/* ============================================================
   Python 学习网站 全局样式
   设计风格：水墨青花 —— 墨黑底 + 花青雾蓝 + 月白，宋体文艺排版
   色板约束：无金色、无红色；NLP 板块用青瓷绿区分
   ============================================================ */

/* ---------- 设计变量 ---------- */
:root {
  /* 主强调色（沿用旧变量名，全站自动换肤）：花青雾蓝 */
  --blue: #93a7bf;
  --blue-dark: #b7c7db;
  --blue-light: rgba(147, 167, 191, .12);
  /* 月白（承担原金色的"亮文字"位置：表头、关键结论等） */
  --yellow: #d4dae2;
  --yellow-dark: #8d99a8;
  /* 语义色（低饱和冷调暗底可读；danger 用藕荷灰紫，绝不用红） */
  --green: #8db3a2;
  --green-light: rgba(141, 179, 162, .12);
  --red: #a891a3;
  --red-light: rgba(168, 145, 163, .12);
  /* 警告语义色：灰青水色（冷调，与蓝/绿/紫提示区分，不用黄、不用金） */
  --amber: #9bb8c2;
  --amber-light: rgba(155, 184, 194, .11);
  /* 青瓷色（NLP 板块标识） */
  --purple: #7fa89b;
  --purple-light: rgba(127, 168, 155, .13);

  /* 墨色阶：冷调墨黑 / 月白文字 */
  --ink: #e4e6ea;
  --ink-2: #adb2bb;
  --ink-3: #74797f;
  --line: #26282d;
  --bg: #0f1012;
  --card: #17181c;

  --sidebar-bg: #0a0b0d;
  --sidebar-group: #6f747c;
  --sidebar-text: #a9aeb7;
  --sidebar-active: #eef1f5;

  --code-bg: #0a0b0d;
  --code-text: #d5d9df;
  --code-comment: #676c74;
  --radius: 10px;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, .4);
  --shadow: 0 6px 22px rgba(0, 0, 0, .5);
  --shadow-lg: 0 16px 48px rgba(0, 0, 0, .65);
  --sidebar-w: 288px;
  --header-h: 64px;
  --font: "Segoe UI", "PingFang SC", "Microsoft YaHei", "Hiragino Sans GB", system-ui, -apple-system, sans-serif;
  --serif: "Noto Serif SC", "Source Han Serif SC", "Songti SC", "STSong", "SimSun", serif;
  --kai: "KaiTi", "STKaiti", "Kaiti SC", "FangSong", serif;
  --mono: "Cascadia Code", "JetBrains Mono", Consolas, "Courier New", monospace;
}

/* ---------- 基础重置 ---------- */
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.8;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}
img { max-width: 100%; }
a { color: var(--blue); text-decoration: none; }
a:hover { color: var(--blue-dark); }
::selection { background: rgba(147, 167, 191, .30); color: #fff; }

/* 滚动条 */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-thumb { background: #2c2e33; border-radius: 8px; border: 2px solid var(--bg); }
::-webkit-scrollbar-thumb:hover { background: #45484f; }

/* ---------- 阅读进度条 ---------- */
#progress-bar {
  position: fixed; top: 0; left: 0; height: 3px; width: 0;
  background: linear-gradient(90deg, var(--blue), var(--purple));
  z-index: 1000; transition: width .1s linear;
}

/* ---------- 顶部导航 ---------- */
.site-header {
  position: fixed; top: 0; left: 0; right: 0; height: var(--header-h);
  background: rgba(14, 15, 18, .86); backdrop-filter: blur(10px);
  border-bottom: 1px solid #25272b;
  display: flex; align-items: center; gap: 14px; padding: 0 20px;
  z-index: 900;
}
.menu-btn {
  display: none; border: none; background: none; font-size: 22px;
  cursor: pointer; color: var(--ink); padding: 6px 10px; border-radius: 8px;
}
.menu-btn:hover { background: var(--blue-light); }
.logo { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 18px; color: #e9ecf1; white-space: nowrap; font-family: var(--serif); letter-spacing: 1px; }
.logo:hover { color: #e9ecf1; }
.logo-mark {
  width: 36px; height: 36px; border-radius: 9px; display: grid; place-items: center;
  background: linear-gradient(135deg, #d2d9e2 50%, #6f839b 50%);
  color: #0e1218; font-family: var(--mono); font-weight: 700; font-size: 15px;
  box-shadow: var(--shadow-sm);
}
.logo small { display: block; font-size: 11px; font-weight: 500; color: var(--ink-3); letter-spacing: 2px; font-family: var(--font); }

