/* ============================================================
   墨 · 自然语言处理学习站  —  黑色文艺主题
   ============================================================ */

:root {
  --ink-black: #0a0a0c;
  --ink-deep: #101014;
  --ink-surface: #16151b;
  --ink-card: #1b1a21;
  --ink-hover: #22212a;
  --line: #2c2a33;
  --line-soft: #232129;
  --paper: #e6dfd0;
  --paper-dim: #b3ac9c;
  --paper-faint: #7d7668;
  --gold: #c4a265;
  --gold-bright: #d9bd85;
  --gold-deep: #9a7d49;
  --seal: #b5483a;
  --jade: #6f8f83;
  --code-bg: #121116;
  --shadow: 0 18px 50px rgba(0, 0, 0, .55);
  --serif: "Noto Serif SC", "Source Han Serif SC", "Songti SC", "STSong", "SimSun", serif;
  --kai: "Kaiti SC", "STKaiti", "KaiTi", serif;
  --mono: "JetBrains Mono", "SFMono-Regular", Consolas, "Courier New", monospace;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  background: var(--ink-black);
  color: var(--paper);
  font-family: var(--serif);
  line-height: 1.9;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

/* 宣纸底纹 + 顶部微光 */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background:
    radial-gradient(ellipse 80% 50% at 50% -10%, rgba(196, 162, 101, .10), transparent 60%),
    radial-gradient(ellipse 60% 40% at 85% 110%, rgba(181, 72, 58, .05), transparent 60%);
}
body::after {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  opacity: .35;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='120' height='120'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2'/%3E%3C/filter%3E%3Crect width='120' height='120' filter='url(%23n)' opacity='0.05'/%3E%3C/svg%3E");
}

::selection { background: rgba(196, 162, 101, .28); color: #fff; }

a { color: var(--gold); text-decoration: none; transition: color .25s; }
a:hover { color: var(--gold-bright); }

img { max-width: 100%; }

.container { width: min(1180px, 92%); margin: 0 auto; position: relative; z-index: 1; }

/* ============ 顶部导航 ============ */
.site-header {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  background: rgba(10, 10, 12, .82);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--line-soft);
  transition: border-color .3s;
}
.site-header.scrolled { border-bottom-color: var(--line); }
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 68px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--paper);
  font-size: 19px;
  letter-spacing: 3px;
  white-space: nowrap;
}
.brand .seal-mark {
  display: inline-grid;
  place-items: center;
  width: 34px; height: 34px;
  background: var(--seal);
  color: #f3ead9;
  font-family: var(--kai);
  font-size: 18px;
  border-radius: 4px;
  transform: rotate(-3deg);
  box-shadow: 0 2px 8px rgba(181, 72, 58, .4);
}
.brand:hover { color: var(--gold-bright); }
.brand small { color: var(--paper-faint); font-size: 11px; letter-spacing: 2px; }

.nav-links { display: flex; gap: 30px; list-style: none; }
.nav-links a {
  color: var(--paper-dim);
  font-size: 15px;
  letter-spacing: 2px;
  position: relative;
  padding: 4px 0;
}
.nav-links a::after {
  content: "";
  position: absolute;
  left: 0; bottom: 0;
  width: 0; height: 1px;
  background: var(--gold);
  transition: width .3s;
}
.nav-links a:hover, .nav-links a.active { color: var(--gold-bright); }
.nav-links a:hover::after, .nav-links a.active::after { width: 100%; }

.nav-toggle {
  display: none;
  background: none;
  border: 1px solid var(--line);
  color: var(--paper);
  width: 40px; height: 36px;
  font-size: 18px;
  cursor: pointer;
  border-radius: 4px;
}

/* ============ 首页 Hero ============ */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  position: relative;
  padding: 120px 0 80px;
  text-align: center;
}
.hero-frame {
  position: absolute;
  inset: clamp(16px, 4vw, 48px);
  border: 1px solid rgba(196, 162, 101, .22);
  pointer-events: none;
}
.hero-frame::before, .hero-frame::after {
  content: "";
  position: absolute;
  width: 26px; height: 26px;
  border: 1px solid var(--gold-deep);
}
.hero-frame::before { top: -1px; left: -1px; border-right: none; border-bottom: none; }
.hero-frame::after { bottom: -1px; right: -1px; border-left: none; border-top: none; }

