/* ============================================================
   textbook-ds.css ── text-books の共通デザインシステム
   ============================================================
   このファイルは index.html / すべての教科書 (docs/*.html) で
   共有される唯一の真実 (single source of truth)。

   ファイル構成:
     1. デザイントークン (:root)
     2. リセット & ベース
     3. 進捗バー / トップナビ / 目次ドロワー
     4. ヒーロー
     5. チャプター本体 (chapter / prose / sidenote / key-concept / summary / figure / chapter-nav / bibliography)
     6. カタログ (index.html 専用 / cover / catalog / entry)
     7. 共通フッター
     8. レスポンシブ / 印刷 / アニメーション

   新しい教科書を作るときは textbook-ds.css と textbook.js を
   読み込むだけで OK。デザインに差を出したい場合は、まずトークン
   (:root の CSS 変数) で表現できないかを検討する。
   ============================================================ */

/* ============================================================
   1. デザイントークン
   ── 古典書の佇まいに着想 ── 鉄紺、墨、辰砂、雁皮
   ============================================================ */
:root {
  /* カラーパレット */
  --color-paper: #faf7f2;
  --color-paper-deep: #f3ede2;
  --color-ink: #1c1917;
  --color-ink-soft: #3f3a35;
  --color-ink-muted: #6b6359;
  --color-rule: #d6cfc1;
  --color-rule-soft: #e8e2d4;
  --color-accent: #a01c1c;       /* 朱・辰砂 ── 強調 */
  --color-accent-soft: #c46868;
  --color-indigo: #1a3a5c;       /* 鉄紺 ── 副次強調 */
  --color-gold: #8b6914;         /* 黄土 ── 章番号など */
  --color-highlight: #f4e8c1;    /* 雁皮 ── ハイライト背景 */

  /* タイポグラフィ */
  --font-serif-jp: 'Noto Serif JP', 'YuMincho', 'Yu Mincho', 'Hiragino Mincho ProN', serif;
  --font-display: 'Cormorant Garamond', 'Noto Serif JP', serif;
  --font-mono: 'JetBrains Mono', 'SF Mono', Consolas, monospace;
  --font-ui: 'Inter', system-ui, sans-serif;

  /* 寸法 */
  --measure: 38rem;              /* 本文の最適行幅 (約 60-70字) */
  --measure-wide: 56rem;
  --side-width: 14rem;
}

/* ============================================================
   2. リセット & ベース
   ============================================================ */
* { margin: 0; padding: 0; box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
}

body {
  font-family: var(--font-serif-jp);
  font-weight: 400;
  font-size: 17px;
  line-height: 1.95;
  letter-spacing: 0.02em;
  color: var(--color-ink);
  background: var(--color-paper);
  background-image:
    radial-gradient(circle at 20% 30%, rgba(180, 160, 120, 0.04) 0%, transparent 50%),
    radial-gradient(circle at 80% 70%, rgba(160, 28, 28, 0.02) 0%, transparent 50%),
    repeating-linear-gradient(0deg, transparent 0, transparent 2px, rgba(140, 120, 90, 0.012) 2px, rgba(140, 120, 90, 0.012) 3px);
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ============================================================
   3. 進捗バー / トップナビ / 目次ドロワー
   ============================================================ */
.progress-bar {
  position: fixed; top: 0; left: 0; width: 100%; height: 3px;
  background: transparent; z-index: 1000;
}
.progress-bar__fill {
  height: 100%; width: 0%;
  background: linear-gradient(90deg, var(--color-accent) 0%, var(--color-gold) 100%);
  transition: width 0.1s ease-out;
}

.top-nav {
  position: fixed; top: 0; left: 0; right: 0;
  background: rgba(250, 247, 242, 0.92);
  backdrop-filter: blur(12px); -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-rule-soft);
  z-index: 100; padding: 0.875rem 2rem;
  display: flex; justify-content: space-between; align-items: center;
  font-family: var(--font-ui); font-size: 0.78rem; letter-spacing: 0.05em;
}
.top-nav__title { color: var(--color-ink-soft); font-weight: 500; }
.top-nav__title em { font-style: italic; color: var(--color-accent); }
.top-nav__toc-toggle {
  background: none; border: 1px solid var(--color-rule); color: var(--color-ink-soft);
  padding: 0.35rem 0.875rem; border-radius: 2px;
  font-family: var(--font-ui); font-size: 0.72rem; cursor: pointer; letter-spacing: 0.1em;
  transition: all 0.2s;
}
.top-nav__toc-toggle:hover {
  background: var(--color-ink); color: var(--color-paper); border-color: var(--color-ink);
}

