/* ============================================================
   AI 大模型自学教材 — 设计系统（Business Blue 定制版）
   离线可用：无外部依赖；中文字体走系统回退
   ============================================================ */

:root {
  /* 页面层 token */
  --page-bg: #FFFFFF;
  --page-surface: #F6F8FB;
  --page-surface-muted: #EDF1F7;
  --page-text: #1C222E;
  --page-text-secondary: #3B4457;
  --page-text-muted: #68738C;
  --page-text-disabled: #9AA4B8;
  --page-border: #DCE2EC;
  --page-brand: #0969DA;
  --page-brand-hover: #085CC0;
  --page-brand-active: #074DA6;
  --page-brand-soft: #EDF3FC;
  --page-brand-soft-strong: #D8E6FA;
  --page-brand-text: #074DA6;

  /* 兼容别名 */
  --bg: #FFFFFF;
  --bg2: #F6F8FB;
  --rule: #DCE2EC;
  --ink: #1C222E;
  --muted: #68738C;
  --text-secondary: #3B4457;
  --text-disabled: #9AA4B8;
  --accent: #0969DA;
  --accent-hover: #085CC0;
  --accent-active: #074DA6;
  --accent-soft: #EDF3FC;
  --accent2: #06B6D4;
  --accent2-soft: #E4F8FB;

  /* 图表层 token */
  --chart-series-1: #0969DA;
  --chart-series-2: #8250DF;
  --chart-series-3: #06B6D4;
  --chart-series-4: #BF3989;
  --chart-other: #DCE2EC;
  --chart-accent: #06B6D4;
  --chart-accent-2: #0969DA;
  --chart-positive: #2DA44E;
  --chart-warning: #FAAD14;
  --chart-negative: #E5484D;
  --chart-grid: rgba(28, 34, 46, 0.12);
  --chart-axis: #68738C;
  --chart-label: #68738C;
  --chart-tooltip-bg: #FFFFFF;

  /* 语义色 */
  --success: #2DA44E;
  --info: #0969DA;
  --reminder: #FF7A45;
  --warning: #D97706;
  --danger: #E5484D;
  --positive: #2DA44E;
  --negative: #E5484D;

  /* 语义浅底（仅用于有真实含义的提示块） */
  --tint-success: #EAF6EC;
  --tint-warning: #FDF3E1;
  --tint-danger: #FDEBEC;

  /* 结构 */
  --radius-s: 8px;
  --radius-m: 12px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
               "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  --font-mono: "SF Mono", "Cascadia Code", Consolas, "Liberation Mono",
               "Courier New", monospace;
  --content-w: 960px;
  --shadow-float: 0 6px 24px rgba(28, 34, 46, 0.10);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--page-bg);
  color: var(--page-text);
  font-family: var(--font-sans);
  font-size: 15px;
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}

.wrap {
  max-width: var(--content-w);
  margin: 0 auto;
  padding: 0 22px;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

h1, h2, h3, h4 { line-height: 1.35; color: var(--page-text); }

h2 {
  font-size: 24px;
  margin: 52px 0 14px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--page-border);
}

h3 { font-size: 18.5px; margin: 32px 0 10px; }
h4 { font-size: 16px; margin: 24px 0 8px; }

p { margin: 12px 0; }
ul, ol { margin: 12px 0; padding-left: 24px; }
li { margin: 6px 0; }

strong { color: var(--page-text); }
mark.key { background: none; color: var(--accent); font-weight: 600; }

hr { border: 0; border-top: 1px solid var(--page-border); margin: 36px 0; }

code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--page-surface-muted);
  border: 1px solid var(--page-border);
  border-radius: 4px;
  padding: 1px 5px;
}

pre {
  background: var(--page-surface-muted);
  border: 1px solid var(--page-border);
  border-radius: var(--radius-m);
  padding: 16px 18px;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 13.5px;
  line-height: 1.65;
}
pre code { background: none; border: 0; padding: 0; font-size: 13.5px; }

