03ポインターの向きで閉じるのを遅らせる安全三角形

<main class="stage">
<div class="pm is-demo" id="pm" data-demo="1">
  <p class="pm__live" data-r="live" aria-live="off" aria-atomic="true"></p>
  <i class="pm__tri" data-r="tri"></i>
  <div class="pm__menu"><button class="pm__item" data-r="item" type="button" aria-haspopup="true" aria-expanded="false">プロフィール</button><button class="pm__item" data-r="item" type="button" aria-haspopup="true" aria-expanded="false">通知</button><button class="pm__item" data-r="item" type="button" aria-haspopup="true" aria-expanded="false">セキュリティ</button></div>
  <div class="pm__sub" data-r="sub"><b class="pm__ttl">プロフィール</b><span class="pm__r">開く</span><span class="pm__r">固定</span><span class="pm__r">削除</span></div><div class="pm__sub" data-r="sub"><b class="pm__ttl">通知</b><span class="pm__r">開く</span><span class="pm__r">固定</span><span class="pm__r">削除</span></div><div class="pm__sub" data-r="sub"><b class="pm__ttl">セキュリティ</b><span class="pm__r">開く</span><span class="pm__r">固定</span><span class="pm__r">削除</span></div>
  <i class="pm__cur" data-r="cur"></i>
</div>
</main>

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

// 핵심: 포인터 속도와 방향으로 앵커에서 팝오버 모서리를 잇는 삼각형을 그리고, 그 안을 지나는 동안엔 닫힘과 전환을 미룬다.

@include stage($stage-ink);

.pm {
  position: relative;
  box-sizing: border-box;
  overflow: hidden;
  width: min(100%, 440px);
  height: min(252px, calc(100vh - 2 * clamp(8px, 4vw, 24px)));
  border-radius: $r-card;
  background: rgba($subject-cream, .07);
  color: $subject-cream;
  font-size: 12px;
  line-height: 16px;
  font-weight: 600;
  user-select: none;
}
.pm b { font-weight: 800; font-variant-numeric: tabular-nums; }
.pm__live {
  position: absolute;
  left: $sp-3;
  top: $sp-2;
  margin: 0;
  z-index: 9;
  color: $tick-mute;
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
  pointer-events: none;
}
.pm button { font-family: inherit; }
.pm button:focus-visible { outline: 3px solid $subject-pink; outline-offset: 2px; }


.pm__tri {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background: rgba($subject-sky, .22);
  pointer-events: none;
}
.pm__tri[data-on="1"] { background: rgba($subject-mint, .4); }
.pm__menu {
  position: absolute;
  left: 12px;
  top: 34px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  width: 112px;
}
.pm__item {
  box-sizing: border-box;
  height: 36px;
  padding: 0 $sp-3;
  border: 0;
  border-radius: $r-control;
  background: rgba($subject-cream, .1);
  color: $subject-cream;
  font-size: 13px;
  line-height: 20px;
  font-weight: 700;
  text-align: left;
  cursor: pointer;
}
.pm__item[data-open] { background: $subject-lilac; color: $subject-ink; }
.pm__sub {
  position: absolute;
  left: 0;
  top: 0;
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  gap: $sp-1;
  height: 132px;
  padding: $sp-3;
  border-radius: $r-card;
  background: $subject-cream;
  color: $subject-ink;
  box-shadow: $shadow-raised;
  visibility: hidden;
}
.pm__ttl { display: block; font-size: 13px; line-height: 20px; }
.pm__r { display: block; padding: $sp-1 $sp-2; border-radius: $r-xs; background: rgba($subject-ink, .07); }
.pm__cur {
  position: absolute;
  left: 0;
  top: 0;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: $subject-pink;
  box-shadow: 0 0 0 3px rgba($subject-ink, .5);
  opacity: 0;
  pointer-events: none;
  z-index: 6;
}
.pm[data-demo] .pm__cur { opacity: 1; }
@media (prefers-reduced-motion: reduce) {
  .pm__cur { display: none; }
}

