04가중치 확률 — 칸 각도를 무게로 나눠 공정하게 뽑기

<main class="stage">
<div class="wt" id="wt">
  <p class="wt__hint">칸의 각도 자체가 확률입니다 — 무게를 누적 비율로 나눠 시작각·끝각을 잡습니다</p>
  <div class="wt__row">
    <div class="wt__field" id="field" role="application" aria-label="가중치 확률 실험판" tabindex="0">
      <canvas class="wt__cv" id="cv"></canvas>
    </div>
    <div class="wt__side">
      <b class="wt__num" id="odds">0%</b>
      <span class="wt__unit">포인터 칸의 기대 확률</span>
      <p class="wt__meta">시행 <b class="wt__count" id="tries">0</b><span class="wt__metaUnit">회</span></p>
      <p class="wt__meta">시드 고정 mulberry32 — 돌릴 때마다 같은 계열의 결과</p>
    </div>
  </div>
</div>
</main>

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

// 가중치 확률(04) — 움직임은 전부 캔버스 rAF 루프다. CSS @keyframes 를 두지 않는다.
// 페이퍼 무대. 칸 네 색은 파스텔 팔레트(채도 .19~.49) — 무게가 큰 칸이 넓게 보이므로
// 색 순환으로 이웃 칸이 같은 색으로 붙지 않게 한다. BD26 vivid 기준 전부 통과.

$duration: $dur-loop;
$easing: $ease-out;
$color: $subject-blue;

@include stage($stage-paper);

.wt {
  --w1: #b3bfd4;   // 파랑빛 파스텔 — 큰 칸
  --w2: #d9c48f;   // 골드 파스텔
  --w3: #a9c4b0;   // 세이지 파스텔
  --w4: #d8a3b4;   // 로즈 파스텔
  --ink: #{$subject-ink};
  --cream: #{$subject-cream};

  display: flex; flex-direction: column; gap: $sp-2;
  width: 100%; max-width: 420px;
}

.wt__hint {
  margin: 0; font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); line-height: 1.35;
  color: $subject-ink;
}

.wt__row { display: flex; gap: $sp-2; align-items: stretch; }

.wt__field {
  position: relative; overflow: hidden;
  flex: 0 0 auto;
  width: clamp(176px, 46vw, 232px);
  height: clamp(176px, 46vw, 232px);
  border-radius: $r-card;
  background: rgba($subject-ink, .05);
  box-shadow: inset 0 0 0 1px rgba($subject-ink, .16);
  cursor: grab; touch-action: none;
}
.wt__field:active { cursor: grabbing; }
.wt__field:focus-visible { outline: 2px solid $color; outline-offset: 2px; }

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

.wt__side {
  flex: 1; min-width: 0;
  display: flex; flex-direction: column; gap: $sp-1;
  padding-top: $sp-1;
}
.wt__num {
  font-weight: 800; font-size: clamp(20px, 6vw, 30px); line-height: 1;
  color: $subject-blue-deep; font-variant-numeric: tabular-nums;
}
.wt__unit { font-weight: 600; font-size: clamp(9px, 2.4vw, 11px); line-height: 1.4; color: rgba($subject-ink, .82); }

.wt__meta { margin: $sp-1 0 0; font-size: clamp(9px, 2.4vw, 11px); line-height: 1.5; color: rgba($subject-ink, .82); }
.wt__meta b { font-weight: 700; color: $subject-blue-deep; font-variant-numeric: tabular-nums; margin-right: $sp-1; }
.wt__metaUnit { color: rgba($subject-ink, .72); }

@media (max-width: 340px) {
  .wt__hint { font-size: 8px; line-height: 1.3; }
  .wt { gap: $sp-1; }
  .wt__field { width: 150px; height: 150px; }
  .wt__num { font-size: 16px; }
  .wt__meta { margin-top: 0; font-size: 8px; }
}

