08Divider Whose Ornament Opens as the Pointer Nears

<main class="stage">
<div class="dv is-demo" id="dvRoot">
  <div class="dv__field" id="dvField">
    <div class="dv__row" id="dvRow" role="separator">
      <span class="dv__line dv__line--left" id="dvLeft"></span>
      <span class="dv__orn" id="dvOrn"></span>
      <span class="dv__line dv__line--right" id="dvRight"></span>
    </div>
    <span class="dv__ghost" id="dvGhost"></span>
  </div>
  <div class="dv__bar">
  <button class="dv__btn" id="dvBtn" type="button" aria-pressed="false">Open ornament</button>
  <p class="dv__meta"><span class="dv__tag">OPEN</span> <b id="dvOpen">0</b>%</p>
  </div>
</div>
</main>

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

// 핵심: 포인터와 장식 사이 거리를 NEAR_RANGE 로 정규화한 값이 열림이 되고, 열림은 매 프레임 일부씩 따라가며 선을 벌린다.

$orn-size: 24px;

@include stage($stage-ink);

.dv {
  width: min(100%, 360px);
  display: grid;
  gap: $sp-2;
}

.dv__field {
  position: relative;
  box-sizing: border-box;
  height: 104px;
  display: grid;
  align-items: center;
  padding: 0 $sp-4;
  border-radius: $r-card;
  background: $tick-panel;
  overflow: hidden;
}

.dv__row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: $sp-3;
}

.dv__line {
  flex: 1;
  height: 6px;
  border-radius: $r-pill;
  background: $subject-pink;
}

.dv__orn {
  flex: none;
  display: block;
  width: $orn-size;
  height: $orn-size;
  border-radius: $r-xs;
  background: $subject-lilac;
  transform: scale(.5);
}

.dv__ghost {
  position: absolute;
  left: 0;
  top: 0;
  width: 12px;
  height: 12px;
  border-radius: $r-pill;
  background: rgba($stage-paper, .85);
  opacity: 0;
  pointer-events: none;
}

.dv__bar {
  box-sizing: border-box;
  width: 100%;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: $sp-2 $sp-3;
}

.dv__btn {
  box-sizing: border-box;
  height: 40px;
  padding: 0 $sp-5;
  border: 0;
  border-radius: $r-control;
  background: $subject-lilac;
  color: $subject-ink;
  font-family: inherit;
  font-size: 14px;
  font-weight: 700;
  line-height: 20px;
  cursor: pointer;
}
.dv__btn[aria-pressed="true"] { background: $subject-pink; }
.dv__btn:focus-visible { outline: 3px solid $stage-paper; outline-offset: 3px; }

.dv__meta {
  margin: 0;
  display: flex;
  align-items: baseline;
  gap: $sp-2;
  font-size: 12px;
  line-height: 16px;
  color: rgba($stage-paper, .78);
}
.dv__tag { font-weight: 700; letter-spacing: .08em; }
.dv__meta b { min-width: 3ch; text-align: right; font-variant-numeric: tabular-nums; color: $stage-paper; }

@media (prefers-reduced-motion: reduce) {
  .dv__btn { transition: 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);
}

.dv {
  width: min(100%, 360px);
  display: grid;
  gap: 8px;
}

.dv__field {
  position: relative;
  box-sizing: border-box;
  height: 104px;
  display: grid;
  align-items: center;
  padding: 0 16px;
  border-radius: 16px;
  background: #231f28;
  overflow: hidden;
}

.dv__row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
}

.dv__line {
  flex: 1;
  height: 6px;
  border-radius: 999px;
  background: #ff9ebb;
}

.dv__orn {
  flex: none;
  display: block;
  width: 24px;
  height: 24px;
  border-radius: 4px;
  background: #b9a0ff;
  transform: scale(0.5);
}

.dv__ghost {
  position: absolute;
  left: 0;
  top: 0;
  width: 12px;
  height: 12px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.85);
  opacity: 0;
  pointer-events: none;
}

.dv__bar {
  box-sizing: border-box;
  width: 100%;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 8px 12px;
}

.dv__btn {
  box-sizing: border-box;
  height: 40px;
  padding: 0 20px;
  border: 0;
  border-radius: 12px;
  background: #b9a0ff;
  color: #17141a;
  font-family: inherit;
  font-size: 14px;
  font-weight: 700;
  line-height: 20px;
  cursor: pointer;
}

.dv__btn[aria-pressed=true] {
  background: #ff9ebb;
}

.dv__btn:focus-visible {
  outline: 3px solid #ffffff;
  outline-offset: 3px;
}

.dv__meta {
  margin: 0;
  display: flex;
  align-items: baseline;
  gap: 8px;
  font-size: 12px;
  line-height: 16px;
  color: rgba(255, 255, 255, 0.78);
}

.dv__tag {
  font-weight: 700;
  letter-spacing: 0.08em;
}

.dv__meta b {
  min-width: 3ch;
  text-align: right;
  font-variant-numeric: tabular-nums;
  color: #ffffff;
}