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);
}

.pm {
  position: relative;
  box-sizing: border-box;
  overflow: hidden;
  width: min(100%, 440px);
  height: min(252px, 100vh - 2 * clamp(8px, 4vw, 24px));
  border-radius: 16px;
  background: rgba(255, 247, 230, 0.07);
  color: #fff7e6;
  font-size: 12px;
  line-height: 16px;
  font-weight: 600;
  user-select: none;
}

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

.pm__live {
  position: absolute;
  left: 12px;
  top: 8px;
  margin: 0;
  z-index: 9;
  color: #9a93a6;
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
  pointer-events: none;
}

.pm button {
  font-family: inherit;
}

.pm button:focus-visible {
  outline: 3px solid #ff9ebb;
  outline-offset: 2px;
}

.pm__tri {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background: rgba(110, 200, 255, 0.22);
  pointer-events: none;
}

.pm__tri[data-on="1"] {
  background: rgba(76, 212, 166, 0.4);
}

.pm__menu {
  position: absolute;
  left: 12px;
  top: 34px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  width: 112px;
}

.pm__item {
  box-sizing: border-box;
  height: 36px;
  padding: 0 12px;
  border: 0;
  border-radius: 12px;
  background: rgba(255, 247, 230, 0.1);
  color: #fff7e6;
  font-size: 13px;
  line-height: 20px;
  font-weight: 700;
  text-align: left;
  cursor: pointer;
}

.pm__item[data-open] {
  background: #b9a0ff;
  color: #17141a;
}

.pm__sub {
  position: absolute;
  left: 0;
  top: 0;
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  gap: 4px;
  height: 132px;
  padding: 12px;
  border-radius: 16px;
  background: #fff7e6;
  color: #17141a;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  visibility: hidden;
}

.pm__ttl {
  display: block;
  font-size: 13px;
  line-height: 20px;
}

.pm__r {
  display: block;
  padding: 4px 8px;
  border-radius: 4px;
  background: rgba(23, 20, 26, 0.07);
}

.pm__cur {
  position: absolute;
  left: 0;
  top: 0;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: #ff9ebb;
  box-shadow: 0 0 0 3px rgba(23, 20, 26, 0.5);
  opacity: 0;
  pointer-events: none;
  z-index: 6;
}

