:root {
  --bg: #f6f4ef;
  --paper: #ffffff;
  --ink: #1f2328;
  --muted: #6b7280;
  --line: #e7e3da;
  --accent: #4f46e5;
  --accent-soft: #eef0fe;
  --code-bg: #1e1e2e;
  --code-ink: #e4e4e7;
  --max: 780px;
  --sidebar-w: 290px;
  --tip: #0f9d76;     --tip-bg: #e7f7f0;
  --focus: #b7791f;   --focus-bg: #fdf4e3;
  --rec: #4f46e5;     --rec-bg: #eef0fe;
  --warn: #c0392b;    --warn-bg: #fdecea;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
          "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.8;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

/* ---------- 布局 ---------- */
.layout { display: flex; min-height: 100vh; }

.sidebar {
  width: var(--sidebar-w);
  flex: 0 0 var(--sidebar-w);
  background: #fbfaf7;
  border-right: 1px solid var(--line);
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  padding: 26px 18px;
  display: flex;
  flex-direction: column;
}
.side-head { margin-bottom: 18px; }
.side-title {
  text-decoration: none;
  color: var(--ink);
  font-weight: 800;
  font-size: 19px;
  letter-spacing: .5px;
  display: block;
  line-height: 1.3;
}
.side-title span {
  display: block;
  font-size: 13px;
  font-weight: 600;
  color: var(--muted);
  letter-spacing: 2px;
}
.side-nav { flex: 1; }
.nav-group {
  font-size: 12px;
  font-weight: 700;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin: 18px 0 8px;
  padding-left: 10px;
}
.side-nav a {
  display: block;
  text-decoration: none;
  color: #3a3f47;
  font-size: 14px;
  padding: 7px 10px;
  border-radius: 8px;
  line-height: 1.45;
  transition: background .15s, color .15s;
}
.side-nav a:hover { background: var(--accent-soft); color: var(--accent); }
.side-nav a.active {
  background: var(--accent);
  color: #fff;
  font-weight: 600;
}
.side-foot {
  margin-top: 18px;
  font-size: 12px;
  color: var(--muted);
  padding-top: 14px;
  border-top: 1px solid var(--line);
}

.content { flex: 1; padding: 48px 40px 96px; }
.chapter, .cover { max-width: var(--max); margin: 0 auto; }

/* ---------- 章节头 ---------- */
.crumbs {
  font-size: 13px;
  color: var(--accent);
  font-weight: 600;
  letter-spacing: .5px;
  margin-bottom: 10px;
}
.chapter h1 {
  font-size: 30px;
  line-height: 1.3;
  margin: 0 0 28px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--line);
}
h2, h3 { line-height: 1.4; }
.body h2, .body h3 {
  margin-top: 34px;
  margin-bottom: 12px;
  font-size: 21px;
  color: var(--ink);
  padding-left: 12px;
  border-left: 4px solid var(--accent);
}
.body h3 { font-size: 17px; border-left-color: var(--muted); }

/* ---------- 正文元素 ---------- */
.body p { margin: 14px 0; }
.body ul, .body ol { padding-left: 24px; margin: 14px 0; }
.body li { margin: 6px 0; }

.body code {
  font-family: var(--mono);
  font-size: 14px;
  background: #efece4;
  color: #b3306b;
  padding: 2px 6px;
  border-radius: 5px;
}
.body pre {
  background: var(--code-bg);
  color: var(--code-ink);
  padding: 18px 20px;
  border-radius: 12px;
  overflow-x: auto;
  margin: 18px 0;
  line-height: 1.6;
}
.body pre code {
  background: none;
  color: inherit;
  padding: 0;
  font-size: 13.5px;
}

.body table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 14.5px;
}
.body th, .body td {
  border: 1px solid var(--line);
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
}
.body thead th { background: var(--accent-soft); color: var(--accent); font-weight: 700; }
.body tbody tr:nth-child(even) { background: #faf9f6; }

