08Liquid type — text pixels born as field sources

<main class="stage">
<div class="cd is-demo" id="cdRoot">
  <p class="cd__hint">
    <span>Draw the text, then sample only the pixels with alpha as field circles — the whole sentence turns into a metaball blob, flowing and reshaping as liquid typography</span>
  </p>
  <div class="cd__field" id="cdField" role="application" aria-label="Liquid-Type Metaball test panel" tabindex="0">
    <canvas class="cd__cv" id="cdCv"></canvas>
  </div>
  <div class="cd__bar">
    <span class="cd__meta"><b class="cd__val" id="cdN">BLOB</b>· text field circles</span>
    <span class="cd__meta cd__meta--dim">measureText · getImageData · quadraticCurveTo</span>
  </div>
</div>
</main>

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

// 액체 글자(08). @keyframes 없음 — 텍스트 필드원(measureText+getImageData) + rAF 시뮬레이션뿐.
// 무대는 잉크. 편 공통 파스텔 팔레트를 --mb-* 로 (07~09 동일 계열, 항목마다 무대만 다름).

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

@include stage($stage-ink);

// ── 편 공통 파스텔 팔레트 ──
$mb-stage: $stage-ink;
$mb-edge:  $subject-lilac;   // 액체 몸통(테두리 임계값)
$mb-core:  $subject-sky;     // 안쪽 밝은 코어
$mb-gloss: $subject-cream;   // 표면을 훑는 광택 스윕
$mb-text:  $subject-cream;

.cd {
  --mb-stage: #{$mb-stage};
  --mb-edge:  #{$mb-edge};
  --mb-core:  #{$mb-core};
  --mb-gloss: #{$mb-gloss};

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

.cd__hint {
  display: flex; align-items: center; gap: $sp-1; margin: 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); line-height: 1.35;
  color: rgba($mb-text, .82);
}

.cd__field {
  position: relative; height: 180px;
  border-radius: $r-card; overflow: hidden;
  background: $mb-stage;
  box-shadow: inset 0 0 0 1px rgba($mb-gloss, .16);
}
.cd__field:focus-visible { outline: 2px solid $mb-edge; outline-offset: 2px; }

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

.cd__bar { display: flex; align-items: baseline; justify-content: space-between; gap: $sp-2; }
.cd__meta { font-size: 10px; font-weight: 500; color: rgba($mb-text, .72); }
.cd__val { color: $mb-edge; font-weight: 700; }
.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 액체 한 장만 남는다.
@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 {
  --mb-stage: #17141a;
  --mb-edge: #b9a0ff;
  --mb-core: #6ec8ff;
  --mb-gloss: #fff7e6;
  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: rgba(255, 247, 230, 0.82);
}

.cd__field {
  position: relative;
  height: 180px;
  border-radius: 16px;
  overflow: hidden;
  background: #17141a;
  box-shadow: inset 0 0 0 1px rgba(255, 247, 230, 0.16);
}

.cd__field:focus-visible {
  outline: 2px solid #b9a0ff;
  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(255, 247, 230, 0.72);
}

.cd__val {
  color: #b9a0ff;
  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;
  }
}

// 액체 글자(08). 오프스크린에 글자를 크게 그리고(measureText 로 폭을 재 캔버스에 맞춤) getImageData 로
// 알파 있는 픽셀만 격자 간격으로 샘플링해 필드원(seed) 목록을 만든다. 매 프레임 각 seed 를 살짝 흔들고
// (liquid jitter) 전체를 숨쉬듯 스케일해, 저해상도 필드 캔버스에 가산 원으로 찍은 뒤 임계값 두 단(테두리·
// 코어)으로 나눠 확대하면 글자가 통째로 출렁이는 메타볼 덩어리가 된다. 표면엔 quadraticCurveTo 로 그린
// 하이라이트 곡선이 시간에 따라 훑고 지나가며 광택을 낸다.
(function () {
  // ── 변형 상수 블록 — 아래 값 하나만 바꿔 변형을 만든다 ──
  var TEXT = 'BLOB';    // 'LIQUID' 로 바꾸면 더 긴 변형
  var STRIDE = 7;       // seed 샘플 간격(px, 텍스트 캔버스 기준) — 작을수록 촘촘하고 느림
  var JITTER = 3.6;      // 액체 흔들림 진폭(px)
  // ────────────────────────────────────────────────────