/* ---------- 首页 Intro（contained 模式） ---------- */
.report-intro {
  position: relative;
  background: var(--page-surface);
  border-bottom: 1px solid var(--page-border);
  overflow: hidden;
}
.report-intro::before,
.report-intro::after {
  content: "";
  position: absolute;
  border-radius: 50%;
  background: var(--page-brand-soft-strong);
  pointer-events: none;
}
.report-intro::before { width: 380px; height: 380px; top: -160px; right: -120px; }
.report-intro::after { width: 260px; height: 260px; bottom: -140px; left: -80px; }
.report-intro__content {
  position: relative;
  max-width: var(--content-w);
  margin: 0 auto;
  padding: 64px 22px 48px;
}
.report-intro__kicker {
  margin: 0 0 14px;
  font-size: 13px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 600;
}
.report-intro h1 {
  margin: 0 0 18px;
  font-size: 38px;
  line-height: 1.25;
}
.report-intro__summary {
  margin: 0;
  max-width: 680px;
  font-size: 17px;
  color: var(--page-text-secondary);
}
.report-intro__meta {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 8px 18px;
  margin: 26px 0 0;
  padding: 0;
  font-size: 13px;
  color: var(--page-text-muted);
}

/* ---------- 章节卡片 ---------- */
.section-label {
  font-size: 13px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 600;
  margin: 0 0 6px;
}

.ch-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(270px, 1fr));
  gap: 16px;
  margin: 20px 0 8px;
}
.ch-card {
  display: block;
  border: 1px solid var(--page-border);
  border-radius: var(--radius-m);
  padding: 18px 18px 16px;
  background: var(--page-bg);
  transition: border-color 0.15s, transform 0.15s, box-shadow 0.15s;
}
.ch-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: var(--shadow-float);
  text-decoration: none;
}
.ch-card__num {
  font-family: var(--font-mono);
  font-size: 12.5px;
  color: var(--accent);
  font-weight: 600;
}
.ch-card h3 { margin: 6px 0 6px; font-size: 17px; }
.ch-card p { margin: 0; font-size: 13.5px; color: var(--page-text-muted); line-height: 1.65; }
.ch-card__tags { margin-top: 10px; display: flex; flex-wrap: wrap; gap: 6px; }

/* ---------- 标签 ---------- */
.tag {
  display: inline-block;
  font-size: 12px;
  line-height: 1;
  padding: 4px 9px;
  border-radius: 999px;
  border: 1px solid var(--page-border);
  background: var(--page-surface);
  color: var(--page-text-secondary);
  white-space: nowrap;
}
.tag--core { background: var(--page-brand-soft); border-color: var(--page-brand-soft-strong); color: var(--page-brand-text); }
.tag--cyan { background: var(--accent2-soft); border-color: #BFEAF2; color: #0A7186; }
.tag--warn { background: var(--tint-warning); border-color: #F0D9A8; color: #8A5A00; }

/* ---------- 章节页头部 ---------- */
.chapter-head { padding: 44px 0 10px; }
.chapter-head__kicker {
  font-size: 13px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 600;
  margin: 0 0 10px;
}
.chapter-head h1 { font-size: 30px; margin: 0 0 10px; }
.chapter-head__lead { margin: 0; font-size: 16.5px; color: var(--page-text-secondary); max-width: 720px; }
.chapter-head__meta {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 6px 18px;
  margin: 16px 0 0;
  padding: 0;
  font-size: 13px;
  color: var(--page-text-muted);
}

/* 章内目录 */
.chapter-toc {
  margin: 28px 0 8px;
  border: 1px solid var(--page-border);
  border-radius: var(--radius-m);
  background: var(--page-surface);
  padding: 16px 20px;
  columns: 2;
  column-gap: 28px;
}
.chapter-toc ol { margin: 0; padding-left: 20px; }
.chapter-toc li { margin: 4px 0; font-size: 14px; }
@media (max-width: 640px) { .chapter-toc { columns: 1; } }