.toc-drawer {
  position: fixed; top: 0; right: -380px; width: 360px; height: 100vh;
  background: var(--color-paper-deep); border-left: 1px solid var(--color-rule);
  z-index: 200; padding: 5rem 2.5rem 2rem; overflow-y: auto;
  transition: right 0.35s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: -10px 0 40px rgba(0, 0, 0, 0.08);
}
.toc-drawer.is-open { right: 0; }
.toc-drawer__close {
  position: absolute; top: 1.5rem; right: 1.5rem;
  background: none; border: none; font-size: 1.5rem; color: var(--color-ink-soft);
  cursor: pointer; font-family: var(--font-serif-jp);
}
.toc-drawer h3 {
  font-family: var(--font-display); font-size: 0.85rem; font-weight: 500;
  letter-spacing: 0.3em; text-transform: uppercase; color: var(--color-ink-muted);
  margin-bottom: 1.5rem; padding-bottom: 1rem; border-bottom: 1px solid var(--color-rule);
}
.toc-drawer ol { list-style: none; counter-reset: toc-counter; }
.toc-drawer li {
  margin-bottom: 0.875rem; padding-left: 2.5rem; position: relative;
  counter-increment: toc-counter; line-height: 1.5;
}
.toc-drawer li::before {
  content: counter(toc-counter, decimal-leading-zero);
  position: absolute; left: 0; top: 0.1rem;
  font-family: var(--font-display); font-size: 0.75rem; color: var(--color-gold);
  letter-spacing: 0.1em; font-style: italic;
}
.toc-drawer a {
  color: var(--color-ink-soft); text-decoration: none; font-size: 0.92rem;
  display: block; padding: 0.2rem 0;
  border-left: 2px solid transparent; padding-left: 0.5rem; margin-left: -0.5rem;
  transition: all 0.2s;
}
.toc-drawer a:hover {
  color: var(--color-accent);
  border-left-color: var(--color-accent);
  background: rgba(160, 28, 28, 0.03);
}

.toc-backdrop {
  position: fixed; inset: 0; background: rgba(28, 25, 23, 0.4); z-index: 150;
  opacity: 0; pointer-events: none; transition: opacity 0.3s;
}
.toc-backdrop.is-open { opacity: 1; pointer-events: auto; }

/* ============================================================
   4. ヒーロー (教科書1ページ目)
   ============================================================ */
.hero {
  min-height: 100vh; display: flex; flex-direction: column;
  justify-content: center; align-items: center; text-align: center;
  padding: 6rem 2rem 4rem; position: relative;
}
.hero__ornament {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.8rem; letter-spacing: 0.5em; text-transform: uppercase;
  color: var(--color-gold);
  margin-bottom: 2.5rem;
  display: flex; align-items: center; gap: 1.5rem;
}
.hero__ornament::before, .hero__ornament::after {
  content: ''; display: block; width: 3rem; height: 1px; background: var(--color-rule);
}
/* タイトル ── 日本語の本文セリフをベースに、字面を上品に */
.hero__title {
  font-family: var(--font-serif-jp);
  font-weight: 500;
  font-size: clamp(1.85rem, 4.4vw, 3.1rem);
  line-height: 1.45;
  letter-spacing: 0.04em;
  color: var(--color-ink);
  margin-bottom: 1.5rem;
  max-width: 34rem;
  text-wrap: balance;
  word-break: keep-all;          /* 単語の途中で折れない (英数字や記号を含むタイトルで効く) */
  overflow-wrap: anywhere;       /* それでも収まらないときは折る */
}
/* タイトル内のアクセント (em) は「メインタイトル直下のサブタイトル」として扱う ──
   新行で、小さく、色だけ強調 */
.hero__title em {
  display: block;
  font-style: normal;            /* JP セリフは合成イタリックを避ける */
  font-weight: 400;
  font-size: 0.5em;              /* メインの半分 ── 明確に階層が落ちる */
  letter-spacing: 0.12em;        /* 字間を空けて静かに */
  line-height: 1.6;
  color: var(--color-accent);
  font-family: inherit;
  margin-top: 0.7em;
}
.hero__title em::after {
  display: none;                 /* 折り返し時に位置がずれる下線は廃止 */
}

