06Mini to expand

<main class="stage is-demo">
  <nav class="rail" tabindex="0" aria-label="Side navigation">
    <div class="rail__inner">
      <a class="rail__item" href="#"><span class="rail__ic" aria-hidden="true"></span><span class="rail__label">Home</span></a>
      <a class="rail__item" href="#"><span class="rail__ic" aria-hidden="true"></span><span class="rail__label">Search</span></a>
      <a class="rail__item" href="#"><span class="rail__ic" aria-hidden="true"></span><span class="rail__label">Settings</span></a>
    </div>
  </nav>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-base;       // 300ms — 넓어지는 시간
$easing: $ease-out;
$color: $stage-yellow;      // 활성 아이콘 강조색(배경 대비용, 아래서 재사용)

// ── 데모 무대 ───────────────────────────────────────────
@include stage($stage-yellow);

$collapsed: 56px;
$expanded: 200px;
$ratio: math.div($collapsed, $expanded);

.rail {
  position: relative;
  overflow: hidden;
  width: $expanded;
  height: min(50vw, 150px);
  border-radius: $r-card;
  background: $stage-ink;
  transform: scaleX($ratio);
  transform-origin: left center; // 규칙8: 레일 좌변 scaleX 접힘·펼침
  transition: transform $duration $easing;
  cursor: pointer;
}

// 안쪽은 바깥의 scaleX 를 역으로 상쇄해, 글자·아이콘이 눌리지 않는다
.rail__inner {
  width: $expanded;
  height: 100%;
  box-sizing: border-box;
  display: flex; flex-direction: column; gap: $sp-2;
  padding: $sp-4 $sp-3;
  transform: scaleX(math.div(1, $ratio));
  transform-origin: left center; // 규칙8: 역상쇄 scaleX 좌변 축
  transition: transform $duration $easing;
}

.rail__item {
  display: flex; align-items: center; gap: $sp-3;
  padding: $sp-2;
  border-radius: $r-sm;
  color: $stage-paper; text-decoration: none;
  &:hover, &:focus-visible { background: rgba($stage-paper, .12); }
}
.rail__ic {
  flex: none;
  width: $sp-4; height: $sp-4;
  border-radius: 50%;
  background: $stage-yellow;
}
.rail__label {
  font-weight: 500;
  font-size: 13px;
  line-height: 1;
  font-family: inherit;
  white-space: nowrap;
  opacity: .9;
}

.rail:hover, .rail:focus-within {
  transform: scaleX(1);
  .rail__inner { transform: scaleX(1); }
}

// 데모 루프: 좁음 → 넓음 → 좁음, 안팎이 반대 배율로 같이 애니메이션
.stage.is-demo .rail        { animation: rail-loop $dur-loop $easing infinite; }
.stage.is-demo .rail__inner { animation: rail-inner-loop $dur-loop $easing infinite; }

@keyframes rail-loop {
  0%, 100% { transform: scaleX(#{$ratio}); }
  30%, 75% { transform: scaleX(1); }
}
@keyframes rail-inner-loop {
  0%, 100% { transform: scaleX(#{math.div(1, $ratio)}); }
  30%, 75% { transform: scaleX(1); }
}

@media (prefers-reduced-motion: reduce) {
  .stage.is-demo .rail, .stage.is-demo .rail__inner { animation: none; }
  .rail, .rail__inner { transition-duration: 1ms; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.rail {
  position: relative;
  overflow: hidden;
  width: 200px;
  height: min(50vw, 150px);
  border-radius: 16px;
  background: #17141a;
  transform: scaleX(0.28);
  transform-origin: left center;
  transition: transform 300ms ease-out;
  cursor: pointer;
}

.rail__inner {
  width: 200px;
  height: 100%;
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 16px 12px;
  transform: scaleX(3.5714285714);
  transform-origin: left center;
  transition: transform 300ms ease-out;
}

.rail__item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 8px;
  border-radius: 8px;
  color: #ffffff;
  text-decoration: none;
}
.rail__item:hover, .rail__item:focus-visible {
  background: rgba(255, 255, 255, 0.12);
}

.rail__ic {
  flex: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: #ffd23f;
}

.rail__label {
  font-weight: 500;
  font-size: 13px;
  line-height: 1;
  font-family: inherit;
  white-space: nowrap;
  opacity: 0.9;
}

.rail:hover, .rail:focus-within {
  transform: scaleX(1);
}
.rail:hover .rail__inner, .rail:focus-within .rail__inner {
  transform: scaleX(1);
}

.stage.is-demo .rail {
  animation: rail-loop 2s ease-out infinite;
}

.stage.is-demo .rail__inner {
  animation: rail-inner-loop 2s ease-out infinite;
}

@keyframes rail-loop {
  0%, 100% {
    transform: scaleX(0.28);
  }
  30%, 75% {
    transform: scaleX(1);
  }
}
@keyframes rail-inner-loop {
  0%, 100% {
    transform: scaleX(3.5714285714);
  }
  30%, 75% {
    transform: scaleX(1);
  }
}
@media (prefers-reduced-motion: reduce) {
  .stage.is-demo .rail, .stage.is-demo .rail__inner {
    animation: none;
  }
  .rail, .rail__inner {
    transition-duration: 1ms;
  }
}

// 실제 hover·focus 는 CSS 만으로 동작한다. 이 한 줄은 데모 루프를 실제 상호작용으로 넘겨주는 역할뿐이다.
document.querySelector('.rail').addEventListener('pointerenter', function () {
  document.querySelector('.stage').classList.remove('is-demo');
});

import type { CSSProperties } from "react";
import styles from "./MiniExpandRail.module.scss";

export type MiniExpandRailProps = {
  duration?: number;
  easing?: string;
  color?: string;
};

const ITEMS = ["홈", "검색", "설정"];

export default function MiniExpandRail({
  duration = 300,
  easing = "ease-out",
  color = "#ffd23f",
}: MiniExpandRailProps) {
  const vars: CSSProperties = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  return (
    <div className={styles.stage} style={vars}>
      <nav className={styles.rail} tabIndex={0} aria-label="사이드 내비게이션">
        <div className={styles.inner}>
          {ITEMS.map((label) => (
            <a key={label} className={styles.item} href="#">
              <span className={styles.ic} aria-hidden="true" />
              <span className={styles.label}>{label}</span>
            </a>
          ))}
        </div>
      </nav>
    </div>
  );
}