.header-search {
  margin-left: auto; display: flex; align-items: center; gap: 8px;
  background: #15161a; border: 1px solid #2a2c31; border-radius: 10px;
  padding: 7px 14px; cursor: pointer; min-width: 240px; color: var(--ink-3);
  font-size: 14px; transition: .2s;
}
.header-search:hover { border-color: var(--blue); box-shadow: 0 0 0 3px rgba(147, 167, 191, .14); }
.header-search kbd {
  margin-left: auto; font-family: var(--font); font-size: 12px;
  background: #1f2126; border: 1px solid #2c2e33; border-bottom-width: 2px;
  border-radius: 5px; padding: 1px 7px; color: #989ea8;
}
.font-toggle { display: flex; gap: 2px; }
.font-toggle button {
  border: 1px solid #2c2e33; background: #1a1b1f; cursor: pointer;
  border-radius: 7px; width: 32px; height: 32px; color: var(--ink-2);
  font-size: 13px; font-weight: 700; transition: .15s;
}
.font-toggle button:hover { border-color: var(--blue); color: var(--blue); }

/* ---------- 侧边栏 ---------- */
.sidebar {
  position: fixed; top: 0; left: 0; bottom: 0; width: var(--sidebar-w);
  background: var(--sidebar-bg); border-right: 1px solid #212328;
  overflow-y: auto; z-index: 950;
  padding: 20px 0 40px; transition: transform .28s ease;
}
.sidebar .side-logo { display: flex; align-items: center; gap: 10px; padding: 4px 22px 18px; color: #e9ecf1; font-weight: 800; font-family: var(--serif); letter-spacing: 1px; }
.sidebar .side-logo .logo-mark { width: 32px; height: 32px; font-size: 13px; }
.nav-group { margin-top: 14px; }
.nav-group-title {
  padding: 6px 22px; font-size: 12px; font-weight: 700; letter-spacing: 3px;
  color: var(--sidebar-group); text-transform: uppercase;
}
.nav-item {
  display: flex; align-items: center; gap: 10px;
  padding: 9px 22px 9px 22px; color: var(--sidebar-text);
  font-size: 14.5px; border-left: 3px solid transparent; transition: .15s;
}
.nav-item .nav-idx {
  font-family: var(--mono); font-size: 11px; color: #545a63; width: 26px; flex: none;
}
.nav-item:hover { background: rgba(255, 255, 255, .045); color: #eef1f5; }
.nav-item.active {
  background: linear-gradient(90deg, rgba(147, 167, 191, .18), transparent);
  border-left-color: var(--blue); color: var(--sidebar-active); font-weight: 600;
}
.nav-item.visited .nav-dot::after { content: "✓"; color: var(--green); font-size: 11px; }
.nav-item .nav-dot { margin-left: auto; font-family: var(--font); }
.sidebar-overlay {
  display: none; position: fixed; inset: 0; background: rgba(0, 0, 0, .6);
  z-index: 940;
}

/* ---------- 主体布局 ---------- */
.main-wrap { margin-left: var(--sidebar-w); padding: calc(var(--header-h) + 28px) 32px 60px; }
.container { max-width: 920px; margin: 0 auto; }

/* 面包屑 */
.breadcrumb { font-size: 13.5px; color: var(--ink-3); margin-bottom: 14px; display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }
.breadcrumb a { color: var(--ink-3); }
.breadcrumb a:hover { color: var(--blue); }
.breadcrumb .sep { color: #3a3d43; }

