05比率を守って八方向に伸びる画像

<main class="stage">
<div class="rh is-demo" id="rh" data-demo="1">
  <div class="rh__img" data-r="img"><i class="rh__sun"></i><i class="rh__hill"></i></div>
  <i class="rh__proj" data-r="proj"></i>
  <button class="rh__h" data-hx="-1" data-hy="-1" type="button" aria-label="サイズ変更つまみ"></button>
  <button class="rh__h" data-hx="0" data-hy="-1" type="button" aria-label="サイズ変更つまみ"></button>
  <button class="rh__h" data-hx="1" data-hy="-1" type="button" aria-label="サイズ変更つまみ"></button>
  <button class="rh__h" data-hx="-1" data-hy="0" type="button" aria-label="サイズ変更つまみ"></button>
  <button class="rh__h" data-hx="1" data-hy="0" type="button" aria-label="サイズ変更つまみ"></button>
  <button class="rh__h" data-hx="-1" data-hy="1" type="button" aria-label="サイズ変更つまみ"></button>
  <button class="rh__h" data-hx="0" data-hy="1" type="button" aria-label="サイズ変更つまみ"></button>
  <button class="rh__h" data-hx="1" data-hy="1" type="button" aria-label="サイズ変更つまみ"></button>
  <p class="rh__meta"><span class="rh__tag">4:3</span> <span class="rh__tag">W</span> <b data-r="w">0</b> <span class="rh__tag">H</span> <b data-r="h">0</b></p>
  <i class="rh__cursor" data-r="cursor"></i>
</div>
</main>

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

// 핵심: 앵커(반대쪽 꼭짓점·변)는 움직이지 않고, 모서리는 포인터 벡터를 비율 대각선 위로 투영해 가로세로를 한 값으로 정한다.

@include stage($stage-paper);

.rh {
  position: relative;
  box-sizing: border-box;
  width: min(100%, 440px);
  height: min(252px, calc(100vh - 2 * clamp(8px, 4vw, 24px)));
  color: $subject-ink;
  font-size: 12px;
  line-height: 16px;
  font-weight: 600;
  user-select: none;
}
.rh b { font-weight: 800; font-variant-numeric: tabular-nums; }
.rh__tag { color: rgba($subject-ink, .72); letter-spacing: .5px; }
.rh__cursor {
  position: absolute;
  left: -10px;
  top: -10px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: $subject-cream;
  box-shadow: 0 0 0 3px rgba($subject-ink, .55), $shadow-press;
  opacity: 0;
  pointer-events: none;
  z-index: 6;
}
.rh[data-demo] .rh__cursor { opacity: 1; }
.rh button:focus-visible { outline: 3px solid $subject-ink; outline-offset: 2px; }
@media (prefers-reduced-motion: reduce) {
  .rh__cursor { display: none; }
}

// 점선은 포인터가 실제로 있는 곳, 손잡이는 투영된 꼭짓점이다.
.rh__img {
  position: absolute;
  left: 0;
  top: 0;
  overflow: hidden;
  border-radius: $r-card;
  background: linear-gradient(160deg, $subject-sky, $subject-lilac);
  box-shadow: 0 8px 16px rgba($subject-ink, .24);
}
.rh__sun {
  position: absolute;
  right: 14%;
  top: 14%;
  width: 20%;
  aspect-ratio: 1;
  border-radius: 50%;
  background: $subject-pink;
}
.rh__hill {
  position: absolute;
  left: -10%;
  bottom: -72%;
  width: 120%;
  height: 100%;
  border-radius: 50%;
  background: $subject-mint;
}
.rh__h {
  position: absolute;
  left: 0;
  top: 0;
  width: 28px;
  height: 28px;
  padding: 0;
  border: 0;
  background: transparent;
  z-index: 3;
  touch-action: none;
}
.rh__h::before {
  content: "";
  position: absolute;
  left: 8px;
  top: 8px;
  width: 12px;
  height: 12px;
  box-sizing: border-box;
  border: 2px solid $subject-ink;
  border-radius: $r-xs;
  background: $subject-cream;
}
.rh__h[data-hx="-1"][data-hy="-1"],
.rh__h[data-hx="1"][data-hy="1"] { cursor: nwse-resize; }
.rh__h[data-hx="1"][data-hy="-1"],
.rh__h[data-hx="-1"][data-hy="1"] { cursor: nesw-resize; }
.rh__h[data-hx="0"] { cursor: ns-resize; }
.rh__h[data-hy="0"] { cursor: ew-resize; }
.rh__h:focus-visible::before { box-shadow: 0 0 0 3px $subject-pink; }
.rh__proj {
  position: absolute;
  left: 0;
  top: 0;
  height: 0;
  border-top: 2px dashed $subject-pink;
  transform-origin: 0 0;
  opacity: 0;
  pointer-events: none;
  z-index: 4;
}
.rh__meta {
  position: absolute;
  left: 0;
  bottom: 0;
  margin: 0;
  padding: 0 $sp-2;
  border-radius: $r-xs;
  background: rgba($subject-ink, .72);
  z-index: 5;
}
.rh__meta { color: $subject-cream; }
.rh__meta .rh__tag { color: rgba($subject-cream, .78); }