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

  var css = getComputedStyle(root);
  function tok(name) { return css.getPropertyValue(name).trim(); }
  var C_STAGE = tok('--mb-stage');
  var C_EDGE = tok('--mb-edge');
  var C_CORE = tok('--mb-core');
  var C_GLOSS = tok('--mb-gloss');

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var W = 0, H = 0;
  var LOWW = 0, LOWH = 0, SCALE = 4;
  var fieldCv = document.createElement('canvas');
  var fieldCtx = fieldCv.getContext('2d');
  var bandCv = document.createElement('canvas');
  var bandCtx = bandCv.getContext('2d');
  var txtCv = document.createElement('canvas');
  var txtCtx = txtCv.getContext('2d');
  var raf = 0, t0 = -1;
  var seeds = [];

  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(0x317A08);

  // ── 텍스트 → 필드원 샘플링 (measureText + getImageData) ──
  function buildSeeds() {
    txtCv.width = W; txtCv.height = H;
    txtCtx.clearRect(0, 0, W, H);
    var fontSize = Math.round(H * 0.94);
    txtCtx.font = '900 ' + fontSize + 'px -apple-system, "Segoe UI", sans-serif';
    var m = txtCtx.measureText(TEXT);
    var targetW = W * 0.92;
    if (m.width > 0) fontSize = Math.max(24, Math.round(fontSize * (targetW / m.width)));
    txtCtx.font = '900 ' + fontSize + 'px -apple-system, "Segoe UI", sans-serif';
    m = txtCtx.measureText(TEXT);
    var asc = m.actualBoundingBoxAscent || fontSize * 0.72;
    var desc = m.actualBoundingBoxDescent || fontSize * 0.18;
    var cx = W / 2, cy = H / 2 + (asc - desc) / 2;
    txtCtx.textAlign = 'center';
    txtCtx.textBaseline = 'alphabetic';
    txtCtx.fillStyle = '#fff';
    txtCtx.fillText(TEXT, cx, cy);

    var img = txtCtx.getImageData(0, 0, W, H);
    var d = img.data;
    seeds = [];
    for (var y = 4; y < H - 4; y += STRIDE) {
      for (var x = 4; x < W - 4; x += STRIDE) {
        var a = d[(y * W + x) * 4 + 3];
        if (a > 120) {
          seeds.push({ x: x, y: y, ph: rand() * Math.PI * 2, sp: 0.8 + rand() * 1.6 });
        }
      }
    }
  }

  function fit() {
    var r = field.getBoundingClientRect();
    W = r.width; H = r.height;
    cv.width = Math.round(W); cv.height = Math.round(H);
    LOWW = Math.max(48, Math.round(W / SCALE));
    LOWH = Math.max(30, Math.round(H / SCALE));
    fieldCv.width = LOWW; fieldCv.height = LOWH;
    bandCv.width = LOWW; bandCv.height = LOWH;
    ctx.imageSmoothingEnabled = true;
    buildSeeds();
  }