/* 文章标题区 */
.article-head { margin-bottom: 30px; }
.article-head .chapter-tag {
  display: inline-block; font-size: 13px; font-weight: 700; color: var(--blue);
  background: var(--blue-light); border: 1px solid rgba(147, 167, 191, .30);
  padding: 3px 14px; border-radius: 20px; margin-bottom: 12px; letter-spacing: 1px;
}
.article-head h1 { font-family: var(--serif); font-size: 34px; line-height: 1.35; color: #eceff3; margin-bottom: 10px; letter-spacing: .5px; }
.article-head .lead { font-size: 17px; color: var(--ink-2); }

/* ---------- 正文排版 ---------- */
article { font-family: var(--serif); }
article h2 {
  font-family: var(--serif); font-size: 25px; margin: 46px 0 16px; padding-bottom: 10px;
  border-bottom: 1px solid var(--line); display: flex; align-items: center; gap: 10px;
  color: #e9ecf1; letter-spacing: 1px;
}
article h2 .h2-num {
  display: inline-grid; place-items: center; width: 30px; height: 30px;
  background: rgba(147, 167, 191, .12); color: var(--blue);
  border: 1px solid rgba(147, 167, 191, .40); border-radius: 8px;
  font-size: 15px; font-family: var(--mono); flex: none;
}
article h3 { font-size: 19.5px; margin: 30px 0 10px; color: var(--blue-dark); }
article h4 { font-size: 17px; margin: 22px 0 8px; color: #e5e8ed; }
article p { margin: 12px 0; }
article ul, article ol { margin: 12px 0 12px 26px; }
article li { margin: 7px 0; }
article strong { color: #f2f4f7; }
article code:not(pre code) {
  font-family: var(--mono); font-size: .88em;
  background: rgba(255, 255, 255, .06); color: #a9bdd4;
  padding: 2px 7px; border-radius: 6px; border: 1px solid rgba(255, 255, 255, .09);
  word-break: break-all;
}

/* ---------- 代码块 ---------- */
pre {
  position: relative; margin: 18px 0; border-radius: var(--radius);
  background: var(--code-bg); padding: 28px 18px 15px; overflow-x: auto;
  box-shadow: var(--shadow-sm); border: 1px solid #222429;
}
pre code {
  font-family: var(--mono); font-size: 14px; line-height: 1.75;
  color: var(--code-text); white-space: pre; display: block;
}
pre.output {
  background: #131418; border: 1px dashed #32353c; box-shadow: none;
}
pre.output::before {
  content: "运行结果"; position: absolute; top: 0; right: 12px;
  font-size: 11px; color: #636870; font-family: var(--font);
}
pre.output code { color: #b0b5be; }
.code-lang {
  position: absolute; top: 0; left: 0; padding: 3px 12px;
  font-size: 11px; font-family: var(--font); color: #8fa0b5;
  background: rgba(255, 255, 255, .04); border-radius: var(--radius) 0 8px 0;
  letter-spacing: 2px; user-select: none;
}
.copy-btn {
  position: absolute; top: 8px; right: 8px; border: 1px solid #33363d;
  background: rgba(255, 255, 255, .05); color: #8b9099; border-radius: 7px;
  font-size: 12px; padding: 3px 10px; cursor: pointer; opacity: 0;
  transition: .15s; font-family: var(--font); z-index: 2;
}
pre:hover .copy-btn { opacity: 1; }
.copy-btn:hover { background: var(--blue); color: #0e1218; border-color: var(--blue); }
.copy-btn.done { background: var(--green); border-color: var(--green); color: #0b120f; opacity: 1; }