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);
}

.rh {
  position: relative;
  box-sizing: border-box;
  width: min(100%, 440px);
  height: min(252px, 100vh - 2 * clamp(8px, 4vw, 24px));
  color: #17141a;
  font-size: 12px;
  line-height: 16px;
  font-weight: 600;
  user-select: none;
}

.rh b {
  font-weight: 800;
  font-variant-numeric: tabular-nums;
}

.rh__tag {
  color: rgba(23, 20, 26, 0.72);
  letter-spacing: 0.5px;
}

.rh__cursor {
  position: absolute;
  left: -10px;
  top: -10px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: #fff7e6;
  box-shadow: 0 0 0 3px rgba(23, 20, 26, 0.55), 0 6px 12px rgba(23, 20, 26, 0.32);
  opacity: 0;
  pointer-events: none;
  z-index: 6;
}

.rh[data-demo] .rh__cursor {
  opacity: 1;
}

.rh button:focus-visible {
  outline: 3px solid #17141a;
  outline-offset: 2px;
}

@media (prefers-reduced-motion: reduce) {
  .rh__cursor {
    display: none;
  }
}
.rh__img {
  position: absolute;
  left: 0;
  top: 0;
  overflow: hidden;
  border-radius: 16px;
  background: linear-gradient(160deg, #6ec8ff, #b9a0ff);
  box-shadow: 0 8px 16px rgba(23, 20, 26, 0.24);
}

.rh__sun {
  position: absolute;
  right: 14%;
  top: 14%;
  width: 20%;
  aspect-ratio: 1;
  border-radius: 50%;
  background: #ff9ebb;
}

.rh__hill {
  position: absolute;
  left: -10%;
  bottom: -72%;
  width: 120%;
  height: 100%;
  border-radius: 50%;
  background: #4cd4a6;
}

.rh__h {
  position: absolute;
  left: 0;
  top: 0;
  width: 28px;
  height: 28px;
  padding: 0;
  border: 0;
  background: transparent;
  z-index: 3;
  touch-action: none;
}

.rh__h::before {
  content: "";
  position: absolute;
  left: 8px;
  top: 8px;
  width: 12px;
  height: 12px;
  box-sizing: border-box;
  border: 2px solid #17141a;
  border-radius: 4px;
  background: #fff7e6;
}

.rh__h[data-hx="-1"][data-hy="-1"],
.rh__h[data-hx="1"][data-hy="1"] {
  cursor: nwse-resize;
}

.rh__h[data-hx="1"][data-hy="-1"],
.rh__h[data-hx="-1"][data-hy="1"] {
  cursor: nesw-resize;
}

.rh__h[data-hx="0"] {
  cursor: ns-resize;
}

.rh__h[data-hy="0"] {
  cursor: ew-resize;
}

.rh__h:focus-visible::before {
  box-shadow: 0 0 0 3px #ff9ebb;
}

.rh__proj {
  position: absolute;
  left: 0;
  top: 0;
  height: 0;
  border-top: 2px dashed #ff9ebb;
  transform-origin: 0 0;
  opacity: 0;
  pointer-events: none;
  z-index: 4;
}

