01The basic fall — one rule: move down when the cell below is empty

<main class="stage">
<div class="cd is-demo" id="cdRoot">
  <p class="cd__hint">
    <span>Sand poured from above moves down only when the cell below is empty</span>
  </p>
  <div class="cd__field" id="cdField" role="application" aria-label="Sand Fall cellular automaton demo" tabindex="0">
    <canvas class="cd__cv" id="cdCv"></canvas>
  </div>
  <div class="cd__bar">
    <span class="cd__meta"><b class="cd__val" id="cdN">1</b>cells fall 1/frame</span>
    <span class="cd__meta cd__meta--dim">canvas · fillRect · requestAnimationFrame</span>
  </div>
</div>
</main>

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

// 기본 낙하(01). @keyframes 를 아예 두지 않는다 —
// 움직임은 전부 캔버스 rAF 루프(셀 오토마타 낙하 스캔)가 만든다.
// 무대는 모래밤. 파스텔 고정 팔레트를 --sand-* 로 편 공통 규격(01~09 동일).

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

@include stage($stage-ink);

// ── 편 공통 파스텔 팔레트(BD26 vivid 0 실측 통과값 — 다른 색 금지) ──
$sand-night: #201c17;
$sand-mist:  #d8d2c6;
$sand-glow:  #f2e2c4;
$sand-grain: #d9b98a;
$sand-gold:  #ecd9b0;
$sand-water: #a9c8dd;
$sand-ice:   #cfe3ee;
$sand-fire:  #ffc9ad;
$sand-flame: #ffe0c4;
$sand-ash:   #b9b2a6;
$sand-smoke: #8e8879;
$sand-plant: #9fd6ad;
$sand-leaf:  #c4e6c9;
$sand-acid:  #c7dd8f;
$sand-stone: #8a8578;
$sand-wood:  #b98a63;

.cd {
  // 렌더러가 읽는 색 — JS 는 getComputedStyle 로 --sand-* 를 받아 쓴다
  --sand-night: #{$sand-night};
  --sand-mist:  #{$sand-mist};
  --sand-glow:  #{$sand-glow};
  --sand-grain: #{$sand-grain};
  --sand-gold:  #{$sand-gold};
  --sand-water: #{$sand-water};
  --sand-ice:   #{$sand-ice};
  --sand-fire:  #{$sand-fire};
  --sand-flame: #{$sand-flame};
  --sand-ash:   #{$sand-ash};
  --sand-smoke: #{$sand-smoke};
  --sand-plant: #{$sand-plant};
  --sand-leaf:  #{$sand-leaf};
  --sand-acid:  #{$sand-acid};
  --sand-stone: #{$sand-stone};
  --sand-wood:  #{$sand-wood};

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

.cd__hint { color: $sand-mist; font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); margin: 0; }

.cd__field {
  position: relative; height: 200px;
  border-radius: $r-card; overflow: hidden;
  background: $sand-night;
  box-shadow: inset 0 0 0 1px rgba($sand-mist, .18);
}
.cd__field:focus-visible { outline: 2px solid $subject-lilac; outline-offset: 2px; }

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

.cd__bar { display: flex; align-items: baseline; justify-content: space-between; gap: $sp-2; }
.cd__meta { font-size: 10px; font-weight: 500; color: rgba($sand-mist, .72); }
.cd__val { color: $subject-lilac; font-weight: 700; }
.cd__meta--dim { font-size: 10px; }

@media (max-width: 340px) {
  .cd { gap: $sp-1; }
  .cd__field { height: 110px; }
  .cd__meta--dim { display: none; }
}

// reduce — rAF 를 돌리지 않고 규칙 몇 틱의 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 {
  --sand-night: #201c17;
  --sand-mist: #d8d2c6;
  --sand-glow: #f2e2c4;
  --sand-grain: #d9b98a;
  --sand-gold: #ecd9b0;
  --sand-water: #a9c8dd;
  --sand-ice: #cfe3ee;
  --sand-fire: #ffc9ad;
  --sand-flame: #ffe0c4;
  --sand-ash: #b9b2a6;
  --sand-smoke: #8e8879;
  --sand-plant: #9fd6ad;
  --sand-leaf: #c4e6c9;
  --sand-acid: #c7dd8f;
  --sand-stone: #8a8578;
  --sand-wood: #b98a63;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 424px;
}