.hero-inner { position: relative; z-index: 2; margin: 0 auto; max-width: 820px; }
.hero .kicker {
  color: var(--gold);
  letter-spacing: 8px;
  font-size: 14px;
  text-indent: 8px;
  margin-bottom: 28px;
}
.hero h1 {
  font-weight: 600;
  font-size: clamp(38px, 6.5vw, 72px);
  letter-spacing: 10px;
  text-indent: 10px;
  line-height: 1.35;
}
.hero h1 .accent { color: var(--gold); }
.hero .sub {
  margin-top: 30px;
  color: var(--paper-dim);
  font-family: var(--kai);
  font-size: clamp(16px, 2.2vw, 20px);
  letter-spacing: 2px;
}
.hero .poem {
  margin-top: 42px;
  color: var(--paper-faint);
  font-family: var(--kai);
  font-size: 15px;
  letter-spacing: 3px;
}
.hero .poem span { display: block; }
.hero-actions { margin-top: 50px; display: flex; gap: 20px; justify-content: center; flex-wrap: wrap; }

.btn {
  display: inline-block;
  padding: 13px 38px;
  font-family: var(--serif);
  font-size: 15px;
  letter-spacing: 4px;
  text-indent: 4px;
  cursor: pointer;
  border: 1px solid var(--gold-deep);
  border-radius: 2px;
  transition: all .3s;
}
.btn-primary { background: var(--gold); color: #14120a; border-color: var(--gold); }
.btn-primary:hover { background: var(--gold-bright); color: #14120a; transform: translateY(-2px); box-shadow: 0 10px 26px rgba(196, 162, 101, .25); }
.btn-ghost { background: transparent; color: var(--paper); }
.btn-ghost:hover { border-color: var(--gold); color: var(--gold-bright); transform: translateY(-2px); }

.scroll-hint {
  position: absolute;
  bottom: 34px; left: 50%;
  transform: translateX(-50%);
  color: var(--paper-faint);
  font-size: 12px;
  letter-spacing: 4px;
  z-index: 2;
}
.scroll-hint::after {
  content: "";
  display: block;
  width: 1px; height: 46px;
  margin: 10px auto 0;
  background: linear-gradient(var(--gold), transparent);
  animation: drip 2s ease-in-out infinite;
}
@keyframes drip { 0%,100% { opacity: .3; transform: scaleY(.7);} 50% { opacity: 1; transform: scaleY(1);} }

/* ============ 通用区块 ============ */
.section { padding: 110px 0; position: relative; }
.section-head { text-align: center; margin-bottom: 70px; }
.section-head .ornament {
  color: var(--gold-deep);
  letter-spacing: 6px;
  font-size: 13px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 18px;
  margin-bottom: 18px;
}
.section-head .ornament::before, .section-head .ornament::after {
  content: "";
  width: 56px; height: 1px;
  background: linear-gradient(90deg, transparent, var(--gold-deep));
}
.section-head .ornament::after { background: linear-gradient(90deg, var(--gold-deep), transparent); }
.section-head h2 {
  font-size: clamp(28px, 3.6vw, 40px);
  letter-spacing: 8px;
  text-indent: 8px;
  font-weight: 600;
}
.section-head p { color: var(--paper-faint); margin-top: 16px; font-family: var(--kai); letter-spacing: 2px; }

.reveal { opacity: 0; transform: translateY(34px); transition: opacity .9s ease, transform .9s ease; }
.reveal.visible { opacity: 1; transform: none; }

/* ============ 序章 · 简介 ============ */
.intro-grid { display: grid; grid-template-columns: 1.2fr 1fr; gap: 56px; align-items: center; }
.intro-text p { color: var(--paper-dim); margin-bottom: 20px; font-size: 16.5px; }
.intro-text p strong { color: var(--gold-bright); font-weight: 500; }
.intro-quote {
  border-left: 2px solid var(--seal);
  padding: 8px 0 8px 26px;
  margin: 30px 0;
  font-family: var(--kai);
  color: var(--paper);
  font-size: 18px;
  letter-spacing: 2px;
}
.intro-quote cite { display: block; margin-top: 10px; color: var(--paper-faint); font-size: 13px; font-style: normal; }