.rh__meta {
  position: absolute;
  left: 0;
  bottom: 0;
  margin: 0;
  padding: 0 8px;
  border-radius: 4px;
  background: rgba(23, 20, 26, 0.72);
  z-index: 5;
}

.rh__meta {
  color: #fff7e6;
}

.rh__meta .rh__tag {
  color: rgba(255, 247, 230, 0.78);
}

(function () {
    const root = document.getElementById("rh");
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo = !reduce;
    let raf = 0;
    let t0 = -1;
    let last = -1;
    const offs = [];
    function q(sel) {
        return root.querySelector(sel);
    }
    function clamp(v, lo, hi) {
        return Math.max(lo, Math.min(hi, v));
    }
    function seg(t, a, b) {
        const c = clamp((t - a) / (b - a), 0, 1);
        return c * c * (3 - 2 * c);
    }
    function on(el, type, fn) {
        el.addEventListener(type, fn);
        offs.push(() => el.removeEventListener(type, fn));
    }
    function stopDemo() {
        demo = false;
        root.removeAttribute("data-demo");
        root.classList.remove("is-demo");
    }
    function pos(e) {
        const r = root.getBoundingClientRect();
        return { x: e.clientX - r.left, y: e.clientY - r.top };
    }
    function spring(x, v, to, k, c, dt) {
        const n = Math.max(1, Math.ceil(dt / 0.008));
        const h = dt / n;
        for (let i = 0; i < n; i += 1) {
            v += (-k * (x - to) - c * v) * h;
            x += v * h;
        }
        return [x, v];
    }
    function sync() {
        if (reduce) {
            snap();
            render();
        }
    }
    // 기법: 잡은 손잡이의 반대쪽(앵커)을 고정하고, 모서리는 앵커에서 포인터까지의 벡터를
    // 비율 대각선 (ASPECT, 1) 위로 투영해 한 변 길이 s 하나로 가로·세로를 같이 정한다.
    const ASPECT = 4 / 3;
    const MIN_SIDE = 48;
    const img = q("[data-r=img]");
    const proj = q("[data-r=proj]");
    const cursor = q("[data-r=cursor]");
    const wEl = q("[data-r=w]");
    const hEl = q("[data-r=h]");
    const handles = Array.prototype.slice.call(root.querySelectorAll("[data-hx]"));
    let x = 0;
    let y = 0;
    let w = 0;
    let h = 0;
    let px = 0;
    let py = 0;
    let active = -1;
    let gx = 0;
    let gy = 0;
    let ready = false;
    function reset() {
        const s = root.clientHeight * 0.4;
        w = s * ASPECT;
        h = s;
        x = root.clientWidth * 0.1;
        y = root.clientHeight * 0.14;
    }
    function init() {
        if (ready)
            return;
        ready = true;
        reset();
    }
    function hx(i) { return Number(handles[i].getAttribute("data-hx")); }
    function hy(i) { return Number(handles[i].getAttribute("data-hy")); }
    function resizeTo(i, qx, qy) {
        const W = root.clientWidth;
        const H = root.clientHeight;
        const sx = hx(i);
        const sy = hy(i);
        const ax = sx > 0 ? x : sx < 0 ? x + w : x + w / 2;
        const ay = sy > 0 ? y : sy < 0 ? y + h : y + h / 2;
        if (sx !== 0 && sy !== 0) {
            const dx = (qx - ax) * sx;
            const dy = (qy - ay) * sy;
            const maxS = Math.min((sx > 0 ? W - ax : ax) / ASPECT, sy > 0 ? H - ay : ay);
            const s = clamp((dx * ASPECT + dy) / (ASPECT * ASPECT + 1), MIN_SIDE, maxS);
            w = s * ASPECT;
            h = s;
            x = sx > 0 ? ax : ax - w;
            y = sy > 0 ? ay : ay - h;
        }
        else if (sx !== 0) {
            const maxW = Math.min(sx > 0 ? W - ax : ax, 2 * Math.min(ay, H - ay) * ASPECT);
            w = clamp((qx - ax) * sx, MIN_SIDE * ASPECT, maxW);
            h = w / ASPECT;
            x = sx > 0 ? ax : ax - w;
            y = ay - h / 2;
        }
        else {
            const maxH = Math.min(sy > 0 ? H - ay : ay, (2 * Math.min(ax, W - ax)) / ASPECT);
            h = clamp((qy - ay) * sy, MIN_SIDE, maxH);
            w = h * ASPECT;
            x = ax - w / 2;
            y = sy > 0 ? ay : ay - h;
        }
    }
    function userTakes() {
        stopDemo();
        active = -1;
        init();
    }
    function handlePoint(i) {
        return [x + ((hx(i) + 1) / 2) * w, y + ((hy(i) + 1) / 2) * h];
    }
    function leg(l, a, b, from, to) {
        const t = seg(l, a, b);
