/* 各年级页面公共样式：修改此处即可全局生效 */
:root {
    --ink: #2c2c2c;
    --ink-light: #5a5a5a;
    --accent: #8b6914;
    --accent-light: #c4a35a;
    --paper: #fdfbf5;
    --paper-dark: #f5f0e1;
    --border: #d4c5a0;
    --dynasty-xianqin: #46593c;
    --dynasty-han: #5a7a3a;
    --dynasty-wei: #6b4f3a;
    --dynasty-jin: #4a6a5a;
    --dynasty-nanbeichao: #5a7a4a;
    --dynasty-tang: #b85450;
    --dynasty-song: #4a7c8c;
    --dynasty-yuan: #3a4f7a;
    --dynasty-ming: #7a6c9d;
    --dynasty-qing: #5c8a5a;
    --dynasty-modern: #2d6b50;
    --recite-bg: #f0ede4;
    --recite-accent: #6b5b3a;
  }
  * { margin: 0; padding: 0; box-sizing: border-box; }
  body {
    font-family: "STKaiti", "KaiTi", "楷体", "Noto Serif CJK SC", serif;
    background: var(--paper);
    color: var(--ink);
    line-height: 1.8;
    padding: 40px 20px;
  }
  .container { max-width: 780px; margin: 0 auto; }
  header {
    text-align: center;
    margin-bottom: 50px;
    padding-bottom: 30px;
    border-bottom: 2px solid var(--border);
    position: relative;
  }
  header::after {
    content: "";
    display: block;
    width: 60px;
    height: 3px;
    background: var(--accent);
    margin: 20px auto 0;
  }
  h1 {
    font-size: 2.2rem;
    color: var(--ink);
    letter-spacing: 0.3em;
    margin-bottom: 10px;
  }
  .subtitle {
    font-size: 0.95rem;
    color: var(--ink-light);
    letter-spacing: 0.1em;
  }
  .summary-box {
    background: var(--paper-dark);
    border-radius: 8px;
    padding: 24px 28px;
    margin-bottom: 40px;
    font-size: 0.95rem;
    line-height: 2;
  }
  .summary-box strong { color: var(--accent); }

  /* ===== Page TOC ===== */
  .page-toc {
    margin: 0 0 36px;
    padding: 22px 24px 20px;
    border: 1px solid var(--border);
    background: var(--paper);
  }
  .page-toc__title {
    font-size: 0.82rem;
    color: var(--accent);
    letter-spacing: 0.2em;
    margin-bottom: 14px;
  }
  .page-toc__group + .page-toc__group {
    margin-top: 14px;
    padding-top: 14px;
    border-top: 1px dashed var(--border);
  }
  .page-toc__label {
    font-size: 0.78rem;
    color: var(--ink-light);
    letter-spacing: 0.12em;
    margin-bottom: 8px;
  }
  .page-toc__list {
    display: flex;
    flex-wrap: wrap;
    gap: 8px 14px;
    list-style: none;
  }
  .page-toc__list a {
    color: var(--ink);
    text-decoration: none;
    font-size: 0.92rem;
    letter-spacing: 0.06em;
    border-bottom: 1px solid transparent;
  }
  .page-toc__list a:hover {
    color: var(--accent);
    border-bottom-color: var(--accent-light);
  }
  .section-label,
  .poem-card {
    scroll-margin-top: 80px;
  }

  /* ===== Back to top ===== */
  .back-to-top {
    position: fixed;
    right: 22px;
    bottom: 28px;
    z-index: 900;
    width: 40px;
    height: 40px;
    display: grid;
    place-items: center;
    border: 1px solid var(--border);
    background: rgba(253, 251, 245, 0.92);
    color: var(--accent);
    text-decoration: none;
    opacity: 0;
    pointer-events: none;
    transform: translateY(8px);
    transition: opacity 0.25s ease, transform 0.25s ease, border-color 0.2s ease, background 0.2s ease;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
  }
  .back-to-top.is-visible {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
  }
  .back-to-top:hover {
    border-color: var(--accent);
    background: var(--paper-dark);
  }
  .back-to-top svg {
    width: 14px;
    height: 14px;
  }

  /* ===== Section Headers ===== */
  .section-label {
    font-size: 1.15rem;
    color: var(--accent);
    margin: 48px 0 24px;
    padding-left: 16px;
    border-left: 4px solid var(--accent);
    letter-spacing: 0.15em;
  }
  .section-label.recite {
    color: var(--recite-accent);
    border-left-color: var(--recite-accent);
  }
  .section-intro {
    font-size: 0.88rem;
    color: var(--ink-light);
    margin-bottom: 24px;
    padding: 12px 16px;
    background: var(--paper-dark);
    border-radius: 6px;
    line-height: 1.9;
  }

