/* ===== 基础 ===== */
* { box-sizing: border-box; }
:root {
  --accent: #2563eb;
  --accent-dark: #1d4ed8;
  --accent-soft: #eff6ff;
  --text: #1f2937;
  --text-soft: #6b7280;
  --border: #e5e7eb;
  --bg: #f8fafc;
  --card: #ffffff;
  --code-bg: #f6f8fa;
  --ok: #16a34a;
  --ok-soft: #f0fdf4;
  --draft: #d97706;
  --draft-soft: #fffbeb;
}
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.75;
  font-size: 16px;
}
.wrap { max-width: 1080px; margin: 0 auto; padding: 0 20px; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
code, pre {
  font-family: "JetBrains Mono", Consolas, "Courier New", monospace;
}

/* ===== 顶部导航 ===== */
.site-header {
  background: #fff;
  border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 10;
}
.header-inner {
  display: flex; align-items: center; justify-content: space-between;
  height: 56px;
}
.brand { font-weight: 700; font-size: 17px; color: var(--text); }
.brand:hover { text-decoration: none; color: var(--accent); }
.topnav a { margin-left: 18px; color: var(--text-soft); font-size: 14px; }
.topnav a:hover { color: var(--accent); }

/* ===== 首页 hero + 卡片 ===== */
.hero {
  background: linear-gradient(135deg, #1e3a8a 0%, #2563eb 60%, #3b82f6 100%);
  color: #fff; padding: 56px 0 48px;
}
.hero h1 { margin: 0 0 12px; font-size: 30px; letter-spacing: .5px; }
.hero-desc { margin: 0 0 10px; font-size: 16px; opacity: .92; }
.hero-sub { margin: 0; font-size: 13px; opacity: .75; }
.hero-sub code { background: rgba(255,255,255,.18); padding: 1px 6px; border-radius: 4px; }

.lesson-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 20px;
  padding: 32px 0 8px;
}
.lesson-card {
  display: block;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px 22px;
  transition: transform .15s ease, box-shadow .15s ease, border-color .15s ease;
}
.lesson-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 24px rgba(15, 23, 42, .08);
  border-color: var(--accent);
  text-decoration: none;
}
.card-top { display: flex; align-items: center; justify-content: space-between; margin-bottom: 10px; }
.badge {
  background: var(--accent-soft); color: var(--accent-dark);
  font-size: 12px; font-weight: 600; padding: 3px 10px; border-radius: 999px;
}
.status { font-size: 12px; padding: 3px 10px; border-radius: 999px; }
.status.ok { background: var(--ok-soft); color: var(--ok); }
.status.draft { background: var(--draft-soft); color: var(--draft); }
.lesson-card h2 { margin: 0 0 8px; font-size: 18px; line-height: 1.5; color: var(--text); }
.lesson-card:hover h2 { color: var(--accent); }
.card-meta { margin: 0 0 12px; font-size: 13px; color: var(--text-soft); }
.card-link { font-size: 13px; font-weight: 600; color: var(--accent); }

/* ===== 讲义页布局 ===== */
.layout { display: grid; grid-template-columns: 240px minmax(0, 1fr); gap: 28px; padding: 28px 20px 40px; }
.toc { position: sticky; top: 76px; align-self: start; }
.toc details { background: var(--card); border: 1px solid var(--border); border-radius: 10px; padding: 12px 14px; }
.toc summary {
  cursor: pointer; font-weight: 600; font-size: 14px; color: var(--text);
  padding-bottom: 6px; user-select: none;
}
.toc nav ul { list-style: none; margin: 4px 0 0; padding: 0; font-size: 13px; }
.toc nav li { margin: 4px 0; }
.toc nav a { color: var(--text-soft); }
.toc nav a:hover { color: var(--accent); text-decoration: none; }
.toc nav ul ul { padding-left: 14px; }