        return [from[0] + (to[0] - from[0]) * t, from[1] + (to[1] - from[1]) * t];
    }
    function script(now) {
        const W = root.clientWidth;
        const H = root.clientHeight;
        const ph = now % 2000;
        const corner = ph < 1000;
        const l = ph % 1000;
        const i = corner ? 7 : 4;
        const s0 = H * 0.4;
        const p0 = [W * 0.1 + s0 * ASPECT, corner ? H * 0.14 + s0 : H * 0.14 + s0 / 2];
        const p1 = corner ? [W * 0.88, H * 0.62] : [W * 0.95, p0[1]];
        const p2 = corner ? [W * 0.46, H * 0.95] : [W * 0.5, p0[1]];
        let q = p0;
        if (l < 200) {
            reset();
            active = -1;
            px = p0[0];
            py = p0[1];
            return;
        }
        if (l < 520)
            q = leg(l, 200, 520, p0, p1);
        else if (l < 640)
            q = p1;
        else if (l < 860)
            q = leg(l, 640, 860, p1, p2);
        else
            q = leg(l, 860, 1000, p2, p0);
        active = i;
        resizeTo(i, q[0], q[1]);
        px = q[0];
        py = q[1];
    }
    function snap() { init(); }
    function step(_dt, now) {
        init();
        if (demo)
            script(now);
    }
    function render() {
        img.style.transform = "translate(" + x.toFixed(1) + "px," + y.toFixed(1) + "px)";
        img.style.width = w.toFixed(1) + "px";
        img.style.height = h.toFixed(1) + "px";
        for (let i = 0; i < handles.length; i += 1) {
            const p = handlePoint(i);
            handles[i].style.transform = "translate(" + (p[0] - 14).toFixed(1) + "px," + (p[1] - 14).toFixed(1) + "px)";
        }
        if (active >= 0 && hx(active) !== 0 && hy(active) !== 0) {
            const c = handlePoint(active);
            const dx = px - c[0];
            const dy = py - c[1];
            proj.style.opacity = "1";
            proj.style.width = Math.hypot(dx, dy).toFixed(1) + "px";
            proj.style.transform = "translate(" + c[0].toFixed(1) + "px," + c[1].toFixed(1) + "px) rotate(" + Math.atan2(dy, dx).toFixed(3) + "rad)";
        }
        else {
            proj.style.opacity = "0";
        }
        wEl.textContent = String(Math.round(w));
        hEl.textContent = String(Math.round(h));
        cursor.style.transform = "translate(" + px.toFixed(1) + "px," + py.toFixed(1) + "px)";
    }
    handles.forEach((el, i) => {
        on(el, "pointerdown", (e) => {
            userTakes();
            el.setPointerCapture(e.pointerId);
            const p = pos(e);
            const c = handlePoint(i);
            gx = c[0] - p.x;
            gy = c[1] - p.y;
            px = p.x;
            py = p.y;
            active = i;
        });
        on(el, "pointermove", (e) => {
            if (active !== i)
                return;
            const p = pos(e);
            px = p.x;
            py = p.y;
            resizeTo(i, px + gx, py + gy);
            sync();
        });
        on(el, "pointerup", () => { active = -1; sync(); });
        on(el, "pointercancel", () => { active = -1; sync(); });
        on(el, "keydown", (e) => {
            const k = e.key;
            if (k !== "ArrowLeft" && k !== "ArrowRight" && k !== "ArrowUp" && k !== "ArrowDown")
                return;
            e.preventDefault();
            userTakes();
            const c = handlePoint(i);
            px = c[0] + (k === "ArrowRight" ? 8 : k === "ArrowLeft" ? -8 : 0);
            py = c[1] + (k === "ArrowDown" ? 8 : k === "ArrowUp" ? -8 : 0);
            resizeTo(i, px, py);
            sync();
        });
    });
    function frame(ts) {
        if (t0 < 0) {
            t0 = ts;
            last = ts;
        }
        const dt = Math.min(0.05, (ts - last) / 1000);
        last = ts;
        step(dt, ts - t0);
        render();
        raf = requestAnimationFrame(frame);
    }
    if (reduce) {
        stopDemo();
        snap();
        render();
    }
    else {
        raf = requestAnimationFrame(frame);
    }
    return () => {
        cancelAnimationFrame(raf);
        offs.forEach((f) => f());
    };
})();

