06ドラゴン曲線 — 折り紙の規則が育てる紙の恐竜

<main class="stage">
<div class="ls is-demo" id="lsRoot">
  <p class="ls__hint">
    <span>FX の一行に X→X+YF+、Y→-FX-Y の二つの規則を繰り返し適用すると、紙を半分に折り続けた跡のように重ならずぎっしり折り重なるドラゴン曲線が育ちます</span>
  </p>
  <div class="ls__field" role="application" aria-label="ドラゴン曲線ラボ" tabindex="0">
    <canvas class="ls__cv" id="lsCv"></canvas>
  </div>
  <div class="ls__bar">
    <span class="ls__meta">規則 X→X+YF+ · 角度90° · 世代 <b id="lsGen">0</b></span>
    <span class="ls__meta ls__meta--dim">canvas · 文字列書き換え · requestAnimationFrame</span>
  </div>
</div>
</main>

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

// 드래곤 커브(06). @keyframes 를 두지 않는다 —
// 움직임은 전부 캔버스 rAF 루프(문자 재쓰기 세대 크로스페이드 + 도는 빛)가 만든다.
// 무대는 편 공통 숲 밤 이끼(01~05 와 동일 팔레트).

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

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

$ls-ink:   #12160e;
$ls-bark2: #e6d8bc;
$ls-leaf:  #bfe3c8;
$ls-mist:  #dfe6d6;

.ls {
  --ls-ink:   #{$ls-ink};
  --ls-bark2: #{$ls-bark2};
  --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-bark2: #e6d8bc;
  --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;
  }
}

// 드래곤 커브(06) — 종이 접기를 문자로 옮긴 L-시스템(FX 축, X→X+YF+, Y→-FX-Y, 90도).
// 세대가 늘수록 접힌 자국(F 전진, +/- 90도 회전)이 촘촘해지며 자기 자신과 닿되 겹치지 않는다.
// 움직임 = 世代 크로스페이드 성장(0→11) + 완성 뒤 곡선을 따라 도는 빛 한 점.
(function () {
  // ── 변형 상수 블록 ──
  var ANGLE  = 90;
  var MAXGEN = 11;
  var CYCLE  = 2.0;
  // ─────────────────

  var root = document.getElementById('lsRoot');
  var field = document.getElementById('lsCv').parentElement;
  var cv = document.getElementById('lsCv');
  var genEl = document.getElementById('lsGen');

  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_LINE = tokRGB('--ls-bark2');
  var C_GLOW = 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 = { 'X': 'X+YF+', 'Y': '-FX-Y' };
  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;
  }

  // 거북 해석 — F 만 전진(점 추가), X·Y 는 자리표시자(전진 없음), +/- 는 90도 회전.
  function turtlePath(str, step) {
    var x = 0, y = 0, a = 0;
    var pts = [{ x: x, y: y }];
    for (var i = 0; i < str.length; i++) {
      var ch = str.charAt(i);
      if (ch === 'F') {
        x += Math.cos(a) * step;
        y += Math.sin(a) * step;
        pts.push({ x: x, y: y });
      } else if (ch === '+') {
        a += ANGLE * Math.PI / 180;
      } else if (ch === '-') {
        a -= ANGLE * Math.PI / 180;
      }
    }
    return pts;
  }

  var AXIOM = 'FX';
  var POLY = [];
  (function precompute() {
    var strs = [];
    for (var g = 0; g <= MAXGEN; g++) strs.push(expand(AXIOM, g));
    var raw = [];
    for (var g2 = 0; g2 <= MAXGEN; g2++) raw.push(turtlePath(strs[g2], 1));
    var last = raw[MAXGEN];
    var minX = Infinity, maxX = -Infinity, minY = Infinity, maxY = -Infinity;
    for (var i = 0; i < last.length; i++) {
      minX = Math.min(minX, last[i].x); maxX = Math.max(maxX, last[i].x);
      minY = Math.min(minY, last[i].y); maxY = Math.max(maxY, last[i].y);
    }
    var span = Math.max(maxX - minX, maxY - minY) || 1;
    for (var g3 = 0; g3 <= MAXGEN; g3++) {
      var norm = [];
      for (var j = 0; j < raw[g3].length; j++) {
        norm.push({ x: (raw[g3][j].x - minX) / span, y: (raw[g3][j].y - minY) / span });
      }
      POLY.push(norm);
    }
  })();