/* ---------- 表格 ---------- */
.table-wrap { overflow-x: auto; margin: 18px 0; border-radius: var(--radius); box-shadow: var(--shadow-sm); border: 1px solid #25272c; font-family: var(--font); }
table { width: 100%; border-collapse: collapse; background: #15161a; font-size: 14.5px; min-width: 480px; }
th { background: #161a20; color: var(--yellow); text-align: left; padding: 11px 16px; font-weight: 600; white-space: nowrap; border-bottom: 1px solid rgba(147, 167, 191, .35); letter-spacing: 1px; }
td { padding: 10px 16px; border-bottom: 1px solid #25272c; vertical-align: top; }
tr:nth-child(even) td { background: rgba(255, 255, 255, .02); }
tr:hover td { background: rgba(147, 167, 191, .08); }
td code { white-space: nowrap; }

/* ---------- 提示框 ---------- */
.callout {
  margin: 18px 0; padding: 14px 18px 14px 50px; border-radius: var(--radius);
  position: relative; font-size: 15px; border: 1px solid;
  font-family: var(--font);
}
.callout::before {
  position: absolute; left: 16px; top: 13px; font-size: 19px; font-weight: 700;
  font-family: var(--font);
}
.callout p:first-child { margin-top: 0; }
.callout p:last-child { margin-bottom: 0; }
.callout.note { background: rgba(147, 167, 191, .09); border-color: rgba(147, 167, 191, .30); color: #ccd7e3; }
.callout.note::before { content: "ℹ"; color: var(--blue); }
.callout.tip { background: rgba(141, 179, 162, .09); border-color: rgba(141, 179, 162, .32); color: #cce8de; }
.callout.tip::before { content: "★"; color: var(--green); }
.callout.warn { background: rgba(155, 184, 194, .09); border-color: rgba(155, 184, 194, .30); color: #cbe2e6; }
.callout.warn::before { content: "!"; color: var(--amber); }
.callout.danger { background: rgba(168, 145, 163, .10); border-color: rgba(168, 145, 163, .32); color: #e2cedb; }
.callout.danger::before { content: "✕"; color: var(--red); }

/* ---------- 卡片 / 网格 ---------- */
.card {
  background: var(--card); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 22px 24px;
  box-shadow: var(--shadow-sm); margin: 18px 0;
  font-family: var(--font);
}
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; margin: 18px 0; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; margin: 18px 0; }

/* 学习目标 */
.objectives {
  background: linear-gradient(135deg, #171c23, #12151a);
  border: 1px solid rgba(147, 167, 191, .22); border-radius: var(--radius);
  padding: 20px 24px; margin: 0 0 30px; font-family: var(--font);
}
.objectives h3 { margin-top: 0; color: var(--blue); display: flex; align-items: center; gap: 8px; }
.objectives ul { margin-bottom: 0; }

/* 本页目录 */
.page-toc {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 16px 22px; margin: 0 0 34px; box-shadow: var(--shadow-sm);
  font-family: var(--font);
}
.page-toc h4 { margin: 0 0 8px; font-size: 14px; color: var(--ink-3); letter-spacing: 2px; }
.page-toc ol { margin: 0 0 0 20px; columns: 2; font-size: 14.5px; }
.page-toc li { margin: 4px 0; }

/* 思考练习 details */
details.quiz {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 14px 20px; margin: 12px 0; box-shadow: var(--shadow-sm);
  font-family: var(--font);
}
details.quiz summary {
  cursor: pointer; font-weight: 600; color: var(--blue-dark);
  list-style: none; display: flex; align-items: center; gap: 8px;
}
details.quiz summary::before { content: "▸"; color: var(--yellow-dark); transition: .2s; }
details.quiz[open] summary::before { transform: rotate(90deg); }
details.quiz .answer { margin-top: 10px; padding-top: 10px; border-top: 1px dashed #2d3036; color: var(--ink-2); }
details.quiz .answer::before { content: "答案与解析："; font-weight: 700; color: var(--green); }

/* 关键结论 */
.key-takeaway {
  border-left: 3px solid var(--blue); background: #131820;
  padding: 14px 20px; margin: 22px 0; border-radius: 0 var(--radius) var(--radius) 0;
  font-family: var(--font);
}
.key-takeaway h4 { margin: 0 0 6px; color: var(--blue-dark); }