/* サブタイトル ── タイトルとの階層差を強くつける */
.hero__subtitle {
  font-family: var(--font-serif-jp);
  font-weight: 300;
  font-size: clamp(0.82rem, 1.05vw, 0.95rem);
  line-height: 1.95;
  letter-spacing: 0.08em;
  color: var(--color-ink-soft);
  max-width: 28rem;
  margin-bottom: 3rem;
  text-wrap: balance;
}
.hero__meta {
  display: flex; gap: 3rem; flex-wrap: wrap; justify-content: center;
  font-family: var(--font-display); font-style: italic;
  font-size: 0.9rem; color: var(--color-ink-muted); letter-spacing: 0.1em;
}
.hero__meta-item { display: flex; flex-direction: column; gap: 0.5rem; align-items: center; }
.hero__meta-label {
  font-family: var(--font-ui); font-style: normal; font-size: 0.7rem;
  letter-spacing: 0.25em; text-transform: uppercase; color: var(--color-ink-muted);
}
.hero__meta-value {
  font-family: var(--font-display); font-style: italic;
  color: var(--color-accent); font-size: 1.1rem; letter-spacing: 0.15em;
}
.hero__scroll-cue {
  position: absolute; bottom: 2rem; left: 50%; transform: translateX(-50%);
  font-family: var(--font-display); font-style: italic;
  font-size: 0.75rem; letter-spacing: 0.35em; text-transform: uppercase;
  color: var(--color-ink-muted); animation: pulse 2.5s ease-in-out infinite;
}
.hero__scroll-cue::after {
  content: '↓'; display: block; margin-top: 0.5rem; font-style: normal; font-size: 1rem;
}
@keyframes pulse { 0%, 100% { opacity: 0.5; } 50% { opacity: 1; } }

/* ============================================================
   5. チャプター本体
   ============================================================ */
.chapter { padding: 6rem 0 5rem; position: relative; }
.chapter:not(:last-child) { border-bottom: 1px solid var(--color-rule-soft); }
.chapter__inner { max-width: 62rem; margin: 0 auto; padding: 0 2rem; }
.chapter__header { text-align: center; margin-bottom: 4rem; padding: 0 1rem; }
.chapter__number {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.8rem; letter-spacing: 0.4em; text-transform: uppercase;
  color: var(--color-gold); display: block; margin-bottom: 1.5rem;
}
.chapter__title {
  font-family: var(--font-serif-jp); font-weight: 500;
  font-size: clamp(1.8rem, 4vw, 2.6rem); line-height: 1.35;
  color: var(--color-ink); margin-bottom: 1.5rem;
  text-wrap: balance; letter-spacing: 0.01em;
}
.chapter__rule { width: 3rem; height: 1px; background: var(--color-accent); margin: 1.5rem auto; }
.chapter__intro {
  font-family: var(--font-display); font-style: italic;
  font-size: 1.2rem; line-height: 1.7; color: var(--color-ink-soft);
  text-align: center; max-width: 36rem; margin: 0 auto;
}

/* --- 本文 (prose) --- */
.prose { max-width: var(--measure); margin: 0 auto; }
.prose p { margin-bottom: 1.5rem; text-align: justify; text-justify: inter-character; }
.prose > p:first-of-type::first-letter {
  font-family: var(--font-display); font-size: 4rem; font-weight: 500;
  float: left; line-height: 0.9; padding-right: 0.5rem; padding-top: 0.4rem;
  color: var(--color-accent);
}