// RatioLockHandles - vanilla 판(05-rh-ratio-lock-eight-handles) 의 React 포트. 같은 계산을 useEffect 안에서 돌린다.
import { useEffect, useRef } from "react";
import styles from "./RatioLockHandles.module.scss";

export default function RatioLockHandles() {
  const rootRef = useRef<HTMLDivElement | null>(null);

  useEffect(() => {
    const rootEl = rootRef.current;
    if (!rootEl) return;
    const root: HTMLElement = rootEl;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo = !reduce;
    let raf = 0;
    let t0 = -1;
    let last = -1;
    const offs: Array<() => void> = [];

    function q<T extends Element>(sel: string): T {
      return root.querySelector(sel) as T;
    }
    function clamp(v: number, lo: number, hi: number): number {
      return Math.max(lo, Math.min(hi, v));
    }
    function seg(t: number, a: number, b: number): number {
      const c = clamp((t - a) / (b - a), 0, 1);
      return c * c * (3 - 2 * c);
    }
    function on(el: EventTarget, type: string, fn: (e: any) => void): void {
      el.addEventListener(type, fn);
      offs.push(() => el.removeEventListener(type, fn));
    }
    function stopDemo(): void {
      demo = false;
      root.removeAttribute("data-demo");
      root.classList.remove("is-demo");
    }
    function pos(e: PointerEvent): { x: number; y: number } {
      const r = root.getBoundingClientRect();
      return { x: e.clientX - r.left, y: e.clientY - r.top };
    }
    function spring(x: number, v: number, to: number, k: number, c: number, dt: number): number[] {
      const n = Math.max(1, Math.ceil(dt / 0.008));
      const h = dt / n;
      for (let i = 0; i < n; i += 1) {
        v += (-k * (x - to) - c * v) * h;
        x += v * h;
      }
      return [x, v];
    }
    function sync(): void {
      if (reduce) {
        snap();
        render();
      }
    }

    // 기법: 잡은 손잡이의 반대쪽(앵커)을 고정하고, 모서리는 앵커에서 포인터까지의 벡터를
    // 비율 대각선 (ASPECT, 1) 위로 투영해 한 변 길이 s 하나로 가로·세로를 같이 정한다.
    const ASPECT = 4 / 3;
    const MIN_SIDE = 48;
    const img = q<HTMLElement>("[data-r=img]");
    const proj = q<HTMLElement>("[data-r=proj]");
    const cursor = q<HTMLElement>("[data-r=cursor]");
    const wEl = q<HTMLElement>("[data-r=w]");
    const hEl = q<HTMLElement>("[data-r=h]");
    const handles = Array.prototype.slice.call(root.querySelectorAll("[data-hx]")) as HTMLElement[];
    let x = 0;
    let y = 0;
    let w = 0;
    let h = 0;
    let px = 0;
    let py = 0;
    let active = -1;
    let gx = 0;
    let gy = 0;
    let ready = false;

    function reset(): void {
      const s = root.clientHeight * 0.4;
      w = s * ASPECT;
      h = s;
      x = root.clientWidth * 0.1;
      y = root.clientHeight * 0.14;
    }

    function init(): void {
      if (ready) return;
      ready = true;
      reset();
    }