.intro-card {
  background: linear-gradient(160deg, var(--ink-card), var(--ink-surface));
  border: 1px solid var(--line);
  padding: 44px 40px;
  position: relative;
}
.intro-card::before {
  content: "語";
  position: absolute;
  top: 18px; right: 22px;
  font-family: var(--kai);
  font-size: 64px;
  color: rgba(196, 162, 101, .08);
}
.intro-card h3 { color: var(--gold); letter-spacing: 4px; font-size: 18px; margin-bottom: 24px; }
.intro-card ul { list-style: none; }
.intro-card li {
  padding: 11px 0;
  border-bottom: 1px dashed var(line);
  border-bottom: 1px dashed var(--line-soft);
  color: var(--paper-dim);
  display: flex;
  gap: 12px;
  font-size: 15px;
}
.intro-card li:last-child { border-bottom: none; }
.intro-card li::before { content: "❖"; color: var(--gold-deep); font-size: 12px; padding-top: 6px; }

/* ============ 章节卡片 ============ */
.chapters-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 26px; }
.chapter-card {
  display: block;
  background: linear-gradient(170deg, var(--ink-card), var(--ink-deep));
  border: 1px solid var(--line-soft);
  padding: 38px 32px 34px;
  position: relative;
  overflow: hidden;
  transition: transform .4s, border-color .4s, box-shadow .4s;
  color: var(--paper);
}
.chapter-card::before {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(420px circle at var(--mx, 50%) var(--my, 0%), rgba(196, 162, 101, .09), transparent 45%);
  opacity: 0;
  transition: opacity .4s;
}
.chapter-card:hover { transform: translateY(-7px); border-color: var(--gold-deep); box-shadow: var(--shadow); color: var(--paper); }
.chapter-card:hover::before { opacity: 1; }
.chapter-card .num {
  font-family: var(--kai);
  color: var(--gold-deep);
  font-size: 15px;
  letter-spacing: 3px;
}
.chapter-card .glyph {
  font-family: var(--kai);
  font-size: 44px;
  color: rgba(196, 162, 101, .14);
  position: absolute;
  right: 24px; top: 26px;
  transition: color .4s, transform .4s;
}
.chapter-card:hover .glyph { color: rgba(196, 162, 101, .3); transform: scale(1.08); }
.chapter-card h3 {
  margin: 16px 0 12px;
  font-size: 21px;
  letter-spacing: 3px;
  font-weight: 600;
}
.chapter-card p { color: var(--paper-faint); font-size: 14px; line-height: 1.85; min-height: 52px; }
.chapter-card .tags { margin-top: 20px; display: flex; flex-wrap: wrap; gap: 8px; }
.chapter-card .tag {
  font-size: 12px;
  color: var(--paper-faint);
  border: 1px solid var(--line);
  padding: 2px 10px;
  border-radius: 2px;
  letter-spacing: 1px;
}
.chapter-card .enter {
  margin-top: 22px;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--gold);
  font-size: 13.5px;
  letter-spacing: 3px;
}
.chapter-card .enter .arrow { transition: transform .3s; }
.chapter-card:hover .enter .arrow { transform: translateX(7px); }

/* ============ 学习路径 ============ */
.path-wrap { max-width: 760px; margin: 0 auto; position: relative; }
.path-wrap::before {
  content: "";
  position: absolute;
  left: 15px; top: 8px; bottom: 8px;
  width: 1px;
  background: linear-gradient(var(--gold-deep), var(--line), var(--seal));
}
.path-item { display: flex; gap: 28px; padding: 18px 0; }
.path-dot {
  flex: 0 0 32px;
  height: 32px;
  width: 32px;
  border-radius: 50%;
  background: var(--ink-black);
  border: 1px solid var(--gold-deep);
  display: grid;
  place-items: center;
  color: var(--gold);
  font-size: 13px;
  font-family: var(--kai);
  z-index: 1;
}
.path-item h4 { font-size: 17px; letter-spacing: 2px; font-weight: 600; }
.path-item h4 small { color: var(--paper-faint); font-weight: 400; font-size: 13px; margin-left: 12px; letter-spacing: 1px; }
.path-item p { color: var(--paper-faint); font-size: 14px; margin-top: 4px; }