.cd__hint {
  color: #d8d2c6;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  margin: 0;
}

.cd__field {
  position: relative;
  height: 200px;
  border-radius: 16px;
  overflow: hidden;
  background: #201c17;
  box-shadow: inset 0 0 0 1px rgba(216, 210, 198, 0.18);
}

.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(216, 210, 198, 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: 110px;
  }
  .cd__meta--dim {
    display: none;
  }
}
@media (prefers-reduced-motion: reduce) {
  .cd.is-still .cd__field {
    cursor: default !important;
  }
}

// 기본 낙하(01). 격자를 Uint8Array 로 두고 매 틱 아래→위 스캔하며
// "아래칸이 비었으면 스왑" 규칙 하나만 적용한다 — 대각선 이동 없음.
// 상단 세 스포너(좌·중·우, 각 10칸 폭)에서 매 틱 확률로 모래(grain/gold 섞임)를 흘려
// 세로 기둥이 쌓이는 셀 오토마타의 첫 장면을 만든다.
(function () {
  // ── 변형 상수 블록 — 아래 값 하나만 바꿔 변형을 만든다 ──
  var FALL = 1;       // 낙하 칸수/프레임 — 1 은 기본, 2~3 은 빠른 폭포
  var SPAWN_P = 0.35; // 스포너 칸별 매 틱 생성 확률
  var ZONE_W = 20;     // 스포너 폭(칸)
  // ────────────────────────────────────────────────────

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

  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(0x318A01);

  // 색은 CSS 커스텀 프로퍼티(--sand-*)에서 getComputedStyle 로 읽는다 — 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_NIGHT = tokRGB('--sand-night');
  var C_GLOW  = tokRGB('--sand-glow');
  var C_GRAIN = tokRGB('--sand-grain');
  var C_GOLD  = tokRGB('--sand-gold');

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var CELL = 4;
  var W = 0, H = 0, cols = 0, rows = 0;
  var grid = null, shade = null;
  var zones = [];
  var raf = 0, t0 = -1, acc = 0;
  var STEP = 1 / 60;

  function idx(x, y) { return y * cols + x; }

  function buildZones() {
    var lz = Math.max(0, Math.round(cols * 0.06));
    var cz = Math.max(0, Math.round(cols / 2 - ZONE_W / 2));
    var rz = Math.max(0, Math.round(cols * 0.94 - ZONE_W));
    zones = [lz, cz, rz];
  }

  function fit() {
    var r = field.getBoundingClientRect();
    W = r.width; H = r.height;
    cv.width = Math.round(W); cv.height = Math.round(H);
    cols = Math.max(1, Math.floor(W / CELL));
    rows = Math.max(1, Math.floor(H / CELL));
    grid = new Uint8Array(cols * rows);
    shade = new Uint8Array(cols * rows);
    buildZones();
  }

  function spawnStep() {
    for (var z = 0; z < zones.length; z++) {
      var x0 = zones[z];
      for (var k = 0; k < ZONE_W; k++) {
        var x = x0 + k;
        if (x < 0 || x >= cols) continue;
        if (rand() < SPAWN_P) {
          var i = idx(x, 0);
          if (grid[i] === 0) { grid[i] = 1; shade[i] = rand() < 0.5 ? 0 : 1; }
        }
      }
    }
  }

  function update() {
    for (var y = rows - 2; y >= 0; y--) {
      for (var x = 0; x < cols; x++) {
        var i = idx(x, y);
        if (grid[i] !== 1) continue;
        var destY = y;
        for (var s = 1; s <= FALL; s++) {
          var yy = y + s;
          if (yy >= rows) break;
          if (grid[idx(x, yy)] === 0) destY = yy; else break;
        }
        if (destY !== y) {
          var di = idx(x, destY);
          grid[di] = 1; shade[di] = shade[i];
          grid[i] = 0;
        }
      }
    }
  }

  function draw(t) {
    ctx.fillStyle = 'rgb(' + C_NIGHT.join(',') + ')';
    ctx.fillRect(0, 0, W, H);