.content { min-width: 0; }
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 32px 40px;
}
.lesson-head { border-bottom: 1px solid var(--border); padding-bottom: 18px; margin-bottom: 8px; }
.lesson-head h1 { margin: 8px 0 0; font-size: 26px; line-height: 1.4; }
.lesson-meta { display: flex; flex-wrap: wrap; gap: 8px 20px; font-size: 13px; color: var(--text-soft); }
.meta-item b { color: var(--text); margin-right: 5px; font-weight: 600; }

/* ===== 正文排版 ===== */
.markdown-body { font-size: 16px; }
.markdown-body h2 {
  font-size: 21px; margin: 34px 0 14px; padding-bottom: 8px;
  border-bottom: 2px solid var(--accent-soft);
}
.markdown-body h3 { font-size: 17px; margin: 26px 0 10px; }
.markdown-body h2, .markdown-body h3 { scroll-margin-top: 76px; }
.markdown-body p { margin: 12px 0; }
.markdown-body strong { color: #111827; }
.markdown-body ul, .markdown-body ol { padding-left: 26px; margin: 12px 0; }
.markdown-body li { margin: 5px 0; }
.markdown-body a code { color: var(--accent); }

.markdown-body code {
  background: var(--code-bg); border: 1px solid #eef0f3;
  padding: 2px 6px; border-radius: 5px; font-size: 13.5px; color: #be185d;
}
.markdown-body pre { background: #fbfcfd; border: 1px solid var(--border); border-radius: 10px; padding: 14px 16px; overflow-x: auto; line-height: 1.6; }
.markdown-body pre code { background: none; border: none; padding: 0; color: inherit; font-size: 13.5px; }

.markdown-body table {
  border-collapse: collapse; width: 100%; margin: 16px 0;
  font-size: 14.5px; display: block; overflow-x: auto;
}
.markdown-body th, .markdown-body td { border: 1px solid var(--border); padding: 8px 12px; text-align: left; }
.markdown-body th { background: #f1f5f9; font-weight: 600; white-space: nowrap; }
.markdown-body tr:nth-child(even) td { background: #fafbfc; }

.markdown-body blockquote {
  margin: 14px 0; padding: 10px 16px;
  border-left: 4px solid var(--accent);
  background: var(--accent-soft); border-radius: 0 8px 8px 0;
  color: #334155; font-size: 14.5px;
}
.markdown-body blockquote p { margin: 6px 0; }

.markdown-body img {
  max-width: 100%; height: auto; display: block;
  margin: 18px auto; border-radius: 10px;
  border: 1px solid var(--border); box-shadow: 0 4px 16px rgba(15,23,42,.06);
}
.markdown-body hr { border: none; border-top: 1px solid var(--border); margin: 28px 0; }

.markdown-body input[type="checkbox"] { margin-right: 6px; accent-color: var(--accent); }
.markdown-body li:has(input[type="checkbox"]) { list-style: none; margin-left: -22px; }

/* ===== 上/下页导航 ===== */
.pager { display: flex; justify-content: space-between; gap: 12px; margin-top: 36px; padding-top: 18px; border-top: 1px solid var(--border); }
.pager a {
  display: inline-block; max-width: 48%;
  background: var(--accent-soft); color: var(--accent-dark);
  padding: 10px 16px; border-radius: 8px; font-size: 14px;
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.pager a:hover { text-decoration: none; background: #dbeafe; }
.pager .next { margin-left: auto; text-align: right; }

.site-footer {
  text-align: center; color: var(--text-soft); font-size: 13px;
  padding: 24px 0 40px;
}
.site-footer code { font-size: 12.5px; }

/* ===== 响应式 ===== */
@media (max-width: 860px) {
  .layout { grid-template-columns: 1fr; padding: 20px 12px 32px; }
  .toc { position: static; }
  .toc details { padding: 8px 12px; }
  .card { padding: 22px 18px; }
  .lesson-head h1 { font-size: 22px; }
  .hero { padding: 36px 0 30px; }
  .hero h1 { font-size: 24px; }
  .lesson-grid { grid-template-columns: 1fr; padding: 20px 0 4px; }
  .pager { flex-direction: column; }
  .pager a { max-width: 100%; }
  .pager .next { margin-left: 0; text-align: left; }
}