03パネルフェード

<main class="stage">
  <div class="fp is-demo">
    <input type="radio" name="fp-tab" id="fp-1" class="fp__radio" checked>
    <input type="radio" name="fp-tab" id="fp-2" class="fp__radio">
    <input type="radio" name="fp-tab" id="fp-3" class="fp__radio">
    <div class="fp__nav">
      <label class="fp__tab" for="fp-1">紹介</label>
      <label class="fp__tab" for="fp-2">レビュー</label>
      <label class="fp__tab" for="fp-3">問い合わせ</label>
    </div>
    <div class="fp__panels">
      <p class="fp__panel fp__panel--1">素材・サイズ・洗濯方法をまとめました。</p>
      <p class="fp__panel fp__panel--2">評価と直近のレビュー342件をまとめました。</p>
      <p class="fp__panel fp__panel--3">交換・返品はここからすぐ申請できます。</p>
    </div>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-quick;                            // 패널이 겹쳐 페이드되는 시간
$easing: $ease-out;                               // 패널 페이드 이징 (실제 클릭)
$color: $subject-ink;                             // 활성 탭 글자색 (주황 면 위 5.50:1 — 크림은 3.11 로 미달)

@include stage($stage-orange);

.fp { width: min(300px, 86vw); }
.fp__radio { position: absolute; opacity: 0; pointer-events: none; }

.fp__nav {
  position: relative;
  display: flex;
  gap: $sp-4;
  border-bottom: 1px solid rgba(255, 247, 230, .25);
  padding-bottom: $sp-2;
}
.fp__tab {
  font-weight: 600;
  font-size: clamp(12px, 3.4vw, 14px);
  line-height: 1;
  font-family: inherit;
  color: rgba($subject-ink, .85);                 // 비활성 탭 — 주황 면 위 4.62:1 (.72 는 3.76 으로 미달)
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}
#fp-1:checked ~ .fp__nav label[for="fp-1"],
#fp-2:checked ~ .fp__nav label[for="fp-2"],
#fp-3:checked ~ .fp__nav label[for="fp-3"] { color: $color; }

// 세 패널을 같은 grid 칸에 포개 두면 자리가 안 흔들린다
.fp__panels { position: relative; display: grid; margin-top: $sp-4; min-height: 40px; }
.fp__panel {
  grid-area: 1 / 1;
  margin: 0;
  color: $subject-ink;                            // 패널 본문 — 5.50:1
  font-weight: 400;
  font-size: clamp(12px, 3.2vw, 13px);
  line-height: 1.5;
  font-family: inherit;
  opacity: 0;
  pointer-events: none;
  transition: opacity $duration $easing;
}
#fp-1:checked ~ .fp__panels .fp__panel--1,
#fp-2:checked ~ .fp__panels .fp__panel--2,
#fp-3:checked ~ .fp__panels .fp__panel--3 { opacity: 1; pointer-events: auto; }

// ── 데모 루프: 클릭 전까지 세 패널을 스스로 오간다 ──────────────
// 한 겹(관성) — 밑줄이 없는 이 항목은 패널 전환에 관성을 얹는다: 등장 패널은 8px 아래에서
// 올라와 -2px 살짝 지나쳤다가(오버슛) 0 에 정착, 사라지는 패널은 반대로 2px 위로 흐르며 fade.
// 정적(:checked) 전환 경로는 opacity 만인 원본 그대로 — 관성은 -inertia 루프 키프레임 안에서만.
.fp.is-demo .fp__panel--1 { animation: fp-loop-1-inertia $dur-loop $easing infinite; }
.fp.is-demo .fp__panel--2 { animation: fp-loop-2-inertia $dur-loop $easing infinite; }
.fp.is-demo .fp__panel--3 { animation: fp-loop-3-inertia $dur-loop $easing infinite; }
@keyframes fp-loop-1-inertia {
  0%, 15%  { opacity: 1; transform: translateY(0); }
  22%      { transform: translateY(-1px); }
  30%, 100% { opacity: 0; transform: translateY(-2px); }
}
@keyframes fp-loop-2-inertia {
  0%, 30%   { opacity: 0; transform: translateY(8px); }
  42%       { transform: translateY(-2px); }
  45%, 63%  { opacity: 1; transform: translateY(0); }
  70%       { transform: translateY(-1px); }
  78%, 100% { opacity: 0; transform: translateY(-2px); }
}
@keyframes fp-loop-3-inertia {
  0%, 63%   { opacity: 0; transform: translateY(8px); }
  75%       { transform: translateY(-2px); }
  78%, 96%  { opacity: 1; transform: translateY(0); }
  98%       { transform: translateY(-1px); }
  100%      { opacity: 0; transform: translateY(-2px); }
}