    function hx(i: number): number { return Number(handles[i].getAttribute("data-hx")); }
    function hy(i: number): number { return Number(handles[i].getAttribute("data-hy")); }

    function resizeTo(i: number, qx: number, qy: number): void {
      const W = root.clientWidth;
      const H = root.clientHeight;
      const sx = hx(i);
      const sy = hy(i);
      const ax = sx > 0 ? x : sx < 0 ? x + w : x + w / 2;
      const ay = sy > 0 ? y : sy < 0 ? y + h : y + h / 2;
      if (sx !== 0 && sy !== 0) {
        const dx = (qx - ax) * sx;
        const dy = (qy - ay) * sy;
        const maxS = Math.min((sx > 0 ? W - ax : ax) / ASPECT, sy > 0 ? H - ay : ay);
        const s = clamp((dx * ASPECT + dy) / (ASPECT * ASPECT + 1), MIN_SIDE, maxS);
        w = s * ASPECT;
        h = s;
        x = sx > 0 ? ax : ax - w;
        y = sy > 0 ? ay : ay - h;
      } else if (sx !== 0) {
        const maxW = Math.min(sx > 0 ? W - ax : ax, 2 * Math.min(ay, H - ay) * ASPECT);
        w = clamp((qx - ax) * sx, MIN_SIDE * ASPECT, maxW);
        h = w / ASPECT;
        x = sx > 0 ? ax : ax - w;
        y = ay - h / 2;
      } else {
        const maxH = Math.min(sy > 0 ? H - ay : ay, (2 * Math.min(ax, W - ax)) / ASPECT);
        h = clamp((qy - ay) * sy, MIN_SIDE, maxH);
        w = h * ASPECT;
        x = ax - w / 2;
        y = sy > 0 ? ay : ay - h;
      }
    }

    function userTakes(): void {
      stopDemo();
      active = -1;
      init();
    }

    function handlePoint(i: number): number[] {
      return [x + ((hx(i) + 1) / 2) * w, y + ((hy(i) + 1) / 2) * h];
    }

    function leg(l: number, a: number, b: number, from: number[], to: number[]): number[] {
      const t = seg(l, a, b);
      return [from[0] + (to[0] - from[0]) * t, from[1] + (to[1] - from[1]) * t];
    }

    function script(now: number): void {
      const W = root.clientWidth;
      const H = root.clientHeight;
      const ph = now % 2000;
      const corner = ph < 1000;
      const l = ph % 1000;
      const i = corner ? 7 : 4;
      const s0 = H * 0.4;
      const p0 = [W * 0.1 + s0 * ASPECT, corner ? H * 0.14 + s0 : H * 0.14 + s0 / 2];
      const p1 = corner ? [W * 0.88, H * 0.62] : [W * 0.95, p0[1]];
      const p2 = corner ? [W * 0.46, H * 0.95] : [W * 0.5, p0[1]];
      let q = p0;
      if (l < 200) { reset(); active = -1; px = p0[0]; py = p0[1]; return; }
      if (l < 520) q = leg(l, 200, 520, p0, p1);
      else if (l < 640) q = p1;
      else if (l < 860) q = leg(l, 640, 860, p1, p2);
      else q = leg(l, 860, 1000, p2, p0);
      active = i;
      resizeTo(i, q[0], q[1]);
      px = q[0];
      py = q[1];
    }

    function snap(): void { init(); }

    function step(_dt: number, now: number): void {
      init();
      if (demo) script(now);
    }

    function render(): void {
      img.style.transform = "translate(" + x.toFixed(1) + "px," + y.toFixed(1) + "px)";
      img.style.width = w.toFixed(1) + "px";
      img.style.height = h.toFixed(1) + "px";
      for (let i = 0; i < handles.length; i += 1) {
        const p = handlePoint(i);
        handles[i].style.transform = "translate(" + (p[0] - 14).toFixed(1) + "px," + (p[1] - 14).toFixed(1) + "px)";
      }
      if (active >= 0 && hx(active) !== 0 && hy(active) !== 0) {
        const c = handlePoint(active);
        const dx = px - c[0];
        const dy = py - c[1];
        proj.style.opacity = "1";
        proj.style.width = Math.hypot(dx, dy).toFixed(1) + "px";
        proj.style.transform = "translate(" + c[0].toFixed(1) + "px," + c[1].toFixed(1) + "px) rotate(" + Math.atan2(dy, dx).toFixed(3) + "rad)";
      } else {
        proj.style.opacity = "0";
      }
      wEl.textContent = String(Math.round(w));
      hEl.textContent = String(Math.round(h));
      cursor.style.transform = "translate(" + px.toFixed(1) + "px," + py.toFixed(1) + "px)";
    }