/* ============ 页脚 ============ */
.site-footer {
  border-top: 1px solid var(--line-soft);
  padding: 54px 0 40px;
  text-align: center;
  color: var(--paper-faint);
  font-size: 13px;
  letter-spacing: 2px;
  background: var(--ink-deep);
  position: relative;
  z-index: 1;
}
.site-footer .footer-seal {
  font-family: var(--kai);
  color: var(--seal);
  border: 1px solid var(--seal);
  display: inline-block;
  padding: 4px 10px;
  margin-bottom: 18px;
  letter-spacing: 4px;
  font-size: 14px;
  transform: rotate(-2deg);
}
.site-footer a { color: var(--paper-dim); }
.site-footer a:hover { color: var(--gold); }

/* ============================================================
   章节内页
   ============================================================ */
.chapter-hero {
  padding: 150px 0 60px;
  text-align: center;
  position: relative;
}
.chapter-hero .ch-num {
  font-family: var(--kai);
  color: var(--gold-deep);
  letter-spacing: 10px;
  font-size: 15px;
}
.chapter-hero h1 {
  font-size: clamp(30px, 4.5vw, 48px);
  letter-spacing: 8px;
  text-indent: 8px;
  margin: 20px 0;
  font-weight: 600;
}
.chapter-hero .ch-sub { font-family: var(--kai); color: var(--paper-faint); letter-spacing: 2px; }
.chapter-hero .divider {
  width: 220px; height: 1px; margin: 34px auto 0;
  background: linear-gradient(90deg, transparent, var(--gold-deep), transparent);
  position: relative;
}
.chapter-hero .divider::after {
  content: "❖";
  position: absolute;
  top: -11px; left: 50%;
  transform: translateX(-50%);
  color: var(--gold-deep);
  background: var(--ink-black);
  padding: 0 12px;
  font-size: 13px;
}

.chapter-layout {
  display: grid;
  grid-template-columns: 230px minmax(0, 1fr);
  gap: 50px;
  padding: 30px 0 90px;
  align-items: start;
}

/* 侧边目录 */
.chapter-toc { position: sticky; top: 96px; }
.chapter-toc .toc-title {
  color: var(--gold);
  font-size: 13px;
  letter-spacing: 5px;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line-soft);
}
.chapter-toc ul { list-style: none; }
.chapter-toc li { margin: 2px 0; }
.chapter-toc a {
  display: block;
  color: var(--paper-faint);
  font-size: 14px;
  padding: 7px 14px;
  border-left: 2px solid transparent;
  letter-spacing: 1px;
  transition: all .25s;
}
.chapter-toc a:hover { color: var(--paper-dim); }
.chapter-toc a.active { color: var(--gold-bright); border-left-color: var(--gold); background: var(--ink-surface); }

/* 正文 */
.article { font-size: 16px; color: var(--paper-dim); min-width: 0; }
.article section { margin-bottom: 64px; scroll-margin-top: 90px; }
.article h2 {
  color: var(--paper);
  font-size: 26px;
  letter-spacing: 3px;
  font-weight: 600;
  margin-bottom: 22px;
  padding-left: 16px;
  border-left: 4px solid var(--gold-deep);
  line-height: 1.5;
}
.article h3 {
  color: var(--gold-bright);
  font-size: 19px;
  letter-spacing: 2px;
  font-weight: 600;
  margin: 34px 0 14px;
}
.article h4 { color: var(--paper); font-size: 16.5px; margin: 24px 0 10px; letter-spacing: 1px; }
.article p { margin-bottom: 16px; }
.article strong { color: var(--paper); font-weight: 600; }
.article ul, .article ol { margin: 0 0 18px 22px; }
.article li { margin-bottom: 8px; }
.article .term { color: var(--gold); border-bottom: 1px dotted var(--gold-deep); cursor: help; }

