04Collision avoidance — nodes push apart by their own radius, never overlap

<main class="stage">
<div class="gd is-demo" id="gdRoot" role="img" aria-label="Demo where nodes push apart by their own radius to avoid overlap" tabindex="0">
  <canvas class="gd__cv" id="gdCv"></canvas>
  <p class="gd__hint">
    <span class="gd__title">Collision avoidance</span>
    <span class="gd__desc">The moment two circles get closer than their combined radius, they push apart instantly</span>
  </p>
  <div class="gd__bar">
    <span class="gd__meta">22 nodes · mixed sizes · rAF</span>
    <span class="gd__meta gd__meta--dim">arc · Math.hypot · beginPath</span>
  </div>
</div>
</main>

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

// 충돌 방지(04) — 무대 종이. 힘 계산 뒤 위치 보정 패스까지 전부 rAF 캔버스가 만든다.

$gd-stage: #f1ecdf;
@include stage($gd-stage);

$gd-panel: #e4dcc8;   // 캔버스 바닥 — 무대보다 어두운 모래
$gd-text:  #3c3324;   // 라벨 글자 — 짙은 카키 브라운
$gd-node:  #7d8f6a;   // 노드 — 올리브 세이지
$gd-ring:  #3c3324;   // 노드 테두리 — 짙은 카키(경계 강조)

$duration: $dur-loop;
$easing: $ease-out;
$color: $gd-node;

.gd {
  --gd-panel: #{$gd-panel};
  --gd-node:  #{$gd-node};
  --gd-ring:  #{$gd-ring};

  position: relative;
  display: flex; flex-direction: column;
  width: 100%; height: 100%; min-height: 164px;
  overflow: hidden;
}

.gd__cv { position: absolute; inset: 0; display: block; width: 100%; height: 100%; }

.gd__hint {
  position: relative; z-index: 1;
  display: flex; flex-direction: column; gap: 0; margin: 0;
  padding: $sp-2 $sp-3 0;
  font-weight: 700; font-size: clamp(10px, 2.8vw, 12px); line-height: 1.35;
  color: $gd-text;
}
.gd__title { text-shadow: 0 1px 6px rgba($gd-panel, .9); }
.gd__desc {
  margin-top: $sp-1;
  font-weight: 500; font-size: clamp(9px, 2.4vw, 10px); line-height: 1.4;
  color: rgba($gd-text, .78);
  text-shadow: 0 1px 6px rgba($gd-panel, .9);
}

.gd__bar {
  position: relative; z-index: 1;
  margin-top: auto;
  display: flex; align-items: baseline; justify-content: space-between; gap: $sp-2;
  padding: 0 $sp-3 $sp-2;
}
.gd__meta {
  font-size: 10px; font-weight: 500; color: rgba($gd-text, .8);
  background: rgba($gd-panel, .82);
  border-radius: $r-xs;
  padding: 4px $sp-1;
}

.gd:focus-visible { outline: 2px solid $gd-node; outline-offset: -2px; }

@media (max-width: 340px) {
  .gd__meta--dim { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  .gd.is-still { 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: #f1ecdf;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.gd {
  --gd-panel: #e4dcc8;
  --gd-node: #7d8f6a;
  --gd-ring: #3c3324;
  position: relative;
  display: flex;
  flex-direction: column;
  width: 100%;
  height: 100%;
  min-height: 164px;
  overflow: hidden;
}

.gd__cv {
  position: absolute;
  inset: 0;
  display: block;
  width: 100%;
  height: 100%;
}

.gd__hint {
  position: relative;
  z-index: 1;
  display: flex;
  flex-direction: column;
  gap: 0;
  margin: 0;
  padding: 8px 12px 0;
  font-weight: 700;
  font-size: clamp(10px, 2.8vw, 12px);
  line-height: 1.35;
  color: #3c3324;
}