.pm[data-demo] .pm__cur {
  opacity: 1;
}

@media (prefers-reduced-motion: reduce) {
  .pm__cur {
    display: none;
  }
}

(function () {
    const root = document.getElementById("pm");
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo = !reduce;
    let raf = 0;
    let t0 = -1;
    let last = -1;
    let acc = 0;
    let clock = 0;
    const offs = [];
    const live = root.querySelector("[data-r=live]");
    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() {
        if (!demo)
            return;
        demo = false;
        root.removeAttribute("data-demo");
        root.classList.remove("is-demo");
        live.setAttribute("aria-live", "polite");
    }
    if (reduce)
        live.setAttribute("aria-live", "polite");
    let shown = "";
    function say(s) {
        if (s === shown)
            return;
        shown = s;
        live.textContent = s;
    }
    function makeRng(seed) {
        let s = seed >>> 0;
        return () => {
            s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
            return s / 4294967296;
        };
    }
    function local(e) {
        const r = root.getBoundingClientRect();
        return { x: e.clientX - r.left, y: e.clientY - r.top };
    }
    function sync() {
        if (reduce) {
            snap();
            render();
        }
    }
    // 기법: 포인터가 떠나는 순간의 위치를 꼭짓점으로 삼고 팝오버 왼쪽 두 모서리를 밑변으로 하는 삼각형을 그린다. 그 안을 SPEED_MIN 이상으로 팝오버 쪽으로 지나는 동안엔 다른 항목에 닿아도 닫지 않는다.
    const INTENT_MS = 260;
    const TRIANGLE_PAD = 10;
    const SPEED_MIN = 60;
    const GRACE = 140;
    const MENU_X = 12;
    const MENU_W = 112;
    const MENU_TOP = 34;
    const ITEM_H = 36;
    const ITEM_GAP = 4;
    const PANEL_X = 132;
    const PANEL_H = 132;
    const TRAIL = 6;
    const CYCLE_MS = 3200;
    const items = Array.from(root.querySelectorAll("[data-r=item]"));
    const subs = Array.from(root.querySelectorAll("[data-r=sub]"));
    const tri = q("[data-r=tri]");
    const cur = q("[data-r=cur]");
    const trail = [];
    const vis = [0, 0, 0];
    let mx = MENU_X + MENU_W / 2;
    let my = MENU_TOP + ITEM_H / 2;
    let openIdx = 0;
    let since = -1;
    let leftAt = -1;
    let inTri = false;
    let spd = 0;
    let lastOpen = -2;
    function itemY(i) {
        return MENU_TOP + i * (ITEM_H + ITEM_GAP);
    }
    function panelTop(i) {
        return clamp(itemY(i), MENU_TOP - 4, root.clientHeight - 8 - PANEL_H);
    }
    function panelW() {
        return Math.min(150, root.clientWidth - PANEL_X - 8);
    }
    function hitItem(x, y) {
        if (x < MENU_X || x > MENU_X + MENU_W)
            return -1;
        for (let i = 0; i < 3; i += 1) {
            if (y >= itemY(i) && y < itemY(i) + ITEM_H + ITEM_GAP)
                return i;
        }
        return -1;
    }
    function inPanel(x, y) {
        if (openIdx < 0)
            return false;
        const t = panelTop(openIdx);
        return x >= PANEL_X && x <= PANEL_X + panelW() && y >= t && y <= t + PANEL_H;
    }
    function side(ax, ay, bx, by, px, py) {
        return (px - bx) * (ay - by) - (ax - bx) * (py - by);
    }
    function inTriangle(px, py, a, b, c) {
        const d1 = side(px, py, a[0], a[1], b[0], b[1]);
        const d2 = side(px, py, b[0], b[1], c[0], c[1]);
        const d3 = side(px, py, c[0], c[1], a[0], a[1]);
        const neg = d1 < 0 || d2 < 0 || d3 < 0;
        const pos = d1 > 0 || d2 > 0 || d3 > 0;
        return !(neg && pos);
    }
    function corners() {
        const t = panelTop(Math.max(0, openIdx));
        return [[PANEL_X, t - TRIANGLE_PAD], [PANEL_X, t + PANEL_H + TRIANGLE_PAD]];
    }
    function script(ms) {
        const t = ms % CYCLE_MS;
        const a = [MENU_X + MENU_W / 2, itemY(0) + ITEM_H / 2];
        const b = [PANEL_X + 40, panelTop(0) + 90];
        const c = [MENU_X + MENU_W / 2, itemY(2) + ITEM_H / 2];
        let p = a;
        let f = 0;
        if (t < 200)
            p = a;
        else if (t < 900) {
            f = seg(t, 200, 900);
            p = [a[0] + (b[0] - a[0]) * f, a[1] + (b[1] - a[1]) * f];
        }
        else if (t < 1200)
            p = b;
        else if (t < 1800) {
            f = seg(t, 1200, 1800);
            p = [b[0] + (c[0] - b[0]) * f, b[1] + (c[1] - b[1]) * f];
        }
        else if (t < 2400)
            p = c;
        else if (t < 3000) {
            f = seg(t, 2400, 3000);