    handles.forEach((el, i) => {
      on(el, "pointerdown", (e: PointerEvent) => {
        userTakes();
        el.setPointerCapture(e.pointerId);
        const p = pos(e);
        const c = handlePoint(i);
        gx = c[0] - p.x;
        gy = c[1] - p.y;
        px = p.x;
        py = p.y;
        active = i;
      });
      on(el, "pointermove", (e: PointerEvent) => {
        if (active !== i) return;
        const p = pos(e);
        px = p.x;
        py = p.y;
        resizeTo(i, px + gx, py + gy);
        sync();
      });
      on(el, "pointerup", () => { active = -1; sync(); });
      on(el, "pointercancel", () => { active = -1; sync(); });
      on(el, "keydown", (e: KeyboardEvent) => {
        const k = e.key;
        if (k !== "ArrowLeft" && k !== "ArrowRight" && k !== "ArrowUp" && k !== "ArrowDown") return;
        e.preventDefault();
        userTakes();
        const c = handlePoint(i);
        px = c[0] + (k === "ArrowRight" ? 8 : k === "ArrowLeft" ? -8 : 0);
        py = c[1] + (k === "ArrowDown" ? 8 : k === "ArrowUp" ? -8 : 0);
        resizeTo(i, px, py);
        sync();
      });
    });

    function frame(ts: number): void {
      if (t0 < 0) {
        t0 = ts;
        last = ts;
      }
      const dt = Math.min(0.05, (ts - last) / 1000);
      last = ts;
      step(dt, ts - t0);
      render();
      raf = requestAnimationFrame(frame);
    }
    if (reduce) {
      stopDemo();
      snap();
      render();
    } else {
      raf = requestAnimationFrame(frame);
    }
    return () => {
      cancelAnimationFrame(raf);
      offs.forEach((f) => f());
    };

  }, []);

  return (
    <main className={styles["stage"]}>
      <div ref={rootRef} className={styles["rh"] + " is-demo"} data-demo="1">
        <div className={styles["rh__img"]} data-r="img"><i className={styles["rh__sun"]}></i><i className={styles["rh__hill"]}></i></div>
        <i className={styles["rh__proj"]} data-r="proj"></i>
        <button className={styles["rh__h"]} data-hx="-1" data-hy="-1" type="button" aria-label="크기 조절 손잡이"></button>
        <button className={styles["rh__h"]} data-hx="0" data-hy="-1" type="button" aria-label="크기 조절 손잡이"></button>
        <button className={styles["rh__h"]} data-hx="1" data-hy="-1" type="button" aria-label="크기 조절 손잡이"></button>
        <button className={styles["rh__h"]} data-hx="-1" data-hy="0" type="button" aria-label="크기 조절 손잡이"></button>
        <button className={styles["rh__h"]} data-hx="1" data-hy="0" type="button" aria-label="크기 조절 손잡이"></button>
        <button className={styles["rh__h"]} data-hx="-1" data-hy="1" type="button" aria-label="크기 조절 손잡이"></button>
        <button className={styles["rh__h"]} data-hx="0" data-hy="1" type="button" aria-label="크기 조절 손잡이"></button>
        <button className={styles["rh__h"]} data-hx="1" data-hy="1" type="button" aria-label="크기 조절 손잡이"></button>
        <p className={styles["rh__meta"]}><span className={styles["rh__tag"]}>4:3</span> <span className={styles["rh__tag"]}>W</span> <b data-r="w">0</b> <span className={styles["rh__tag"]}>H</span> <b data-r="h">0</b></p>
        <i className={styles["rh__cursor"]} data-r="cursor"></i>
      </div>
    </main>
  );
}