@media (prefers-reduced-motion: reduce) {
  .dv__btn {
    transition: none;
  }
}

(function () {
  // 기법: 포인터와 장식 중심 사이 거리를 NEAR_RANGE 로 정규화해 목표 열림(0~1)을 만들고, 현재 열림은 매 프레임 남은 거리의 일부(OPEN_RATE)만 따라간다.
  // 선 두 쪽은 OPEN_MAX_PX 만큼 벌어지고 장식은 열림에 따라 회전·확대된다. 데모는 가상 포인터(유령 점)가 좌우로 오간다.
  var NEAR_RANGE = 120;
  var OPEN_RATE = 9;
  var OPEN_MAX_PX = 72;
  var CYCLE_MS = 2000;

  var root = document.getElementById('dvRoot');
  var field = document.getElementById('dvField');
  var orn = document.getElementById('dvOrn');
  var left = document.getElementById('dvLeft');
  var right = document.getElementById('dvRight');
  var ghost = document.getElementById('dvGhost');
  var btn = document.getElementById('dvBtn');
  var openEl = document.getElementById('dvOpen');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var open = 0;
  var pointer = null;
  var pinned = false;
  var lastTs = null;
  var t0 = null;

  function smooth(t) { return t * t * (3 - 2 * t); }
  function paint() {
    var half = OPEN_MAX_PX * open / 2;
    left.style.transform = 'translateX(' + (-half).toFixed(2) + 'px)';
    right.style.transform = 'translateX(' + half.toFixed(2) + 'px)';
    orn.style.transform = 'rotate(' + (open * 135).toFixed(1) + 'deg) scale(' + (0.5 + open * 0.9).toFixed(3) + ')';
    openEl.textContent = String(Math.round(open * 100));
  }
  function goalOf() {
    if (pinned) return 1;
    if (!pointer) return 0;
    var box = orn.getBoundingClientRect();
    var dx = pointer.x - (box.left + box.width / 2);
    var dy = pointer.y - (box.top + box.height / 2);
    var dist = Math.sqrt(dx * dx + dy * dy);
    return smooth(Math.min(1, Math.max(0, 1 - dist / NEAR_RANGE)));
  }
  function stopDemo() { root.classList.remove('is-demo'); ghost.style.opacity = '0'; }

  document.addEventListener('pointermove', function (e) {
    stopDemo();
    pointer = { x: e.clientX, y: e.clientY };
    if (reduce) { open = goalOf(); paint(); }
  });
  document.addEventListener('pointerleave', function () {
    pointer = null;
    if (reduce) { open = goalOf(); paint(); }
  });
  btn.addEventListener('click', function () {
    stopDemo();
    pinned = !pinned;
    btn.setAttribute('aria-pressed', String(pinned));
    if (reduce) { open = goalOf(); paint(); }
  });

  function tick(ts) {
    if (t0 === null) t0 = ts;
    var dt = lastTs === null ? 0.016 : Math.min(0.05, (ts - lastTs) / 1000);
    lastTs = ts;
    if (root.classList.contains('is-demo')) {
      var fb = field.getBoundingClientRect();
      var ob = orn.getBoundingClientRect();
      var phase = ((ts - t0) % CYCLE_MS) / CYCLE_MS * Math.PI * 2;
      var gx = ob.left + ob.width / 2 + 170 * Math.cos(phase);
      var gy = ob.top + ob.height / 2 + 22 * Math.sin(phase);
      pointer = { x: gx, y: gy };
      ghost.style.transform = 'translate(' + (gx - fb.left - 6).toFixed(1) + 'px,' + (gy - fb.top - 6).toFixed(1) + 'px)';
    }
    var k = 1 - Math.exp(-dt * OPEN_RATE);
    open += (goalOf() - open) * k;
    paint();
    requestAnimationFrame(tick);
  }

  if (reduce) {
    stopDemo();
    paint();
  } else {
    ghost.style.opacity = '1';
    requestAnimationFrame(tick);
  }
})();

// ProximityOrnament — vanilla 판(08-divl-ornament-proximity-open) 의 React 포트.
// 포인터와 장식 사이 거리를 NEAR_RANGE 로 정규화한 값이 열림이 되고, 열림은 매 프레임 일부(OPEN_RATE)씩 따라간다.
import { useEffect, useRef, useState } from "react";
import styles from "./ProximityOrnament.module.scss";

type Box<T> = { current: T };
type Point = { x: number; y: number };

const NEAR_RANGE = 120;
const OPEN_RATE = 9;
const OPEN_MAX_PX = 72;
const CYCLE_MS = 2000;

const smooth = (t: number): number => t * t * (3 - 2 * t);