            p = [c[0] + (a[0] - c[0]) * f, c[1] + (a[1] - c[1]) * f];
        }
        mx = p[0];
        my = p[1];
    }
    function tick(ms) {
        if (demo)
            script(ms);
        trail.push([mx, my]);
        if (trail.length > TRAIL + 1)
            trail.shift();
        const old = trail[0];
        const dx = mx - old[0];
        const dy = my - old[1];
        spd = (Math.hypot(dx, dy) / (trail.length - 1 || 1)) * 60;
        const hover = hitItem(mx, my);
        const c = corners();
        inTri = spd >= SPEED_MIN && dx > 0 && inTriangle(mx, my, old, c[0], c[1]);
        if (hover >= 0 && hover !== openIdx) {
            if (inTri && openIdx >= 0) {
                if (since < 0)
                    since = ms;
                if (ms - since > INTENT_MS)
                    openIdx = hover;
            }
            else {
                openIdx = hover;
                since = -1;
            }
            leftAt = -1;
        }
        else if (hover === openIdx || inPanel(mx, my)) {
            since = -1;
            leftAt = -1;
        }
        else {
            since = -1;
            if (leftAt < 0)
                leftAt = ms;
            if (ms - leftAt > GRACE && hover < 0 && mx < MENU_X - 4)
                openIdx = -1;
        }
        for (let i = 0; i < 3; i += 1)
            vis[i] += ((i === openIdx ? 1 : 0) - vis[i]) * 0.3;
    }
    function snap() {
        for (let i = 0; i < 3; i += 1)
            vis[i] = i === openIdx ? 1 : 0;
        inTri = false;
    }
    function render() {
        const w = panelW();
        for (let i = 0; i < 3; i += 1) {
            subs[i].style.width = w + "px";
            subs[i].style.transform = "translate3d(" + (PANEL_X + (1 - vis[i]) * -10).toFixed(1) + "px," + panelTop(i).toFixed(1) + "px,0)";
            subs[i].style.opacity = vis[i].toFixed(2);
            subs[i].style.visibility = vis[i] > 0.02 ? "visible" : "hidden";
        }
        if (openIdx !== lastOpen) {
            lastOpen = openIdx;
            for (let i = 0; i < 3; i += 1) {
                items[i].setAttribute("aria-expanded", i === openIdx ? "true" : "false");
                if (i === openIdx)
                    items[i].setAttribute("data-open", "1");
                else
                    items[i].removeAttribute("data-open");
            }
        }
        const old = trail.length ? trail[0] : [mx, my];
        const c = corners();
        tri.style.clipPath = "polygon(" + old[0].toFixed(1) + "px " + old[1].toFixed(1) + "px," + c[0][0] + "px " + c[0][1].toFixed(1) + "px," + c[1][0] + "px " + c[1][1].toFixed(1) + "px)";
        tri.setAttribute("data-on", inTri ? "1" : "0");
        tri.style.visibility = openIdx >= 0 && mx < PANEL_X ? "visible" : "hidden";
        cur.style.transform = "translate3d(" + (mx - 7).toFixed(1) + "px," + (my - 7).toFixed(1) + "px,0)";
        say("speed " + Math.round(spd) + "  triangle " + (inTri ? "in" : "out") + "  open " + (openIdx + 1));
    }
    on(root, "pointermove", (e) => {
        stopDemo();
        const p = local(e);
        mx = p.x;
        my = p.y;
        if (reduce && hitItem(mx, my) >= 0)
            openIdx = hitItem(mx, my);
        sync();
    });
    items.forEach((el, i) => {
        on(el, "focus", () => {
            stopDemo();
            openIdx = i;
            sync();
        });
    });
    on(root, "keydown", (e) => {
        if (e.key !== "Escape" || openIdx < 0)
            return;
        e.preventDefault();
        stopDemo();
        openIdx = -1;
        sync();
    });
    const FRAME_MS = 1000 / 60;
    function frame(ts) {
        if (t0 < 0) {
            t0 = ts;
            last = ts;
        }
        acc += Math.min(100, ts - last);
        last = ts;
        let n = 0;
        while (acc >= FRAME_MS && n < 6) {
            clock += FRAME_MS;
            tick(clock);
            acc -= FRAME_MS;
            n += 1;
        }
        if (n === 6)
            acc = 0;
        render();
        raf = requestAnimationFrame(frame);
    }
    const ro = new ResizeObserver(() => sync());
    ro.observe(root);
    if (reduce) {
        stopDemo();
        snap();
        render();
    }
    else {
        raf = requestAnimationFrame(frame);
    }
    return () => {
        cancelAnimationFrame(raf);
        offs.forEach((f) => f());
        ro.disconnect();
    };
})();