  /* ===== Poem Cards ===== */
  .poem-card {
    background: var(--paper);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 36px 40px;
    margin-bottom: 28px;
    position: relative;
    box-shadow: 0 2px 12px rgba(139, 105, 20, 0.06);
    transition: box-shadow 0.3s;
  }
  .poem-card:hover {
    box-shadow: 0 4px 20px rgba(139, 105, 20, 0.12);
  }
  .poem-card.recite-card {
    background: var(--recite-bg);
    border-color: var(--recite-accent);
    box-shadow: 0 2px 12px rgba(107, 91, 58, 0.08);
  }
  .poem-card.recite-card:hover {
    box-shadow: 0 4px 20px rgba(107, 91, 58, 0.15);
  }
  .poem-number {
    position: absolute;
    top: 20px;
    right: 28px;
    font-size: 3rem;
    color: var(--accent-light);
    opacity: 0.35;
    font-family: "Georgia", serif;
  }
  .poem-title {
    font-size: 1.5rem;
    font-weight: 400;
    color: var(--ink);
    margin: 0 0 6px;
    letter-spacing: 0.08em;
  }
  .poem-meta {
    font-size: 0.9rem;
    color: var(--ink-light);
    margin-bottom: 24px;
  }
  .dynasty-tag {
    display: inline-block;
    padding: 1px 8px;
    border-radius: 3px;
    font-size: 0.8rem;
    margin-right: 6px;
  }
  .dynasty-tag.xianqin { background: rgba(70, 89, 60, 0.12); color: var(--dynasty-xianqin); }
  .dynasty-tag.han { background: rgba(90, 122, 58, 0.12); color: var(--dynasty-han); }
  .dynasty-tag.wei { background: rgba(107, 79, 58, 0.12); color: var(--dynasty-wei); }
  .dynasty-tag.jin { background: rgba(74, 106, 90, 0.12); color: var(--dynasty-jin); }
  .dynasty-tag.nanbeichao { background: rgba(90, 122, 74, 0.12); color: var(--dynasty-nanbeichao); }
  .dynasty-tag.tang { background: rgba(184, 84, 80, 0.12); color: var(--dynasty-tang); }
  .dynasty-tag.song { background: rgba(74, 124, 140, 0.12); color: var(--dynasty-song); }
  .dynasty-tag.yuan { background: rgba(58, 79, 122, 0.12); color: var(--dynasty-yuan); }
  .dynasty-tag.ming { background: rgba(122, 108, 157, 0.12); color: var(--dynasty-ming); }
  .dynasty-tag.qing { background: rgba(92, 138, 90, 0.12); color: var(--dynasty-qing); }
  .dynasty-tag.modern { background: rgba(45, 107, 80, 0.12); color: var(--dynasty-modern); }
  .poem-body {
    font-size: 1.25rem;
    line-height: 2.4;
    text-align: center;
    margin: 20px 0;
    letter-spacing: 0.1em;
  }
  .poem-body p { margin-bottom: 2px; }
  .poem-body .preface {
    font-size: 0.95rem;
    color: var(--ink-light);
    margin-bottom: 12px;
    line-height: 1.9;
  }
  /* 拼音仅叠加注音；显示时略增行高，并拉开字距避免长音节挤在一起 */
  body:not(.hide-pinyin) .poem-body.with-pinyin {
    line-height: 2.55;
    letter-spacing: 0.22em;
  }
  body:not(.hide-pinyin) .poem-title.with-pinyin {
    line-height: 1.75;
    letter-spacing: 0.18em;
  }
  body:not(.hide-pinyin) .poem-body.with-pinyin ruby,
  body:not(.hide-pinyin) .poem-title.with-pinyin ruby {
    margin: 0 0.04em;
  }
  ruby {
    ruby-align: center;
    ruby-position: over;
  }
  rt {
    font-family: "STKaiti", "KaiTi", "楷体", "Noto Serif CJK SC", serif;
    font-size: 0.58em;
    font-weight: 400;
    color: var(--ink-light);
    letter-spacing: 0;
    user-select: none;
  }
  body.hide-pinyin rt {
    visibility: hidden;
  }
  .pinyin-toggle {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    margin: 0 0 28px;
    padding: 6px 12px;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: var(--paper-dark);
    color: var(--ink-light);
    font-size: 0.82rem;
    letter-spacing: 0.05em;
    cursor: pointer;
    font-family: inherit;
  }
  .pinyin-toggle:hover {
    border-color: var(--accent);
    color: var(--accent);
  }
  .pinyin-toggle__switch {
    width: 30px;
    height: 16px;
    border-radius: 999px;
    background: #d4c5a0;
    position: relative;
    transition: background 0.2s ease;
  }
  .pinyin-toggle__switch::after {
    content: "";
    position: absolute;
    top: 2px;
    left: 2px;
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: #fff;
    transition: transform 0.2s ease;
  }
  body:not(.hide-pinyin) .pinyin-toggle__switch {
    background: var(--accent);
  }
  body:not(.hide-pinyin) .pinyin-toggle__switch::after {
    transform: translateX(14px);
  }
  .poem-notes {
    margin-top: 24px;
    padding-top: 16px;
    border-top: 1px dashed var(--border);
    font-size: 0.85rem;
    color: var(--ink-light);
    line-height: 1.9;
  }
  .poem-notes .notes-title {
    font-weight: bold;
    color: var(--accent);
    margin-bottom: 6px;
    display: block;
  }
  .poem-note-item {
    display: block;
    margin-bottom: 3px;
    padding-left: 1em;
  }
  .source-tag {
    display: inline-block;
    font-size: 0.78rem;
    color: var(--accent);
    background: rgba(196, 163, 90, 0.1);
    padding: 2px 10px;
    border-radius: 12px;
    margin-bottom: 12px;
    letter-spacing: 0.05em;
  }

