01スプリングで開く基本セレクト

<main class="stage">
  <div class="ss is-demo">
    <span class="ss__label" id="ss-label">配送方法</span>
    <button class="ss__btn" type="button" id="ss-btn" role="combobox" aria-haspopup="listbox" aria-expanded="false" aria-controls="ss-list" aria-labelledby="ss-label ss-value">
      <span class="ss__value" id="ss-value">通常配送</span>
      <span class="ss__caret" aria-hidden="true"><svg viewBox="0 0 256 256" width="12" height="12"><g fill="currentColor"><path d="m208 96l-80 80l-80-80Z" opacity=".2"/><path d="M215.39 92.94A8 8 0 0 0 208 88H48a8 8 0 0 0-5.66 13.66l80 80a8 8 0 0 0 11.32 0l80-80a8 8 0 0 0 1.73-8.72M128 164.69L67.31 104h121.38Z"/></g></svg></span>
    </button>
    <ul class="ss__list" id="ss-list" role="listbox" aria-labelledby="ss-label" tabindex="-1">
      <li class="ss__opt is-sel" id="ss-o1" role="option" aria-selected="true"><span>通常配送</span><span class="ss__tick" aria-hidden="true"><svg viewBox="0 0 256 256" width="13" height="13"><g fill="currentColor"><path d="M224 128a96 96 0 1 1-96-96a96 96 0 0 1 96 96" opacity=".2"/><path d="M173.66 98.34a8 8 0 0 1 0 11.32l-56 56a8 8 0 0 1-11.32 0l-24-24a8 8 0 0 1 11.32-11.32L112 148.69l50.34-50.35a8 8 0 0 1 11.32 0M232 128A104 104 0 1 1 128 24a104.11 104.11 0 0 1 104 104m-16 0a88 88 0 1 0-88 88a88.1 88.1 0 0 0 88-88"/></g></svg></span></li>
      <li class="ss__opt" id="ss-o2" role="option" aria-selected="false"><span>早朝配送</span><span class="ss__tick" aria-hidden="true"><svg viewBox="0 0 256 256" width="13" height="13"><g fill="currentColor"><path d="M224 128a96 96 0 1 1-96-96a96 96 0 0 1 96 96" opacity=".2"/><path d="M173.66 98.34a8 8 0 0 1 0 11.32l-56 56a8 8 0 0 1-11.32 0l-24-24a8 8 0 0 1 11.32-11.32L112 148.69l50.34-50.35a8 8 0 0 1 11.32 0M232 128A104 104 0 1 1 128 24a104.11 104.11 0 0 1 104 104m-16 0a88 88 0 1 0-88 88a88.1 88.1 0 0 0 88-88"/></g></svg></span></li>
      <li class="ss__opt" id="ss-o3" role="option" aria-selected="false"><span>当日配送</span><span class="ss__tick" aria-hidden="true"><svg viewBox="0 0 256 256" width="13" height="13"><g fill="currentColor"><path d="M224 128a96 96 0 1 1-96-96a96 96 0 0 1 96 96" opacity=".2"/><path d="M173.66 98.34a8 8 0 0 1 0 11.32l-56 56a8 8 0 0 1-11.32 0l-24-24a8 8 0 0 1 11.32-11.32L112 148.69l50.34-50.35a8 8 0 0 1 11.32 0M232 128A104 104 0 1 1 128 24a104.11 104.11 0 0 1 104 104m-16 0a88 88 0 1 0-88 88a88.1 88.1 0 0 0 88-88"/></g></svg></span></li>
      <li class="ss__opt" id="ss-o4" role="option" aria-selected="false"><span>店舗受取</span><span class="ss__tick" aria-hidden="true"><svg viewBox="0 0 256 256" width="13" height="13"><g fill="currentColor"><path d="M224 128a96 96 0 1 1-96-96a96 96 0 0 1 96 96" opacity=".2"/><path d="M173.66 98.34a8 8 0 0 1 0 11.32l-56 56a8 8 0 0 1-11.32 0l-24-24a8 8 0 0 1 11.32-11.32L112 148.69l50.34-50.35a8 8 0 0 1 11.32 0M232 128A104 104 0 1 1 128 24a104.11 104.11 0 0 1 104 104m-16 0a88 88 0 1 0-88 88a88.1 88.1 0 0 0 88-88"/></g></svg></span></li>
    </ul>
  </div>
</main>

