08Tree in wind — a sway whose phase drifts per generation

<main class="stage">
<div class="ls is-demo" id="lsRoot">
  <p class="ls__hint">
    <span>Leave the string F→F[+F]F[-F] untouched, and just add a sine wave — growing with each generation's depth — to the turtle's turning angle at every step: the root barely moves while only the twig tips whip into wind</span>
  </p>
  <div class="ls__field" role="application" aria-label="Wind-sway tree lab" tabindex="0">
    <canvas class="ls__cv" id="lsCv"></canvas>
  </div>
  <div class="ls__bar">
    <span class="ls__meta">rule F→F[+F]F[-F] · wind strength <b id="lsWind">0</b></span>
    <span class="ls__meta ls__meta--dim">canvas · globalAlpha</span>
  </div>
</div>
</main>

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

// 바람 흔들림 나무(08). @keyframes 를 두지 않는다 —
// 움직임은 전부 캔버스 rAF 루프(고정 문자열 + 깊이비례 사인파 흔들림)가 만든다.
// 무대는 편 공통 숲 밤 이끼(01~07 과 동일 팔레트).

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

$ls-stage: #1a2116;
@include stage($ls-stage);

$ls-ink:  #12160e;
$ls-bark: #d8c4a0;
$ls-leaf: #bfe3c8;
$ls-mist: #dfe6d6;

.ls {
  --ls-ink:  #{$ls-ink};
  --ls-bark: #{$ls-bark};
  --ls-leaf: #{$ls-leaf};
  --ls-mist: #{$ls-mist};

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

.ls__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: $ls-mist;
}

.ls__field {
  position: relative; height: 180px;
  border-radius: $r-card; overflow: hidden;
  background: $ls-ink;
  box-shadow: inset 0 0 0 1px rgba($ls-mist, .18);
}
.ls__field:focus-visible { outline: 2px solid $subject-mint; outline-offset: 2px; }

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

.ls__bar { display: flex; align-items: baseline; justify-content: space-between; gap: $sp-2; }
.ls__meta { font-size: 10px; font-weight: 500; color: rgba($ls-mist, .72); }
.ls__meta--dim { font-size: 10px; }
.ls__meta b { font-weight: 700; color: $ls-mist; }

@media (max-width: 340px) {
  .ls { gap: $sp-1; }
  .ls__field { height: 100px; }
  .ls__meta--dim { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  .ls.is-still .ls__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: #1a2116;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.ls {
  --ls-ink: #12160e;
  --ls-bark: #d8c4a0;
  --ls-leaf: #bfe3c8;
  --ls-mist: #dfe6d6;
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 424px;
}

.ls__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: #dfe6d6;
}

.ls__field {
  position: relative;
  height: 180px;
  border-radius: 16px;
  overflow: hidden;
  background: #12160e;
  box-shadow: inset 0 0 0 1px rgba(223, 230, 214, 0.18);
}

.ls__field:focus-visible {
  outline: 2px solid #4cd4a6;
  outline-offset: 2px;
}

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

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

.ls__meta {
  font-size: 10px;
  font-weight: 500;
  color: rgba(223, 230, 214, 0.72);
}

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

.ls__meta b {
  font-weight: 700;
  color: #dfe6d6;
}

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

// 바람 흔들림 Trees(08) — 문자열 자체(F→F[+F]F[-F])는 고정. 거북이 걸을 때 방향각에
// "깊이(gen)에 비례하는 사인파"를 더해서, 같은 문자열이 매 프레임 다른 모양으로 보인다.
// 뿌리는 위상이 0 이라 거의 안 흔들리고, 잎 끝은 깊이가 깊어 크게 흔들린다(자연스러운 바람 감쇠).
(function () {
  // ── 변형 상수 블록 ──
  var ANGLE    = 24;
  var MAXGEN   = 5;
  var WIND_AMP = 30;   // 잎 끝 최대 흔들림(도)
  var WIND_HZ  = 1.6;  // 바람 진동수(회/루프)
  var CYCLE    = 2.0;
  // ─────────────────

  var root = document.getElementById('lsRoot');
  var field = document.getElementById('lsCv').parentElement;
  var cv = document.getElementById('lsCv');
  var windEl = document.getElementById('lsWind');

