function setLabels() {
    if (angLab) angLab.textContent = 'Spread ' + sensorAngleDeg + '°';
    if (distLab) distLab.textContent = 'Distance ' + sensorDist;
    if (angRng) angRng.value = String(sensorAngleDeg);
    if (distRng) distRng.value = String(sensorDist);
  }

  function stillFrame() {
    sensorAngleDeg = 45; sensorDist = 20; setLabels();
    for (var k = 0; k < 280; k++) { stepAgents(); diffuseEvap(); }
    render(2.6);
  }

  // .is-demo 자동 시연 각본 — 사람이 안 만져도 슬라이더가 스스로 움직여 형태가 모프된다.
  // 각 구간은 (Spread 목표, Distance 목표) 쌍. 사인으로 왕복해 끊김 없이 잇는다.
  function autoParams(t) {
    var ang = 29 + 28 * Math.sin(t * 0.42) + 8 * Math.sin(t * 0.13);
    var dist = 15 + 9 * Math.sin(t * 0.31 + 1.2);
    if (ang < 10) ang = 10; if (ang > 90) ang = 90;
    if (dist < 4) dist = 4; if (dist > 30) dist = 30;
    sensorAngleDeg = Math.round(ang);
    sensorDist = Math.round(dist);
  }

  var humanTouch = false;
  angRng.addEventListener('input', function () {
    humanTouch = true;
    sensorAngleDeg = parseInt(angRng.value, 10);
    setLabels();
  });
  distRng.addEventListener('input', function () {
    humanTouch = true;
    sensorDist = parseInt(distRng.value, 10);
    setLabels();
  });

  function frame(now) {
    if (t0 < 0) t0 = now;
    var t = (now - t0) / 1000;
    if (root.classList.contains('is-demo') && !humanTouch) {
      autoParams(t);
      setLabels();
    }
    for (var i = 0; i < SUBSTEPS; i++) { stepAgents(); diffuseEvap(); }
    render(t);
    raf = requestAnimationFrame(frame);
  }

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

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

// SensorAngleMorph — vanilla 판(run/320/demo/07-slime-sensor-angle-morph/index.html) 의 React 포트.
// 센서 각도 모프. 센서 벌림각(도)과 센서 거리 두 값을 range 슬라이더로 바꾼다 — 좁은 각도+짧은
// 거리는 촘촘한 산호, 넓은 각도+긴 거리는 성긴 혈관·격자형 도시망을 그린다. 사람이 슬라이더를
// 만지기 전까지는 자동 각본이 두 값을 사인파로 왕복시켜 스스로 형태가 모프된다.
import { useEffect, useRef, useState } from "react";
import type { ChangeEvent, CSSProperties } from "react";
import styles from "./SensorAngleMorph.module.scss";

export type SensorAngleMorphProps = {
  duration?: string;
  easing?: string;
  color?: string;
  agents?: number;
  decay?: number;
};

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

const FIELD_LABEL = "센서 각도 모프 점균 실험판";
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 SensorAngleMorph({
  duration = "2s",
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#2c3326",
  agents = 1500,
  decay = 0.045,
}: SensorAngleMorphProps) {
  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; trail: RGB; acct: RGB } | null>(null);
  const agentsRef = useRef(agents) as Box<number>;
  const decayRef = useRef(decay) as Box<number>;
  const randRef = useRef(makePRNG(0x320a07)) 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 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 sensorAngleDegRef = useRef(29) as Box<number>;
  const sensorDistRef = useRef(15) as Box<number>;
  const humanTouchRef = useRef(false) as Box<boolean>;
  const rafRef = useRef(0) as Box<number>;
  const [angLab, setAngLab] = useState("벌림각 29°");
  const [distLab, setDistLab] = useState("거리 15");
  const [angVal, setAngVal] = useState(29);
  const [distVal, setDistVal] = useState(15);
  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 sense(x: number, y: number): number {
    return trailRef.current[clampIdx(x, y)];
  }