// reduce — 루프가 안 돈다. 펄스 링이 퍼진 정지 한 장이 남는다.
@media (prefers-reduced-motion: reduce) {
  .wt.is-still .wt__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: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.wt {
  --w1: #b3bfd4;
  --w2: #d9c48f;
  --w3: #a9c4b0;
  --w4: #d8a3b4;
  --ink: #17141a;
  --cream: #fff7e6;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 420px;
}

.wt__hint {
  margin: 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  line-height: 1.35;
  color: #17141a;
}

.wt__row {
  display: flex;
  gap: 8px;
  align-items: stretch;
}

.wt__field {
  position: relative;
  overflow: hidden;
  flex: 0 0 auto;
  width: clamp(176px, 46vw, 232px);
  height: clamp(176px, 46vw, 232px);
  border-radius: 16px;
  background: rgba(23, 20, 26, 0.05);
  box-shadow: inset 0 0 0 1px rgba(23, 20, 26, 0.16);
  cursor: grab;
  touch-action: none;
}

.wt__field:active {
  cursor: grabbing;
}

.wt__field:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: 2px;
}

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

.wt__side {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding-top: 4px;
}

.wt__num {
  font-weight: 800;
  font-size: clamp(20px, 6vw, 30px);
  line-height: 1;
  color: #0a4fe8;
  font-variant-numeric: tabular-nums;
}

.wt__unit {
  font-weight: 600;
  font-size: clamp(9px, 2.4vw, 11px);
  line-height: 1.4;
  color: rgba(23, 20, 26, 0.82);
}

.wt__meta {
  margin: 4px 0 0;
  font-size: clamp(9px, 2.4vw, 11px);
  line-height: 1.5;
  color: rgba(23, 20, 26, 0.82);
}

.wt__meta b {
  font-weight: 700;
  color: #0a4fe8;
  font-variant-numeric: tabular-nums;
  margin-right: 4px;
}

.wt__metaUnit {
  color: rgba(23, 20, 26, 0.72);
}

@media (max-width: 340px) {
  .wt__hint {
    font-size: 8px;
    line-height: 1.3;
  }
  .wt {
    gap: 4px;
  }
  .wt__field {
    width: 150px;
    height: 150px;
  }
  .wt__num {
    font-size: 16px;
  }
  .wt__meta {
    margin-top: 0;
    font-size: 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .wt.is-still .wt__field {
    cursor: default !important;
  }
}

// 가중치 확률(04) — 모든 칸을 같은 각도로 그리면 칸 수만큼 균등 확률이 되지만,
// 항목마다 무게를 두면 시작각·끝각을 누적 비율로 잡아 각도 자체가 확률이 된다.
// 결과는 멈춘 뒤 각도로 판정하므로 조작 없이 눈에 보이는 확률 그대로 당첨된다.
// 난수는 mulberry32 로 시드를 고정한다 — 데모 재현성.
(function () {
  function mulberry32(seed) {
    var a = seed >>> 0;
    return function () {
      a |= 0; a = (a + 0x6D2B79F5) | 0;
      var t = Math.imul(a ^ (a >>> 15), 1 | a);
      t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
      return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
    };
  }
  var rnd = mulberry32(332004);
  var root = document.getElementById('wt');
  var field = document.getElementById('field');
  var cv = document.getElementById('cv');
  var oddsEl = document.getElementById('odds');
  var triesEl = document.getElementById('tries');
  if (!root || !field || !cv || !oddsEl || !triesEl) return;
  var ctx = cv.getContext('2d');
  var css = getComputedStyle(root);
  var PAL = [];
  for (var i = 1; i <= 4; i++) PAL.push(css.getPropertyValue('--w' + i).trim());
  var INK = css.getPropertyValue('--ink').trim();
  var CREAM = css.getPropertyValue('--cream').trim();
  var TAU = Math.PI * 2;
  // 무게 — 각도 분할의 출처. 기대 비율 그대로 칸이 넓어진다
  var W = [5, 3, 2, 1, 3, 2];
  var TOT = W.reduce(function (a, b) { return a + b; }, 0);
  var bounds = [], acc = 0;
  for (var q = 0; q < W.length; q++) { bounds.push(acc / TOT); acc += W[q]; }
  bounds.push(1);

