07Pointer seeding — a second crystal grows wherever you click

<main class="stage">
<div class="cd is-demo" id="cdRoot">
  <p class="cd__hint">
    <svg class="cd__ico" viewBox="0 0 256 256" aria-hidden="true"><g fill="none" stroke="currentColor" stroke-width="14" stroke-linecap="round"><path d="M128 22v212"/><path d="M38.9 73.5l178.2 129"/><path d="M217.1 73.5L38.9 202.5"/><path d="M104 46l24 20 24-20"/><path d="M104 210l24-20 24 20"/></g></svg>
    <span>Plant an extra seed at every spot you click, in addition to the central crystal, and particles drift between the crystals, sticking wherever they compete — branches meet and intertwine in mutual growth</span>
  </p>
  <div class="cd__field" id="cdField" role="application" aria-label="Pointer Seed Competing-Crystal Growth Demo" tabindex="0">
    <canvas class="cd__cv" id="cdCv" width="424" height="180"></canvas>
  </div>
  <div class="cd__bar">
    <span class="cd__meta"><b class="cd__val" id="cdVal">1</b>crystals · click to add a seed</span>
    <span class="cd__meta cd__meta--dim">pointermove · ImageData · requestAnimationFrame</span>
  </div>
</div>
</main>

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

// 포인터 씨앗(07). CSS 애니메이션·@keyframes 를 아예 두지 않는다 —
// 움직임은 전부 캔버스 rAF 루프(6각 격자 DLA 응집 + 광륜 blur + 잔광 꼬리)가 만든다.
// 무대는 밤하늘 잉크. 결정은 파스텔 화이트 코어에 결정마다 라일락·민트·핑크 고유 색.

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

@include stage($stage-ink);

// ── 편 공통 파스텔 팔레트(BD26: vivid 순색 없음 — 전부 파스텔이거나 어스름 무채색) ──
$flake-ink:   #141720;   // 밤하늘 무대
$flake-sky:   #232840;   // 깊은 슬레이트
$flake-core:  #f4f7ff;   // 결정 코어 — 서리 화이트
$flake-lilac: #dbd6eb;   // 결정 1 라일락
$flake-mint:  #a8dbc8;   // 결정 2 민트
$flake-pink:  #f2b9cf;   // 결정 3 핑크
$flake-node:  #d5d9e4;   // 안개색 글자·테두리

.cd {
  // 렌더러가 읽는 색 — JS 는 getComputedStyle 로 --flake-* 를 받아 쓴다
  --flake-ink:   #{$flake-ink};
  --flake-sky:   #{$flake-sky};
  --flake-core:  #{$flake-core};
  --flake-lilac: #{$flake-lilac};
  --flake-mint:  #{$flake-mint};
  --flake-pink:  #{$flake-pink};
  --flake-node:  #{$flake-node};

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

.cd__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: $flake-node;                        // 잉크 무대 위 — 안개색 글자(대비 10.9:1)
}
.cd__ico { width: 16px; height: 16px; flex: 0 0 auto; color: $flake-lilac; }

.cd__field {
  position: relative; height: 180px;
  border-radius: $r-card; overflow: hidden;
  background: $flake-ink;
  box-shadow: inset 0 0 0 1px rgba($flake-node, .18);
  cursor: crosshair;
  touch-action: none;
}
.cd__field:focus-visible { outline: 2px solid $flake-lilac; outline-offset: 2px; }

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

.cd__bar { display: flex; align-items: baseline; justify-content: space-between; gap: $sp-2; }
.cd__meta { font-size: 10px; font-weight: 500; color: rgba($flake-node, .78); }
.cd__val { color: $flake-mint; font-weight: 700; }     // 잉크 위 민트 라벨(대비 9.9:1)
.cd__meta--dim { font-size: 10px; }

@media (max-width: 340px) {
  .cd { gap: $sp-1; }
  .cd__field { height: 100px; }
  .cd__meta--dim { display: none; }
}

// reduce — rAF 를 돌리지 않고 결정이 다 자란 한 장만 남는다(JS 가 is-still 부착).
@media (prefers-reduced-motion: reduce) {
  .cd.is-still .cd__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: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.cd {
  --flake-ink: #141720;
  --flake-sky: #232840;
  --flake-core: #f4f7ff;
  --flake-lilac: #dbd6eb;
  --flake-mint: #a8dbc8;
  --flake-pink: #f2b9cf;
  --flake-node: #d5d9e4;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 424px;
}

.cd__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: #d5d9e4;
}

.cd__ico {
  width: 16px;
  height: 16px;
  flex: 0 0 auto;
  color: #dbd6eb;
}

.cd__field {
  position: relative;
  height: 180px;
  border-radius: 16px;
  overflow: hidden;
  background: #141720;
  box-shadow: inset 0 0 0 1px rgba(213, 217, 228, 0.18);
  cursor: crosshair;
  touch-action: none;
}

.cd__field:focus-visible {
  outline: 2px solid #dbd6eb;
  outline-offset: 2px;
}

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

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

.cd__meta {
  font-size: 10px;
  font-weight: 500;
  color: rgba(213, 217, 228, 0.78);
}