/* ---------- 提示块 ---------- */
.callout {
  border: 1px solid var(--page-border);
  border-radius: var(--radius-m);
  padding: 16px 18px;
  margin: 20px 0;
  background: var(--page-surface);
}
.callout__title {
  display: block;
  font-weight: 700;
  font-size: 14.5px;
  margin-bottom: 6px;
}
.callout--analogy { background: var(--page-brand-soft); }
.callout--analogy .callout__title { color: var(--page-brand-text); }
.callout--power { background: var(--accent2-soft); }
.callout--power .callout__title { color: #0A7186; }
.callout--note { background: var(--page-surface-muted); }
.callout--note .callout__title { color: var(--page-text-secondary); }
.callout--warn { background: var(--tint-warning); }
.callout--warn .callout__title { color: var(--warning); }
.callout--danger { background: var(--tint-danger); }
.callout--danger .callout__title { color: var(--danger); }
.callout p:first-of-type { margin-top: 2px; }
.callout p:last-child { margin-bottom: 2px; }

/* ---------- 图示 ---------- */
.fig { margin: 26px 0; }
.fig__cap {
  margin-top: 10px;
  text-align: center;
  font-size: 13px;
  color: var(--page-text-muted);
}
.fig__cap strong { color: var(--page-text-secondary); }

.diag {
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 18px 14px;
  border: 1px solid var(--page-border);
  border-radius: var(--radius-m);
  background: var(--page-surface);
}
.diag__row { display: flex; flex-wrap: wrap; justify-content: center; align-items: stretch; gap: 10px; }
.diag__col { display: flex; flex-direction: column; align-items: center; gap: 10px; }
.diag__node {
  border: 1.5px solid var(--page-border);
  background: var(--page-bg);
  border-radius: 10px;
  padding: 10px 14px;
  font-size: 13.5px;
  line-height: 1.5;
  text-align: center;
  min-width: 92px;
}
.diag__node b { display: block; font-size: 14px; }
.diag__node--accent { border-color: var(--accent); background: var(--page-brand-soft); }
.diag__node--core { border-color: var(--accent); background: var(--page-brand-soft-strong); }
.diag__node--dim { background: var(--page-surface-muted); color: var(--page-text-muted); }
.diag__node--cyan { border-color: #0E9CB8; background: var(--accent2-soft); }
.diag__arrow { align-self: center; color: var(--page-text-muted); font-size: 17px; font-weight: 700; line-height: 1; }
.diag__arrow--accent { color: var(--accent); }
.diag__label { font-size: 12px; color: var(--page-text-muted); text-align: center; line-height: 1.5; }
.diag__group {
  border: 1.5px dashed var(--page-border);
  border-radius: var(--radius-m);
  padding: 14px 12px 10px;
  position: relative;
  flex: 1;
  min-width: 200px;
}
.diag__group-label {
  position: absolute;
  top: -10px;
  left: 12px;
  background: var(--page-surface);
  padding: 0 8px;
  font-size: 12px;
  color: var(--page-text-muted);
}
.diag__flow-v { display: flex; flex-direction: column; align-items: center; gap: 8px; }

/* 注意力热力图 */
.heat {
  display: grid;
  gap: 4px;
  margin: 12px auto;
  width: fit-content;
}
.heat__cell {
  width: 52px;
  height: 40px;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--page-text);
}
.heat__row-label, .heat__col-label {
  font-size: 12.5px;
  color: var(--page-text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
}

/* ---------- 表格 ---------- */
.table-wrap { overflow-x: auto; margin: 18px 0; }
table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
  background: var(--page-bg);
}
caption {
  caption-side: top;
  text-align: left;
  font-size: 13.5px;
  font-weight: 600;
  color: var(--page-text-secondary);
  padding: 0 0 8px;
}
th {
  background: var(--page-surface-muted);
  font-size: 12.5px;
  text-transform: none;
  letter-spacing: 0.02em;
  color: var(--page-text-secondary);
  text-align: left;
  padding: 10px 12px;
  border-bottom: 1px solid var(--page-border);
  white-space: nowrap;
}
td {
  padding: 10px 12px;
  border-bottom: 1px solid var(--page-border);
  vertical-align: top;
}
tr:last-child td { border-bottom: 0; }
tbody tr:hover { background: var(--page-surface); }