  var ang = -0.9, vel = 0, tries = 0;
  var FRICTION = 0.24, STOP = 0.5;
  var settle = -1, pulse = -1, dpr = 1, lastIdx = -1;
  var flicks = [11, -8, 13];
  var fi = 1;

  function fit() {
    var w = field.clientWidth, h = field.clientHeight;
    dpr = Math.min(2, window.devicePixelRatio || 1);
    cv.width = Math.round(w * dpr); cv.height = Math.round(h * dpr);
  }

  function norm(a) { a %= TAU; return a < 0 ? a + TAU : a; }
  // 정지 각도 → 부채꼴 인덱스 (12시 고정 포인터)
  function idxAt(a) {
    var u = norm(-Math.PI / 2 - a);
    for (var k = 0; k < W.length; k++) if (u >= bounds[k] && u < bounds[k + 1]) return k;
    return W.length - 1;
  }

  function draw() {
    var w = cv.width / dpr, h = cv.height / dpr;
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    ctx.clearRect(0, 0, w, h);
    var cx = w / 2, cy = h / 2, R = Math.min(w, h) / 2 - 10;
    ctx.save(); ctx.translate(cx, cy); ctx.rotate(ang);
    for (var k = 0; k < W.length; k++) {
      var a0 = bounds[k] * TAU, a1 = bounds[k + 1] * TAU;
      ctx.beginPath(); ctx.moveTo(0, 0);
      ctx.arc(0, 0, R, a0, a1); ctx.closePath();
      ctx.fillStyle = PAL[k % PAL.length]; ctx.fill();
      ctx.strokeStyle = 'rgba(23,20,26,.20)'; ctx.lineWidth = 1; ctx.stroke();
      // 무게 라벨 — 칸 가운데 각도에 확률 % 를 적는다
      var mid = (a0 + a1) / 2;
      ctx.save(); ctx.rotate(mid);
      ctx.fillStyle = INK;
      ctx.font = '700 12px sans-serif';
      ctx.textAlign = 'right'; ctx.textBaseline = 'middle';
      ctx.fillText(Math.round(W[k] / TOT * 100) + '%', R - 12, 0);
      ctx.restore();
    }
    ctx.beginPath(); ctx.arc(0, 0, 13, 0, TAU);
    ctx.fillStyle = CREAM; ctx.fill(); ctx.strokeStyle = 'rgba(23,20,26,.35)'; ctx.stroke();
    if (pulse >= 0) {
      ctx.beginPath(); ctx.arc(0, 0, 13 + pulse * 22, 0, TAU);
      ctx.strokeStyle = 'rgba(23,20,26,' + (1 - pulse) * 0.5 + ')';
      ctx.lineWidth = 2; ctx.stroke();
    }
    ctx.restore();
    ctx.beginPath();
    ctx.moveTo(cx - 7, cy - R - 8); ctx.lineTo(cx + 7, cy - R - 8); ctx.lineTo(cx, cy - R + 8);
    ctx.closePath(); ctx.fillStyle = INK; ctx.fill();
  }