.cd__val {
  color: #a8dbc8;
  font-weight: 700;
}

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

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

// 포인터 씨앗(07). DLA(확산제한응집) — 바깥 링에서 태어난 입자가 6각 grid cells 위를 랜덤워크하다
// 결정에 닿는 순간 붙는다. 씨앗(결정 중심)을 여러 개 심으면 입자들이 어느 결정에 닿느냐를
// 두고 경쟁하며, 가지가 만나는 지점에서 서로 얽혀 붙는다(만나도 규칙은 그대로 — 닿는 쪽에 붙는 것뿐).
// 화면은 4겹으로 산다: ① 숨쉬는 조명·떠도는 워시 배경 ② 결정 광륜(grid cells 확대 blur + lighter)
// ③ grid cells ImageData 를 2배로 확대한 결정 본체 ④ 잔광 꼬리를 남기는 부유 입자 + 반짝임.
(function () {
  // ── 변형 상수 블록 — 아래 값 하나만 바꿔 변형을 만든다 ──
  var STICKS_PER_FRAME = 58;    // 한 프레임에 붙일 입자 수 — 늘리면 결정이 빨리 자란다
  var RMAX             = 34;    // 결정 최대 반경(셀) — 이 안에서만 붙는다
  var WALKER_MAX_STEPS = 420;   // 입자 하나의 최대 걸음 — 넘으면 죽고 새 입자가 태어난다
  var ATTEMPT_CAP      = 420;   // 프레임당 입자 시도 상한 — 결정이 다 차도 루프가 안 멈추게
  var MAX_CRYSTALS     = 5;     // 씨앗 상한
  // 포인터가 없는 자동 렌더(측정 gif/mp4) 폴백 — [시각ms, 가로비, 세로비]마다 씨앗을 자동으로 심는다
  var AUTO_SEEDS = [[450, 0.72, 0.34], [1150, 0.26, 0.30]];
  // ────────────────────────────────────────────────

  var root = document.getElementById('cdRoot');
  var field = document.getElementById('cdField');
  var cv = document.getElementById('cdCv');
  var ctx = cv.getContext('2d');
  var valOut = document.getElementById('cdVal');

  // 내부 해상도는 424×180 로 고정 — CSS 로 축소하므로 창 크기가 바뀌어도 grid cells 상태가 안 흔들린다
  var W = cv.width, H = cv.height;
  var CELL = 2, GW = W / CELL, GH = H / CELL;   // grid cells 212×90

  // 시드 고정 PRNG — mulberry32. 결정의 둥근 결이 매 실행 같은 성격으로 흐른다
  var prngState = 0x31907a >>> 0;
  function rand() {
    prngState = (prngState + 0x6D2B79F5) >>> 0;
    var t = prngState;
    t = Math.imul(t ^ (t >>> 15), t | 1);
    t ^= t + Math.imul(t ^ (t >>> 7), t | 61);
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  }

  // 색은 scss 의 --flake-* 에서 getComputedStyle 로 — 파스텔 토큰이 scss 한 곳에
  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('--flake-ink');
  var C_CORE = tokRGB('--flake-core');
  var C_LILAC = tokRGB('--flake-lilac');
  var C_MINT = tokRGB('--flake-mint');
  var C_PINK = tokRGB('--flake-pink');
  var TINTS = [C_LILAC, C_MINT, C_PINK];   // 결정마다 고유 파스텔 — 경쟁하는 둘을 눈으로 구분한다

  function rgba(c, a) { return 'rgba(' + c[0] + ',' + c[1] + ',' + c[2] + ',' + a + ')'; }

  // ── grid cells 상태 ──
  var tStick = new Int32Array(GW * GH);   // 셀에 붙은 시각(ms), -1 = 빈칸
  var owner = new Int8Array(GW * GH);     // 셀을 소유한 결정 번호
  for (var i0 = 0; i0 < tStick.length; i0++) { tStick[i0] = -1; owner[i0] = -1; }

  // 6각 인접(odd-r 행 오프셋) — 정사각 픽셀 위에 60° 방향의 가지를 세우는 눈결정 위상
  var NX_EVEN = [1, -1, 0, -1, 0, -1], NY_EVEN = [0, 0, -1, -1, 1, 1];
  var NX_ODD  = [1, -1, 0,  1, 0,  1], NY_ODD  = [0, 0, -1, -1, 1, 1];

  var crystals = [];   // {cx, cy, maxR, born, count, id}
  var sparkles = [];   // {x, y, t} 갓 붙은 자리의 반짝임
  var rings = [];      // {x, y, t} 씨앗을 심은 순간의 확산 링
  var motes = [];      // 부유 입자 — 잔광 꼬리

  function idx(x, y) { return y * GW + x; }
  function inside(x, y) { return x >= 0 && x < GW && y >= 0 && y < GH; }
  function hexNbr(y) { return (y & 1) ? NX_ODD : NX_EVEN; }
  function hexNbrY(y) { return (y & 1) ? NY_ODD : NY_EVEN; }

  function filledNb(x, y) {
    var nx = hexNbr(y), ny = hexNbrY(y), n = 0;
    for (var k = 0; k < 6; k++) {
      var ax = x + nx[k], ay = y + ny[k];
      if (inside(ax, ay) && tStick[idx(ax, ay)] >= 0) n++;
    }
    return n;
  }

  function stick(x, y, own, now) {
    var id = idx(x, y);
    tStick[id] = now; owner[id] = own;
    if (sparkles.length > 96) sparkles.shift();
    sparkles.push({ x: x * CELL + 1, y: y * CELL + 1, t: now });
  }

  function plantSeed(fx, fy, now) {
    if (crystals.length >= MAX_CRYSTALS) return;
    var cx = Math.round(fx * GW), cy = Math.round(fy * GH);
    if (!inside(cx, cy) || tStick[idx(cx, cy)] >= 0) return;
    var id = crystals.length;
    crystals.push({ cx: cx, cy: cy, maxR: 2, born: now, count: 0, id: id });
    tStick[idx(cx, cy)] = now; owner[idx(cx, cy)] = id;
    var nx = hexNbr(cy), ny = hexNbrY(cy);   // 씨앗 주변 한 바퀴를 얼려 출발점을 만든다
    for (var k = 0; k < 6; k++) {
      var ax = cx + nx[k], ay = cy + ny[k];
      if (inside(ax, ay) && tStick[idx(ax, ay)] < 0) { tStick[idx(ax, ay)] = now; owner[idx(ax, ay)] = id; }
    }
    rings.push({ x: cx * CELL + 1, y: cy * CELL + 1, t: now });
  }