/* 代码块 */
pre {
  background: var(--code-bg);
  border: 1px solid var(--line-soft);
  border-left: 3px solid var(--gold-deep);
  padding: 20px 22px;
  overflow-x: auto;
  margin: 20px 0 26px;
  border-radius: 3px;
  position: relative;
}
pre .code-head {
  position: absolute;
  top: 0; right: 0;
  font-family: var(--mono);
  font-size: 11px;
  color: var(--paper-faint);
  background: var(--ink-surface);
  padding: 3px 12px;
  border-left: 1px solid var(--line-soft);
  border-bottom: 1px solid var(--line-soft);
  letter-spacing: 1px;
}
code {
  font-family: var(--mono);
  font-size: 13.5px;
  line-height: 1.8;
  color: #d6cdb8;
}
p code, li code, td code {
  background: var(--ink-surface);
  border: 1px solid var(--line-soft);
  padding: 1px 7px;
  border-radius: 3px;
  font-size: 13px;
  color: var(--gold-bright);
}
/* 简易代码着色 */
.tok-com { color: #6f6a5d; font-style: italic; }
.tok-kw { color: #c98a6b; }
.tok-str { color: #9fae86; }
.tok-num { color: #c4a265; }
.tok-fn { color: #8fa9b8; }

/* 引文 / 提示框 */
.block-quote {
  background: var(--ink-surface);
  border: 1px solid var(--line-soft);
  border-left: 3px solid var(--jade);
  padding: 18px 24px;
  margin: 22px 0;
  font-family: var(--kai);
  color: var(--paper);
  letter-spacing: 1px;
  border-radius: 0 3px 3px 0;
}
.note, .warn {
  padding: 16px 20px 16px 52px;
  margin: 22px 0;
  border: 1px solid var(--line);
  border-radius: 3px;
  position: relative;
  font-size: 14.5px;
  background: var(--ink-surface);
}
.note::before, .warn::before {
  position: absolute;
  left: 18px; top: 15px;
  font-family: var(--kai);
  font-size: 18px;
}
.note { border-left: 3px solid var(--jade); }
.note::before { content: "注"; color: var(--jade); }
.warn { border-left: 3px solid var(--seal); }
.warn::before { content: "戒"; color: var(--seal); }

/* 表格 */
.table-wrap { overflow-x: auto; margin: 22px 0 28px; border: 1px solid var(--line-soft); }
table { width: 100%; border-collapse: collapse; font-size: 14.5px; }
th {
  background: var(--ink-surface);
  color: var(--gold);
  font-weight: 600;
  letter-spacing: 2px;
  text-align: left;
  padding: 13px 18px;
  border-bottom: 1px solid var(--line);
  white-space: nowrap;
}
td { padding: 12px 18px; border-bottom: 1px solid var(--line-soft); color: var(--paper-dim); }
tr:last-child td { border-bottom: none; }
tr:hover td { background: rgba(196, 162, 101, .03); }