  function drawField(t) {
    fieldCtx.clearRect(0, 0, LOWW, LOWH);
    fieldCtx.fillStyle = '#000';
    fieldCtx.fillRect(0, 0, LOWW, LOWH);
    fieldCtx.globalCompositeOperation = 'lighter';
    var breathe = 1 + Math.sin(t * 0.7) * 0.11;   // 숨쉬듯 전체 스케일
    var r = 6.4 + Math.sin(t * 0.5) * 0.7;
    // 문장 전체가 천천히 필드를 가로지러 흐른다(타이포가 자리를 바꾸며 모양을 다시 만든다)
    var driftX = Math.sin(t * 0.33) * LOWW * 0.22 + Math.sin(t * 0.11) * LOWW * 0.08;
    var driftY = Math.cos(t * 0.26) * LOWH * 0.20;
    function blob(px, py, rad) {
      var g = fieldCtx.createRadialGradient(px, py, 0, px, py, rad);
      g.addColorStop(0, 'rgba(255,255,255,0.95)');
      g.addColorStop(1, 'rgba(255,255,255,0)');
      fieldCtx.fillStyle = g;
      fieldCtx.fillRect(px - rad, py - rad, rad * 2, rad * 2);
    }
    for (var i = 0; i < seeds.length; i++) {
      var s = seeds[i];
      var jx = Math.sin(t * s.sp + s.ph) * JITTER;
      var jy = Math.cos(t * s.sp * 1.2 + s.ph) * JITTER;
      var px = ((s.x + jx) / SCALE - LOWW / 2) * breathe + LOWW / 2 + driftX;
      var py = ((s.y + jy) / SCALE - LOWH / 2) * breathe + LOWH / 2 + driftY;
      blob(px, py, r);
    }
    // 위성 방울 — 글자 주위를 돌며 스쳐 병합하는 메타볼(모양이 더 크게 바뀐다)
    var SAT = [[0.9, 0.5, 0.16], [0.6, 0.85, 0.21], [1.25, 0.32, 0.13], [0.45, 0.15, 0.12], [1.05, 0.72, 0.17]];
    for (var k = 0; k < SAT.length; k++) {
      var o = SAT[k];
      var ox = LOWW / 2 + Math.sin(t * o[0] + k * 2.1) * LOWW * 0.42 + driftX * 0.4;
      var oy = LOWH / 2 + Math.cos(t * o[1] + k * 1.4) * LOWH * 0.38 + driftY * 0.4;
      blob(ox, oy, r * 1.5);
    }
    fieldCtx.globalCompositeOperation = 'source-over';
  }

  function classify() {
    var img = fieldCtx.getImageData(0, 0, LOWW, LOWH);
    var d = img.data;
    for (var y = 0; y < LOWH; y++) {
      for (var x = 0; x < LOWW; x++) {
        var v = d[(y * LOWW + x) * 4] / 255;
        var col = v > 0.56 ? C_CORE : (v > 0.15 ? C_EDGE : C_STAGE);
        bandCtx.fillStyle = col;
        bandCtx.fillRect(x, y, 1, 1);
      }
    }
  }

  function gloss(t) {
    // 광택 스윕 — quadraticCurveTo 로 그린 곡선이 시간에 따라 왼쪽에서 오른쪽으로 훑는다
    var u = (t * 0.28) % 1.4 - 0.2;
    var x0 = -W * 0.2 + u * W, y0 = H * 0.32;
    var cx1 = x0 + W * 0.22, cy1 = H * 0.08;
    var x1 = x0 + W * 0.44, y1 = H * 0.4;
    ctx.save();
    ctx.globalCompositeOperation = 'lighter';
    ctx.strokeStyle = C_GLOSS;
    ctx.lineWidth = Math.max(10, H * 0.09);
    ctx.lineCap = 'round';
    ctx.globalAlpha = 0.16;
    ctx.beginPath();
    ctx.moveTo(x0, y0);
    ctx.quadraticCurveTo(cx1, cy1, x1, y1);
    ctx.stroke();
    ctx.restore();
  }

  function draw(t) {
    drawField(t);
    classify();
    ctx.clearRect(0, 0, W, H);
    ctx.fillStyle = C_STAGE;
    ctx.fillRect(0, 0, W, H);
    ctx.drawImage(bandCv, 0, 0, LOWW, LOWH, 0, 0, W, H);
    gloss(t);
  }

  function stillFrame() { draw(0.35); }

  function frame(now) {
    if (t0 < 0) t0 = now;
    var t = (now - t0) / 1000;
    draw(t);
    raf = requestAnimationFrame(frame);
  }