export default function ProximityOrnament() {
  const fieldRef = useRef<HTMLDivElement | null>(null) as Box<HTMLDivElement | null>;
  const ornRef = useRef<HTMLSpanElement | null>(null) as Box<HTMLSpanElement | null>;
  const leftRef = useRef<HTMLSpanElement | null>(null) as Box<HTMLSpanElement | null>;
  const rightRef = useRef<HTMLSpanElement | null>(null) as Box<HTMLSpanElement | null>;
  const ghostRef = useRef<HTMLSpanElement | null>(null) as Box<HTMLSpanElement | null>;
  const openRef = useRef<HTMLElement | null>(null) as Box<HTMLElement | null>;
  const pinnedRef = useRef(false) as Box<boolean>;
  const stopRef = useRef<() => void>(() => undefined) as Box<() => void>;
  const [pinned, setPinned] = useState(false);

  useEffect(() => {
    const field = fieldRef.current;
    const orn = ornRef.current;
    const left = leftRef.current;
    const right = rightRef.current;
    const ghost = ghostRef.current;
    const openEl = openRef.current;
    if (!field || !orn || !left || !right || !ghost || !openEl) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo = !reduce;
    let open = 0;
    let pointer: Point | null = null;
    let lastTs: number | null = null;
    let t0: number | null = null;
    let raf = 0;

    const paint = (): void => {
      const half = (OPEN_MAX_PX * open) / 2;
      left.style.transform = "translateX(" + (-half).toFixed(2) + "px)";
      right.style.transform = "translateX(" + half.toFixed(2) + "px)";
      orn.style.transform = "rotate(" + (open * 135).toFixed(1) + "deg) scale(" + (0.5 + open * 0.9).toFixed(3) + ")";
      openEl.textContent = String(Math.round(open * 100));
    };
    const goalOf = (): number => {
      if (pinnedRef.current) return 1;
      if (!pointer) return 0;
      const box = orn.getBoundingClientRect();
      const dx = pointer.x - (box.left + box.width / 2);
      const dy = pointer.y - (box.top + box.height / 2);
      const dist = Math.sqrt(dx * dx + dy * dy);
      return smooth(Math.min(1, Math.max(0, 1 - dist / NEAR_RANGE)));
    };
    const stopDemo = (): void => {
      demo = false;
      ghost.style.opacity = "0";
    };
    stopRef.current = () => {
      stopDemo();
      if (reduce) {
        open = goalOf();
        paint();
      }
    };
    const onMove = (e: { clientX: number; clientY: number }): void => {
      stopDemo();
      pointer = { x: e.clientX, y: e.clientY };
      if (reduce) {
        open = goalOf();
        paint();
      }
    };
    const onLeave = (): void => {
      pointer = null;
      if (reduce) {
        open = goalOf();
        paint();
      }
    };
    document.addEventListener("pointermove", onMove);
    document.addEventListener("pointerleave", onLeave);

    const tick = (ts: number): void => {
      if (t0 === null) t0 = ts;
      const dt = lastTs === null ? 0.016 : Math.min(0.05, (ts - lastTs) / 1000);
      lastTs = ts;
      if (demo) {
        const fb = field.getBoundingClientRect();
        const ob = orn.getBoundingClientRect();
        const phase = (((ts - t0) % CYCLE_MS) / CYCLE_MS) * Math.PI * 2;
        const gx = ob.left + ob.width / 2 + 170 * Math.cos(phase);
        const gy = ob.top + ob.height / 2 + 22 * Math.sin(phase);
        pointer = { x: gx, y: gy };
        ghost.style.transform = "translate(" + (gx - fb.left - 6).toFixed(1) + "px," + (gy - fb.top - 6).toFixed(1) + "px)";
      }
      const k = 1 - Math.exp(-dt * OPEN_RATE);
      open += (goalOf() - open) * k;
      paint();
      raf = requestAnimationFrame(tick);
    };

    paint();
    if (!reduce) {
      ghost.style.opacity = "1";
      raf = requestAnimationFrame(tick);
    }
    return () => {
      cancelAnimationFrame(raf);
      document.removeEventListener("pointermove", onMove);
      document.removeEventListener("pointerleave", onLeave);
    };
  }, []);

  const toggle = (): void => {
    pinnedRef.current = !pinnedRef.current;
    setPinned(pinnedRef.current);
    stopRef.current();
  };

  return (
    <div className={styles.dv}>
      <div className={styles.field} ref={fieldRef}>
        <div className={styles.row} role="separator">
          <span className={styles.line} ref={leftRef} />
          <span className={styles.orn} ref={ornRef} />
          <span className={styles.line} ref={rightRef} />
        </div>
        <span className={styles.ghost} ref={ghostRef} />
      </div>
      <div className={styles.bar}>
        <button className={styles.btn} type="button" aria-pressed={pinned} onClick={toggle}>장식 열기</button>
        <p className={styles.meta}>
          <span className={styles.tag}>OPEN</span> <b ref={openRef}>0</b>%
        </p>
      </div>
    </div>
  );
}