04Exclusive pressed state — when one button's pressed value turns on, every other button's pressed value turns off at the same instant

<main class="stage">
<div class="rep is-demo" id="rep" role="radiogroup" aria-label="View mode">
  <button class="rep__btn" role="radio" aria-checked="true" tabindex="0" data-i="0">List type</button>
  <button class="rep__btn" role="radio" aria-checked="false" tabindex="-1" data-i="1">Grid type</button>
  <button class="rep__btn" role="radio" aria-checked="false" tabindex="-1" data-i="2">Board type</button>
</div>
</main>

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

// 계산 겹: index.html 이 버튼마다 눌림 깊이(depth)를 감쇠 스프링으로 적분한다. 한 버튼이 켜지는
// 순간 나머지가 동시에 0으로 되돌아가고, 켜지는 버튼은 depth 1을 살짝 넘겼다가 정착한다(오버슛).
// translateY·box-shadow 는 그 깊이값의 함수다 — 레이아웃에 영향 없는 transform·paint 만 바뀐다.
@include stage($stage-orange);

.rep {
  display: flex;
  gap: $sp-3;
}

.rep__btn {
  appearance: none;
  border: none;
  border-radius: $r-control;
  background: $subject-cream;
  color: $subject-ink;
  font-size: 13px;
  font-weight: 700;
  padding: $sp-3 $sp-5;
  cursor: pointer;
  box-shadow: 0 8px 14px rgba(23, 20, 26, .34);
  will-change: transform, box-shadow;

  &:focus-visible { outline: 2px solid $subject-blue-deep; outline-offset: 2px; }
}

.rep__btn--on {
  background: $subject-blue-deep;
  color: $subject-cream;
}

@media (max-width: 340px) {
  .rep { gap: $sp-2; }
  .rep__btn { font-size: 12px; padding: $sp-2 $sp-4; }
}

@media (prefers-reduced-motion: reduce) {
  .rep__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: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.rep {
  display: flex;
  gap: 12px;
}

.rep__btn {
  appearance: none;
  border: none;
  border-radius: 12px;
  background: #fff7e6;
  color: #17141a;
  font-size: 13px;
  font-weight: 700;
  padding: 12px 20px;
  cursor: pointer;
  box-shadow: 0 8px 14px rgba(23, 20, 26, 0.34);
  will-change: transform, box-shadow;
}
.rep__btn:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

.rep__btn--on {
  background: #0a4fe8;
  color: #fff7e6;
}

@media (max-width: 340px) {
  .rep {
    gap: 8px;
  }
  .rep__btn {
    font-size: 12px;
    padding: 8px 16px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .rep__btn {
    transition: none;
  }
}

(function () {
  var CYCLE_MS = 950; // 자동 루프가 다음 버튼을 누르는 간격
  var STIFF = 320; // 계산 겹 상수: 눌림 깊이 스프링 강성
  var DAMP = 14; // 계산 겹 상수: 감쇠 — 작을수록 눌린 뒤 살짝 되튀는 오버슛이 남는다
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var root = document.getElementById('rep');
  var btns = Array.prototype.slice.call(root.querySelectorAll('.rep__btn'));
  var isDemo = true;
  var checkedIdx = 0;

  // 계산 겹: 버튼마다 눌림 깊이(depth 0~1)를 감쇠 스프링으로 적분한다 — 켜지는 버튼은
  // depth 1을 살짝 넘겼다가(오버슛) 정착하고, 나머지는 동시에 0으로 되돌아간다.
  var depth = btns.map(function () { return 0; });
  var vel = btns.map(function () { return 0; });
  var target = btns.map(function (b, i) { return i === 0 ? 1 : 0; });

  function setChecked(idx) {
    checkedIdx = idx;
    btns.forEach(function (b, i) {
      var on = i === idx;
      b.setAttribute('aria-checked', String(on));
      b.setAttribute('tabindex', on ? '0' : '-1');
      target[i] = on ? 1 : 0;
      if (reduce) { depth[i] = target[i]; vel[i] = 0; }
    });
  }

  function human() {
    if (isDemo) { root.classList.remove('is-demo'); isDemo = false; }
  }

  btns.forEach(function (b, i) {
    b.addEventListener('click', function () { human(); setChecked(i); b.focus({ preventScroll: true }); });
  });

  root.addEventListener('keydown', function (e) {
    if (e.key !== 'ArrowRight' && e.key !== 'ArrowLeft') return;
    human();
    var dir = e.key === 'ArrowRight' ? 1 : -1;
    var next = (checkedIdx + dir + btns.length) % btns.length;
    setChecked(next);
    btns[next].focus({ preventScroll: true });
    e.preventDefault();
  });

  function render(i) {
    var d = depth[i];
    var overshootLift = Math.max(0, -(d - 1)) * -2; // 오버슛 구간(d>1)에서 살짝 더 눌리는 표현
    var y = d * 3 + (d > 1 ? (d - 1) * 4 : 0);
    var blur = 14 - d * 8;
    var offY = 8 - d * 6;
    btns[i].style.transform = 'translateY(' + y.toFixed(2) + 'px)';
    btns[i].style.boxShadow = '0 ' + Math.max(1, offY).toFixed(1) + 'px ' + Math.max(4, blur).toFixed(1) + 'px rgba(23,20,26,.34)';
    btns[i].classList.toggle('rep__btn--on', d > 0.5);
  }

  var cycleStart = 0, lastIdx = -1;
  function loop(ts) {
    if (!cycleStart) cycleStart = ts;
    if (isDemo && !reduce) {
      var idx = Math.floor((ts - cycleStart) / CYCLE_MS) % btns.length;
      if (idx !== lastIdx) { lastIdx = idx; setChecked(idx); }
    }

    for (var i = 0; i < btns.length; i++) {
      var acc = STIFF * (target[i] - depth[i]) - DAMP * vel[i];
      vel[i] += acc * (1 / 60);
      depth[i] += vel[i] * (1 / 60);
      render(i);
    }

    requestAnimationFrame(loop);
  }
  requestAnimationFrame(loop);
})();