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

$duration: $dur-quick;
$easing: $ease-pop;
$color: $subject-blue;

@include stage($stage-ink);

.ss {
  position: relative;
  box-sizing: border-box;
  width: min(232px, 84vw);
  // 열린 목록은 absolute 라 높이에 안 잡힌다 — 그만큼 아래를 비워 둬야 무대 가운데 정렬이 맞는다
  padding-bottom: 116px;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: $stage-ink;
}
.ss__label {
  display: block;
  font-size: 10px; line-height: 12px; font-weight: 700;
  letter-spacing: .04em;
  color: rgba(255, 255, 255, .6);
  margin: 0 0 $sp-1;
}
.ss__btn {
  box-sizing: border-box;
  width: 100%; height: 32px;
  display: flex; align-items: center; justify-content: space-between; gap: $sp-2;
  padding: 0 $sp-3;
  border: 1px solid rgba(255, 255, 255, .14);
  background: rgba(255, 255, 255, .06);
  border-radius: $r-control;
  color: #fff;
  font-family: inherit;
  font-size: 12px; font-weight: 600;
  cursor: pointer;
  transition: border-color $duration $easing, background $duration $easing;
}
.ss__btn:hover { background: rgba(255, 255, 255, .1); }
.ss.is-open .ss__btn { border-color: $color; }
.ss__caret { display: inline-flex; color: rgba(255, 255, 255, .55); transition: transform $duration $easing; }
.ss.is-open .ss__caret { transform: rotate(180deg); }

.ss__list {
  position: absolute;
  top: 52px; left: 0; right: 0;
  box-sizing: border-box;
  margin: 0; padding: $sp-1;
  list-style: none;
  background: #fff;
  border-radius: $r-card;
  box-shadow: $shadow-raised;
  transform-origin: top center; // 규칙8: 버튼 아래변에서 펼침
  transform: translateY(-6px) scaleY(.72);
  opacity: 0;
  pointer-events: none;
  transition: transform $duration $easing, opacity $duration $easing;
}
.ss.is-open .ss__list { transform: translateY(0) scaleY(1); opacity: 1; pointer-events: auto; }
.ss__list:focus-visible { outline: 2px solid $color; outline-offset: 2px; }

.ss__opt {
  box-sizing: border-box;
  height: 26px;
  display: flex; align-items: center; justify-content: space-between; gap: $sp-2;
  padding: 0 $sp-2;
  border-radius: $r-sm;
  font-size: 12px; font-weight: 600;
  cursor: pointer;
}
.ss__opt.is-active { background: rgba(47, 109, 246, .12); }
.ss__tick { display: inline-flex; color: $color; opacity: 0; }
.ss__opt.is-sel .ss__tick { opacity: 1; }

// ── 자동 루프: 열림 → 유지 → 닫힘. 끝 프레임이 첫 프레임과 같아 이어 붙어도 튀지 않는다 ──
.ss.is-demo .ss__list { animation: ss-open $dur-loop $easing infinite; }
@keyframes ss-open {
  0%, 100% { opacity: 0; transform: translateY(-6px) scaleY(.72); }
  22%      { opacity: 1; transform: translateY(0) scaleY(1); }
  78%      { opacity: 1; transform: translateY(0) scaleY(1); }
}

@media (prefers-reduced-motion: reduce) {
  .ss.is-demo .ss__list { animation: none !important; }
  .ss__list, .ss__btn, .ss__caret { 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);
}

.ss {
  position: relative;
  box-sizing: border-box;
  width: min(232px, 84vw);
  padding-bottom: 116px;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: #17141a;
}