  var drag = { on: false, lastA: 0, lastT: 0, v: 0 };
  function angleAt(e) {
    var b = field.getBoundingClientRect();
    return Math.atan2(e.clientY - (b.top + b.height / 2), e.clientX - (b.left + b.width / 2));
  }
  field.addEventListener('pointerdown', function (e) {
    drag.on = true; drag.lastA = angleAt(e); drag.lastT = performance.now(); drag.v = 0;
    if (field.setPointerCapture) { try { field.setPointerCapture(e.pointerId); } catch (err) { /* 캡처 실패는 회전에 영향 없다 */ } }
  });
  field.addEventListener('pointermove', function (e) {
    if (!drag.on) return;
    var a = angleAt(e), now = performance.now();
    var dA = a - drag.lastA;
    if (dA > Math.PI) dA -= TAU;
    if (dA < -Math.PI) dA += TAU;
    ang += dA;
    var dt = Math.max(1, now - drag.lastT) / 1000;
    drag.v = 0.65 * drag.v + 0.35 * (dA / dt);
    drag.lastA = a; drag.lastT = now;
    idle = 0;
  });
  function endDrag() {
    if (!drag.on) return;
    drag.on = false;
    // 손으로 뗀 스픈은 Math.random 가감 — 자동 루프(시드 고정)와 달리 사람 손에 온도를 준다
    vel = Math.max(-24, Math.min(24, drag.v * (0.85 + Math.random() * 0.3)));
    if (Math.abs(vel) < 1) vel = flicks[0];
    settle = -1; pulse = -1;
    tries++; triesEl.textContent = String(tries);
  }
  field.addEventListener('pointerup', endDrag);
  field.addEventListener('pointercancel', endDrag);
  field.addEventListener('keydown', function (e) {
    if (e.key === ' ' || e.key === 'Enter') {
      e.preventDefault();
      vel = flicks[fi++ % flicks.length];
      settle = -1; pulse = -1;
      tries++; triesEl.textContent = String(tries);
    }
  });

  var idle = 0;
  function auto(dt) {
    if (idle > 0) { idle -= dt; return; }
    if (settle >= 0) {
      settle += dt; pulse = Math.min(1, settle / 0.3);
      if (settle > 0.4) {
        vel = flicks[Math.floor(rnd() * flicks.length)] * (0.8 + rnd() * 0.5);
        fi++;
        settle = -1; pulse = -1;
        tries++; triesEl.textContent = String(tries);
      }
      return;
    }
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var last = performance.now();
  function step(now) {
    var dt = Math.min(64, now - last) / 1000; last = now;
    if (!drag.on) {
      if (vel !== 0) {
        ang += vel * dt;
        vel *= Math.pow(FRICTION, dt);
        if (Math.abs(vel) < STOP) { vel = 0; settle = 0; pulse = 0; }
      } else { auto(dt); }
    }
    draw();
    var idx = idxAt(ang);
    if (idx !== lastIdx) {
      oddsEl.textContent = Math.round(W[idx] / TOT * 100) + '%';
      lastIdx = idx;
    }
    requestAnimationFrame(step);
  }

  fit();
  window.addEventListener('resize', fit);
  if (reduce) {
    // 정지 한 장 — 펄스 링이 퍼진 상태로 고정하고 루프는 돌지 않는다
    pulse = 0.4;
    draw();
    oddsEl.textContent = Math.round(W[idxAt(ang)] / TOT * 100) + '%';
    root.classList.add('is-still');
  } else {
    vel = flicks[0];
    tries = 1; triesEl.textContent = '1';
    requestAnimationFrame(step);
  }
})();

// SpinWheelWeightedOdds — vanilla 판(run/332/demo/04-spin-wheel-weighted-odds/index.html) 의 React 포트.
// 모든 칸을 같은 각도로 그리면 균등 확률이지만, 무게(W)를 누적 비율로 시작각·끝각에 반영하면
// 각도 자체가 확률이 된다. 자동 루프는 mulberry32(332004) 로 시드 고정 — 항상 같은 결과 계열.
// 손으로 튕길 때만 Math.random 온도(0.85~1.15배)를 더해 자동 데모와 결을 다르게 한다.
// 움직임은 전부 캔버스 rAF 루프가 그리므로 CSS 애니메이션이 없다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties, PointerEvent } from "react";
import styles from "./SpinWheelWeightedOdds.module.scss";