/* ---------- 折叠答案 ---------- */
details {
  border: 1px solid var(--page-border);
  border-radius: var(--radius-m);
  background: var(--page-bg);
  margin: 12px 0;
}
details summary {
  cursor: pointer;
  padding: 12px 16px;
  font-weight: 600;
  font-size: 14.5px;
  color: var(--page-text-secondary);
  list-style: none;
}
details summary::before { content: "▸ "; color: var(--accent); }
details[open] summary::before { content: "▾ "; }
details .answer-body { padding: 4px 18px 14px; }

/* ---------- 网格 ---------- */
.grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin: 20px 0; }
@media (max-width: 800px) { .grid2 { grid-template-columns: 1fr; } }

/* ---------- 前后章导航 ---------- */
.prevnext {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin: 56px 0 16px;
}
.prevnext a {
  flex: 1;
  border: 1px solid var(--page-border);
  border-radius: var(--radius-m);
  padding: 14px 18px;
  background: var(--page-bg);
  font-size: 14px;
}
.prevnext a:hover { border-color: var(--accent); text-decoration: none; }
.prevnext .pn-label { display: block; font-size: 12px; color: var(--page-text-muted); }
.prevnext .pn-title { font-weight: 600; color: var(--page-text); }

/* ---------- 页脚 ---------- */
footer.site-foot {
  margin-top: 64px;
  border-top: 1px solid var(--page-border);
  padding: 28px 0 48px;
  font-size: 13px;
  color: var(--page-text-muted);
}
footer.site-foot ol { font-size: 13px; color: var(--page-text-muted); }
footer.site-foot li { margin: 4px 0; word-break: break-all; }

/* ---------- 回到顶部 ---------- */
.backtop {
  position: fixed;
  right: 22px;
  bottom: 22px;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 1px solid var(--page-border);
  background: var(--page-bg);
  color: var(--accent);
  font-size: 18px;
  cursor: pointer;
  box-shadow: var(--shadow-float);
  display: none;
  z-index: 50;
}
.backtop.show { display: block; }

/* ---------- 视频清单 ---------- */
.video-card {
  display: flex;
  gap: 14px;
  border: 1px solid var(--page-border);
  border-radius: var(--radius-m);
  padding: 14px 16px;
  margin: 10px 0;
  background: var(--page-bg);
}
.video-card__idx {
  flex: 0 0 auto;
  width: 40px; height: 40px;
  border-radius: 10px;
  background: var(--page-brand-soft);
  color: var(--accent);
  font-weight: 700;
  font-size: 15px;
  display: flex; align-items: center; justify-content: center;
}
.video-card__body h4 { margin: 0 0 4px; font-size: 15.5px; }
.video-card__body h4 a { color: var(--page-text); }
.video-card__body h4 a:hover { color: var(--accent); }
.video-card__meta { font-size: 12.5px; color: var(--page-text-muted); margin-top: 6px; }

/* ---------- 响应式 ---------- */
@media (max-width: 720px) {
  body { font-size: 14.5px; }
  .report-intro h1 { font-size: 28px; }
  .chapter-head h1 { font-size: 24px; }
  h2 { font-size: 21px; }
  .report-intro__content { padding: 44px 18px 36px; }
  .prevnext { flex-direction: column; }
}

/* ---------- 打印 ---------- */
@media print {
  .backtop, .prevnext, .chapter-toc { display: none !important; }
  body { font-size: 12pt; }
  a { color: inherit; text-decoration: none; }
  .report-intro, .chapter-head { background: #fff !important; }
}