.ss__label {
  display: block;
  font-size: 10px;
  line-height: 12px;
  font-weight: 700;
  letter-spacing: 0.04em;
  color: rgba(255, 255, 255, 0.6);
  margin: 0 0 4px;
}

.ss__btn {
  box-sizing: border-box;
  width: 100%;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 0 12px;
  border: 1px solid rgba(255, 255, 255, 0.14);
  background: rgba(255, 255, 255, 0.06);
  border-radius: 12px;
  color: #fff;
  font-family: inherit;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  transition: border-color 220ms cubic-bezier(0.2, 1.4, 0.4, 1), background 220ms cubic-bezier(0.2, 1.4, 0.4, 1);
}

.ss__btn:hover {
  background: rgba(255, 255, 255, 0.1);
}

.ss.is-open .ss__btn {
  border-color: #2f6df6;
}

.ss__caret {
  display: inline-flex;
  color: rgba(255, 255, 255, 0.55);
  transition: transform 220ms cubic-bezier(0.2, 1.4, 0.4, 1);
}

.ss.is-open .ss__caret {
  transform: rotate(180deg);
}

.ss__list {
  position: absolute;
  top: 52px;
  left: 0;
  right: 0;
  box-sizing: border-box;
  margin: 0;
  padding: 4px;
  list-style: none;
  background: #fff;
  border-radius: 16px;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  transform-origin: top center;
  transform: translateY(-6px) scaleY(0.72);
  opacity: 0;
  pointer-events: none;
  transition: transform 220ms cubic-bezier(0.2, 1.4, 0.4, 1), opacity 220ms cubic-bezier(0.2, 1.4, 0.4, 1);
}

.ss.is-open .ss__list {
  transform: translateY(0) scaleY(1);
  opacity: 1;
  pointer-events: auto;
}

.ss__list:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: 2px;
}

.ss__opt {
  box-sizing: border-box;
  height: 26px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 0 8px;
  border-radius: 8px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
}

.ss__opt.is-active {
  background: rgba(47, 109, 246, 0.12);
}

.ss__tick {
  display: inline-flex;
  color: #2f6df6;
  opacity: 0;
}

.ss__opt.is-sel .ss__tick {
  opacity: 1;
}

.ss.is-demo .ss__list {
  animation: ss-open 2s cubic-bezier(0.2, 1.4, 0.4, 1) infinite;
}

@keyframes ss-open {
  0%, 100% {
    opacity: 0;
    transform: translateY(-6px) scaleY(0.72);
  }
  22% {
    opacity: 1;
    transform: translateY(0) scaleY(1);
  }
  78% {
    opacity: 1;
    transform: translateY(0) scaleY(1);
  }
}
@media (prefers-reduced-motion: reduce) {
  .ss.is-demo .ss__list {
    animation: none !important;
  }
  .ss__list, .ss__btn, .ss__caret {
    transition: none;
  }
}

// 실제 동작: 버튼으로 열고 닫고, 화살표로 옮기고, Enter 로 고르고, Escape 로 닫는다.
var root = document.querySelector('.ss');
var btn = document.getElementById('ss-btn');
var list = document.getElementById('ss-list');
var value = document.getElementById('ss-value');
var opts = [].slice.call(list.querySelectorAll('.ss__opt'));
var active = 0;
function paint() {
  opts.forEach(function (o, i) { o.classList.toggle('is-active', i === active); });
  list.setAttribute('aria-activedescendant', opts[active].id);
}
function open(on) {
  root.classList.remove('is-demo');
  root.classList.toggle('is-open', on);
  btn.setAttribute('aria-expanded', String(on));
  if (on) { paint(); list.focus({ preventScroll: true }); }
}
function pick(i) {
  opts.forEach(function (o, k) {
    o.classList.toggle('is-sel', k === i);
    o.setAttribute('aria-selected', String(k === i));
  });
  value.textContent = opts[i].firstElementChild.textContent;
  open(false);
  btn.focus({ preventScroll: true });
}
btn.addEventListener('click', function () { open(!root.classList.contains('is-open')); });
opts.forEach(function (o, i) {
  o.addEventListener('click', function () { pick(i); });
  o.addEventListener('mousemove', function () { active = i; paint(); });
});
list.addEventListener('keydown', function (e) {
  if (e.key === 'ArrowDown') { active = Math.min(active + 1, opts.length - 1); paint(); e.preventDefault(); }
  else if (e.key === 'ArrowUp') { active = Math.max(active - 1, 0); paint(); e.preventDefault(); }
  else if (e.key === 'Enter' || e.key === ' ') { pick(active); e.preventDefault(); }
  else if (e.key === 'Escape') { open(false); btn.focus({ preventScroll: true }); }
});
document.addEventListener('click', function (e) { if (!e.target.closest('.ss')) open(false); });