.prose h3 {
  font-family: var(--font-serif-jp); font-weight: 600;
  font-size: 1.35rem; line-height: 1.5;
  margin-top: 3.5rem; margin-bottom: 1.5rem;
  color: var(--color-ink); letter-spacing: 0.02em;
  position: relative; padding-left: 1.25rem;
}
.prose h3::before {
  content: ''; position: absolute; left: 0; top: 0.7rem;
  width: 0.5rem; height: 0.5rem;
  background: var(--color-accent); transform: rotate(45deg);
}
/* 二段構え用バリアント ── 思想 / 実務 */
.prose h3.h3--thought::before { background: var(--color-indigo); }
.prose h3.h3--practice::before { background: var(--color-gold); }
.prose h3 .h3__tag {
  display: inline-block;
  font-family: var(--font-display); font-style: italic;
  font-size: 0.7rem; letter-spacing: 0.3em; text-transform: uppercase;
  color: var(--color-ink-muted); margin-right: 0.75rem; vertical-align: 0.15em;
}
.prose h3.h3--thought .h3__tag { color: var(--color-indigo); }
.prose h3.h3--practice .h3__tag { color: var(--color-gold); }

.prose strong {
  font-weight: 700; color: var(--color-ink);
  background: linear-gradient(transparent 65%, var(--color-highlight) 65%);
  padding: 0 0.1em;
}
.prose em { font-style: italic; color: var(--color-indigo); }
.prose a {
  color: var(--color-accent); text-decoration: none;
  border-bottom: 1px solid var(--color-accent-soft); transition: all 0.2s;
}
.prose a:hover { background: var(--color-highlight); }

.prose ul, .prose ol { margin: 1.5rem 0; padding-left: 2rem; }
.prose li { margin-bottom: 0.6rem; line-height: 1.85; }
.prose ul li { list-style: none; position: relative; }
.prose ul li::before {
  content: '•'; position: absolute; left: -1.25rem;
  color: var(--color-accent); font-weight: bold;
}

.prose code {
  font-family: var(--font-mono); font-size: 0.88em;
  background: var(--color-paper-deep); color: var(--color-indigo);
  padding: 0.1em 0.4em; border-radius: 2px;
  border: 1px solid var(--color-rule-soft);
}

.prose pre {
  font-family: var(--font-mono); background: #1c1917; color: #f4e8c1;
  padding: 1.5rem; border-radius: 4px; overflow-x: auto;
  margin: 2rem 0; font-size: 0.85rem; line-height: 1.7;
  border-left: 3px solid var(--color-accent); position: relative;
}
.prose pre::before {
  content: 'code'; position: absolute; top: 0.5rem; right: 0.875rem;
  font-family: var(--font-display); font-style: italic;
  font-size: 0.7rem; color: var(--color-gold); letter-spacing: 0.2em;
}
.prose pre code { background: none; border: none; color: inherit; padding: 0; font-size: inherit; }

.prose table { width: 100%; border-collapse: collapse; margin: 2rem 0; font-size: 0.95rem; }
.prose th, .prose td {
  text-align: left; padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--color-rule); line-height: 1.6;
}
.prose th {
  font-weight: 600; background: var(--color-paper-deep);
  font-family: var(--font-serif-jp); color: var(--color-ink);
  border-bottom: 2px solid var(--color-ink); letter-spacing: 0.03em;
}
.prose tbody tr:hover { background: rgba(244, 232, 193, 0.3); }

.prose blockquote {
  margin: 2rem -2rem; padding: 1.5rem 2rem;
  font-family: var(--font-display); font-style: italic;
  font-size: 1.15rem; line-height: 1.7; color: var(--color-ink-soft);
  border-left: 3px solid var(--color-accent); background: var(--color-paper-deep);
}