// demo.py 의 ambient react 스텁은 KeyboardEvent 를 export 하지 않는다 — 최소 자체 타입으로 대체
type KeyEvt = { key: string; preventDefault(): void };

export type SpinWheelWeightedOddsProps = {
  duration?: string;
  easing?: string;
  color?: string;
};

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

function mulberry32(seed: number): () => number {
  let a = seed >>> 0;
  return function () {
    a |= 0; a = (a + 0x6D2B79F5) | 0;
    let t = Math.imul(a ^ (a >>> 15), 1 | a);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}

const TAU = Math.PI * 2;
const W = [5, 3, 2, 1, 3, 2];
const TOT = W.reduce((a, b) => a + b, 0);
const FRICTION = 0.24, STOP = 0.5;
const FLICKS = [11, -8, 13];
const PAL = ["#b3bfd4", "#d9c48f", "#a9c4b0", "#d8a3b4"];
const INK = "#17141a";
const CREAM = "#fff7e6";
const HINT = "칸의 각도 자체가 확률입니다 — 무게를 누적 비율로 나눠 시작각·끝각을 잡습니다";
const ARIA_FIELD = "가중치 확률 실험판";
const UNIT = "포인터 칸의 기대 확률";
const META_TRIES = "시행 ";
const META_TRIES_UNIT = "회";
const META_SEED = "시드 고정 mulberry32 — 돌릴 때마다 같은 계열의 결과";

function computeBounds(): number[] {
  const bounds: number[] = [];
  let acc = 0;
  for (let q = 0; q < W.length; q++) { bounds.push(acc / TOT); acc += W[q]; }
  bounds.push(1);
  return bounds;
}
const BOUNDS = computeBounds();

export default function SpinWheelWeightedOdds({
  duration = "2s",
  easing = "ease-out",
  color = "#2f6df6"
}: SpinWheelWeightedOddsProps) {
  const fieldRef = useRef<HTMLDivElement | null>(null);
  const cvRef = useRef<HTMLCanvasElement | null>(null);
  const oddsRef = useRef<HTMLSpanElement | null>(null);
  const triesRef = useRef<HTMLSpanElement | null>(null);
  const ctxRef = useRef<CanvasRenderingContext2D | null>(null);
  const rndRef = useRef(mulberry32(332004)) as Box<() => number>;
  const stRef = useRef({
    ang: -0.9, vel: 0, tries: 0, settle: -1, pulse: -1, dpr: 1, lastIdx: -1, fi: 1, idle: 0,
    drag: { on: false, lastA: 0, lastT: 0, v: 0 }
  }) as Box<{
    ang: number; vel: number; tries: number; settle: number; pulse: number; dpr: number; lastIdx: number; fi: number; idle: number;
    drag: { on: boolean; lastA: number; lastT: number; v: number };
  }>;
  const lastRef = useRef(0) as Box<number>;
  const rafRef = useRef(0) as Box<number>;
  const [still, setStill] = useState(false);

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

  function fit(): void {
    const st = stRef.current;
    const field = fieldRef.current, cv = cvRef.current;
    if (!field || !cv) return;
    const ctx = cv.getContext("2d");
    if (!ctx) return;
    st.dpr = Math.min(2, window.devicePixelRatio || 1);
    cv.width = Math.round(field.clientWidth * st.dpr);
    cv.height = Math.round(field.clientHeight * st.dpr);
    ctxRef.current = ctx;
  }

  function norm(a: number): number {
    const r = a % TAU;
    return r < 0 ? r + TAU : r;
  }
  function idxAt(a: number): number {
    const u = norm(-Math.PI / 2 - a);
    for (let k = 0; k < W.length; k++) if (u >= BOUNDS[k] && u < BOUNDS[k + 1]) return k;
    return W.length - 1;
  }