  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_BARK = tokRGB('--ls-bark');
  var C_LEAF = tokRGB('--ls-leaf');
  var C_INK  = tokRGB('--ls-ink');

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var raf = 0, t0 = -1;
  var W = 0, H = 0;

  function fit() {
    var r = field.getBoundingClientRect();
    W = Math.round(r.width); H = Math.round(r.height);
    cv.width = W; cv.height = H;
  }

  var RULE = { 'F': 'F[+F]F[-F]' };
  function expand(axiom, gen) {
    var s = axiom;
    for (var g = 0; g < gen; g++) {
      var out = '';
      for (var i = 0; i < s.length; i++) {
        var ch = s.charAt(i);
        out += RULE[ch] !== undefined ? RULE[ch] : ch;
      }
      s = out;
    }
    return s;
  }
  var STR = expand('F', MAXGEN);

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

  // 거북 렌더러 — 매 F 걸음마다 깊이 비례 사인파를 각도에 더해(바람) 그린다.
  function drawWind(ctx, str, x0, y0, stepLen, ox, oy, sc, windPhase, windAmp, windGust) {
    var x = x0, y = y0, a = -Math.PI / 2;
    var stack = [];
    var depth = 0, maxDepth = MAXGEN;
    for (var i = 0; i < str.length; i++) {
      var ch = str.charAt(i);
      if (ch === 'F') {
        var depthT = depth / maxDepth;
        // gen 깊이에 비례(선형)해 커지는 사인파 — 잔가지뿐 아니라 중간 가지도 함께 휘어야
        // 프레임마다 바뀌는 픽셀 면적이 뿌리 근처 몇 개 선분에만 갇히지 않는다.
        var sway = windAmp * depthT * Math.sin(windPhase + depth * 0.8) * Math.PI / 180;
        a += sway;
        var segLen = stepLen * Math.pow(0.78, depth);
        var nx = x + Math.cos(a) * segLen;
        var ny = y + Math.sin(a) * segLen;
        var cr = C_BARK[0] + (C_LEAF[0] - C_BARK[0]) * depthT;
        var cg = C_BARK[1] + (C_LEAF[1] - C_BARK[1]) * depthT;
        var cb = C_BARK[2] + (C_LEAF[2] - C_BARK[2]) * depthT;
        ctx.globalAlpha = 0.6 + 0.4 * depthT;
        ctx.strokeStyle = 'rgb(' + (cr | 0) + ',' + (cg | 0) + ',' + (cb | 0) + ')';
        ctx.lineWidth = Math.max(1.5, 5.2 * Math.pow(0.66, depth));
        ctx.beginPath();
        ctx.moveTo(ox + x * sc, oy + y * sc);
        ctx.lineTo(ox + nx * sc, oy + ny * sc);
        ctx.stroke();
        if (depth >= maxDepth - 1) {
          // 잎 끝 무리 — 반경 자체도 돌풍 세기를 따라 커지고 작아져 정지 상태로 겹치지 않는다.
          var glowR = 7 + 5 * windGust;
          var coreR = 3 + 2 * windGust;
          ctx.fillStyle = 'rgb(' + (cr | 0) + ',' + (cg | 0) + ',' + (cb | 0) + ')';
          ctx.globalAlpha = 0.2;
          ctx.beginPath();
          ctx.arc(ox + nx * sc, oy + ny * sc, glowR, 0, Math.PI * 2);
          ctx.fill();
          ctx.globalAlpha = 0.62;
          ctx.beginPath();
          ctx.arc(ox + nx * sc, oy + ny * sc, coreR, 0, Math.PI * 2);
          ctx.fill();
        }
        x = nx; y = ny;
      } else if (ch === '[') {
        stack.push({ x: x, y: y, a: a, d: depth });
        depth++;
      } else if (ch === ']') {
        var st = stack.pop();
        if (st) { x = st.x; y = st.y; a = st.a; depth = st.d; }
      } else if (ch === '+') {
        a += ANGLE * Math.PI / 180;
      } else if (ch === '-') {
        a -= ANGLE * Math.PI / 180;
      }
    }
    ctx.globalAlpha = 1;
  }