/* --- サイドノート (補足 / 引用) --- */
.sidenote {
  background: linear-gradient(180deg, var(--color-paper-deep) 0%, var(--color-paper) 100%);
  border-left: 3px solid var(--color-gold);
  padding: 1.25rem 1.5rem; margin: 2rem 0;
  font-size: 0.9rem; line-height: 1.75; color: var(--color-ink-soft);
  position: relative;
}
.sidenote__label {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.75rem; letter-spacing: 0.2em; text-transform: uppercase;
  color: var(--color-gold); display: block; margin-bottom: 0.5rem;
}
/* 引用バリアント (英語原文を残す用途) */
.sidenote--quote { border-left-color: var(--color-accent); }
.sidenote--quote .sidenote__label { color: var(--color-accent); }
.sidenote__original {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.95rem; line-height: 1.6; color: var(--color-ink-soft);
  display: block; margin-bottom: 0.5rem;
}
.sidenote__attr {
  display: block; margin-top: 0.5rem;
  font-family: var(--font-ui); font-style: normal;
  font-size: 0.72rem; letter-spacing: 0.05em;
  color: var(--color-ink-muted);
}
.sidenote__attr a { color: var(--color-ink-muted); border-bottom: 1px dotted var(--color-ink-muted); text-decoration: none; }
.sidenote__attr a:hover { color: var(--color-accent); border-bottom-color: var(--color-accent); }

/* --- KEY CONCEPT カード (要点強調) --- */
.key-concept {
  background: var(--color-ink); color: var(--color-paper);
  padding: 2rem 2.25rem; margin: 3rem 0; position: relative; border-radius: 2px;
}
.key-concept::before {
  content: '✦'; position: absolute; top: -0.6rem; left: 1.5rem;
  background: var(--color-paper); color: var(--color-accent);
  width: 1.5rem; height: 1.5rem;
  display: flex; align-items: center; justify-content: center; font-size: 0.9rem;
}
.key-concept__label {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.78rem; letter-spacing: 0.3em; text-transform: uppercase;
  color: var(--color-gold); display: block; margin-bottom: 0.875rem;
}
.key-concept__text {
  font-family: var(--font-serif-jp); font-size: 1.05rem;
  line-height: 1.75; color: var(--color-paper); font-weight: 400;
}
.key-concept__text strong { color: #f4e8c1; background: none; font-weight: 600; }

/* --- 章末まとめ (Chunking) --- */
.summary {
  background: var(--color-paper-deep);
  border-top: 2px solid var(--color-ink);
  padding: 2rem 2.5rem; margin: 4rem 0 0; position: relative;
}
.summary__label {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.8rem; letter-spacing: 0.3em; text-transform: uppercase;
  color: var(--color-accent); display: block; margin-bottom: 1rem;
}
.summary__title {
  font-family: var(--font-serif-jp); font-weight: 600;
  font-size: 1.15rem; margin-bottom: 1.25rem; color: var(--color-ink);
}
.summary ul { list-style: none; padding: 0; margin: 0; }
.summary li {
  padding: 0.4rem 0 0.4rem 1.75rem; position: relative;
  line-height: 1.7; font-size: 0.95rem;
}
.summary li::before {
  content: '→'; position: absolute; left: 0;
  color: var(--color-gold); font-weight: bold;
}
.summary li b {
  font-family: var(--font-display); font-style: italic;
  font-weight: 500; color: var(--color-accent); margin-right: 0.5rem;
  letter-spacing: 0.05em;
}

/* --- 図解 (SVG figure) --- */
.figure {
  margin: 3rem -2rem;
  padding: 2rem 0;
  background: var(--color-paper-deep);
  border-top: 1px solid var(--color-rule);
  border-bottom: 1px solid var(--color-rule);
}
.figure__inner { max-width: 52rem; margin: 0 auto; padding: 0 2rem; }
.figure__label {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.78rem; letter-spacing: 0.3em; text-transform: uppercase;
  color: var(--color-gold); text-align: center; margin-bottom: 0.5rem; display: block;
}
.figure__title {
  font-family: var(--font-serif-jp); font-weight: 600;
  font-size: 1.05rem; text-align: center; color: var(--color-ink);
  margin-bottom: 1.75rem; letter-spacing: 0.03em;
}
.figure__svg { width: 100%; height: auto; display: block; margin: 0 auto; }
.figure__caption {
  font-family: var(--font-serif-jp); font-size: 0.85rem; line-height: 1.7;
  color: var(--color-ink-muted); text-align: center;
  margin-top: 1.5rem; padding: 0 2rem; font-style: italic;
}

