/* ============================================================
   《深入理解 AI Agent》中文图文教程站 — 样式表
   设计风格：深色科技感 + 卡片化图文布局，强调配图可读性
   ============================================================ */

:root {
  --bg: #0b1020;
  --bg-soft: #111832;
  --panel: #171f3d;
  --panel-2: #1d2749;
  --border: #2a3560;
  --text: #e8ecf8;
  --text-dim: #9aa7c8;
  --accent: #5b8cff;
  --accent-2: #7de3ff;
  --gold: #ffc857;
  --green: #6ee7a0;
  --purple: #b39dff;
  --pink: #ff9ecb;
  --orange: #ffb066;
  --shadow: 0 8px 30px rgba(0,0,0,.35);
  --radius: 14px;
  --font: "PingFang SC", "Microsoft YaHei", "Noto Sans SC", "Source Han Sans SC", sans-serif;
  --mono: "JetBrains Mono", "Cascadia Code", Consolas, monospace;
}

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

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  line-height: 1.75;
  font-size: 16px;
  background-image:
    radial-gradient(1200px 500px at 80% -10%, rgba(91,140,255,.14), transparent 60%),
    radial-gradient(900px 400px at 10% 10%, rgba(125,227,255,.08), transparent 60%);
  background-attachment: fixed;
}

/* ---------- 顶部导航 ---------- */
.topnav {
  position: sticky; top: 0; z-index: 100;
  display: flex; align-items: center; gap: 18px;
  padding: 12px 28px;
  background: rgba(11,16,32,.88);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
}
.topnav .brand {
  font-weight: 800; font-size: 17px; color: #fff;
  text-decoration: none; letter-spacing: .3px;
  white-space: nowrap;
}
.topnav .brand span { color: var(--accent); }
.topnav .links { display: flex; gap: 4px; flex-wrap: wrap; }
.topnav .links a {
  color: var(--text-dim); text-decoration: none;
  font-size: 13.5px; padding: 6px 10px; border-radius: 8px;
  transition: all .15s;
}
.topnav .links a:hover { color: #fff; background: var(--panel); }
.topnav .links a.active { color: var(--accent-2); background: rgba(91,140,255,.12); }

/* ---------- 页面容器 ---------- */
.wrap { max-width: 1180px; margin: 0 auto; padding: 34px 22px 80px; }

/* ---------- 首页 Hero ---------- */
.hero { text-align: center; padding: 56px 10px 26px; }
.hero .kicker {
  display: inline-block; font-size: 13px; letter-spacing: 2px;
  color: var(--accent-2); border: 1px solid rgba(125,227,255,.35);
  padding: 5px 16px; border-radius: 999px; margin-bottom: 22px;
  background: rgba(125,227,255,.07);
}
.hero h1 { font-size: 46px; line-height: 1.25; font-weight: 900; }
.hero h1 .grad {
  background: linear-gradient(100deg, var(--accent), var(--accent-2) 55%, var(--purple));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero .sub { color: var(--text-dim); font-size: 18px; margin-top: 14px; }
.hero .sub b { color: var(--gold); }

.formula-box {
  display: inline-flex; align-items: center; gap: 14px;
  margin: 34px auto 8px; padding: 20px 38px;
  background: linear-gradient(135deg, var(--panel), var(--panel-2));
  border: 1px solid var(--border); border-radius: var(--radius);
  font-family: var(--mono); font-size: 30px; font-weight: 700;
  box-shadow: var(--shadow); flex-wrap: wrap; justify-content: center;
}
.formula-box .op { color: var(--text-dim); font-weight: 400; }
.formula-box .t1 { color: var(--accent-2); }
.formula-box .t2 { color: var(--green); }
.formula-box .t3 { color: var(--orange); }
.hero .meta { color: var(--text-dim); font-size: 13.5px; margin-top: 14px; }

/* ---------- 章节导航网格 ---------- */
.section-title {
  font-size: 24px; font-weight: 800; margin: 46px 0 6px;
  display: flex; align-items: center; gap: 12px;
}
.section-title::after { content: ""; flex: 1; height: 1px; background: var(--border); }
.section-sub { color: var(--text-dim); font-size: 14px; margin-bottom: 22px; }