  function render(loop) {
    var ctx = cv.getContext('2d');
    ctx.fillStyle = rgb(C_INK, 1);
    ctx.fillRect(0, 0, W, H);

    var sc = Math.min(W, H) * 0.24;
    var ox = W * 0.5, oy = H * 0.95;
    var windPhase = loop * Math.PI * 2 * WIND_HZ;
    var windGust = 0.55 + 0.45 * Math.sin(loop * Math.PI * 2 * 0.5);   // 돌풍 세기 자체도 서서히 오르내린다
    var windAmp = WIND_AMP * windGust;

    if (windEl) windEl.textContent = String(Math.round(windGust * 10));

    drawWind(ctx, STR, 0, 0, 1, ox, oy, sc, windPhase, windAmp, windGust);
  }

  function frame(now) {
    if (t0 < 0) t0 = now;
    var loop = (((now - t0) / 1000) % CYCLE) / CYCLE;
    render(loop);
    raf = requestAnimationFrame(frame);
  }

  window.addEventListener('resize', function () {
    fit();
    render(0.3);
  });

  fit();
  if (reduce) {
    render(0.3);
    root.classList.add('is-still');
  } else {
    raf = requestAnimationFrame(frame);
  }
})();

// LsysTreeWindSway — vanilla 판(run/328/demo/08-lsys-tree-wind-sway/index.html) 의 React 포트.
// F 축 나무(F→F[+F]F[-F]F, 24도)를 완성해 둔 채 각 마디의 흔들림 위상을 깊이(depth)에 비례해 지연시켜
// 바람이 뿌리에서 가지 끝으로 퍼져 나가는 것처럼 보이게 한다. 세기는 sin(t·WIND_HZ) 로 계산.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./LsysTreeWindSway.module.scss";

export type LsysTreeWindSwayProps = {
  duration?: string;
  easing?: string;
  color?: string;
  angle?: number;
  maxGen?: number;
  windAmp?: number;
  windHz?: number;
  cycle?: number;
};

const ANGLE = 24;
const MAXGEN = 5;
const WIND_AMP = 30;
const WIND_HZ = 1.6;
const CYCLE = 2.0;

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

const HINT_TEXT = "F→F[+F]F[-F]F 로 완성해 둔 나무에 깊이(depth)마다 위상을 지연시킨 sin(t·1.6Hz) 바람을 더하면, 뿌리는 그대로인데 가지 끝만 크게 흔들리는 실제 나무의 바람 반응을 흉내 낼 수 있습니다";
const META_LEFT_PREFIX = "규칙 F→F[+F]F[-F]F · 바람 ";
const META_RIGHT = "canvas · 위상 지연 · requestAnimationFrame";
const FIELD_LABEL = "바람 흔들림 나무 실험판";

const RULE: Record<string, string> = { F: "F[+F]F[-F]F" };
function expand(axiom: string, gen: number): string {
  let s = axiom;
  for (let g = 0; g < gen; g++) {
    let out = "";
    for (let i = 0; i < s.length; i++) {
      const ch = s.charAt(i);
      out += RULE[ch] !== undefined ? RULE[ch] : ch;
    }
    s = out;
  }
  return s;
}

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

export default function LsysTreeWindSway({
  duration = "2s",
  easing = "ease-spring",
  color = "#bfe3c8",
  angle = ANGLE,
  maxGen = MAXGEN,
  windAmp = WIND_AMP,
  windHz = WIND_HZ,
  cycle = CYCLE
}: LsysTreeWindSwayProps) {
  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<{ bark: RGB; leaf: RGB; ink: RGB } | null>(null);
  const strRef = useRef("") as Box<string>;
  const wRef = useRef(0) as Box<number>;
  const hRef = useRef(0) as Box<number>;
  const rafRef = useRef(0) as Box<number>;
  const [still, setStill] = useState(false);
  const [wind, setWind] = useState(0);
  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 fit(): void {
    const field = fieldRef.current;
    const cv = cvRef.current;
    if (!field || !cv) return;
    const r = field.getBoundingClientRect();
    wRef.current = Math.round(r.width);
    hRef.current = Math.round(r.height);
    cv.width = wRef.current;
    cv.height = hRef.current;
  }