/* --- 章間ナビゲーション --- */
.chapter-nav {
  max-width: var(--measure); margin: 4rem auto 0;
  padding: 2rem 0 0; border-top: 1px solid var(--color-rule);
  display: flex; justify-content: space-between; gap: 1rem;
  font-family: var(--font-ui); font-size: 0.85rem;
}
.chapter-nav a {
  color: var(--color-ink-soft); text-decoration: none;
  display: flex; flex-direction: column; gap: 0.25rem;
  padding: 0.875rem 1.25rem;
  border: 1px solid var(--color-rule); border-radius: 2px;
  transition: all 0.2s; max-width: 45%;
}
.chapter-nav a:hover { border-color: var(--color-ink); background: var(--color-paper-deep); }
.chapter-nav__label {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.72rem; color: var(--color-gold); letter-spacing: 0.15em;
}
.chapter-nav__title { font-weight: 500; color: var(--color-ink); }
.chapter-nav__prev { text-align: left; }
.chapter-nav__next { text-align: right; margin-left: auto; }

/* --- カラム (callout) ── .sidenote より軽い、短い注釈や Tip 用 --- */
.callout {
  padding: 1rem 1.25rem;
  margin: 1.5rem 0;
  font-size: 0.92rem;
  line-height: 1.75;
  border-left: 3px solid var(--color-ink-muted);
  background: var(--color-paper-deep);
}
.callout--info { border-left-color: var(--color-indigo); }
.callout--warn {
  border-left-color: var(--color-accent);
  background: rgba(160, 28, 28, 0.04);
}
.callout--note { border-left-color: var(--color-gold); }

/* --- 参考文献リスト --- */
.bibliography {
  max-width: var(--measure); margin: 0 auto;
  font-family: var(--font-ui); font-size: 0.85rem; line-height: 1.8;
}
.bibliography li {
  padding: 0.5rem 0; border-bottom: 1px dotted var(--color-rule-soft);
  list-style: none; position: relative; padding-left: 1.75rem;
}
.bibliography li::before {
  content: '§'; position: absolute; left: 0; top: 0.55rem;
  color: var(--color-gold); font-family: var(--font-display); font-style: italic;
}
.bibliography a { color: var(--color-ink-soft); text-decoration: none; border-bottom: 1px solid var(--color-rule); }
.bibliography a:hover { color: var(--color-accent); border-bottom-color: var(--color-accent); }
.bibliography .bib__title { color: var(--color-ink); font-weight: 500; }

/* ============================================================
   6. カタログ (index.html 専用)
   ── cover + catalog + entry
   ============================================================ */
body.catalog-page { min-height: 100vh; display: flex; flex-direction: column; line-height: 1.85; }

.cover {
  padding: clamp(5rem, 10vw, 9rem) 1.5rem clamp(3rem, 6vw, 5rem);
  text-align: center; position: relative;
}
.cover__ornament {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.78rem; letter-spacing: 0.55em; text-transform: uppercase;
  color: var(--color-gold); margin-bottom: 2.25rem;
  display: flex; align-items: center; justify-content: center; gap: 1.5rem;
}
.cover__ornament::before, .cover__ornament::after {
  content: ''; display: block;
  width: clamp(2.5rem, 8vw, 5rem); height: 1px; background: var(--color-rule);
}
.cover__title {
  font-family: var(--font-display); font-weight: 500;
  font-size: clamp(3.2rem, 9vw, 6rem); line-height: 1;
  letter-spacing: 0.32em; color: var(--color-ink);
  margin-left: 0.32em; margin-bottom: 1.4rem; text-wrap: balance;
}
.cover__diamond {
  display: flex; align-items: center; justify-content: center; gap: 0.85rem;
  margin: 1.5rem 0 1.75rem; color: var(--color-accent); font-size: 0.9rem;
}
.cover__diamond::before, .cover__diamond::after {
  content: ''; display: block;
  width: clamp(3rem, 10vw, 6rem); height: 1px;
  background: var(--color-accent); opacity: 0.5;
}
.cover__subtitle {
  font-family: var(--font-serif-jp); font-weight: 300;
  font-size: clamp(0.95rem, 1.6vw, 1.05rem); line-height: 1.9;
  color: var(--color-ink-soft); max-width: 30rem; margin: 0 auto; text-wrap: balance;
}
.cover__meta {
  margin-top: 2.75rem;
  font-family: var(--font-display); font-style: italic;
  font-size: 0.85rem; letter-spacing: 0.2em; color: var(--color-ink-muted);
}
.cover__meta strong { font-style: normal; font-weight: 600; color: var(--color-ink); }