.gd__title {
  text-shadow: 0 1px 6px rgba(228, 220, 200, 0.9);
}

.gd__desc {
  margin-top: 4px;
  font-weight: 500;
  font-size: clamp(9px, 2.4vw, 10px);
  line-height: 1.4;
  color: rgba(60, 51, 36, 0.78);
  text-shadow: 0 1px 6px rgba(228, 220, 200, 0.9);
}

.gd__bar {
  position: relative;
  z-index: 1;
  margin-top: auto;
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
  padding: 0 12px 8px;
}

.gd__meta {
  font-size: 10px;
  font-weight: 500;
  color: rgba(60, 51, 36, 0.8);
  background: rgba(228, 220, 200, 0.82);
  border-radius: 4px;
  padding: 4px 4px;
}

.gd:focus-visible {
  outline: 2px solid #7d8f6a;
  outline-offset: -2px;
}

@media (max-width: 340px) {
  .gd__meta--dim {
    display: none;
  }
}
@media (prefers-reduced-motion: reduce) {
  .gd.is-still {
    cursor: default !important;
  }
}

// Collision avoidance(04) — 척력만으로는 순간적으로 겹칠 수 있다. 매 프레임 위치를 적분한
// 뒤, 반지름 합보다 중심 거리가 가까운 쌍을 찾아 그 자리에서 즉시 밀어내는
// 보정 패스(하드 충돌 해소)를 한 겹 더 끼운다 — 힘이 아니라 위치 자체를 고친다.
(function () {
  // ── 변형 상수 블록 ──
  var N = 22;
  var REPEL = 420;
  var SPEED = 78;      // 자유 유영 속도(무작위 방향 힘의 크기)
  // ────────────────────────
  var DAMP = 0.965;
  var CENTER_K = 0.0016;
  var OMEGA = 0.6;
  var RMIN = 6, RMAX = 15;

  var root = document.getElementById('gdRoot');
  var cvEl = document.getElementById('gdCv');
  if (!root || !cvEl) return;

  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_PANEL = tokRGB('--gd-panel');
  var C_NODE  = tokRGB('--gd-node');
  var C_RING  = tokRGB('--gd-ring');

  var ctx = cvEl.getContext('2d');
  var W = 0, H = 0, dpr = Math.min(window.devicePixelRatio || 1, 2);

  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(0x327004);

  var px, py, vx, vy, rad;

  function buildGraph() {
    px = new Float32Array(N); py = new Float32Array(N);
    vx = new Float32Array(N); vy = new Float32Array(N);
    rad = new Float32Array(N);
    for (var i = 0; i < N; i++) {
      px[i] = rand() * W; py[i] = rand() * H;
      rad[i] = RMIN + rand() * (RMAX - RMIN);
    }
  }

  function fit() {
    var r = root.getBoundingClientRect();
    W = Math.round(r.width); H = Math.round(r.height);
    cvEl.width = Math.round(W * dpr); cvEl.height = Math.round(H * dpr);
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    buildGraph();
  }

  function step(dt) {
    var fx = new Float32Array(N), fy = new Float32Array(N);
    for (var i = 0; i < N; i++) {
      for (var j = i + 1; j < N; j++) {
        var dx = px[j] - px[i], dy = py[j] - py[i];
        var d = Math.hypot(dx, dy) || 0.001;
        var d2 = d * d; if (d2 < 4) d2 = 4;
        var f = REPEL / d2;
        var ux = dx / d, uy = dy / d;
        fx[i] -= ux * f; fy[i] -= uy * f;
        fx[j] += ux * f; fy[j] += uy * f;
      }
    }
    var cx = W / 2, cy = H / 2;
    for (var n = 0; n < N; n++) {
      fx[n] += (cx - px[n]) * CENTER_K;
      fy[n] += (cy - py[n]) * CENTER_K;
      fx[n] += (rand() - 0.5) * SPEED;
      fy[n] += (rand() - 0.5) * SPEED;
      vx[n] = (vx[n] + fx[n] * dt) * DAMP;
      vy[n] = (vy[n] + fy[n] * dt) * DAMP;
      px[n] += vx[n] * dt; py[n] += vy[n] * dt;
    }
    // 하드 충돌 해소 — 반지름 합보다 가까운 쌍을 그 자리에서 절반씩 밀어낸다
    for (var a = 0; a < N; a++) {
      for (var b = a + 1; b < N; b++) {
        var ddx = px[b] - px[a], ddy = py[b] - py[a];
        var dist = Math.hypot(ddx, ddy) || 0.001;
        var minDist = rad[a] + rad[b];
        if (dist < minDist) {
          var push = (minDist - dist) / 2;
          var nx = ddx / dist, ny = ddy / dist;
          px[a] -= nx * push; py[a] -= ny * push;
          px[b] += nx * push; py[b] += ny * push;
        }
      }
    }
  }