  function draw(): void {
    const st = stRef.current;
    const ctx = ctxRef.current;
    if (!ctx) return;
    const w = cvRef.current!.width / st.dpr, h = cvRef.current!.height / st.dpr;
    ctx.setTransform(st.dpr, 0, 0, st.dpr, 0, 0);
    ctx.clearRect(0, 0, w, h);
    const cx = w / 2, cy = h / 2, R = Math.min(w, h) / 2 - 10;
    ctx.save(); ctx.translate(cx, cy); ctx.rotate(st.ang);
    for (let k = 0; k < W.length; k++) {
      const a0 = BOUNDS[k] * TAU, a1 = BOUNDS[k + 1] * TAU;
      ctx.beginPath(); ctx.moveTo(0, 0);
      ctx.arc(0, 0, R, a0, a1); ctx.closePath();
      ctx.fillStyle = PAL[k % PAL.length]; ctx.fill();
      ctx.strokeStyle = "rgba(23,20,26,.20)"; ctx.lineWidth = 1; ctx.stroke();
      const mid = (a0 + a1) / 2;
      ctx.save(); ctx.rotate(mid);
      ctx.fillStyle = INK;
      ctx.font = "700 12px sans-serif";
      ctx.textAlign = "right"; ctx.textBaseline = "middle";
      ctx.fillText(Math.round(W[k] / TOT * 100) + "%", R - 12, 0);
      ctx.restore();
    }
    ctx.beginPath(); ctx.arc(0, 0, 13, 0, TAU);
    ctx.fillStyle = CREAM; ctx.fill(); ctx.strokeStyle = "rgba(23,20,26,.35)"; ctx.stroke();
    if (st.pulse >= 0) {
      ctx.beginPath(); ctx.arc(0, 0, 13 + st.pulse * 22, 0, TAU);
      ctx.strokeStyle = "rgba(23,20,26," + (1 - st.pulse) * 0.5 + ")";
      ctx.lineWidth = 2; ctx.stroke();
    }
    ctx.restore();
    ctx.beginPath();
    ctx.moveTo(cx - 7, cy - R - 8); ctx.lineTo(cx + 7, cy - R - 8); ctx.lineTo(cx, cy - R + 8);
    ctx.closePath(); ctx.fillStyle = INK; ctx.fill();
  }

  function angleAt(e: PointerEvent<HTMLDivElement>): number {
    const b = e.currentTarget.getBoundingClientRect();
    return Math.atan2(e.clientY - (b.top + b.height / 2), e.clientX - (b.left + b.width / 2));
  }
  function onPointerDown(e: PointerEvent<HTMLDivElement>): void {
    const st = stRef.current;
    st.drag.on = true; st.drag.lastA = angleAt(e); st.drag.lastT = performance.now(); st.drag.v = 0;
    try { e.currentTarget.setPointerCapture(e.pointerId); } catch { /* 캡처 실패는 회전에 영향 없다 */ }
  }
  function onPointerMove(e: PointerEvent<HTMLDivElement>): void {
    const st = stRef.current;
    if (!st.drag.on) return;
    const a = angleAt(e), now = performance.now();
    let dA = a - st.drag.lastA;
    if (dA > Math.PI) dA -= TAU;
    if (dA < -Math.PI) dA += TAU;
    st.ang += dA;
    const dt = Math.max(1, now - st.drag.lastT) / 1000;
    st.drag.v = 0.65 * st.drag.v + 0.35 * (dA / dt);
    st.drag.lastA = a; st.drag.lastT = now;
    st.idle = 0;
  }
  function bumpTries(): void {
    const st = stRef.current;
    st.tries++;
    const tr = triesRef.current;
    if (tr) tr.textContent = String(st.tries);
  }
  function endDrag(): void {
    const st = stRef.current;
    if (!st.drag.on) return;
    st.drag.on = false;
    // 손으로 뗀 스핀은 Math.random 가감 — 자동 루프(시드 고정)와 달리 사람 손에 온도를 준다
    st.vel = Math.max(-24, Math.min(24, st.drag.v * (0.85 + Math.random() * 0.3)));
    if (Math.abs(st.vel) < 1) st.vel = FLICKS[0];
    st.settle = -1; st.pulse = -1;
    bumpTries();
  }
  function onKeyDown(e: KeyEvt): void {
    const st = stRef.current;
    if (e.key === " " || e.key === "Enter") {
      e.preventDefault();
      st.vel = FLICKS[st.fi++ % FLICKS.length];
      st.settle = -1; st.pulse = -1;
      bumpTries();
    }
  }