/* 交互演示面板 */
.demo {
  border: 1px solid var(--line);
  border-radius: 4px;
  margin: 26px 0 32px;
  overflow: hidden;
  background: linear-gradient(180deg, var(--ink-card), var(--ink-deep));
}
.demo-head {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 13px 20px;
  border-bottom: 1px solid var(--line-soft);
  background: rgba(196, 162, 101, .04);
  font-size: 14px;
  letter-spacing: 3px;
  color: var(--gold-bright);
}
.demo-head .dot { width: 7px; height: 7px; border-radius: 50%; background: var(--gold-deep); }
.demo-head .demo-badge {
  margin-left: auto;
  font-size: 11px;
  letter-spacing: 2px;
  color: var(--paper-faint);
  border: 1px solid var(--line);
  padding: 1px 9px;
  border-radius: 2px;
}
.demo-body { padding: 22px; }
.demo textarea, .demo input[type="text"] {
  width: 100%;
  background: var(--code-bg);
  border: 1px solid var(--line);
  color: var(--paper);
  font-family: var(--mono);
  font-size: 13.5px;
  padding: 13px 15px;
  border-radius: 3px;
  resize: vertical;
  outline: none;
  transition: border-color .25s;
}
.demo textarea:focus, .demo input[type="text"]:focus { border-color: var(--gold-deep); }
.demo textarea { min-height: 92px; line-height: 1.8; }
.demo .row { display: flex; gap: 12px; margin-top: 14px; flex-wrap: wrap; align-items: center; }
.demo select {
  background: var(--code-bg);
  border: 1px solid var(--line);
  color: var(--paper);
  padding: 9px 12px;
  font-family: var(--serif);
  font-size: 14px;
  border-radius: 3px;
  outline: none;
}
.btn-sm {
  background: var(--gold);
  color: #14120a;
  border: none;
  padding: 9px 22px;
  font-family: var(--serif);
  font-size: 14px;
  letter-spacing: 2px;
  border-radius: 3px;
  cursor: pointer;
  transition: all .25s;
}
.btn-sm:hover { background: var(--gold-bright); transform: translateY(-1px); }
.btn-sm.ghost { background: transparent; color: var(--paper-dim); border: 1px solid var(--line); }
.btn-sm.ghost:hover { border-color: var(--gold-deep); color: var(--gold-bright); }

.demo-output {
  margin-top: 16px;
  background: var(--code-bg);
  border: 1px solid var(--line-soft);
  border-radius: 3px;
  padding: 16px 18px;
  font-size: 14px;
  min-height: 48px;
  color: var(--paper-dim);
  line-height: 2;
  white-space: pre-wrap;
  word-break: break-word;
}
.demo-output:empty::before { content: "结果将在此呈现……"; color: var(--paper-faint); font-family: var(--kai); }
.demo-output .pill {
  display: inline-block;
  margin: 2px 4px 2px 0;
  padding: 1px 11px;
  border: 1px solid var(--gold-deep);
  color: var(--gold-bright);
  border-radius: 20px;
  font-size: 13px;
}
.demo-output .pill.pos { border-color: var(--jade); color: #93b3a6; }
.demo-output .pill.neg { border-color: var(--seal); color: #d08274; }
.demo-output .vec { font-family: var(--mono); color: var(--gold-bright); font-size: 13px; }
.demo-output .bar-row { display: flex; align-items: center; gap: 10px; margin: 4px 0; }
.demo-output .bar-row .bar { height: 8px; background: linear-gradient(90deg, var(--gold-deep), var(--gold)); border-radius: 4px; }
.demo-output .bar-label { width: 88px; flex-shrink: 0; color: var(--paper-dim); font-size: 13px; }
.demo-output .bar-val { font-family: var(--mono); font-size: 12px; color: var(--paper-faint); }

/* 聊天机器人面板 */
.chat-box { display: flex; flex-direction: column; height: 420px; }
.chat-log { flex: 1; overflow-y: auto; padding: 6px 4px 14px; }
.chat-msg { display: flex; margin-bottom: 14px; gap: 10px; }
.chat-msg .avatar {
  flex-shrink: 0;
  width: 34px; height: 34px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-family: var(--kai);
  font-size: 15px;
}
.chat-msg.bot .avatar { background: rgba(196, 162, 101, .14); color: var(--gold); border: 1px solid var(--gold-deep); }
.chat-msg.user { flex-direction: row-reverse; }
.chat-msg.user .avatar { background: rgba(111, 143, 131, .16); color: var(--jade); border: 1px solid var(--jade); }
.chat-bubble {
  max-width: 78%;
  padding: 10px 16px;
  border-radius: 4px;
  font-size: 14.5px;
  line-height: 1.8;
}
.chat-msg.bot .chat-bubble { background: var(--ink-surface); border: 1px solid var(--line-soft); color: var(--paper); }
.chat-msg.user .chat-bubble { background: rgba(111, 143, 131, .12); border: 1px solid rgba(111, 143, 131, .35); color: var(--paper); }
.chat-input-row { display: flex; gap: 10px; padding-top: 14px; border-top: 1px solid var(--line-soft); }
.chat-input-row input { flex: 1; }