.ch-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(340px, 1fr)); gap: 18px; }
.ch-card {
  display: block; text-decoration: none; color: inherit;
  background: var(--panel); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 20px 22px;
  transition: transform .18s, border-color .18s, box-shadow .18s;
  position: relative; overflow: hidden;
}
.ch-card:hover { transform: translateY(-4px); border-color: var(--accent); box-shadow: var(--shadow); }
.ch-card .ch-no { font-size: 12px; letter-spacing: 1.5px; color: var(--accent-2); font-weight: 700; }
.ch-card h3 { font-size: 18.5px; margin: 6px 0 8px; color: #fff; }
.ch-card .ch-formula { font-family: var(--mono); font-size: 12.5px; color: var(--gold); margin-bottom: 8px; }
.ch-card p { font-size: 13.5px; color: var(--text-dim); }
.ch-card .ch-tags { margin-top: 12px; display: flex; gap: 6px; flex-wrap: wrap; }
.ch-card .tag {
  font-size: 11.5px; padding: 3px 9px; border-radius: 6px;
  background: rgba(91,140,255,.12); color: var(--accent-2);
}
.ch-card .arrow { position: absolute; right: 18px; bottom: 14px; font-size: 20px; color: var(--border); transition: color .18s, transform .18s; }
.ch-card:hover .arrow { color: var(--accent); transform: translateX(4px); }

/* ---------- 章节页头部 ---------- */
.ch-header { padding: 26px 4px 8px; }
.ch-header .breadcrumb { font-size: 13px; color: var(--text-dim); margin-bottom: 14px; }
.ch-header .breadcrumb a { color: var(--accent-2); text-decoration: none; }
.ch-header h1 { font-size: 34px; font-weight: 900; }
.ch-header .ch-lead {
  margin-top: 14px; font-size: 16px; color: var(--text-dim);
  border-left: 3px solid var(--accent); padding-left: 16px;
}
.ch-header .ch-meta { display: flex; gap: 14px; margin-top: 16px; flex-wrap: wrap; }
.ch-header .ch-meta .pill {
  font-size: 12.5px; padding: 5px 13px; border-radius: 999px;
  background: var(--panel); border: 1px solid var(--border); color: var(--text-dim);
}

/* ---------- 要点区块 ---------- */
.keypoints { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 14px; margin: 26px 0; }
.kp {
  background: var(--panel); border: 1px solid var(--border); border-radius: 12px;
  padding: 16px 18px; display: flex; gap: 12px; align-items: flex-start;
}
.kp .num {
  flex: none; width: 30px; height: 30px; border-radius: 8px;
  background: linear-gradient(135deg, var(--accent), var(--purple));
  display: flex; align-items: center; justify-content: center;
  font-weight: 800; font-size: 14px; color: #fff;
}
.kp p { font-size: 14.5px; }

/* ---------- 概念卡片 ---------- */
.concept-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(330px, 1fr)); gap: 14px; margin: 22px 0; }
.concept {
  background: var(--panel); border: 1px solid var(--border); border-radius: 12px;
  padding: 16px 18px; transition: border-color .15s;
}
.concept:hover { border-color: var(--accent); }
.concept h4 { font-size: 15.5px; color: var(--accent-2); margin-bottom: 5px; display: flex; gap: 8px; align-items: center; }
.concept .def { font-size: 13.5px; color: var(--text); }
.concept .def small { display: block; color: var(--text-dim); margin-top: 4px; font-size: 12.5px; }

/* ---------- 配图区 ---------- */
.fig-block { margin: 34px 0; }
.fig-block .fig-head { display: flex; align-items: baseline; gap: 12px; margin-bottom: 12px; }
.fig-block .fig-num { font-family: var(--mono); font-size: 13px; color: var(--gold); font-weight: 700; }
.fig-block h3 { font-size: 19px; }
.fig-card {
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  overflow: hidden; box-shadow: var(--shadow);
}
.fig-card .svg-wrap {
  background: #fff; padding: 18px; display: flex; justify-content: center;
  min-height: 120px;
}
.fig-card .svg-wrap svg, .fig-card .svg-wrap img { max-width: 100%; height: auto; display: block; }
.fig-card .fig-caption { padding: 13px 18px; font-size: 13.5px; color: var(--text-dim); border-top: 1px solid var(--border); }
.fig-card .fig-caption b { color: var(--accent-2); }