/* 上一章/下一章 */
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin: 48px 0 10px; }
.pager a {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 16px 20px; box-shadow: var(--shadow-sm); transition: .2s;
  display: block;
}
.pager a:hover { border-color: var(--blue); transform: translateY(-2px); box-shadow: var(--shadow); }
.pager .pager-label { font-size: 12.5px; color: var(--ink-3); }
.pager .pager-title { font-weight: 700; margin-top: 2px; color: var(--ink); }
.pager a.next { text-align: right; }

/* 返回顶部 */
#back-top {
  position: fixed; right: 26px; bottom: 26px; width: 44px; height: 44px;
  border-radius: 50%; border: none; cursor: pointer; font-size: 19px;
  background: var(--blue); color: #0e1218; box-shadow: var(--shadow);
  opacity: 0; pointer-events: none; transition: .25s; z-index: 800;
}
#back-top.show { opacity: 1; pointer-events: auto; }
#back-top:hover { background: var(--blue-dark); transform: translateY(-3px); }

/* ---------- 搜索弹层 ---------- */
.search-modal {
  position: fixed; inset: 0; background: rgba(0, 0, 0, .66); backdrop-filter: blur(3px);
  z-index: 1100; display: none; align-items: flex-start; justify-content: center; padding-top: 12vh;
}
.search-modal.open { display: flex; }
.search-box {
  width: min(620px, 92vw); background: #15161a; border: 1px solid #2c2e33; border-radius: 14px;
  box-shadow: var(--shadow-lg); overflow: hidden;
}
.search-box input {
  width: 100%; border: none; outline: none; font-size: 17px; padding: 18px 22px;
  font-family: var(--font); border-bottom: 1px solid #292b30;
  background: transparent; color: var(--ink);
}
.search-box input::placeholder { color: #5f646c; }
.search-results { max-height: 50vh; overflow-y: auto; padding: 8px 0; }
.search-results a {
  display: flex; flex-direction: column; padding: 10px 22px; color: var(--ink);
}
.search-results a:hover, .search-results a.cur { background: rgba(147, 167, 191, .12); }
.search-results .sr-group { font-size: 12px; color: var(--ink-3); }
.search-empty { padding: 24px; text-align: center; color: var(--ink-3); }

/* ============================================================
   首页专属样式
   ============================================================ */
.hero {
  background: radial-gradient(1000px 420px at 85% -10%, rgba(147, 167, 191, .16), transparent 60%),
              radial-gradient(800px 420px at 0% 0%, rgba(127, 168, 155, .08), transparent 55%),
              linear-gradient(180deg, #121419, #0f1012);
  border-bottom: 1px solid var(--line);
  margin: calc(-1 * var(--header-h) - 28px) -32px 0;
  padding: calc(var(--header-h) + 70px) 32px 64px;
}
.hero-inner { max-width: 1000px; margin: 0 auto; text-align: center; }
.hero h1 { font-family: var(--serif); font-size: 46px; line-height: 1.3; margin-bottom: 18px; color: #eef1f5; letter-spacing: 2px; }
.hero h1 .hl { color: var(--blue); }
.hero h1 .hl2 { color: #b2c2d4; background: linear-gradient(transparent 62%, rgba(147, 167, 191, .35) 62%); }
.hero p.sub { font-family: var(--serif); font-size: 18px; color: var(--ink-2); max-width: 720px; margin: 0 auto 30px; letter-spacing: .5px; }
.hero-btns { display: flex; gap: 14px; justify-content: center; flex-wrap: wrap; }
.btn {
  display: inline-block; padding: 12px 28px; border-radius: 10px;
  font-weight: 700; font-size: 16px; transition: .2s; border: 2px solid transparent;
  letter-spacing: 2px;
}
.btn-primary { background: var(--blue); color: #0e1218; box-shadow: 0 8px 24px rgba(147, 167, 191, .22); }
.btn-primary:hover { background: var(--blue-dark); color: #0e1218; transform: translateY(-2px); }
.btn-yellow { background: var(--purple); color: #0b120f; }
.btn-yellow:hover { background: #94bcaf; color: #0b120f; transform: translateY(-2px); }
.btn-ghost { border-color: #373a41; background: transparent; color: #c0c5cd; }
.btn-ghost:hover { border-color: var(--blue); color: var(--blue); }