.catalog {
  flex: 1; max-width: var(--measure-wide); margin: 0 auto;
  padding: clamp(2rem, 5vw, 4rem) 1.5rem clamp(4rem, 8vw, 7rem); width: 100%;
}
.catalog__header { text-align: center; margin-bottom: clamp(3rem, 6vw, 5rem); }
.catalog__label {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.78rem; letter-spacing: 0.45em; text-transform: uppercase;
  color: var(--color-gold); display: block; margin-bottom: 1rem;
}
.catalog__heading {
  font-family: var(--font-serif-jp); font-weight: 500;
  font-size: clamp(1.3rem, 2.5vw, 1.6rem);
  letter-spacing: 0.06em; color: var(--color-ink);
}
.catalog__rule { width: 4rem; height: 1px; background: var(--color-rule); margin: 1.4rem auto 0; }

.entry {
  display: grid;
  grid-template-columns: 7rem 1fr;
  gap: clamp(1.5rem, 4vw, 3rem);
  padding: clamp(2.5rem, 5vw, 3.5rem) 0;
  border-top: 1px solid var(--color-rule-soft);
  position: relative;
}
.entry:first-of-type {
  border-top: 2px solid var(--color-ink);
  padding-top: clamp(2.5rem, 5vw, 3.5rem);
}
.entry:last-of-type { border-bottom: 1px solid var(--color-rule-soft); }

.entry__volume {
  text-align: right; padding-top: 0.4rem;
  border-right: 1px solid var(--color-rule-soft);
  padding-right: clamp(1rem, 2.5vw, 1.75rem);
}
.entry__volume-roman {
  font-family: var(--font-display); font-weight: 500; font-style: italic;
  font-size: clamp(2.4rem, 5vw, 3.2rem); line-height: 1;
  color: var(--color-accent); letter-spacing: 0.05em;
}
.entry__volume-label {
  display: block;
  font-family: var(--font-display); font-style: italic;
  font-size: 0.7rem; letter-spacing: 0.32em; text-transform: uppercase;
  color: var(--color-ink-muted); margin-top: 0.6rem;
}

.entry__body { padding-top: 0.2rem; }
.entry__title {
  font-family: var(--font-serif-jp); font-weight: 500;
  font-size: clamp(1.45rem, 2.6vw, 1.85rem); line-height: 1.45;
  color: var(--color-ink); margin-bottom: 0.85rem; text-wrap: balance;
}
.entry__title a {
  color: inherit; text-decoration: none;
  background-image: linear-gradient(transparent 92%, var(--color-accent) 92%, var(--color-accent) 96%, transparent 96%);
  background-size: 0% 100%; background-repeat: no-repeat;
  transition: background-size 0.4s ease;
}
.entry__title a:hover { background-size: 100% 100%; }
.entry__subtitle {
  font-family: var(--font-serif-jp); font-weight: 300;
  font-size: 0.98rem; line-height: 1.85;
  color: var(--color-ink-soft); margin-bottom: 1.5rem;
  max-width: var(--measure); text-wrap: balance;
}
.entry__meta {
  display: flex; flex-wrap: wrap; gap: 1.5rem; margin-bottom: 1.75rem;
  font-family: var(--font-display); font-style: italic;
  font-size: 0.85rem; letter-spacing: 0.18em; color: var(--color-ink-muted);
}
.entry__meta-item { display: flex; align-items: baseline; gap: 0.55rem; }
.entry__meta-item + .entry__meta-item::before {
  content: '·'; color: var(--color-rule);
  margin-right: 0.95rem; margin-left: -0.4rem; font-style: normal;
}
.entry__meta-value {
  font-style: normal; font-weight: 600;
  color: var(--color-ink); letter-spacing: 0.12em;
}
.entry__cta {
  display: inline-flex; align-items: baseline; gap: 0.85rem;
  font-family: var(--font-display); font-style: italic;
  font-size: 0.95rem; letter-spacing: 0.18em; text-transform: uppercase;
  color: var(--color-accent); text-decoration: none;
  padding-bottom: 0.3rem;
  border-bottom: 1px solid var(--color-accent);
  transition: gap 0.25s ease, color 0.25s ease;
}
.entry__cta:hover {
  gap: 1.25rem; color: var(--color-ink); border-bottom-color: var(--color-ink);
}
.entry__cta::after { content: '→'; font-style: normal; letter-spacing: 0; }