// SafeTriangleMenu - vanilla 판(03-pm-hover-intent-safe-triangle) 의 React 포트. 같은 계산을 useEffect 안에서 돌린다.
import { useEffect, useRef } from "react";
import styles from "./SafeTriangleMenu.module.scss";

export default function SafeTriangleMenu() {
  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;
    let acc = 0;
    let clock = 0;
    const offs: Array<() => void> = [];
    const live = root.querySelector("[data-r=live]") as HTMLElement;

    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 {
      if (!demo) return;
      demo = false;
      root.removeAttribute("data-demo");
      root.classList.remove("is-demo");
      live.setAttribute("aria-live", "polite");
    }
    if (reduce) live.setAttribute("aria-live", "polite");
    let shown = "";
    function say(s: string): void {
      if (s === shown) return;
      shown = s;
      live.textContent = s;
    }
    function makeRng(seed: number): () => number {
      let s = seed >>> 0;
      return () => {
        s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
        return s / 4294967296;
      };
    }
    function local(e: PointerEvent): { x: number; y: number } {
      const r = root.getBoundingClientRect();
      return { x: e.clientX - r.left, y: e.clientY - r.top };
    }
    function sync(): void {
      if (reduce) {
        snap();
        render();
      }
    }

    // 기법: 포인터가 떠나는 순간의 위치를 꼭짓점으로 삼고 팝오버 왼쪽 두 모서리를 밑변으로 하는 삼각형을 그린다. 그 안을 SPEED_MIN 이상으로 팝오버 쪽으로 지나는 동안엔 다른 항목에 닿아도 닫지 않는다.
    const INTENT_MS = 260;
    const TRIANGLE_PAD = 10;
    const SPEED_MIN = 60;
    const GRACE = 140;
    const MENU_X = 12;
    const MENU_W = 112;
    const MENU_TOP = 34;
    const ITEM_H = 36;
    const ITEM_GAP = 4;
    const PANEL_X = 132;
    const PANEL_H = 132;
    const TRAIL = 6;
    const CYCLE_MS = 3200;
    const items = Array.from(root.querySelectorAll("[data-r=item]")) as HTMLElement[];
    const subs = Array.from(root.querySelectorAll("[data-r=sub]")) as HTMLElement[];
    const tri = q<HTMLElement>("[data-r=tri]");
    const cur = q<HTMLElement>("[data-r=cur]");
    const trail: number[][] = [];
    const vis = [0, 0, 0];
    let mx = MENU_X + MENU_W / 2;
    let my = MENU_TOP + ITEM_H / 2;
    let openIdx = 0;
    let since = -1;
    let leftAt = -1;
    let inTri = false;
    let spd = 0;
    let lastOpen = -2;