  function rotateAll(dtheta) {
    var cx = W / 2, cy = H / 2, cs = Math.cos(dtheta), sn = Math.sin(dtheta);
    for (var i = 0; i < N; i++) {
      var rx = px[i] - cx, ry = py[i] - cy;
      px[i] = cx + rx * cs - ry * sn;
      py[i] = cy + rx * sn + ry * cs;
    }
  }

  function draw() {
    ctx.clearRect(0, 0, W, H);
    ctx.fillStyle = 'rgb(' + C_PANEL.join(',') + ')';
    ctx.fillRect(0, 0, W, H);
    for (var i = 0; i < N; i++) {
      ctx.beginPath();
      ctx.fillStyle = 'rgb(' + C_NODE.join(',') + ')';
      ctx.arc(px[i], py[i], rad[i], 0, Math.PI * 2);
      ctx.fill();
      ctx.lineWidth = 1;
      ctx.strokeStyle = 'rgba(' + C_RING.join(',') + ',0.7)';
      ctx.stroke();
    }
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var t0 = -1, last = -1;
  function frame(now) {
    if (t0 < 0) { t0 = now; last = now; }
    var dt = Math.min((now - last) / 1000, 0.05); last = now;
    step(dt);
    rotateAll(OMEGA * dt);
    draw();
    requestAnimationFrame(frame);
  }
  function settle() {
    for (var s = 0; s < 260; s++) step(1 / 60);
    draw();
  }
  window.addEventListener('resize', function () {
    fit();
    if (reduce) settle();
  });

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

// GraphForceCollisionAvoid — vanilla 판(run/327/demo/04-graph-force-collision-avoid/index.html) 의 React 포트.
// 척력만으로는 순간적으로 겹칠 수 있다. 매 프레임 위치를 적분한 뒤, 반지름 합보다 중심 거리가
// 가까운 쌍을 찾아 그 자리에서 즉시 밀어내는 보정 패스(하드 충돌 해소)를 한 겹 더 끼운다 —
// 힘이 아니라 위치 자체를 고친다. 전체는 rotateAll 로 천천히 강체 회전한다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./GraphForceCollisionAvoid.module.scss";

export type GraphForceCollisionAvoidProps = {
  duration?: string;
  easing?: string;
  color?: string;
  n?: number;
  repel?: number;
  speed?: number;   // 자유 유영 속도(무작위 방향 힘의 크기)
};

// ── 변형 상수(기본값) — vanilla 판과 동일 ──
const N     = 22;
const REPEL = 420;
const SPEED = 78;
const DAMP     = 0.965;
const CENTER_K = 0.0016;
const OMEGA    = 0.6;
const RMIN = 6, RMAX = 15;
const SEED = 0x327004;