// RadioExclusivePress — vanilla 판(run/369/demo/04-btn-group-radio-exclusive-press/index.html) 의 React 포트.
// 버튼마다 눌림 깊이(depth)를 감쇠 스프링으로 적분한다. 한 버튼이 켜지는 순간 나머지가 동시에
// 0으로 되돌아가고, 켜지는 버튼은 depth 1을 살짝 넘겼다가 정착한다(오버슛).
import { useEffect, useRef } from "react";
import styles from "./RadioExclusivePress.module.scss";

type Box<T> = { current: T };

const LABELS = ["목록형", "격자형", "보드형"];

export default function RadioExclusivePress() {
  const rootRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const btnRefs = useRef([]) as unknown as Box<HTMLButtonElement[]>;
  const rafRef = useRef(0) as unknown as Box<number>;

  useEffect(() => {
    const CYCLE_MS = 950;
    const STIFF = 320; // 계산 겹 상수: 눌림 깊이 스프링 강성
    const DAMP = 14; // 계산 겹 상수: 감쇠
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;

    const root = rootRef.current;
    const btns = btnRefs.current;
    if (!root || btns.length === 0) return;

    let isDemo = true;
    let checkedIdx = 0;
    const depth = btns.map(() => 0);
    const vel = btns.map(() => 0);
    const target = btns.map((_, i) => (i === 0 ? 1 : 0));

    function setChecked(idx: number) {
      checkedIdx = idx;
      btns.forEach((b, i) => {
        const on = i === idx;
        b.setAttribute("aria-checked", String(on));
        b.setAttribute("tabindex", on ? "0" : "-1");
        target[i] = on ? 1 : 0;
        if (reduce) { depth[i] = target[i]; vel[i] = 0; }
      });
    }

    function human() { if (isDemo) { root!.classList.remove(styles.isDemo); isDemo = false; } }

    const clicks: (() => void)[] = [];
    btns.forEach((b, i) => {
      const fn = () => { human(); setChecked(i); b.focus({ preventScroll: true }); };
      b.addEventListener("click", fn);
      clicks.push(fn);
    });

    function onKeydown(e: KeyboardEvent) {
      if (e.key !== "ArrowRight" && e.key !== "ArrowLeft") return;
      human();
      const dir = e.key === "ArrowRight" ? 1 : -1;
      const next = (checkedIdx + dir + btns.length) % btns.length;
      setChecked(next);
      btns[next].focus({ preventScroll: true });
      e.preventDefault();
    }
    root.addEventListener("keydown", onKeydown);

    function render(i: number) {
      const d = depth[i];
      const y = d * 3 + (d > 1 ? (d - 1) * 4 : 0);
      const blur = 14 - d * 8;
      const offY = 8 - d * 6;
      btns[i].style.transform = "translateY(" + y.toFixed(2) + "px)";
      btns[i].style.boxShadow = "0 " + Math.max(1, offY).toFixed(1) + "px " + Math.max(4, blur).toFixed(1) + "px rgba(23,20,26,.34)";
      btns[i].classList.toggle(styles.btnOn, d > 0.5);
    }

    let cycleStart = 0, lastIdx = -1;
    function loop(ts: number) {
      if (!cycleStart) cycleStart = ts;
      if (isDemo && !reduce) {
        const idx = Math.floor((ts - cycleStart) / CYCLE_MS) % btns.length;
        if (idx !== lastIdx) { lastIdx = idx; setChecked(idx); }
      }

      for (let i = 0; i < btns.length; i++) {
        const acc = STIFF * (target[i] - depth[i]) - DAMP * vel[i];
        vel[i] += acc * (1 / 60);
        depth[i] += vel[i] * (1 / 60);
        render(i);
      }

      rafRef.current = requestAnimationFrame(loop);
    }
    rafRef.current = requestAnimationFrame(loop);

    return () => {
      btns.forEach((b, i) => b.removeEventListener("click", clicks[i]));
      root.removeEventListener("keydown", onKeydown);
      cancelAnimationFrame(rafRef.current);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.rep + " " + styles.isDemo} ref={rootRef} role="radiogroup" aria-label="보기 방식">
        {LABELS.map((label, i) => (
          <button
            key={label}
            className={styles.btn}
            role="radio"
            aria-checked={i === 0}
            tabIndex={i === 0 ? 0 : -1}
            ref={(el: HTMLButtonElement | null) => { if (el) btnRefs.current[i] = el; }}
          >
            {label}
          </button>
        ))}
      </div>
    </main>
  );
}