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

  function drawPath(ctx, pts, ox, oy, sc, col, alpha, lw) {
    if (pts.length < 2) return;
    ctx.strokeStyle = rgb(col, alpha);
    ctx.lineWidth = lw;
    ctx.beginPath();
    ctx.moveTo(ox + pts[0].x * sc, oy + pts[0].y * sc);
    for (var i = 1; i < pts.length; i++) ctx.lineTo(ox + pts[i].x * sc, oy + pts[i].y * sc);
    ctx.stroke();
  }

  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) * 0.8;
    var ox = (W - sc) / 2, oy = (H - sc) / 2;

    var grPhase = Math.min(loop / 0.7, 1);
    var genF = grPhase * MAXGEN;
    var gA = Math.min(MAXGEN, Math.floor(genF));
    var gB = Math.min(MAXGEN, gA + 1);
    var f = genF - gA;

    drawPath(ctx, POLY[gA], ox, oy, sc, C_LINE, 1, 2.1);
    if (f > 0 && gB !== gA) drawPath(ctx, POLY[gB], ox, oy, sc, C_GLOW, f, 1.9);

    if (genEl) genEl.textContent = String(gA);

    if (loop >= 0.7) {
      var t = (loop - 0.7) / 0.3;
      var pts = POLY[MAXGEN];
      var idxF = t * (pts.length - 1);
      var i0 = Math.floor(idxF) % (pts.length - 1);
      var lf = idxF - Math.floor(idxF);
      var p0 = pts[i0], p1 = pts[i0 + 1] || pts[pts.length - 1];
      var lx = ox + (p0.x + (p1.x - p0.x) * lf) * sc;
      var ly = oy + (p0.y + (p1.y - p0.y) * lf) * sc;
      ctx.fillStyle = rgb(C_GLOW, 0.9);
      ctx.beginPath();
      ctx.arc(lx, ly, 2.6, 0, Math.PI * 2);
      ctx.fill();
    }
  }

  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(reduce ? 0.85 : 0.8);
  });

  fit();
  if (reduce) {
    render(0.85);
    root.classList.add('is-still');
  } else {
    raf = requestAnimationFrame(frame);
  }
})();

// LsysDragonCurve — vanilla 판(run/328/demo/06-lsys-dragon-curve/index.html) 의 React 포트.
// 종이 접기를 문자로 옮긴 L-시스템(FX 축, X→X+YF+, Y→-FX-Y, 90도).
// 세대가 늘수록 접힌 자국(F 전진, +/- 90도 회전)이 촘촘해지며 자기 자신과 닿되 겹치지 않는다.
// 움직임 = 세대 크로스페이드 성장(0→11) + 완성 뒤 곡선을 따라 도는 빛 한 점.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./LsysDragonCurve.module.scss";

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

const ANGLE = 90;
const MAXGEN = 11;
const CYCLE = 2.0;

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

const HINT_TEXT = "FX 한 줄에서 X→X+YF+, Y→-FX-Y 두 규칙을 되풀이 적용하면 종이를 반으로 접었다 편 자국처럼 겹치지 않고 빼곡히 접히는 용(드래곤) 곡선이 자랍니다";
const META_LEFT_PREFIX = "규칙 X→X+YF+ · 각도 90° · 세대 ";
const META_RIGHT = "canvas · 문자 재쓰기 · requestAnimationFrame";
const FIELD_LABEL = "드래곤 커브 실험판";

const RULE: Record<string, string> = { X: "X+YF+", Y: "-FX-Y" };
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 turtlePath(str: string, step: number, angle: number): XY[] {
  let x = 0, y = 0, a = 0;
  const pts: XY[] = [{ x, y }];
  for (let i = 0; i < str.length; i++) {
    const ch = str.charAt(i);
    if (ch === "F") {
      x += Math.cos(a) * step;
      y += Math.sin(a) * step;
      pts.push({ x, y });
    } else if (ch === "+") {
      a += angle * Math.PI / 180;
    } else if (ch === "-") {
      a -= angle * Math.PI / 180;
    }
  }
  return pts;
}