@media (prefers-reduced-motion: reduce) {
  .fp__panel { transition: none; }
  .fp.is-demo .fp__panel--1,
  .fp.is-demo .fp__panel--2,
  .fp.is-demo .fp__panel--3 { animation: none !important; }
}

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);
}

.fp {
  width: min(300px, 86vw);
}

.fp__radio {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.fp__nav {
  position: relative;
  display: flex;
  gap: 16px;
  border-bottom: 1px solid rgba(255, 247, 230, 0.25);
  padding-bottom: 8px;
}

.fp__tab {
  font-weight: 600;
  font-size: clamp(12px, 3.4vw, 14px);
  line-height: 1;
  font-family: inherit;
  color: rgba(23, 20, 26, 0.85);
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

#fp-1:checked ~ .fp__nav label[for=fp-1],
#fp-2:checked ~ .fp__nav label[for=fp-2],
#fp-3:checked ~ .fp__nav label[for=fp-3] {
  color: #17141a;
}

.fp__panels {
  position: relative;
  display: grid;
  margin-top: 16px;
  min-height: 40px;
}

.fp__panel {
  grid-area: 1/1;
  margin: 0;
  color: #17141a;
  font-weight: 400;
  font-size: clamp(12px, 3.2vw, 13px);
  line-height: 1.5;
  font-family: inherit;
  opacity: 0;
  pointer-events: none;
  transition: opacity 220ms ease-out;
}

#fp-1:checked ~ .fp__panels .fp__panel--1,
#fp-2:checked ~ .fp__panels .fp__panel--2,
#fp-3:checked ~ .fp__panels .fp__panel--3 {
  opacity: 1;
  pointer-events: auto;
}

.fp.is-demo .fp__panel--1 {
  animation: fp-loop-1-inertia 2s ease-out infinite;
}

.fp.is-demo .fp__panel--2 {
  animation: fp-loop-2-inertia 2s ease-out infinite;
}

.fp.is-demo .fp__panel--3 {
  animation: fp-loop-3-inertia 2s ease-out infinite;
}

@keyframes fp-loop-1-inertia {
  0%, 15% {
    opacity: 1;
    transform: translateY(0);
  }
  22% {
    transform: translateY(-1px);
  }
  30%, 100% {
    opacity: 0;
    transform: translateY(-2px);
  }
}
@keyframes fp-loop-2-inertia {
  0%, 30% {
    opacity: 0;
    transform: translateY(8px);
  }
  42% {
    transform: translateY(-2px);
  }
  45%, 63% {
    opacity: 1;
    transform: translateY(0);
  }
  70% {
    transform: translateY(-1px);
  }
  78%, 100% {
    opacity: 0;
    transform: translateY(-2px);
  }
}
@keyframes fp-loop-3-inertia {
  0%, 63% {
    opacity: 0;
    transform: translateY(8px);
  }
  75% {
    transform: translateY(-2px);
  }
  78%, 96% {
    opacity: 1;
    transform: translateY(0);
  }
  98% {
    transform: translateY(-1px);
  }
  100% {
    opacity: 0;
    transform: translateY(-2px);
  }
}
@media (prefers-reduced-motion: reduce) {
  .fp__panel {
    transition: none;
  }
  .fp.is-demo .fp__panel--1,
  .fp.is-demo .fp__panel--2,
  .fp.is-demo .fp__panel--3 {
    animation: none !important;
  }
}

// 페이드는 :checked 만으로 이미 동작한다. 실제 클릭이 오면 데모 루프(.is-demo)만 뗀다.
document.querySelectorAll('.fp__radio').forEach(function (r) {
  r.addEventListener('pointerdown', function () { document.querySelector('.fp').classList.remove('is-demo'); });
});

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

const TABS = [
  { label: "소개", panel: "소재·사이즈·세탁법을 정리했습니다." },
  { label: "리뷰", panel: "별점과 최근 구매평 342건을 모았습니다." },
  { label: "문의", panel: "교환·환불은 여기서 바로 신청하세요." },
];

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

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };

export default function FadePanel({ duration = 220, easing = "ease-out", color = "#17141a" }: FadePanelProps) { // 주황 무대 위 활성 탭 글자 — 크림은 3.11 로 미달
  const [active, setActive] = useState(0);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  return (
    <div className={styles.fp} style={vars}>
      <div className={styles.nav} role="tablist">
        {TABS.map((t, i) => (
          <button key={t.label} type="button" role="tab" aria-selected={i === active}
                  className={styles.tab} onClick={() => setActive(i)}>
            {t.label}
          </button>
        ))}
      </div>
      <div className={styles.panels}>
        {TABS.map((t, i) => (
          <p key={t.label} className={styles.panel} style={{ opacity: i === active ? 1 : 0 }} aria-hidden={i !== active}>
            {t.panel}
          </p>
        ))}
      </div>
    </div>
  );
}