    // 느린 잔광 — 중심이 sin/cos 로 천천히 도는 radial gradient(안개, 알파 0.06 내외)
    var gx = W * (0.5 + 0.36 * Math.sin(t * 0.17));
    var gy = H * (0.5 + 0.30 * Math.cos(t * 0.13));
    var gr = Math.max(W, H) * 0.7;
    var g = ctx.createRadialGradient(gx, gy, 0, gx, gy, gr);
    g.addColorStop(0, 'rgba(' + C_GLOW.join(',') + ',0.07)');
    g.addColorStop(1, 'rgba(' + C_GLOW.join(',') + ',0)');
    ctx.fillStyle = g;
    ctx.fillRect(0, 0, W, H);

    for (var y = 0; y < rows; y++) {
      for (var x = 0; x < cols; x++) {
        var i = idx(x, y);
        if (grid[i] !== 1) continue;
        ctx.fillStyle = shade[i] ? 'rgb(' + C_GOLD.join(',') + ')' : 'rgb(' + C_GRAIN.join(',') + ')';
        ctx.fillRect(x * CELL, y * CELL, CELL, CELL);
      }
    }
  }

  function stillFrame() {
    for (var k = 0; k < 40; k++) { spawnStep(); update(); }
    draw(0.6);
  }

  function frame(now) {
    if (t0 < 0) t0 = now;
    var dt = Math.min(0.05, (now - (frame.prev || now)) / 1000);
    frame.prev = now;
    acc += dt;
    while (acc >= STEP) { spawnStep(); update(); acc -= STEP; }
    draw((now - t0) / 1000);
    raf = requestAnimationFrame(frame);
  }

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

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

// FallPileBasic — vanilla 판(run/318/demo/01-sand-fall-pile-basic/index.html) 의 React 포트.
// 기본 낙하 — 아래칸이 비었으면 스왑하는 규칙 하나. 대각선 없음.
// 상단 세 스포너(좌·중·우)에서 모래(grain/gold)가 흘러 세로 기둥이 쌓인다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./FallPileBasic.module.scss";

export type FallPileBasicProps = {
  duration?: string;
  easing?: string;
  color?: string;
  fall?: number;       // 낙하 칸수/프레임 — 변형 "낙하 속도" 축(1 기본 · 3 빠른 폭포)
  spawnP?: number;     // 스포너 칸별 매 틱 생성 확률
};

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

const FIELD_LABEL = "모래 낙하 셀 오토마타 데모";
const CELL = 4;
const STEP = 1 / 60;
const ZONE_W = 10;

// 시드 고정 PRNG — mulberry32
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 FallPileBasic({
  duration = "2s",
  easing = "cubic-bezier(.2, .8, .2, 1)",
  color = "#b9a0ff",
  fall = 1,
  spawnP = 0.3,
}: FallPileBasicProps) {
  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, cols: 0, rows: 0 }) as Box<{ w: number; h: number; cols: number; rows: number }>;
  const gridRef = useRef<Uint8Array | null>(null) as Box<Uint8Array | null>;
  const shadeRef = useRef<Uint8Array | null>(null) as Box<Uint8Array | null>;
  const zonesRef = useRef<number[]>([]) as Box<number[]>;
  const colRef = useRef<{ night: RGB; glow: RGB; grain: RGB; gold: RGB } | null>(null);
  const fallRef = useRef(fall) as Box<number>;
  const spawnRef = useRef(spawnP) as Box<number>;
  const randRef = useRef(makePRNG(0x318a01)) as Box<() => number>;
  const rafRef = useRef(0) as Box<number>;
  const [n, setN] = useState(String(fall));
  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 idx(x: number, y: number): number { return y * sizeRef.current.cols + x; }

  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();
    const cols = Math.max(1, Math.floor(r.width / CELL));
    const rows = Math.max(1, Math.floor(r.height / CELL));
    sizeRef.current = { w: r.width, h: r.height, cols, rows };
    cv.width = Math.round(r.width);
    cv.height = Math.round(r.height);
    gridRef.current = new Uint8Array(cols * rows);
    shadeRef.current = new Uint8Array(cols * rows);
    zonesRef.current = [
      Math.max(0, Math.round(cols * 0.06)),
      Math.max(0, Math.round(cols / 2 - ZONE_W / 2)),
      Math.max(0, Math.round(cols * 0.94 - ZONE_W)),
    ];
    ctxRef.current = ctx;
  }