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

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

// LiquidText — vanilla 판(run/317/demo/08-metaball-text-liquid-fillet/index.html) 의 React 포트.
// 액체 글자 — 오프스크린에 글자를 measureText 로 재 맞춰 그리고 getImageData 로 알파 픽셀만
// 필드원으로 샘플링해, 저해상도 가산 필드 + 두 단 임계값으로 글자 전체가 출렁이는 메타볼 타이포를 만든다.
// 표면을 quadraticCurveTo 곡선 광택이 주기적으로 훑는다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./LiquidText.module.scss";

export type LiquidTextProps = {
  duration?: string;
  easing?: string;
  color?: string;
  text?: string;     // 모핑 원본 문장
  stride?: number;   // seed 샘플 간격(px) — 작을수록 촘촘
  jitter?: number;   // 액체 흔들림 진폭(px)
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type Box<T> = { current: T };
type Seed = { x: number; y: number; ph: number; sp: number };

const FIELD_LABEL = "액체 글자 메타볼 실험판";
const SCALE = 4;

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 LiquidText({
  duration = "2s",
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#b9a0ff",
  text = "BLOB",
  stride = 7,
  jitter = 3.6,
}: LiquidTextProps) {
  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 sizeRef = useRef({ w: 0, h: 0 }) as Box<{ w: number; h: number }>;
  const lowRef = useRef({ w: 0, h: 0 }) as Box<{ w: number; h: number }>;
  const fieldCvRef = useRef<HTMLCanvasElement | null>(null);
  const bandCvRef = useRef<HTMLCanvasElement | null>(null);
  const txtCvRef = useRef<HTMLCanvasElement | null>(null);
  const fieldCtxRef = useRef<CanvasRenderingContext2D | null>(null);
  const bandCtxRef = useRef<CanvasRenderingContext2D | null>(null);
  const colRef = useRef<{ stage: string; edge: string; core: string; gloss: string } | null>(null);
  const seedsRef = useRef<Seed[]>([]) as Box<Seed[]>;
  const strideRef = useRef(stride) as Box<number>;
  const jitterRef = useRef(jitter) as Box<number>;
  const rafRef = useRef(0) as Box<number>;
  const [label, setLabel] = useState(text);
  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;
  }

  // ── 텍스트 → 필드원 샘플링 (measureText + getImageData) ──
  function buildSeeds(): void {
    const txtCv = txtCvRef.current;
    const { w: W, h: H } = sizeRef.current;
    if (!txtCv || W <= 0) return;
    const txtCtx = txtCv.getContext("2d");
    if (!txtCtx) return;
    txtCv.width = W; txtCv.height = H;
    txtCtx.clearRect(0, 0, W, H);
    let fontSize = Math.round(H * 0.94);
    const font = (fs: number) => `900 ${fs}px -apple-system, "Segoe UI", sans-serif`;
    txtCtx.font = font(fontSize);
    let m = txtCtx.measureText(text);
    const targetW = W * 0.92;
    if (m.width > 0) fontSize = Math.max(24, Math.round(fontSize * (targetW / m.width)));
    txtCtx.font = font(fontSize);
    m = txtCtx.measureText(text);
    const asc = m.actualBoundingBoxAscent || fontSize * 0.72;
    const desc = m.actualBoundingBoxDescent || fontSize * 0.18;
    const cy = H / 2 + (asc - desc) / 2;
    txtCtx.textAlign = "center";
    txtCtx.textBaseline = "alphabetic";
    txtCtx.fillStyle = "#fff";
    txtCtx.fillText(text, W / 2, cy);