  // ── DLA 응집 — 씨앗 링에서 입자를 뿌려 6각 랜덤워크, 닿으면 확률로 붙는다 ──
  function aggregate(now) {
    if (!crystals.length) return;
    var stuck = 0, attempts = 0;
    while (stuck < STICKS_PER_FRAME && attempts < ATTEMPT_CAP) {
      attempts++;
      var cr = crystals[(rand() * crystals.length) | 0];
      var ang = rand() * Math.PI * 2;
      var rr = cr.maxR + 6 + rand() * 14;
      var x = Math.round(cr.cx + Math.cos(ang) * rr);
      var y = Math.round(cr.cy + Math.sin(ang) * rr * 0.92);
      var steps = 0;
      while (steps < WALKER_MAX_STEPS) {
        steps++;
        var dir = (rand() * 6) | 0;
        var nb = hexNbr(y), sb = hexNbrY(y);
        x += nb[dir]; y += sb[dir];
        if (!inside(x, y)) break;
        if (tStick[idx(x, y)] >= 0) { x -= nb[dir]; y -= sb[dir]; continue; }  // 언 셀엔 못 들어간다
        var n = filledNb(x, y);
        if (n > 0) {
          var p = n === 1 ? 1 : n === 2 ? 0.55 : 0.14;              // 팁 바이어스 — 가지가 뻗는다
          var dist = Math.hypot(x - cr.cx, y - cr.cy);
          p *= 0.35 + 0.65 * Math.min(1, dist / (cr.maxR + 4));     // 바깥쪽에 더 잘 붙는다
          if (dist < RMAX && rand() < p) {
            var own = ownerOfNeighbor(x, y);
            stick(x, y, own, now);
            cr.count++; stuck++;
            if (dist > cr.maxR) cr.maxR = dist;
            break;
          }
        }
      }
    }
  }

  function ownerOfNeighbor(x, y) {
    var nx = hexNbr(y), ny = hexNbrY(y);
    for (var k = 0; k < 6; k++) {
      var ax = x + nx[k], ay = y + ny[k];
      if (inside(ax, ay) && tStick[idx(ax, ay)] >= 0) return owner[idx(ax, ay)];  // 닿은 결정의 소유가 된다 — 경쟁
    }
    return 0;
  }

  // ── grid cells → ImageData → 2배 확대 캔버스 ──
  var gridCv = document.createElement('canvas'); gridCv.width = GW; gridCv.height = GH;
  var gtx = gridCv.getContext('2d');
  var img = gtx.createImageData(GW, GH);
  var px = img.data;

  function repaintGrid(now) {
    for (var y = 0; y < GH; y++) {
      for (var x = 0; x < GW; x++) {
        var id = y * GW + x, o = id * 4;
        var t0 = tStick[id];
        if (t0 < 0) { px[o + 3] = 0; continue; }
        var age = now - t0;
        var tint = TINTS[owner[id] % TINTS.length];
        var k = Math.min(1, age / 900);        // 갓 붙은 하양 → 결정 고유 파스텔로 정착
        var lift = filledNb(x, y) <= 2 ? 30 : 0;   // 팁(인접 ≤2)은 서리 반짝임으로 더 밝다
        px[o]     = Math.min(255, C_CORE[0] + (tint[0] - C_CORE[0]) * k + lift);
        px[o + 1] = Math.min(255, C_CORE[1] + (tint[1] - C_CORE[1]) * k + lift);
        px[o + 2] = Math.min(255, C_CORE[2] + (tint[2] - C_CORE[2]) * k + lift);
        px[o + 3] = 255;
      }
    }
    gtx.putImageData(img, 0, 0);
  }

  // ── 배경 — 숨쉬는 중앙 조명 + 리사주로 떠도는 민트 워시 ──
  var bgCv = document.createElement('canvas'); bgCv.width = W; bgCv.height = H;
  var btx = bgCv.getContext('2d');
  function repaintBg(now) {
    btx.globalCompositeOperation = 'source-over';
    btx.fillStyle = rgba(C_INK, 1);
    btx.fillRect(0, 0, W, H);
    var a1 = 0.13 + 0.09 * Math.sin(now / 700);
    var g1 = btx.createRadialGradient(W / 2, H / 2, 0, W / 2, H / 2, 235);
    g1.addColorStop(0, rgba(C_LILAC, a1));
    g1.addColorStop(1, rgba(C_LILAC, 0));
    btx.fillStyle = g1; btx.fillRect(0, 0, W, H);
    var wx = W * (0.5 + 0.30 * Math.sin(now / 2600));
    var wy = H * (0.5 + 0.26 * Math.sin(now / 1900 + 1.7));
    var g2 = btx.createRadialGradient(wx, wy, 0, wx, wy, 170);
    g2.addColorStop(0, rgba(C_MINT, 0.10));
    g2.addColorStop(1, rgba(C_MINT, 0));
    btx.fillStyle = g2; btx.fillRect(0, 0, W, H);
    // 반대편에서 도는 핑크 안개 — 배경 세 겹이 각기 다른 주기로 숨쉰다
    var px2 = W * (0.5 - 0.32 * Math.sin(now / 3100));
    var py2 = H * (0.5 - 0.24 * Math.sin(now / 2200 + 0.8));
    var g3 = btx.createRadialGradient(px2, py2, 0, px2, py2, 160);
    g3.addColorStop(0, rgba(C_PINK, 0.085));
    g3.addColorStop(1, rgba(C_PINK, 0));
    btx.fillStyle = g3; btx.fillRect(0, 0, W, H);
  }