/* 双图并排 */
.fig-pair { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; }
@media (max-width: 860px) { .fig-pair { grid-template-columns: 1fr; } }

/* ---------- 表格 ---------- */
.data-table { width: 100%; border-collapse: collapse; margin: 20px 0; font-size: 14px; background: var(--panel); border-radius: 12px; overflow: hidden; }
.data-table th { background: var(--panel-2); color: var(--accent-2); padding: 11px 14px; text-align: left; font-weight: 700; }
.data-table td { padding: 10px 14px; border-top: 1px solid var(--border); color: var(--text); }
.data-table tr:hover td { background: rgba(91,140,255,.06); }

/* ---------- 代码块 ---------- */
.code-block { background: #0d1428; border: 1px solid var(--border); border-radius: 10px; padding: 16px 18px; font-family: var(--mono); font-size: 13px; overflow-x: auto; margin: 16px 0; color: #cfe3ff; line-height: 1.7; }

/* ---------- 金句 ---------- */
.quotes { display: grid; gap: 14px; margin: 24px 0; }
.quote {
  background: linear-gradient(135deg, rgba(91,140,255,.09), rgba(179,157,255,.07));
  border-left: 3px solid var(--purple); border-radius: 10px;
  padding: 16px 20px; font-size: 15px; color: #d9e2ff;
}
.quote::before { content: "❝ "; color: var(--purple); font-size: 20px; }

/* ---------- 章节底部导航 ---------- */
.pager { display: flex; justify-content: space-between; gap: 16px; margin-top: 60px; }
.pager a {
  text-decoration: none; color: var(--text); background: var(--panel);
  border: 1px solid var(--border); border-radius: 12px; padding: 16px 22px;
  flex: 1; max-width: 380px; transition: border-color .15s, transform .15s;
}
.pager a:hover { border-color: var(--accent); transform: translateY(-2px); }
.pager .dir { font-size: 12px; color: var(--text-dim); letter-spacing: 1px; }
.pager .t { font-weight: 700; margin-top: 4px; }
.pager a.next { text-align: right; margin-left: auto; }

/* ---------- 页脚 ---------- */
footer {
  border-top: 1px solid var(--border); padding: 30px 28px 40px;
  text-align: center; color: var(--text-dim); font-size: 13px;
  background: rgba(11,16,32,.6);
}
footer a { color: var(--accent-2); text-decoration: none; }

/* ---------- 目录侧栏 ---------- */
.toc {
  background: var(--panel); border: 1px solid var(--border); border-radius: 12px;
  padding: 16px 20px; margin: 24px 0; font-size: 14px;
}
.toc b { color: var(--accent-2); }
.toc ol { margin: 8px 0 0 20px; color: var(--text-dim); }
.toc li { margin: 3px 0; }
.toc a { color: var(--text-dim); text-decoration: none; }
.toc a:hover { color: var(--accent-2); }

/* ---------- 实验列表 ---------- */
.exp-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 12px; margin: 18px 0; }
.exp-item {
  background: var(--panel); border: 1px solid var(--border); border-radius: 10px;
  padding: 13px 16px; font-size: 13.5px;
}
.exp-item b { color: var(--gold); font-family: var(--mono); }
.exp-item .diff { color: var(--text-dim); font-size: 12px; margin-left: 6px; }

/* ---------- 首页全景图 ---------- */
.pano { background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 18px; margin: 22px 0; box-shadow: var(--shadow); }
.pano .svg-wrap { background: #fff; border-radius: 8px; padding: 12px; display: flex; justify-content: center; }
.pano .svg-wrap svg, .pano .svg-wrap img { max-width: 100%; height: auto; }

/* 响应式 */
@media (max-width: 720px) {
  .hero h1 { font-size: 32px; }
  .formula-box { font-size: 21px; padding: 16px 20px; }
  .ch-header h1 { font-size: 26px; }
  .wrap { padding: 22px 14px 60px; }
  .topnav { padding: 10px 14px; }
}