/* 键值信息栅格 */
.info-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 16px; margin: 22px 0; }
.info-cell {
  background: var(--ink-surface);
  border: 1px solid var(--line-soft);
  padding: 20px;
  border-radius: 3px;
}
.info-cell .ic-num { font-family: var(--kai); font-size: 26px; color: var(--gold); }
.info-cell .ic-label { color: var(--paper-faint); font-size: 13px; letter-spacing: 2px; margin-top: 6px; }
.info-cell .ic-desc { color: var(--paper-dim); font-size: 13px; margin-top: 8px; line-height: 1.7; }

/* 树形结构 */
.tree { font-family: var(--mono); font-size: 14px; line-height: 2; color: var(--paper-dim); overflow-x: auto; }
.tree .root { color: var(--seal); font-weight: 600; }
.tree .rel { color: var(--jade); }
.tree .word { color: var(--gold-bright); }

/* 步骤 */
.steps { list-style: none; margin-left: 0 !important; counter-reset: step; }
.steps li {
  counter-increment: step;
  position: relative;
  padding: 6px 0 18px 52px;
}
.steps li::before {
  content: counter(step);
  position: absolute;
  left: 0; top: 6px;
  width: 32px; height: 32px;
  border: 1px solid var(--gold-deep);
  color: var(--gold);
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-family: var(--kai);
  font-size: 15px;
}
.steps li::after {
  content: "";
  position: absolute;
  left: 16px; top: 40px; bottom: -2px;
  width: 1px;
  background: var(--line);
}
.steps li:last-child::after { display: none; }

/* 章节底翻页 */
.chapter-pager {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  margin-top: 80px;
  padding-top: 34px;
  border-top: 1px solid var(--line-soft);
}
.chapter-pager a {
  display: block;
  border: 1px solid var(--line);
  padding: 18px 26px;
  flex: 1;
  transition: all .3s;
  border-radius: 3px;
}
.chapter-pager a:hover { border-color: var(--gold-deep); background: var(--ink-surface); }
.chapter-pager a.next { text-align: right; }
.chapter-pager .pager-label { color: var(--paper-faint); font-size: 12px; letter-spacing: 3px; }
.chapter-pager .pager-title { color: var(--paper); font-size: 16px; margin-top: 6px; letter-spacing: 2px; }
.chapter-pager a:hover .pager-title { color: var(--gold-bright); }

/* 返回顶部 */
.back-top {
  position: fixed;
  right: 30px; bottom: 34px;
  width: 44px; height: 44px;
  border: 1px solid var(--gold-deep);
  background: rgba(16, 16, 20, .85);
  color: var(--gold);
  cursor: pointer;
  border-radius: 50%;
  font-size: 17px;
  opacity: 0;
  pointer-events: none;
  transition: all .3s;
  z-index: 90;
}
.back-top.show { opacity: 1; pointer-events: auto; }
.back-top:hover { background: var(--gold); color: #14120a; }

/* ============ 响应式 ============ */
@media (max-width: 980px) {
  .chapters-grid { grid-template-columns: repeat(2, 1fr); }
  .intro-grid { grid-template-columns: 1fr; gap: 36px; }
  .chapter-layout { grid-template-columns: 1fr; gap: 0; }
  .chapter-toc { position: static; display: none; }
}
@media (max-width: 720px) {
  body { font-size: 15px; }
  .nav-links {
    display: none;
    position: absolute;
    top: 68px; left: 0; right: 0;
    flex-direction: column;
    gap: 0;
    background: var(--ink-deep);
    border-bottom: 1px solid var(--line);
    padding: 8px 0;
  }
  .nav-links.open { display: flex; }
  .nav-links a { display: block; padding: 14px 28px; }
  .nav-links a::after { display: none; }
  .nav-toggle { display: block; }
  .chapters-grid { grid-template-columns: 1fr; }
  .section { padding: 76px 0; }
  .chapter-hero { padding: 120px 0 44px; }
  .article h2 { font-size: 22px; }
  .hero h1 { letter-spacing: 6px; }
  .chapter-pager { flex-direction: column; }
}