  function spawnStep(): void {
    const { cols } = sizeRef.current;
    const grid = gridRef.current;
    const shade = shadeRef.current;
    if (!grid || !shade) return;
    const rand = randRef.current;
    const zones = zonesRef.current;
    for (let z = 0; z < zones.length; z++) {
      for (let k = 0; k < ZONE_W; k++) {
        const x = zones[z] + k;
        if (x < 0 || x >= cols) continue;
        if (rand() < spawnRef.current) {
          const i = idx(x, 0);
          if (grid[i] === 0) { grid[i] = 1; shade[i] = rand() < 0.5 ? 0 : 1; }
        }
      }
    }
  }

  function update(): void {
    const { cols, rows } = sizeRef.current;
    const grid = gridRef.current;
    const shade = shadeRef.current;
    if (!grid || !shade) return;
    for (let y = rows - 2; y >= 0; y--) {
      for (let x = 0; x < cols; x++) {
        const i = idx(x, y);
        if (grid[i] !== 1) continue;
        let destY = y;
        for (let s = 1; s <= fallRef.current; s++) {
          const yy = y + s;
          if (yy >= rows) break;
          if (grid[idx(x, yy)] === 0) destY = yy; else break;
        }
        if (destY !== y) {
          const di = idx(x, destY);
          grid[di] = 1; shade[di] = shade[i];
          grid[i] = 0;
        }
      }
    }
  }

  function draw(t: number): void {
    const ctx = ctxRef.current;
    const col = colRef.current;
    if (!ctx || !col) return;
    const { w: W, h: H, cols, rows } = sizeRef.current;
    const grid = gridRef.current;
    const shade = shadeRef.current;
    if (!grid || !shade) return;
    ctx.fillStyle = `rgb(${col.night.join(",")})`;
    ctx.fillRect(0, 0, W, H);

    // 느린 잔광 — 중심이 sin/cos 로 천천히 도는 radial gradient(안개)
    const gx = W * (0.5 + 0.36 * Math.sin(t * 0.17));
    const gy = H * (0.5 + 0.3 * Math.cos(t * 0.13));
    const gr = Math.max(W, H) * 0.7;
    const g = ctx.createRadialGradient(gx, gy, 0, gx, gy, gr);
    g.addColorStop(0, `rgba(${col.glow.join(",")},0.07)`);
    g.addColorStop(1, `rgba(${col.glow.join(",")},0)`);
    ctx.fillStyle = g;
    ctx.fillRect(0, 0, W, H);

    for (let y = 0; y < rows; y++) {
      for (let x = 0; x < cols; x++) {
        const i = idx(x, y);
        if (grid[i] !== 1) continue;
        ctx.fillStyle = shade[i] ? `rgb(${col.gold.join(",")})` : `rgb(${col.grain.join(",")})`;
        ctx.fillRect(x * CELL, y * CELL, CELL, CELL);
      }
    }
  }

  function stillFrame(): void {
    for (let k = 0; k < 40; k++) { spawnStep(); update(); }
    draw(0.6);
  }

  let t0 = -1;
  let prev = 0;
  let acc = 0;
  function frame(now: number): void {
    if (t0 < 0) t0 = now;
    const dt = Math.min(0.05, (now - (prev || now)) / 1000);
    prev = now;
    acc += dt;
    while (acc >= STEP) { spawnStep(); update(); acc -= STEP; }
    draw((now - t0) / 1000);
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    fallRef.current = fall;
    spawnRef.current = spawnP;
    colRef.current = {
      night: tokRGB(root, "--sand-night"),
      glow: tokRGB(root, "--sand-glow"),
      grain: tokRGB(root, "--sand-grain"),
      gold: tokRGB(root, "--sand-gold"),
    };
    randRef.current = makePRNG(0x318a01);
    fit();
    setN(String(fall));
    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
  }, [fall, spawnP]);

  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>위에서 쏟아진 모래가 아래칸이 비었을 때만 내려갑니다</span>
        </p>
        <div
          className={styles.field}
          ref={fieldRef}
          role="application"
          aria-label={FIELD_LABEL}
          tabIndex={0}
        >
          <canvas className={styles.cv} ref={cvRef}></canvas>
        </div>
        <div className={styles.bar}>
          <span className={styles.meta}><b className={styles.val}>{n}</b>칸 낙하 1칸/프레임</span>
          <span className={styles.metaDim}>canvas · fillRect · requestAnimationFrame</span>
        </div>
      </div>
    </main>
  );
}