  // ── 잔광 꼬리 레이어 — 지우지 않고 destination-out 로 녹여 꼬리를 남긴다 ──
  var trailCv = document.createElement('canvas'); trailCv.width = W; trailCv.height = H;
  var ttx = trailCv.getContext('2d');
  function initMotes() {
    var cols = [C_LILAC, C_MINT, C_PINK, C_CORE];
    for (var m = 0; m < 44; m++) {
      motes.push({
        x: rand() * W, y: rand() * H,
        vx: (rand() - 0.5) * 1.3, vy: (rand() - 0.5) * 0.85,
        soft: rand() < 0.3, col: cols[(rand() * cols.length) | 0]
      });
    }
  }
  function repaintTrails() {
    ttx.globalCompositeOperation = 'destination-out';
    ttx.fillStyle = 'rgba(0,0,0,0.13)';
    ttx.fillRect(0, 0, W, H);
    ttx.globalCompositeOperation = 'lighter';
    for (var i = 0; i < motes.length; i++) {
      var mo = motes[i];
      mo.x += mo.vx; mo.y += mo.vy;
      if (mo.x < -8) mo.x = W + 8; else if (mo.x > W + 8) mo.x = -8;
      if (mo.y < -8) mo.y = H + 8; else if (mo.y > H + 8) mo.y = -8;
      if (mo.soft) {
        var g = ttx.createRadialGradient(mo.x, mo.y, 0, mo.x, mo.y, 5);
        g.addColorStop(0, rgba(mo.col, 0.20));
        g.addColorStop(1, rgba(mo.col, 0));
        ttx.fillStyle = g;
        ttx.fillRect(mo.x - 5, mo.y - 5, 10, 10);
      } else {
        ttx.fillStyle = rgba(mo.col, 0.5);
        ttx.fillRect(mo.x, mo.y, 1.6, 1.6);
      }
    }
  }

  // ── 포인터 — 움직이면 헤일로가 따라오고, 누르면 그 자리에 씨앗 ──
  var ptr = { x: -99, y: -99, t: -9999, on: false };
  function toLocal(e) {
    var r = cv.getBoundingClientRect();
    return [(e.clientX - r.left) * (W / r.width), (e.clientY - r.top) * (H / r.height)];
  }
  field.addEventListener('pointermove', function (e) {
    var p = toLocal(e);
    ptr.x = p[0]; ptr.y = p[1]; ptr.t = perfNow(); ptr.on = true;
  });
  field.addEventListener('pointerleave', function () { ptr.on = false; });
  field.addEventListener('pointerdown', function (e) {
    var p = toLocal(e);
    plantSeed(p[0] / W, p[1] / H, perfNow());
    valOut.textContent = String(crystals.length);
  });

  var t0 = -1;
  function perfNow() { return t0 < 0 ? 0 : performance.now() - t0; }

  // ── 합성 ──
  function draw(now) {
    repaintBg(now);
    ctx.globalCompositeOperation = 'source-over';
    ctx.globalAlpha = 1; ctx.filter = 'none';
    ctx.imageSmoothingEnabled = true;
    ctx.drawImage(bgCv, 0, 0);
    // 결정 광륜 — 격자를 뿌옇게 확대해 lighter 로 쌓는다(호흡하는 할로)
    ctx.globalCompositeOperation = 'lighter';
    ctx.filter = 'blur(5px)';
    ctx.globalAlpha = 0.26 + 0.08 * Math.sin(now / 820);
    ctx.drawImage(gridCv, 0, 0, W, H);
    ctx.filter = 'none'; ctx.globalAlpha = 1;
    // 결정 본체 — 픽셀 그대로 (셀 2px 각진 서리 결)
    ctx.globalCompositeOperation = 'source-over';
    ctx.imageSmoothingEnabled = false;
    ctx.drawImage(gridCv, 0, 0, W, H);
    // 잔광 꼬리
    ctx.globalCompositeOperation = 'lighter';
    ctx.drawImage(trailCv, 0, 0);
    // 씨앗 확산 링
    for (var i = rings.length - 1; i >= 0; i--) {
      var r = rings[i], ra = now - r.t;
      if (ra > 620) { rings.splice(i, 1); continue; }
      ctx.beginPath();
      ctx.arc(r.x, r.y, 5 + ra * 0.085, 0, Math.PI * 2);
      ctx.strokeStyle = rgba(C_LILAC, 0.38 * (1 - ra / 620));
      ctx.lineWidth = 1.6;
      ctx.stroke();
    }
    // 갓 붙은 입자의 반짝임
    for (var s = sparkles.length - 1; s >= 0; s--) {
      var sp = sparkles[s], sa = now - sp.t;
      if (sa > 340) { sparkles.splice(s, 1); continue; }
      var fal = 1 - sa / 340;
      ctx.fillStyle = rgba(C_CORE, 0.75 * fal);
      ctx.fillRect(sp.x - 1.2, sp.y - 1.2, 2.4, 2.4);
    }
    // 포인터 헤일로 — 결정 위를 스치는 은은한 수증기
    if (ptr.on && now - ptr.t < 420) {
      var pg = ctx.createRadialGradient(ptr.x, ptr.y, 0, ptr.x, ptr.y, 26);
      pg.addColorStop(0, rgba(C_CORE, 0.16));
      pg.addColorStop(1, rgba(C_CORE, 0));
      ctx.fillStyle = pg;
      ctx.fillRect(ptr.x - 26, ptr.y - 26, 52, 52);
    }
    ctx.globalCompositeOperation = 'source-over';
  }