  function initAgents(): void {
    const rand = randRef.current;
    const fw = fwRef.current, fh = fhRef.current;
    const A = agentsRef.current;
    const ax = new Float32Array(A), ay = new Float32Array(A), ah = new Float32Array(A);
    const cx = fw / 2, cy = fh / 2, r = Math.min(fw, fh) * 0.15;
    for (let i = 0; i < A; 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;
    }
    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 sa = sensorAngleDegRef.current * Math.PI / 180;
    const sd = sensorDistRef.current / 3;
    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) * sd, y + Math.sin(h) * sd);
      const sl = sense(x + Math.cos(h + sa) * sd, y + Math.sin(h + sa) * sd);
      const sr = sense(x + Math.cos(h - sa) * sd, y + Math.sin(h - sa) * sd);
      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));
      trail[ii] = Math.min(CAP, trail[ii] + DEPOSIT);
    }
  }

  function diffuseEvap(): void {
    const fw = fwRef.current, fh = fhRef.current;
    const trail = trailRef.current, trailB = trailBRef.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 = (trail[rowY + xm] + trail[rowY + xp] + trail[rowYm + x] + trail[rowYp + 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 angDeg = sensorAngleDegRef.current;
    const dist = sensorDistRef.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 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 meterX = x / fw;
        const inAng = y < 5 && meterX < angDeg / 90;
        const inDist = y >= 6 && y < 11 && meterX < (dist - 4) / 26;
        if (inAng || inDist) {
          rr += (col.acct[0] - rr) * 0.5; gg += (col.acct[1] - gg) * 0.5; bb += (col.acct[2] - bb) * 0.5;
        }
        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) * 28 + (n2 - 0.5) * 18;
        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);
    initAgents();
  }

  function setLabels(): void {
    setAngLab(`벌림각 ${sensorAngleDegRef.current}°`);
    setDistLab(`거리 ${sensorDistRef.current}`);
    setAngVal(sensorAngleDegRef.current);
    setDistVal(sensorDistRef.current);
  }

  function stillFrame(): void {
    sensorAngleDegRef.current = 45; sensorDistRef.current = 20; setLabels();
    for (let k = 0; k < 280; k++) { stepAgents(); diffuseEvap(); }
    render(2.6);
  }

  function autoParams(t: number): void {
    let ang = 29 + 28 * Math.sin(t * 0.42) + 8 * Math.sin(t * 0.13);
    let dist = 15 + 9 * Math.sin(t * 0.31 + 1.2);
    if (ang < 10) ang = 10; if (ang > 90) ang = 90;
    if (dist < 4) dist = 4; if (dist > 30) dist = 30;
    sensorAngleDegRef.current = Math.round(ang);
    sensorDistRef.current = Math.round(dist);
  }

  function onAngInput(e: ChangeEvent<HTMLInputElement>): void {
    humanTouchRef.current = true;
    sensorAngleDegRef.current = parseInt(e.target.value, 10);
    setLabels();
  }
  function onDistInput(e: ChangeEvent<HTMLInputElement>): void {
    humanTouchRef.current = true;
    sensorDistRef.current = parseInt(e.target.value, 10);
    setLabels();
  }

  let t0 = -1;
  function frame(now: number): void {
    if (t0 < 0) t0 = now;
    const t = (now - t0) / 1000;
    if (!humanTouchRef.current) {
      autoParams(t);
      setLabels();
    }
    for (let i = 0; i < SUBSTEPS; i++) { stepAgents(); diffuseEvap(); }
    render(t);
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    agentsRef.current = agents;
    decayRef.current = decay;
    randRef.current = makePRNG(0x320a07);
    colRef.current = {
      floor: tokRGB(root, "--sm-floor"),
      trail: tokRGB(root, "--sm-trail"),
      acct: tokRGB(root, "--sm-acct"),
    };
    buildPerm();
    fit();
    setLabels();
    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]);

  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>센서 벌림각과 거리 두 숫자만 슬라이더로 바꾸면 같은 규칙이 촘촘한 산호 모양, 성긴 혈관 모양, 격자형 도시 모양까지 완전히 다른 네트워크를 그려냅니다</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}>
          <label className={styles.ctl}>
            <span className={styles.lab}>{angLab}</span>
            <input
              className={styles.rng}
              type="range"
              min={10}
              max={90}
              step={1}
              value={angVal}
              aria-label="센서 벌림각"
              onChange={onAngInput}
            />
          </label>
          <label className={styles.ctl}>
            <span className={styles.lab}>{distLab}</span>
            <input
              className={styles.rng}
              type="range"
              min={4}
              max={30}
              step={1}
              value={distVal}
              aria-label="센서 거리"
              onChange={onDistInput}
            />
          </label>
        </div>
      </div>
    </main>
  );
}