    const img = txtCtx.getImageData(0, 0, W, H);
    const d = img.data;
    const rand = makePRNG(0x317a08);
    const arr: Seed[] = [];
    const st = strideRef.current;
    for (let y = 4; y < H - 4; y += st) {
      for (let x = 4; x < W - 4; x += st) {
        const a = d[(y * W + x) * 4 + 3];
        if (a > 120) arr.push({ x, y, ph: rand() * Math.PI * 2, sp: 0.8 + rand() * 1.6 });
      }
    }
    seedsRef.current = arr;
  }

  function drawField(t: number): void {
    const fieldCtx = fieldCtxRef.current;
    const { w: lw, h: lh } = lowRef.current;
    if (!fieldCtx) return;
    fieldCtx.globalCompositeOperation = "source-over";
    fieldCtx.fillStyle = "#000";
    fieldCtx.fillRect(0, 0, lw, lh);
    fieldCtx.globalCompositeOperation = "lighter";
    const breathe = 1 + Math.sin(t * 0.7) * 0.11;
    const r = 6.4 + Math.sin(t * 0.5) * 0.7;
    // 문장 전체가 천천히 필드를 가로지러 흐른다(타이포가 자리를 바꾸며 모양을 다시 만든다)
    const driftX = Math.sin(t * 0.33) * lw * 0.22 + Math.sin(t * 0.11) * lw * 0.08;
    const driftY = Math.cos(t * 0.26) * lh * 0.2;
    const blob = (px: number, py: number, rad: number): void => {
      const g = fieldCtx.createRadialGradient(px, py, 0, px, py, rad);
      g.addColorStop(0, "rgba(255,255,255,0.95)");
      g.addColorStop(1, "rgba(255,255,255,0)");
      fieldCtx.fillStyle = g;
      fieldCtx.fillRect(px - rad, py - rad, rad * 2, rad * 2);
    };
    const seeds = seedsRef.current;
    for (let i = 0; i < seeds.length; i++) {
      const s = seeds[i];
      const jx = Math.sin(t * s.sp + s.ph) * jitterRef.current;
      const jy = Math.cos(t * s.sp * 1.2 + s.ph) * jitterRef.current;
      const px = ((s.x + jx) / SCALE - lw / 2) * breathe + lw / 2 + driftX;
      const py = ((s.y + jy) / SCALE - lh / 2) * breathe + lh / 2 + driftY;
      blob(px, py, r);
    }
    // 위성 방울 — 글자 주위를 돌며 스쳐 병합하는 메타볼(모양이 더 크게 바뀐다)
    const SAT: Array<[number, number, number]> = [[0.9, 0.5, 0.16], [0.6, 0.85, 0.21], [1.25, 0.32, 0.13], [0.45, 0.15, 0.12], [1.05, 0.72, 0.17]];
    for (let k = 0; k < SAT.length; k++) {
      const o = SAT[k];
      const ox = lw / 2 + Math.sin(t * o[0] + k * 2.1) * lw * 0.42 + driftX * 0.4;
      const oy = lh / 2 + Math.cos(t * o[1] + k * 1.4) * lh * 0.38 + driftY * 0.4;
      blob(ox, oy, r * 1.5);
    }
    fieldCtx.globalCompositeOperation = "source-over";
  }

  function classify(): void {
    const fieldCtx = fieldCtxRef.current;
    const bandCtx = bandCtxRef.current;
    const col = colRef.current;
    const { w: lw, h: lh } = lowRef.current;
    if (!fieldCtx || !bandCtx || !col) return;
    const img = fieldCtx.getImageData(0, 0, lw, lh);
    const d = img.data;
    for (let y = 0; y < lh; y++) {
      for (let x = 0; x < lw; x++) {
        const v = d[(y * lw + x) * 4] / 255;
        bandCtx.fillStyle = v > 0.56 ? col.core : (v > 0.15 ? col.edge : col.stage);
        bandCtx.fillRect(x, y, 1, 1);
      }
    }
  }