  var lastVal = 0;
  function frame(nowRaw) {
    if (t0 < 0) t0 = nowRaw;
    var now = nowRaw - t0;
    // 자동 씨앗 폴백 — 포인터가 없는 측정 렌더에서도 결정이 여럿 경쟁하게 한다
    for (var i = 0; i < AUTO_SEEDS.length; i++) {
      if (AUTO_SEEDS[i][0] > 0 && now >= AUTO_SEEDS[i][0]) {
        plantSeed(AUTO_SEEDS[i][1], AUTO_SEEDS[i][2], now);
        AUTO_SEEDS[i][0] = 0;
      }
    }
    aggregate(now);
    repaintGrid(now);
    repaintTrails();
    draw(now);
    if (now - lastVal > 480) { lastVal = now; valOut.textContent = String(crystals.length); }
    requestAnimationFrame(frame);
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  initMotes();
  plantSeed(0.46, 0.50, 0);
  if (reduce) {
    // 결정이 다 자란 한 장만 남긴다 — 3초치 응집을 동기로 몰아 그린다
    for (var w = 0; w < 90; w++) aggregate(w * 16.7);
    repaintGrid(3000);
    repaintBg(3000);
    draw(3000);
    root.classList.add('is-still');
  } else {
    requestAnimationFrame(frame);
  }
})();

// PointerSeedGrow — vanilla 판(run/319/demo/07-snowflake-pointer-seed-grow/index.html) 의 React 포트.
// 6각 격자 DLA(확산제한응집) — 바깥에서 태어난 입자가 랜덤워크하다 결정에 닿으면 붙는다.
// 클릭(포인터다운)한 자리에 씨앗을 더 심으면 입자들이 여러 결정 사이에서 경쟁하며 붙는다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties, PointerEvent } from "react";
import styles from "./PointerSeedGrow.module.scss";

export type PointerSeedGrowProps = {
  duration?: string;
  easing?: string;
  color?: string;
  sticksPerFrame?: number;   // 한 프레임에 붙일 입자 수 — 늘리면 결정이 빨리 자란다
  rMax?: number;             // 결정 최대 반경(셀)
  maxCrystals?: number;      // 씨앗 상한
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Box<T> = { current: T };
type RGB = [number, number, number];
type Crystal = { cx: number; cy: number; maxR: number; count: number };
type Sparkle = { x: number; y: number; t: number };
type Ring = { x: number; y: number; t: number };
type Mote = { x: number; y: number; vx: number; vy: number; soft: boolean; col: RGB };

const FIELD_LABEL = "포인터 씨앗 결정 경쟁 성장 실험판";
const AUTO_SEEDS_INIT: [number, number, number][] = [[450, 0.72, 0.34], [1150, 0.26, 0.30]];

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;
  };
}

const NX_EVEN = [1, -1, 0, -1, 0, -1], NY_EVEN = [0, 0, -1, -1, 1, 1];
const NX_ODD = [1, -1, 0, 1, 0, 1], NY_ODD = [0, 0, -1, -1, 1, 1];

export default function PointerSeedGrow({
  duration = "2s",
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#b9a8ef",
  sticksPerFrame = 58,
  rMax = 34,
  maxCrystals = 5,
}: PointerSeedGrowProps) {
  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; core: RGB; lilac: RGB; mint: RGB; pink: RGB } | null>(null);
  const randRef = useRef(makePRNG(0x31907a)) as Box<() => number>;
  const [valLabel, setValLabel] = useState(1);
  const [still, setStill] = useState(false);
  const vars: Vars = { "--duration": duration, "--easing": easing, "--color": color };

  // 격자 상태 — 캔버스 내부 해상도는 424x180 고정
  const W = 424, H = 180, CELL = 2, GW = W / CELL, GH = H / CELL;
  const tStickRef = useRef<Int32Array>(new Int32Array(GW * GH).fill(-1)) as Box<Int32Array>;
  const ownerRef = useRef<Int8Array>(new Int8Array(GW * GH).fill(-1)) as Box<Int8Array>;
  const crystalsRef = useRef<Crystal[]>([]) as Box<Crystal[]>;
  const sparklesRef = useRef<Sparkle[]>([]) as Box<Sparkle[]>;
  const ringsRef = useRef<Ring[]>([]) as Box<Ring[]>;
  const motesRef = useRef<Mote[]>([]) as Box<Mote[]>;
  const autoSeedsRef = useRef<[number, number, number][]>(AUTO_SEEDS_INIT.map((s) => [...s] as [number, number, number])) as Box<[number, number, number][]>;
  const ptrRef = useRef({ x: -99, y: -99, t: -9999, on: false }) as Box<{ x: number; y: number; t: number; on: boolean }>;
  const gridCvRef = useRef<HTMLCanvasElement | null>(null);
  const bgCvRef = useRef<HTMLCanvasElement | null>(null);
  const trailCvRef = useRef<HTMLCanvasElement | null>(null);
  const rafRef = useRef(0) as Box<number>;