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

const BOARD_LABEL = "노드 반지름만큼 서로 밀어내 겹치지 않는 실험판";
const META_LEFT = "노드 22개 · 크기 다양 · rAF";
const META_RIGHT = "arc · Math.hypot · beginPath";
const HINT_TITLE = "충돌 방지";
const HINT_DESC = "반지름 합보다 가까워지면 즉시 밀어내 라벨이 겹치지 않습니다";

function makeRand(seed: number): () => number {
  let st = seed >>> 0;
  return function () {
    st = (st + 0x6d2b79f5) >>> 0;
    let 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;
  };
}

export default function GraphForceCollisionAvoid({
  duration = "2s",
  easing = "ease-out",
  color = "#7d8f6a",
  n = N,
  repel = REPEL,
  speed = SPEED
}: GraphForceCollisionAvoidProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const cvRef = useRef<HTMLCanvasElement | null>(null);
  const ctxRef = useRef<CanvasRenderingContext2D | null>(null);
  const colRef = useRef<{ panel: RGB; node: RGB; ring: RGB } | null>(null);
  const wRef = useRef(0) as Box<number>;
  const hRef = useRef(0) as Box<number>;
  const rafRef = useRef(0) as Box<number>;
  const randRef = useRef(makeRand(SEED)) as Box<() => number>;
  const pxRef = useRef<Float32Array | null>(null);
  const pyRef = useRef<Float32Array | null>(null);
  const vxRef = useRef<Float32Array | null>(null);
  const vyRef = useRef<Float32Array | null>(null);
  const radRef = useRef<Float32Array | null>(null);
  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 buildGraph(): void {
    const rand = randRef.current;
    const W = wRef.current, H = hRef.current;
    const px = new Float32Array(n), py = new Float32Array(n);
    const vx = new Float32Array(n), vy = new Float32Array(n);
    const rad = new Float32Array(n);
    for (let i = 0; i < n; i++) {
      px[i] = rand() * W; py[i] = rand() * H;
      rad[i] = RMIN + rand() * (RMAX - RMIN);
    }
    pxRef.current = px; pyRef.current = py; vxRef.current = vx; vyRef.current = vy;
    radRef.current = rad;
  }

  function fit(): void {
    const root = rootRef.current;
    const cv = cvRef.current;
    const ctx = ctxRef.current;
    if (!root || !cv || !ctx) return;
    const r = root.getBoundingClientRect();
    const dpr = Math.min(window.devicePixelRatio || 1, 2);
    wRef.current = Math.round(r.width);
    hRef.current = Math.round(r.height);
    cv.width = Math.round(wRef.current * dpr);
    cv.height = Math.round(hRef.current * dpr);
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    buildGraph();
  }

  function step(dt: number): void {
    const px = pxRef.current, py = pyRef.current, vx = vxRef.current, vy = vyRef.current, rad = radRef.current;
    const rand = randRef.current;
    const W = wRef.current, H = hRef.current;
    if (!px || !py || !vx || !vy || !rad) return;
    const fx = new Float32Array(n), fy = new Float32Array(n);
    for (let i = 0; i < n; i++) {
      for (let j = i + 1; j < n; j++) {
        const dx = px[j] - px[i], dy = py[j] - py[i];
        const d = Math.hypot(dx, dy) || 0.001;
        let d2 = d * d; if (d2 < 4) d2 = 4;
        const f = repel / d2;
        const ux = dx / d, uy = dy / d;
        fx[i] -= ux * f; fy[i] -= uy * f;
        fx[j] += ux * f; fy[j] += uy * f;
      }
    }
    const cx = W / 2, cy = H / 2;
    for (let i = 0; i < n; i++) {
      fx[i] += (cx - px[i]) * CENTER_K;
      fy[i] += (cy - py[i]) * CENTER_K;
      fx[i] += (rand() - 0.5) * speed;
      fy[i] += (rand() - 0.5) * speed;
      vx[i] = (vx[i] + fx[i] * dt) * DAMP;
      vy[i] = (vy[i] + fy[i] * dt) * DAMP;
      px[i] += vx[i] * dt; py[i] += vy[i] * dt;
    }
    // 하드 충돌 해소 — 반지름 합보다 가까운 쌍을 그 자리에서 절반씩 밀어낸다
    for (let a = 0; a < n; a++) {
      for (let b = a + 1; b < n; b++) {
        const ddx = px[b] - px[a], ddy = py[b] - py[a];
        const dist = Math.hypot(ddx, ddy) || 0.001;
        const minDist = rad[a] + rad[b];
        if (dist < minDist) {
          const push = (minDist - dist) / 2;
          const nx = ddx / dist, ny = ddy / dist;
          px[a] -= nx * push; py[a] -= ny * push;
          px[b] += nx * push; py[b] += ny * push;
        }
      }
    }
  }