/* ---------- 引用 / 提示框 ---------- */
.body blockquote {
  margin: 18px 0;
  padding: 14px 18px;
  border-left: 4px solid var(--muted);
  background: #faf9f6;
  border-radius: 0 10px 10px 0;
  color: #2c3138;
}
.body blockquote p { margin: 8px 0; }
.bq-tip   { border-left-color: var(--tip);   background: var(--tip-bg); }
.bq-focus { border-left-color: var(--focus); background: var(--focus-bg); }
.bq-rec   { border-left-color: var(--rec);   background: var(--rec-bg); }
.bq-warn  { border-left-color: var(--warn);  background: var(--warn-bg); }
.body blockquote strong { color: var(--ink); }

.bridge {
  display: inline-block;
  font-weight: 700;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 1px 8px;
  border-radius: 6px;
  margin-right: 4px;
}

/* ---------- 翻页 ---------- */
.pager {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}
.pager-btn {
  flex: 1;
  text-decoration: none;
  color: var(--ink);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 14px 16px;
  font-size: 14px;
  font-weight: 600;
  transition: all .15s;
  background: #fff;
}
.pager-btn:hover { border-color: var(--accent); color: var(--accent); }
.pager-btn.next { text-align: right; }
.pager-gap { flex: 1; }

/* ---------- 封面 / 首页 ---------- */
.cover-badge {
  display: inline-block;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 2px;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 6px 14px;
  border-radius: 999px;
  margin-bottom: 22px;
}
.cover-title {
  font-size: 46px;
  line-height: 1.15;
  margin: 0 0 14px;
  font-weight: 800;
  letter-spacing: .5px;
}
.cover-sub {
  font-size: 17px;
  color: var(--muted);
  font-style: italic;
  margin: 0 0 8px;
}
.byline { color: var(--muted); margin: 6px 0 18px; }
.badges { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 26px; }
.badge {
  font-size: 12.5px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 6px 10px;
  color: #3a3f47;
}
.start-btn {
  display: inline-block;
  background: var(--accent);
  color: #fff;
  text-decoration: none;
  font-weight: 700;
  font-size: 16px;
  padding: 14px 30px;
  border-radius: 10px;
  transition: transform .12s, box-shadow .12s;
  box-shadow: 0 6px 18px rgba(79,70,229,.25);
}
.start-btn:hover { transform: translateY(-2px); box-shadow: 0 10px 24px rgba(79,70,229,.32); }
.intro {
  margin: 30px 0 10px;
  font-size: 16px;
  color: #2c3138;
  padding: 18px 20px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 12px;
}
.section-h {
  margin-top: 44px;
  font-size: 22px;
  padding-bottom: 10px;
  border-bottom: 2px solid var(--line);
}

/* 目录 */
.toc { display: flex; flex-direction: column; gap: 6px; }
.toc-group {
  font-size: 12px;
  font-weight: 700;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin: 16px 0 4px;
}
.toc-item {
  display: flex;
  align-items: baseline;
  gap: 12px;
  text-decoration: none;
  color: var(--ink);
  padding: 10px 12px;
  border-radius: 9px;
  border: 1px solid transparent;
  transition: all .15s;
}
.toc-item:hover { background: #fff; border-color: var(--line); }
.toc-num {
  font-weight: 800;
  color: var(--accent);
  font-size: 14px;
  min-width: 42px;
}
.toc-title { font-size: 15px; }
.reading-guide table { font-size: 14px; }

/* 移动端菜单按钮 */
.menu-toggle {
  display: none;
  position: fixed;
  top: 14px;
  left: 14px;
  z-index: 50;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 8px;
  padding: 9px 14px;
  font-size: 14px;
  font-weight: 700;
  cursor: pointer;
  box-shadow: 0 4px 12px rgba(0,0,0,.18);
}

/* ---------- 响应式 ---------- */
@media (max-width: 920px) {
  .menu-toggle { display: block; }
  .sidebar {
    position: fixed;
    left: 0; top: 0;
    z-index: 40;
    transform: translateX(-100%);
    transition: transform .25s ease;
    box-shadow: 4px 0 24px rgba(0,0,0,.12);
  }
  .sidebar.open { transform: translateX(0); }
  .content { padding: 72px 22px 80px; }
  .cover-title { font-size: 36px; }
  .chapter h1 { font-size: 25px; }
}