  function idx(x: number, y: number): number { return y * GW + x; }
  function inside(x: number, y: number): boolean { return x >= 0 && x < GW && y >= 0 && y < GH; }
  function nbX(y: number): number[] { return (y & 1) ? NX_ODD : NX_EVEN; }
  function nbY(y: number): number[] { return (y & 1) ? NY_ODD : NY_EVEN; }

  function filledNb(x: number, y: number): number {
    const tStick = tStickRef.current;
    const nx = nbX(y), ny = nbY(y);
    let n = 0;
    for (let k = 0; k < 6; k++) {
      const ax = x + nx[k], ay = y + ny[k];
      if (inside(ax, ay) && tStick[idx(ax, ay)] >= 0) n++;
    }
    return n;
  }

  function stick(x: number, y: number, own: number, now: number): void {
    const id = idx(x, y);
    tStickRef.current[id] = now;
    ownerRef.current[id] = own;
    const sp = sparklesRef.current;
    if (sp.length > 96) sp.shift();
    sp.push({ x: x * CELL + 1, y: y * CELL + 1, t: now });
  }

  function ownerOfNeighbor(x: number, y: number): number {
    const tStick = tStickRef.current, owner = ownerRef.current;
    const nx = nbX(y), ny = nbY(y);
    for (let k = 0; k < 6; k++) {
      const ax = x + nx[k], ay = y + ny[k];
      if (inside(ax, ay) && tStick[idx(ax, ay)] >= 0) return owner[idx(ax, ay)];
    }
    return 0;
  }

  function plantSeed(fx: number, fy: number, now: number): void {
    const crystals = crystalsRef.current;
    if (crystals.length >= maxCrystals) return;
    const cx = Math.round(fx * GW), cy = Math.round(fy * GH);
    if (!inside(cx, cy) || tStickRef.current[idx(cx, cy)] >= 0) return;
    const id = crystals.length;
    crystals.push({ cx, cy, maxR: 2, count: 0 });
    stick(cx, cy, id, now);
    const nx = nbX(cy), ny = nbY(cy);
    for (let k = 0; k < 6; k++) {
      const ax = cx + nx[k], ay = cy + ny[k];
      if (inside(ax, ay) && tStickRef.current[idx(ax, ay)] < 0) stick(ax, ay, id, now);
    }
    ringsRef.current.push({ x: cx * CELL + 1, y: cy * CELL + 1, t: now });
  }

  function aggregate(now: number): void {
    const crystals = crystalsRef.current;
    if (!crystals.length) return;
    const rand = randRef.current, tStick = tStickRef.current;
    let stuck = 0, attempts = 0;
    const ATTEMPT_CAP = 420, WALKER_MAX_STEPS = 420;
    while (stuck < sticksPerFrame && attempts < ATTEMPT_CAP) {
      attempts++;
      const cr = crystals[(rand() * crystals.length) | 0];
      const ang = rand() * Math.PI * 2;
      const rr = cr.maxR + 6 + rand() * 14;
      let x = Math.round(cr.cx + Math.cos(ang) * rr);
      let y = Math.round(cr.cy + Math.sin(ang) * rr * 0.92);
      let steps = 0;
      while (steps < WALKER_MAX_STEPS) {
        steps++;
        const dir = (rand() * 6) | 0;
        const bx = nbX(y), by = nbY(y);
        x += bx[dir]; y += by[dir];
        if (!inside(x, y)) break;
        if (tStick[idx(x, y)] >= 0) { x -= bx[dir]; y -= by[dir]; continue; }
        const n = filledNb(x, y);
        if (n > 0) {
          let p = n === 1 ? 1 : n === 2 ? 0.55 : 0.14;
          const dist = Math.hypot(x - cr.cx, y - cr.cy);
          p *= 0.35 + 0.65 * Math.min(1, dist / (cr.maxR + 4));
          if (dist < rMax && rand() < p) {
            const own = ownerOfNeighbor(x, y);
            stick(x, y, own, now);
            cr.count++; stuck++;
            if (dist > cr.maxR) cr.maxR = dist;
            break;
          }
        }
      }
    }
  }

  function rgba(c: RGB, a: number): string { return "rgba(" + c[0] + "," + c[1] + "," + c[2] + "," + a + ")"; }

  function repaintGrid(now: number): void {
    const gridCv = gridCvRef.current;
    if (!gridCv) return;
    const gtx = gridCv.getContext("2d");
    if (!gtx) return;
    const col = colRef.current;
    if (!col) return;
    const tStick = tStickRef.current, owner = ownerRef.current;
    const TINTS: RGB[] = [col.lilac, col.mint, col.pink];
    const img = gtx.createImageData(GW, GH);
    const px = img.data;
    for (let y = 0; y < GH; y++) {
      for (let x = 0; x < GW; x++) {
        const id = y * GW + x, o = id * 4;
        const t0 = tStick[id];
        if (t0 < 0) { px[o + 3] = 0; continue; }
        const age = now - t0;
        const tint = TINTS[((owner[id] % 3) + 3) % 3];
        const k = Math.min(1, age / 900);
        const lift = filledNb(x, y) <= 2 ? 30 : 0;
        px[o] = Math.min(255, col.core[0] + (tint[0] - col.core[0]) * k + lift);
        px[o + 1] = Math.min(255, col.core[1] + (tint[1] - col.core[1]) * k + lift);
        px[o + 2] = Math.min(255, col.core[2] + (tint[2] - col.core[2]) * k + lift);
        px[o + 3] = 255;
      }
    }
    gtx.putImageData(img, 0, 0);
  }