import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./SpringSelect.module.scss";

export type SpringSelectProps = {
  label?: string;
  options?: string[];
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };
type KeyEvt = { key: string; preventDefault: () => void };
type ChangeEvt = { target: { value: string } };
type ClickEvt = { stopPropagation: () => void };

export default function SpringSelect({
  label = "Shipping method",
  options = ["Standard", "Dawn delivery", "Same day", "Store pickup"],
  duration = 220,
  easing = "cubic-bezier(.2,1.4,.4,1)",
  color = "#2f6df6",
}: SpringSelectProps) {
  const [open, setOpen] = useState(false);
  const [picked, setPicked] = useState(0);
  const [active, setActive] = useState(0);
  const rootRef = useRef<HTMLDivElement>(null);
  const btnRef = useRef<HTMLButtonElement>(null);
  const listRef = useRef<HTMLUListElement>(null);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  useEffect(() => {
    function onDocClick(e: MouseEvent) {
      if (rootRef.current && !rootRef.current.contains(e.target as Node)) setOpen(false);
    }
    document.addEventListener("click", onDocClick);
    return () => document.removeEventListener("click", onDocClick);
  }, []);

  useEffect(() => {
    if (open) listRef.current?.focus({ preventScroll: true });
  }, [open]);

  function pick(i: number) {
    setPicked(i);
    setOpen(false);
    btnRef.current?.focus({ preventScroll: true });
  }

  return (
    <div className={`${styles.ss} ${open ? styles.isOpen : ""}`} style={vars} ref={rootRef}>
      <span className={styles.label} id="ss-label">{label}</span>
      <button
        ref={btnRef}
        type="button"
        className={styles.btn}
        role="combobox"
        aria-haspopup="listbox"
        aria-expanded={open}
        aria-controls="ss-list"
        onClick={() => setOpen((o) => !o)}
      >
        <span>{options[picked]}</span>
        <span className={styles.caret} aria-hidden="true">▾</span>
      </button>
      <ul
        ref={listRef}
        id="ss-list"
        className={styles.list}
        role="listbox"
        aria-labelledby="ss-label"
        aria-activedescendant={`ss-o${active}`}
        tabIndex={-1}
        onKeyDown={(e: KeyEvt) => {
          if (e.key === "ArrowDown") { setActive((a) => Math.min(a + 1, options.length - 1)); e.preventDefault(); }
          else if (e.key === "ArrowUp") { setActive((a) => Math.max(a - 1, 0)); e.preventDefault(); }
          else if (e.key === "Enter" || e.key === " ") { pick(active); e.preventDefault(); }
          else if (e.key === "Escape") { setOpen(false); btnRef.current?.focus({ preventScroll: true }); }
        }}
      >
        {options.map((o, i) => (
          <li
            key={o}
            id={`ss-o${i}`}
            className={`${styles.opt} ${i === active ? styles.isActive : ""}`}
            role="option"
            aria-selected={i === picked}
            onMouseMove={() => setActive(i)}
            onClick={() => pick(i)}
          >
            <span>{o}</span>
            <span className={styles.tick} aria-hidden="true">{i === picked ? "●" : ""}</span>
          </li>
        ))}
      </ul>
    </div>
  );
}