  function drawWind(ctx: CanvasRenderingContext2D, str: string, ox: number, oy: number, sc: number, stepLen: number, t: number, windStrength: number): void {
    const col = colRef.current;
    if (!col) return;
    let x = 0, y = 0, a = -Math.PI / 2, d = 0;
    const stack: Stack[] = [];
    for (let i = 0; i < str.length; i++) {
      const ch = str.charAt(i);
      if (ch === "F") {
        const phase = t * windHz * Math.PI * 2 - d * 0.35;
        const sway = Math.sin(phase) * (windAmp * Math.PI / 180) * windStrength * Math.min(1, d / 3);
        const aa = a + sway;
        const nx = x + Math.cos(aa) * stepLen;
        const ny = y + Math.sin(aa) * stepLen;
        const tcol = Math.min(1, d / 6);
        const cr = col.bark[0] + (col.leaf[0] - col.bark[0]) * tcol;
        const cg = col.bark[1] + (col.leaf[1] - col.bark[1]) * tcol;
        const cb = col.bark[2] + (col.leaf[2] - col.bark[2]) * tcol;
        ctx.strokeStyle = "rgb(" + (cr | 0) + "," + (cg | 0) + "," + (cb | 0) + ")";
        ctx.lineWidth = Math.max(0.9, 3 * Math.pow(0.74, d));
        ctx.beginPath();
        ctx.moveTo(ox + x * sc, oy + y * sc);
        ctx.lineTo(ox + nx * sc, oy + ny * sc);
        ctx.stroke();
        if (d >= 4) {
          ctx.beginPath();
          ctx.arc(ox + nx * sc, oy + ny * sc, 2.6, 0, Math.PI * 2);
          ctx.fillStyle = "rgb(" + (cr | 0) + "," + (cg | 0) + "," + (cb | 0) + ")";
          ctx.fill();
        }
        x = nx; y = ny; a = aa;
      } else if (ch === "+") {
        a += angle * Math.PI / 180;
      } else if (ch === "-") {
        a -= angle * Math.PI / 180;
      } else if (ch === "[") {
        stack.push({ x, y, a, d });
        d++;
      } else if (ch === "]") {
        const st = stack.pop();
        if (st) { x = st.x; y = st.y; a = st.a; d = st.d; }
      }
    }
  }

  function draw(loop: number): void {
    const ctx = ctxRef.current;
    const col = colRef.current;
    const str = strRef.current;
    const W = wRef.current, H = hRef.current;
    if (!ctx || !col || !str) return;
    ctx.fillStyle = rgba(col.ink, 1);
    ctx.fillRect(0, 0, W, H);

    const sc = Math.min(W, H) * 0.5;
    const ox = W * 0.5, oy = H * 0.95;
    const t = loop * cycle;

    const windStrength = 0.35 + 0.65 * Math.abs(Math.sin(t * windHz * Math.PI * 0.5));
    setWind(Math.round(windStrength * 100));

    drawWind(ctx, str, ox, oy, sc, sc / Math.pow(1.6, maxGen) * 0.5, t, windStrength);
  }

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

  useEffect(() => {
    const root = rootRef.current;
    const cv = cvRef.current;
    if (!root || !cv) return;
    colRef.current = {
      bark: tokRGB(root, "--ls-bark"),
      leaf: tokRGB(root, "--ls-leaf"),
      ink: tokRGB(root, "--ls-ink")
    };
    strRef.current = expand("F", maxGen);
    ctxRef.current = cv.getContext("2d");
    fit();
    const reduce = reduced();
    function onResize(): void {
      fit();
      draw(0.3);
    }
    window.addEventListener("resize", onResize);
    if (reduce) {
      draw(0.3);
      setStill(true);
    } else {
      t0 = -1;
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [angle, maxGen, windAmp, windHz, cycle]);

  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>{HINT_TEXT}</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}>{META_LEFT_PREFIX}<b>{wind}</b>%</span>
          <span className={`${styles.meta} ${styles.metaDim}`}>{META_RIGHT}</span>
        </div>
      </div>
    </main>
  );
}