  function repaintBg(now: number): void {
    const bgCv = bgCvRef.current, col = colRef.current;
    if (!bgCv || !col) return;
    const btx = bgCv.getContext("2d");
    if (!btx) return;
    btx.globalCompositeOperation = "source-over";
    btx.fillStyle = rgba(col.ink, 1);
    btx.fillRect(0, 0, W, H);
    const a1 = 0.09 + 0.07 * Math.sin(now / 700);
    const g1 = btx.createRadialGradient(W / 2, H / 2, 0, W / 2, H / 2, 205);
    g1.addColorStop(0, rgba(col.lilac, a1));
    g1.addColorStop(1, rgba(col.lilac, 0));
    btx.fillStyle = g1; btx.fillRect(0, 0, W, H);
    const wx = W * (0.5 + 0.30 * Math.sin(now / 2600));
    const wy = H * (0.5 + 0.26 * Math.sin(now / 1900 + 1.7));
    const g2 = btx.createRadialGradient(wx, wy, 0, wx, wy, 150);
    g2.addColorStop(0, rgba(col.mint, 0.07));
    g2.addColorStop(1, rgba(col.mint, 0));
    btx.fillStyle = g2; btx.fillRect(0, 0, W, H);
  }

  function initMotes(): void {
    const col = colRef.current;
    if (!col) return;
    const rand = randRef.current;
    const cols: RGB[] = [col.lilac, col.mint, col.pink, col.core];
    const motes = motesRef.current;
    for (let m = 0; m < 26; m++) {
      motes.push({
        x: rand() * W, y: rand() * H,
        vx: (rand() - 0.5) * 1.15, vy: (rand() - 0.5) * 0.75,
        soft: rand() < 0.22, col: cols[(rand() * cols.length) | 0],
      });
    }
  }

  function repaintTrails(): void {
    const trailCv = trailCvRef.current;
    if (!trailCv) return;
    const ttx = trailCv.getContext("2d");
    if (!ttx) return;
    ttx.globalCompositeOperation = "destination-out";
    ttx.fillStyle = "rgba(0,0,0,0.13)";
    ttx.fillRect(0, 0, W, H);
    ttx.globalCompositeOperation = "lighter";
    const motes = motesRef.current;
    for (let i = 0; i < motes.length; i++) {
      const mo = motes[i];
      mo.x += mo.vx; mo.y += mo.vy;
      if (mo.x < -8) mo.x = W + 8; else if (mo.x > W + 8) mo.x = -8;
      if (mo.y < -8) mo.y = H + 8; else if (mo.y > H + 8) mo.y = -8;
      if (mo.soft) {
        const g = ttx.createRadialGradient(mo.x, mo.y, 0, mo.x, mo.y, 5);
        g.addColorStop(0, rgba(mo.col, 0.20));
        g.addColorStop(1, rgba(mo.col, 0));
        ttx.fillStyle = g;
        ttx.fillRect(mo.x - 5, mo.y - 5, 10, 10);
      } else {
        ttx.fillStyle = rgba(mo.col, 0.5);
        ttx.fillRect(mo.x, mo.y, 1.6, 1.6);
      }
    }
  }

  function draw(now: number): void {
    const ctx = ctxRef.current, col = colRef.current;
    const gridCv = gridCvRef.current, bgCv = bgCvRef.current, trailCv = trailCvRef.current;
    if (!ctx || !col || !gridCv || !bgCv || !trailCv) return;
    repaintBg(now);
    ctx.globalCompositeOperation = "source-over";
    ctx.globalAlpha = 1; ctx.filter = "none";
    ctx.imageSmoothingEnabled = true;
    ctx.drawImage(bgCv, 0, 0);
    ctx.globalCompositeOperation = "lighter";
    ctx.filter = "blur(5px)";
    ctx.globalAlpha = 0.26 + 0.08 * Math.sin(now / 820);
    ctx.drawImage(gridCv, 0, 0, W, H);
    ctx.filter = "none"; ctx.globalAlpha = 1;
    ctx.globalCompositeOperation = "source-over";
    ctx.imageSmoothingEnabled = false;
    ctx.drawImage(gridCv, 0, 0, W, H);
    ctx.globalCompositeOperation = "lighter";
    ctx.drawImage(trailCv, 0, 0);
    const rings = ringsRef.current;
    for (let i = rings.length - 1; i >= 0; i--) {
      const r = rings[i], ra = now - r.t;
      if (ra > 620) { rings.splice(i, 1); continue; }
      ctx.beginPath();
      ctx.arc(r.x, r.y, 5 + ra * 0.085, 0, Math.PI * 2);
      ctx.strokeStyle = rgba(col.lilac, 0.38 * (1 - ra / 620));
      ctx.lineWidth = 1.6;
      ctx.stroke();
    }
    const sparkles = sparklesRef.current;
    for (let s = sparkles.length - 1; s >= 0; s--) {
      const sp = sparkles[s], sa = now - sp.t;
      if (sa > 340) { sparkles.splice(s, 1); continue; }
      const fal = 1 - sa / 340;
      ctx.fillStyle = rgba(col.core, 0.75 * fal);
      ctx.fillRect(sp.x - 1.2, sp.y - 1.2, 2.4, 2.4);
    }
    const ptr = ptrRef.current;
    if (ptr.on && now - ptr.t < 420) {
      const pg = ctx.createRadialGradient(ptr.x, ptr.y, 0, ptr.x, ptr.y, 26);
      pg.addColorStop(0, rgba(col.core, 0.16));
      pg.addColorStop(1, rgba(col.core, 0));
      ctx.fillStyle = pg;
      ctx.fillRect(ptr.x - 26, ptr.y - 26, 52, 52);
    }
    ctx.globalCompositeOperation = "source-over";
  }