/* 「執筆中」プレースホルダ */
.entry--upcoming .entry__volume-roman { color: var(--color-ink-muted); }
.entry--upcoming .entry__title,
.entry--upcoming .entry__subtitle { color: var(--color-ink-muted); }
.entry--upcoming .entry__cta {
  color: var(--color-ink-muted);
  border-bottom-color: var(--color-rule);
  pointer-events: none;
}

/* ============================================================
   7. フッター ── 教科書本体用 (.footer) と カタログ用 (.footer--catalog) を区別
   ============================================================ */
.footer {
  background: var(--color-ink); padding: 4rem 2rem; text-align: center;
  font-family: var(--font-display); font-style: italic;
  font-size: 0.95rem; line-height: 1.8; color: rgba(250, 247, 242, 0.7);
}
.footer__rule { width: 3rem; height: 1px; background: var(--color-gold); margin: 2rem auto; }
.footer__date {
  font-family: var(--font-ui); font-style: normal;
  font-size: 0.75rem; letter-spacing: 0.2em; text-transform: uppercase;
  color: var(--color-gold);
}
/* カタログ用フッターは紙地のまま、テキストは ink-muted */
.footer--catalog {
  background: var(--color-paper-deep);
  border-top: 1px solid var(--color-rule-soft);
  color: var(--color-ink-muted);
  padding: 3rem 1.5rem 4rem;
}
.footer--catalog .footer__ornament {
  font-family: var(--font-display); font-style: italic;
  font-size: 0.75rem; letter-spacing: 0.4em; text-transform: uppercase;
  color: var(--color-gold); margin-bottom: 1rem;
}
.footer--catalog .footer__text {
  font-family: var(--font-serif-jp); font-weight: 300;
  font-size: 0.85rem; color: var(--color-ink-muted);
  line-height: 1.8; max-width: 28rem; margin: 0 auto;
}
.footer--catalog a { color: var(--color-ink-soft); }

/* ============================================================
   8. レスポンシブ / 印刷 / アニメーション
   ============================================================ */
@media (max-width: 768px) {
  body { font-size: 16px; line-height: 1.85; }
  .top-nav { padding: 0.75rem 1rem; }
  .top-nav__title { font-size: 0.7rem; max-width: 60%; }
  .chapter { padding: 4rem 0 3rem; }
  .chapter__inner { padding: 0 1.5rem; }
  .hero__meta { flex-direction: column; gap: 1.25rem; }
  .prose blockquote { margin: 2rem 0; }
  .toc-drawer { width: 90%; right: -100%; }
  .summary, .key-concept { padding: 1.5rem; }
  .chapter-nav { flex-direction: column; }
  .chapter-nav a { max-width: 100%; }
  .prose > p:first-of-type::first-letter { font-size: 3rem; }
  .figure { margin: 2rem -1.5rem; }
  .figure__inner { padding: 0 1rem; }
}

@media (max-width: 640px) {
  .entry { grid-template-columns: 1fr; gap: 1rem; }
  .entry__volume {
    text-align: left; border-right: none;
    border-bottom: 1px solid var(--color-rule-soft);
    padding-right: 0; padding-bottom: 0.75rem;
    display: flex; align-items: baseline; gap: 1rem;
  }
  .entry__volume-roman { font-size: 2rem; }
  .entry__volume-label { margin-top: 0; }
}

@media print {
  .top-nav, .progress-bar, .toc-drawer, .toc-backdrop, .hero__scroll-cue { display: none; }
  body { background: white; color: black; font-size: 11pt; }
  .chapter { page-break-before: always; padding: 1rem 0; }
  .entry__cta { display: none; }
}

.fade-in {
  opacity: 0; transform: translateY(20px);
  transition: opacity 0.8s ease-out, transform 0.8s ease-out;
}
.fade-in.is-visible { opacity: 1; transform: translateY(0); }