const AXIOM = "FX";
function buildPoly(angle: number, maxGen: number): XY[][] {
  const strs: string[] = [];
  for (let g = 0; g <= maxGen; g++) strs.push(expand(AXIOM, g));
  const raw: XY[][] = [];
  for (let g2 = 0; g2 <= maxGen; g2++) raw.push(turtlePath(strs[g2], 1, angle));
  const last = raw[maxGen];
  let minX = Infinity, maxX = -Infinity, minY = Infinity, maxY = -Infinity;
  for (let i = 0; i < last.length; i++) {
    minX = Math.min(minX, last[i].x); maxX = Math.max(maxX, last[i].x);
    minY = Math.min(minY, last[i].y); maxY = Math.max(maxY, last[i].y);
  }
  const span = Math.max(maxX - minX, maxY - minY) || 1;
  const poly: XY[][] = [];
  for (let g3 = 0; g3 <= maxGen; g3++) {
    const norm: XY[] = [];
    for (let j = 0; j < raw[g3].length; j++) {
      norm.push({ x: (raw[g3][j].x - minX) / span, y: (raw[g3][j].y - minY) / span });
    }
    poly.push(norm);
  }
  return poly;
}

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

export default function LsysDragonCurve({
  duration = "2s",
  easing = "ease-spring",
  color = "#bfe3c8",
  angle = ANGLE,
  maxGen = MAXGEN,
  cycle = CYCLE
}: LsysDragonCurveProps) {
  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<{ line: RGB; glow: RGB; ink: RGB } | null>(null);
  const polyRef = useRef<XY[][]>([]) as Box<XY[][]>;
  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 [gen, setGen] = 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 drawPath(ctx: CanvasRenderingContext2D, pts: XY[], ox: number, oy: number, sc: number, col: RGB, alpha: number, lw: number): void {
    if (pts.length < 2) return;
    ctx.strokeStyle = rgba(col, alpha);
    ctx.lineWidth = lw;
    ctx.beginPath();
    ctx.moveTo(ox + pts[0].x * sc, oy + pts[0].y * sc);
    for (let i = 1; i < pts.length; i++) ctx.lineTo(ox + pts[i].x * sc, oy + pts[i].y * sc);
    ctx.stroke();
  }

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

    const sc = Math.min(W, H) * 0.8;
    const ox = (W - sc) / 2, oy = (H - sc) / 2;

    const grPhase = Math.min(loop / 0.7, 1);
    const genF = grPhase * maxGen;
    const gA = Math.min(maxGen, Math.floor(genF));
    const gB = Math.min(maxGen, gA + 1);
    const f = genF - gA;

    drawPath(ctx, POLY[gA], ox, oy, sc, col.line, 1, 2.1);
    if (f > 0 && gB !== gA) drawPath(ctx, POLY[gB], ox, oy, sc, col.glow, f, 1.9);

    setGen(gA);

    if (loop >= 0.7) {
      const t = (loop - 0.7) / 0.3;
      const pts = POLY[maxGen];
      const idxF = t * (pts.length - 1);
      const i0 = Math.floor(idxF) % (pts.length - 1);
      const lf = idxF - Math.floor(idxF);
      const p0 = pts[i0], p1 = pts[i0 + 1] || pts[pts.length - 1];
      const lx = ox + (p0.x + (p1.x - p0.x) * lf) * sc;
      const ly = oy + (p0.y + (p1.y - p0.y) * lf) * sc;
      ctx.fillStyle = rgba(col.glow, 0.9);
      ctx.beginPath();
      ctx.arc(lx, ly, 2.6, 0, Math.PI * 2);
      ctx.fill();
    }
  }

  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 = {
      line: tokRGB(root, "--ls-bark2"),
      glow: tokRGB(root, "--ls-leaf"),
      ink: tokRGB(root, "--ls-ink")
    };
    polyRef.current = buildPoly(angle, maxGen);
    ctxRef.current = cv.getContext("2d");
    fit();
    const reduce = reduced();
    function onResize(): void {
      fit();
      draw(0.8);
    }
    window.addEventListener("resize", onResize);
    if (reduce) {
      draw(0.85);
      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, 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>{gen}</b></span>
          <span className={`${styles.meta} ${styles.metaDim}`}>{META_RIGHT}</span>
        </div>
      </div>
    </main>
  );
}