  function handlePointerMove(e: PointerEvent<HTMLDivElement>): void {
    const cv = cvRef.current;
    if (!cv) return;
    const r = cv.getBoundingClientRect();
    const ptr = ptrRef.current;
    ptr.x = (e.clientX - r.left) * (W / r.width);
    ptr.y = (e.clientY - r.top) * (H / r.height);
    ptr.on = true;
  }
  function handlePointerLeave(): void { ptrRef.current.on = false; }
  function handlePointerDown(e: PointerEvent<HTMLDivElement>): void {
    const cv = cvRef.current;
    if (!cv) return;
    const r = cv.getBoundingClientRect();
    const fx = ((e.clientX - r.left) * (W / r.width)) / W;
    const fy = ((e.clientY - r.top) * (H / r.height)) / H;
    plantSeed(fx, fy, performance.now());
    setValLabel(crystalsRef.current.length);
  }

  useEffect(() => {
    const root = rootRef.current, cv = cvRef.current;
    if (!root || !cv) return;
    const ctx = cv.getContext("2d");
    if (!ctx) return;
    ctxRef.current = ctx;
    gridCvRef.current = document.createElement("canvas");
    gridCvRef.current.width = GW; gridCvRef.current.height = GH;
    bgCvRef.current = document.createElement("canvas");
    bgCvRef.current.width = W; bgCvRef.current.height = H;
    trailCvRef.current = document.createElement("canvas");
    trailCvRef.current.width = W; trailCvRef.current.height = H;

    function tokRGB(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)];
    }
    colRef.current = {
      ink: tokRGB("--flake-ink"), core: tokRGB("--flake-core"),
      lilac: tokRGB("--flake-lilac"), mint: tokRGB("--flake-mint"), pink: tokRGB("--flake-pink"),
    };
    randRef.current = makePRNG(0x31907a);
    tStickRef.current = new Int32Array(GW * GH).fill(-1);
    ownerRef.current = new Int8Array(GW * GH).fill(-1);
    crystalsRef.current = [];
    sparklesRef.current = [];
    ringsRef.current = [];
    motesRef.current = [];
    autoSeedsRef.current = AUTO_SEEDS_INIT.map((s) => [...s] as [number, number, number]);
    initMotes();
    plantSeed(0.46, 0.50, 0);

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let t0 = -1, lastVal = 0;
    function frame(nowRaw: number): void {
      if (t0 < 0) t0 = nowRaw;
      const now = nowRaw - t0;
      const seeds = autoSeedsRef.current;
      for (let i = 0; i < seeds.length; i++) {
        if (seeds[i][0] > 0 && now >= seeds[i][0]) {
          plantSeed(seeds[i][1], seeds[i][2], now);
          seeds[i][0] = 0;
        }
      }
      aggregate(now);
      repaintGrid(now);
      repaintTrails();
      draw(now);
      if (now - lastVal > 480) { lastVal = now; setValLabel(crystalsRef.current.length); }
      rafRef.current = requestAnimationFrame(frame);
    }
    if (reduce) {
      for (let w = 0; w < 90; w++) aggregate(w * 16.7);
      repaintGrid(3000);
      repaintBg(3000);
      draw(3000);
      setStill(true);
    } else {
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => cancelAnimationFrame(rafRef.current);
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [sticksPerFrame, rMax, maxCrystals]);

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

  return (
    <main className={styles.stage}>
      <div className={rootCls} ref={rootRef} style={vars}>
        <p className={styles.hint}>
          <svg className={styles.ico} viewBox="0 0 256 256" aria-hidden="true"><g fill="none" stroke="currentColor" strokeWidth={14} strokeLinecap="round"><path d="M128 22v212" /><path d="M38.9 73.5l178.2 129" /><path d="M217.1 73.5L38.9 202.5" /><path d="M104 46l24 20 24-20" /><path d="M104 210l24-20 24 20" /></g></svg>
          <span>중앙 결정에 더해 클릭한 자리마다 씨앗을 하나 더 심으면 입자들이 결정들 사이를 오가며 경쟁으로 붙습니다 — 가지가 만나 얽히는 상호 성장입니다</span>
        </p>
        <div
          className={styles.field}
          ref={fieldRef}
          role="application"
          aria-label={FIELD_LABEL}
          tabIndex={0}
          onPointerMove={handlePointerMove}
          onPointerLeave={handlePointerLeave}
          onPointerDown={handlePointerDown}
        >
          <canvas className={styles.cv} ref={cvRef} width={W} height={H}></canvas>
        </div>
        <div className={styles.bar}>
          <span className={styles.meta}><b className={styles.val}>{valLabel}</b>개 결정 · 클릭으로 씨앗 추가</span>
          <span className={styles.metaDim}>pointermove · ImageData · requestAnimationFrame</span>
        </div>
      </div>
    </main>
  );
}