.hero-stats { display: flex; gap: 44px; justify-content: center; margin-top: 42px; flex-wrap: wrap; }
.hero-stat b { display: block; font-size: 32px; color: var(--blue); font-family: var(--mono); }
.hero-stat span { font-size: 14px; color: var(--ink-3); }

.section { max-width: 1000px; margin: 0 auto; padding: 56px 0 8px; }
.section > h2 {
  font-family: var(--serif); font-size: 28px; text-align: center; border: none; margin-bottom: 6px;
  display: block; padding: 0; color: #e5e8ed; letter-spacing: 3px;
}
.section > h2::after {
  content: ""; display: block; width: 48px; height: 2px; margin: 12px auto 0;
  background: linear-gradient(90deg, transparent, var(--blue), transparent);
}
.section > p.desc { text-align: center; color: var(--ink-3); margin-bottom: 30px; }

.feature-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.feature {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 26px 24px; box-shadow: var(--shadow-sm); transition: .2s;
}
.feature:hover { transform: translateY(-4px); box-shadow: var(--shadow); border-color: rgba(147, 167, 191, .42); }
.feature .ico {
  width: 48px; height: 48px; border-radius: 12px; display: grid; place-items: center;
  font-size: 24px; margin-bottom: 14px;
}
.ico.blue { background: var(--blue-light); }
.ico.yellow { background: var(--amber-light); }
.ico.green { background: var(--green-light); }
.ico.purple { background: var(--purple-light); }
.ico.amber { background: var(--amber-light); }
.ico.red { background: var(--red-light); }
.feature h3 { font-family: var(--serif); font-size: 18px; margin-bottom: 8px; color: #e5e8ed; letter-spacing: 1px; }
.feature p { color: var(--ink-3); font-size: 14.5px; margin: 0; }

/* 首页两大板块卡 */
.part-card {
  position: relative; border-radius: 16px; padding: 34px 32px; color: #e3e6eb;
  overflow: hidden; box-shadow: var(--shadow); transition: .25s;
}
.part-card:hover { transform: translateY(-5px); box-shadow: var(--shadow-lg); }
.part-card.syntax { background: linear-gradient(135deg, #1a2029, #10131a); border: 1px solid rgba(147, 167, 191, .30); }
.part-card.nlp { background: linear-gradient(135deg, #131f1b, #0d1512); border: 1px solid rgba(127, 168, 155, .28); }
.part-card h3 { font-family: var(--serif); font-size: 26px; margin-bottom: 10px; letter-spacing: 2px; }
.part-card p { opacity: .85; margin-bottom: 18px; }
.part-card .chips { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 22px; }
.part-card .chips span {
  background: rgba(255, 255, 255, .06); border: 1px solid rgba(255, 255, 255, .14);
  border-radius: 20px; padding: 3px 13px; font-size: 13px;
}
.part-card .go {
  display: inline-block; background: var(--blue); color: #0e1218; font-weight: 700;
  padding: 10px 24px; border-radius: 10px; letter-spacing: 2px;
}
.part-card .go:hover { color: #0e1218; background: var(--blue-dark); }
.part-card.nlp .go { background: var(--purple); color: #0b120f; }
.part-card.nlp .go:hover { background: #94bcaf; }
.part-card.syntax .deco { position: absolute; right: -30px; bottom: -40px; font-size: 180px; opacity: .12; font-family: var(--mono); color: var(--blue); }
.part-card.nlp .deco { position: absolute; right: -10px; bottom: -36px; font-size: 150px; opacity: .14; color: var(--purple); }