  /* ===== Recite Cards ===== */
  .recite-card .lesson-tag {
    display: inline-block;
    font-size: 0.78rem;
    color: var(--recite-accent);
    background: rgba(107, 91, 58, 0.1);
    padding: 2px 10px;
    border-radius: 12px;
    margin-bottom: 8px;
    letter-spacing: 0.05em;
  }
  .recite-card .recite-requirement {
    font-size: 0.85rem;
    color: var(--recite-accent);
    margin-bottom: 20px;
    padding: 8px 14px;
    background: rgba(107, 91, 58, 0.06);
    border-left: 3px solid var(--recite-accent);
    border-radius: 0 4px 4px 0;
    line-height: 1.8;
  }
  .recite-card .recite-requirement strong {
    color: var(--recite-accent);
  }
  .recite-card .recite-text {
    font-size: 1.18rem;
    line-height: 2.3;
    margin: 20px 0;
    letter-spacing: 0.06em;
    text-align: justify;
  }
  .recite-card .recite-text p {
    margin-bottom: 8px;
    text-indent: 2em;
  }
  .recite-card .recite-text .highlight {
    background: rgba(196, 163, 90, 0.18);
    border-radius: 4px;
    padding: 2px 4px;
    margin: 2px -4px;
    box-shadow: 0 0 0 1px rgba(196, 163, 90, 0.3);
  }
  .recite-card .recite-text .highlight-label {
    display: inline-block;
    font-size: 0.72rem;
    color: var(--accent);
    background: rgba(196, 163, 90, 0.2);
    padding: 1px 6px;
    border-radius: 3px;
    margin-right: 4px;
    vertical-align: super;
    letter-spacing: 0.05em;
  }
  .recite-card .recite-text.centered {
    text-align: center;
  }
  .recite-card .recite-text.centered p {
    text-indent: 0;
  }
  .recite-ref {
    font-size: 0.85rem;
    color: var(--ink-light);
    margin: 16px 0;
    padding: 10px 14px;
    background: rgba(196, 163, 90, 0.06);
    border-radius: 4px;
    line-height: 1.8;
  }
  .recite-ref a {
    color: var(--accent);
    text-decoration: none;
    border-bottom: 1px dashed var(--accent);
  }

  footer {
    text-align: center;
    margin-top: 50px;
    padding-top: 30px;
    border-top: 1px solid var(--border);
    color: var(--ink-light);
    font-size: 0.85rem;
  }
  @media (max-width: 600px) {
    body { padding: 20px 10px; }
    .poem-card { padding: 28px 20px; }
    .poem-body { font-size: 1.1rem; }
    .recite-card .recite-text { font-size: 1.05rem; }
    h1 { font-size: 1.6rem; }
    .back-to-top { right: 14px; bottom: 18px; width: 36px; height: 36px; }
  }