  function auto(dt: number): void {
    const st = stRef.current;
    const rnd = rndRef.current;
    if (st.idle > 0) { st.idle -= dt; return; }
    if (st.settle >= 0) {
      st.settle += dt; st.pulse = Math.min(1, st.settle / 0.3);
      if (st.settle > 0.4) {
        st.vel = FLICKS[Math.floor(rnd() * FLICKS.length)] * (0.8 + rnd() * 0.5);
        st.fi++;
        st.settle = -1; st.pulse = -1;
        bumpTries();
      }
    }
  }

  function step(now: number): void {
    const st = stRef.current;
    const dt = Math.min(64, now - lastRef.current) / 1000; lastRef.current = now;
    if (!st.drag.on) {
      if (st.vel !== 0) {
        st.ang += st.vel * dt;
        st.vel *= Math.pow(FRICTION, dt);
        if (Math.abs(st.vel) < STOP) { st.vel = 0; st.settle = 0; st.pulse = 0; }
      } else { auto(dt); }
    }
    draw();
    const idx = idxAt(st.ang);
    if (idx !== st.lastIdx) {
      const odds = oddsRef.current;
      if (odds) odds.textContent = Math.round(W[idx] / TOT * 100) + "%";
      st.lastIdx = idx;
    }
    rafRef.current = requestAnimationFrame(step);
  }

  useEffect(() => {
    fit();
    function onResize(): void { fit(); }
    window.addEventListener("resize", onResize);
    if (reduced()) {
      // 정지 한 장 — 펄스 링이 퍼진 상태로 고정하고 루프는 돌지 않는다
      const st = stRef.current;
      st.pulse = 0.4;
      draw();
      const odds = oddsRef.current;
      if (odds) odds.textContent = Math.round(W[idxAt(st.ang)] / TOT * 100) + "%";
      setStill(true);
    } else {
      const st = stRef.current;
      st.vel = FLICKS[0]; st.tries = 1;
      const tr = triesRef.current;
      if (tr) tr.textContent = "1";
      lastRef.current = performance.now();
      rafRef.current = requestAnimationFrame(step);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  const rootCls = still ? styles.wt + " " + styles.isStill : styles.wt;
  return (
    <main className={styles.stage}>
      <div className={rootCls} style={{ "--duration": duration, "--easing": easing, "--color": color } as Vars}>
        <p className={styles.hint}>{HINT}</p>
        <div className={styles.row}>
          <div
            className={styles.field}
            ref={fieldRef}
            role="application"
            aria-label={ARIA_FIELD}
            tabIndex={0}
            onKeyDown={onKeyDown}
            onPointerDown={onPointerDown}
            onPointerMove={onPointerMove}
            onPointerUp={endDrag}
            onPointerCancel={endDrag}
          >
            <canvas className={styles.cv} ref={cvRef}></canvas>
          </div>
          <div className={styles.side}>
            <b className={styles.num} ref={oddsRef}>0%</b>
            <span className={styles.unit}>{UNIT}</span>
            <p className={styles.meta}>{META_TRIES}<b className={styles.count} ref={triesRef}>0</b><span className={styles.metaUnit}>{META_TRIES_UNIT}</span></p>
            <p className={styles.meta}>{META_SEED}</p>
          </div>
        </div>
      </div>
    </main>
  );
}