    function itemY(i: number): number {
      return MENU_TOP + i * (ITEM_H + ITEM_GAP);
    }
    function panelTop(i: number): number {
      return clamp(itemY(i), MENU_TOP - 4, root.clientHeight - 8 - PANEL_H);
    }
    function panelW(): number {
      return Math.min(150, root.clientWidth - PANEL_X - 8);
    }
    function hitItem(x: number, y: number): number {
      if (x < MENU_X || x > MENU_X + MENU_W) return -1;
      for (let i = 0; i < 3; i += 1) {
        if (y >= itemY(i) && y < itemY(i) + ITEM_H + ITEM_GAP) return i;
      }
      return -1;
    }
    function inPanel(x: number, y: number): boolean {
      if (openIdx < 0) return false;
      const t = panelTop(openIdx);
      return x >= PANEL_X && x <= PANEL_X + panelW() && y >= t && y <= t + PANEL_H;
    }
    function side(ax: number, ay: number, bx: number, by: number, px: number, py: number): number {
      return (px - bx) * (ay - by) - (ax - bx) * (py - by);
    }
    function inTriangle(px: number, py: number, a: number[], b: number[], c: number[]): boolean {
      const d1 = side(px, py, a[0], a[1], b[0], b[1]);
      const d2 = side(px, py, b[0], b[1], c[0], c[1]);
      const d3 = side(px, py, c[0], c[1], a[0], a[1]);
      const neg = d1 < 0 || d2 < 0 || d3 < 0;
      const pos = d1 > 0 || d2 > 0 || d3 > 0;
      return !(neg && pos);
    }
    function corners(): number[][] {
      const t = panelTop(Math.max(0, openIdx));
      return [[PANEL_X, t - TRIANGLE_PAD], [PANEL_X, t + PANEL_H + TRIANGLE_PAD]];
    }
    function script(ms: number): void {
      const t = ms % CYCLE_MS;
      const a = [MENU_X + MENU_W / 2, itemY(0) + ITEM_H / 2];
      const b = [PANEL_X + 40, panelTop(0) + 90];
      const c = [MENU_X + MENU_W / 2, itemY(2) + ITEM_H / 2];
      let p = a;
      let f = 0;
      if (t < 200) p = a;
      else if (t < 900) {
        f = seg(t, 200, 900);
        p = [a[0] + (b[0] - a[0]) * f, a[1] + (b[1] - a[1]) * f];
      } else if (t < 1200) p = b;
      else if (t < 1800) {
        f = seg(t, 1200, 1800);
        p = [b[0] + (c[0] - b[0]) * f, b[1] + (c[1] - b[1]) * f];
      } else if (t < 2400) p = c;
      else if (t < 3000) {
        f = seg(t, 2400, 3000);
        p = [c[0] + (a[0] - c[0]) * f, c[1] + (a[1] - c[1]) * f];
      }
      mx = p[0];
      my = p[1];
    }
    function tick(ms: number): void {
      if (demo) script(ms);
      trail.push([mx, my]);
      if (trail.length > TRAIL + 1) trail.shift();
      const old = trail[0];
      const dx = mx - old[0];
      const dy = my - old[1];
      spd = (Math.hypot(dx, dy) / (trail.length - 1 || 1)) * 60;
      const hover = hitItem(mx, my);
      const c = corners();
      inTri = spd >= SPEED_MIN && dx > 0 && inTriangle(mx, my, old, c[0], c[1]);
      if (hover >= 0 && hover !== openIdx) {
        if (inTri && openIdx >= 0) {
          if (since < 0) since = ms;
          if (ms - since > INTENT_MS) openIdx = hover;
        } else {
          openIdx = hover;
          since = -1;
        }
        leftAt = -1;
      } else if (hover === openIdx || inPanel(mx, my)) {
        since = -1;
        leftAt = -1;
      } else {
        since = -1;
        if (leftAt < 0) leftAt = ms;
        if (ms - leftAt > GRACE && hover < 0 && mx < MENU_X - 4) openIdx = -1;
      }
      for (let i = 0; i < 3; i += 1) vis[i] += ((i === openIdx ? 1 : 0) - vis[i]) * 0.3;
    }
    function snap(): void {
      for (let i = 0; i < 3; i += 1) vis[i] = i === openIdx ? 1 : 0;
      inTri = false;
    }
    function render(): void {
      const w = panelW();
      for (let i = 0; i < 3; i += 1) {
        subs[i].style.width = w + "px";
        subs[i].style.transform = "translate3d(" + (PANEL_X + (1 - vis[i]) * -10).toFixed(1) + "px," + panelTop(i).toFixed(1) + "px,0)";
        subs[i].style.opacity = vis[i].toFixed(2);
        subs[i].style.visibility = vis[i] > 0.02 ? "visible" : "hidden";
      }
      if (openIdx !== lastOpen) {
        lastOpen = openIdx;
        for (let i = 0; i < 3; i += 1) {
          items[i].setAttribute("aria-expanded", i === openIdx ? "true" : "false");
          if (i === openIdx) items[i].setAttribute("data-open", "1");
          else items[i].removeAttribute("data-open");
        }
      }
      const old = trail.length ? trail[0] : [mx, my];
      const c = corners();
      tri.style.clipPath = "polygon(" + old[0].toFixed(1) + "px " + old[1].toFixed(1) + "px," + c[0][0] + "px " + c[0][1].toFixed(1) + "px," + c[1][0] + "px " + c[1][1].toFixed(1) + "px)";
      tri.setAttribute("data-on", inTri ? "1" : "0");
      tri.style.visibility = openIdx >= 0 && mx < PANEL_X ? "visible" : "hidden";
      cur.style.transform = "translate3d(" + (mx - 7).toFixed(1) + "px," + (my - 7).toFixed(1) + "px,0)";
      say("speed " + Math.round(spd) + "  triangle " + (inTri ? "in" : "out") + "  open " + (openIdx + 1));
    }
    on(root, "pointermove", (e: PointerEvent) => {
      stopDemo();
      const p = local(e);
      mx = p.x;
      my = p.y;
      if (reduce && hitItem(mx, my) >= 0) openIdx = hitItem(mx, my);
      sync();
    });
    items.forEach((el, i) => {
      on(el, "focus", () => {
        stopDemo();
        openIdx = i;
        sync();
      });
    });
    on(root, "keydown", (e: KeyboardEvent) => {
      if (e.key !== "Escape" || openIdx < 0) return;
      e.preventDefault();
      stopDemo();
      openIdx = -1;
      sync();
    });