/* 路线图 */
.roadmap { display: grid; grid-template-columns: repeat(4, 1fr); gap: 0; margin-top: 30px; }
.road-step { position: relative; text-align: center; padding: 0 12px; }
.road-step .step-num {
  width: 52px; height: 52px; margin: 0 auto 12px; border-radius: 50%;
  display: grid; place-items: center; font-weight: 800; font-size: 18px;
  background: var(--card); border: 2px solid var(--blue); color: var(--blue);
  position: relative; z-index: 2;
}
.road-step:not(:last-child)::after {
  content: ""; position: absolute; top: 25px; left: calc(50% + 32px); right: calc(-50% + 32px);
  height: 2px; background: #2c2f36; z-index: 1;
}
.road-step h4 { margin-bottom: 4px; color: #e5e8ed; }
.road-step p { font-size: 13.5px; color: var(--ink-3); margin: 0; }

/* 首页章节列表 */
.chapter-list { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
.chapter-list a {
  display: flex; gap: 14px; align-items: flex-start;
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 16px 18px; box-shadow: var(--shadow-sm); transition: .2s; color: var(--ink);
}
.chapter-list a:hover { border-color: var(--blue); transform: translateX(4px); }
.chapter-list .ch-num {
  flex: none; width: 40px; height: 40px; border-radius: 10px; display: grid; place-items: center;
  font-family: var(--mono); font-weight: 700; font-size: 14px;
}
.ch-num.blue { background: var(--blue-light); color: var(--blue); }
.ch-num.purple { background: var(--purple-light); color: var(--purple); }
.chapter-list h4 { margin: 0 0 2px; font-size: 15.5px; font-family: var(--serif); letter-spacing: .5px; }
.chapter-list p { margin: 0; font-size: 13px; color: var(--ink-3); }

.home-footer {
  margin-top: 70px; border-top: 1px solid var(--line);
  text-align: center; padding: 28px; color: var(--ink-3); font-size: 14px;
}

/* ---------- 响应式 ---------- */
@media (max-width: 1024px) {
  .feature-grid { grid-template-columns: 1fr 1fr; }
  .roadmap { grid-template-columns: 1fr 1fr; gap: 24px 0; }
  .road-step::after { display: none; }
}
@media (max-width: 860px) {
  .menu-btn { display: block; }
  .header-search { min-width: 0; }
  .header-search .hs-text, .header-search kbd { display: none; }
  .header-search { padding: 8px 11px; }
  .sidebar { transform: translateX(-100%); box-shadow: var(--shadow-lg); }
  body.nav-open .sidebar { transform: translateX(0); }
  body.nav-open .sidebar-overlay { display: block; }
  .main-wrap { margin-left: 0; padding-left: 18px; padding-right: 18px; }
  .hero { margin-left: -18px; margin-right: -18px; padding-left: 20px; padding-right: 20px; }
  .hero h1 { font-size: 32px; }
  .grid-2, .grid-3 { grid-template-columns: 1fr; }
  .chapter-list { grid-template-columns: 1fr; }
  .page-toc ol { columns: 1; }
  .pager { grid-template-columns: 1fr; }
  .article-head h1 { font-size: 26px; }
}

/* 字号控制 */
body.fs-large { font-size: 17.5px; }
body.fs-large pre code { font-size: 15px; }
body.fs-small { font-size: 15px; }
body.fs-small pre code { font-size: 13px; }

/* 打印：自动切换为宣纸浅色，便于打印阅读 */
@media print {
  body { background: #fff; color: #1a1a1a; }
  .sidebar, .site-header, #back-top, #progress-bar, .pager, .copy-btn { display: none !important; }
  .main-wrap { margin: 0; padding: 0; }
  .hero { background: none; margin: 0; padding: 20px 0; }
  pre, .card, .callout, table, .page-toc, details.quiz, .part-card, .chapter-list a { box-shadow: none !important; }
}