  function gloss(t: number): void {
    const ctx = ctxRef.current;
    const col = colRef.current;
    const { w: W, h: H } = sizeRef.current;
    if (!ctx || !col) return;
    const u = (t * 0.28) % 1.4 - 0.2;
    const x0 = -W * 0.2 + u * W, y0 = H * 0.32;
    const cx1 = x0 + W * 0.22, cy1 = H * 0.08;
    const x1 = x0 + W * 0.44, y1 = H * 0.4;
    ctx.save();
    ctx.globalCompositeOperation = "lighter";
    ctx.strokeStyle = col.gloss;
    ctx.lineWidth = Math.max(10, H * 0.09);
    ctx.lineCap = "round";
    ctx.globalAlpha = 0.16;
    ctx.beginPath();
    ctx.moveTo(x0, y0);
    ctx.quadraticCurveTo(cx1, cy1, x1, y1);
    ctx.stroke();
    ctx.restore();
  }

  function draw(t: number): void {
    const ctx = ctxRef.current;
    const col = colRef.current;
    const bandCv = bandCvRef.current;
    const { w: W, h: H } = sizeRef.current;
    const { w: lw, h: lh } = lowRef.current;
    if (!ctx || !bandCv || !col) return;
    drawField(t);
    classify();
    ctx.clearRect(0, 0, W, H);
    ctx.fillStyle = col.stage;
    ctx.fillRect(0, 0, W, H);
    ctx.drawImage(bandCv, 0, 0, lw, lh, 0, 0, W, H);
    gloss(t);
  }

  function fit(): void {
    const field = fieldRef.current;
    const cv = cvRef.current;
    if (!field || !cv) return;
    const ctx = cv.getContext("2d");
    if (!ctx) return;
    const r = field.getBoundingClientRect();
    sizeRef.current.w = r.width;
    sizeRef.current.h = r.height;
    cv.width = Math.round(r.width);
    cv.height = Math.round(r.height);
    const lw = Math.max(48, Math.round(r.width / SCALE));
    const lh = Math.max(30, Math.round(r.height / SCALE));
    lowRef.current = { w: lw, h: lh };
    const fc = fieldCvRef.current as HTMLCanvasElement; fc.width = lw; fc.height = lh;
    const bc = bandCvRef.current as HTMLCanvasElement; bc.width = lw; bc.height = lh;
    fieldCtxRef.current = fc.getContext("2d");
    bandCtxRef.current = bc.getContext("2d");
    ctx.imageSmoothingEnabled = true;
    ctxRef.current = ctx;
    buildSeeds();
  }

  function stillFrame(): void { draw(0.35); }

  let t0 = -1;
  function frame(now: number): void {
    if (t0 < 0) t0 = now;
    const t = (now - t0) / 1000;
    draw(t);
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    strideRef.current = stride;
    jitterRef.current = jitter;
    const cs = getComputedStyle(root);
    const tok = (name: string) => cs.getPropertyValue(name).trim();
    colRef.current = {
      stage: tok("--mb-stage"),
      edge: tok("--mb-edge"),
      core: tok("--mb-core"),
      gloss: tok("--mb-gloss"),
    };
    fit();
    setLabel(text);
    function onResize(): void {
      fit();
      if (reduced()) stillFrame();
    }
    window.addEventListener("resize", onResize);
    if (reduced()) {
      stillFrame();
      setStill(true);
    } else {
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [text, stride, jitter]);

  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>글자를 그린 뒤 알파가 있는 픽셀만 필드원으로 샘플링하면 문장 전체가 메타볼 덩어리로 변해 흐르며 모양을 바꾸는 타이포가 됩니다</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}>{label}</b>· 텍스트 필드원</span>
          <span className={styles.metaDim}>measureText · getImageData · quadraticCurveTo</span>
        </div>
      </div>
    </main>
  );
}