    const FRAME_MS = 1000 / 60;
    function frame(ts: number): void {
      if (t0 < 0) {
        t0 = ts;
        last = ts;
      }
      acc += Math.min(100, ts - last);
      last = ts;
      let n = 0;
      while (acc >= FRAME_MS && n < 6) {
        clock += FRAME_MS;
        tick(clock);
        acc -= FRAME_MS;
        n += 1;
      }
      if (n === 6) acc = 0;
      render();
      raf = requestAnimationFrame(frame);
    }
    const ro = new ResizeObserver(() => sync());
    ro.observe(root);
    if (reduce) {
      stopDemo();
      snap();
      render();
    } else {
      raf = requestAnimationFrame(frame);
    }
    return () => {
      cancelAnimationFrame(raf);
      offs.forEach((f) => f());
      ro.disconnect();
    };

  }, []);

  return (
    <main className={styles["stage"]}>
      <div ref={rootRef} className={styles["pm"] + " is-demo"} data-demo="1">
        <p className={styles["pm__live"]} data-r="live" aria-live="off" aria-atomic="true"></p>
        <i className={styles["pm__tri"]} data-r="tri"></i>
        <div className={styles["pm__menu"]}><button className={styles["pm__item"]} data-r="item" type="button" aria-haspopup="true" aria-expanded="false">프로필</button><button className={styles["pm__item"]} data-r="item" type="button" aria-haspopup="true" aria-expanded="false">알림</button><button className={styles["pm__item"]} data-r="item" type="button" aria-haspopup="true" aria-expanded="false">보안</button></div>
        <div className={styles["pm__sub"]} data-r="sub"><b className={styles["pm__ttl"]}>프로필</b><span className={styles["pm__r"]}>열기</span><span className={styles["pm__r"]}>고정</span><span className={styles["pm__r"]}>삭제</span></div><div className={styles["pm__sub"]} data-r="sub"><b className={styles["pm__ttl"]}>알림</b><span className={styles["pm__r"]}>열기</span><span className={styles["pm__r"]}>고정</span><span className={styles["pm__r"]}>삭제</span></div><div className={styles["pm__sub"]} data-r="sub"><b className={styles["pm__ttl"]}>보안</b><span className={styles["pm__r"]}>열기</span><span className={styles["pm__r"]}>고정</span><span className={styles["pm__r"]}>삭제</span></div>
        <i className={styles["pm__cur"]} data-r="cur"></i>
      </div>
    </main>
  );
}