  function rotateAll(dtheta: number): void {
    const px = pxRef.current, py = pyRef.current;
    if (!px || !py) return;
    const W = wRef.current, H = hRef.current;
    const cx = W / 2, cy = H / 2, cs = Math.cos(dtheta), sn = Math.sin(dtheta);
    for (let i = 0; i < n; i++) {
      const rx = px[i] - cx, ry = py[i] - cy;
      px[i] = cx + rx * cs - ry * sn;
      py[i] = cy + rx * sn + ry * cs;
    }
  }

  function draw(): void {
    const ctx = ctxRef.current;
    const col = colRef.current;
    const px = pxRef.current, py = pyRef.current, rad = radRef.current;
    const W = wRef.current, H = hRef.current;
    if (!ctx || !col || !px || !py || !rad) return;
    ctx.clearRect(0, 0, W, H);
    ctx.fillStyle = "rgb(" + col.panel.join(",") + ")";
    ctx.fillRect(0, 0, W, H);
    for (let i = 0; i < n; i++) {
      ctx.beginPath();
      ctx.fillStyle = "rgb(" + col.node.join(",") + ")";
      ctx.arc(px[i], py[i], rad[i], 0, Math.PI * 2);
      ctx.fill();
      ctx.lineWidth = 1;
      ctx.strokeStyle = "rgba(" + col.ring.join(",") + ",0.7)";
      ctx.stroke();
    }
  }

  function settle(): void {
    for (let s = 0; s < 260; s++) step(1 / 60);
    draw();
  }

  let t0 = -1, last = -1;
  function frame(now: number): void {
    if (t0 < 0) { t0 = now; last = now; }
    const dt = Math.min((now - last) / 1000, 0.05); last = now;
    step(dt);
    rotateAll(OMEGA * dt);
    draw();
    rafRef.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    const root = rootRef.current;
    const cv = cvRef.current;
    if (!root || !cv) return;
    colRef.current = {
      panel: tokRGB(root, "--gd-panel"),
      node: tokRGB(root, "--gd-node"),
      ring: tokRGB(root, "--gd-ring")
    };
    ctxRef.current = cv.getContext("2d");
    fit();
    function onResize(): void {
      fit();
      if (reduced()) settle();
    }
    window.addEventListener("resize", onResize);
    if (reduced()) {
      settle();
      setStill(true);
    } else {
      t0 = -1; last = -1;
      rafRef.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafRef.current);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [n, repel, speed]);

  const rootCls = still ? `${styles.root} ${styles.isStill}` : styles.root;

  return (
    <main className={styles.stage}>
      <div
        className={rootCls}
        ref={rootRef}
        style={vars}
        role="img"
        aria-label={BOARD_LABEL}
        tabIndex={0}
      >
        <canvas className={styles.cv} ref={cvRef}></canvas>
        <p className={styles.hint}>
          <span className={styles.title}>{HINT_TITLE}</span>
          <span className={styles.desc}>{HINT_DESC}</span>
        </p>
        <div className={styles.bar}>
          <span className={styles.meta}>{META_LEFT}</span>
          <span className={styles.metaDim}>{META_RIGHT}</span>
        </div>
      </div>
    </main>
  );
}