:root {
  --bg: #f7f7f7;
  --fg: #1a1a1a;
  --sidebar-bg: #1e293b;
  --sidebar-fg: #e2e8f0;
  --accent: #2563eb;
  --accent-fg: #ffffff;
  --border: #e2e8f0;
  --card-bg: #ffffff;
  --code-bg: #f1f5f9;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.6;
}

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

.sidebar {
  width: 280px;
  background: var(--sidebar-bg);
  color: var(--sidebar-fg);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  overflow-y: auto;
  z-index: 100;
}

.brand {
  padding: 24px;
  border-bottom: 1px solid rgba(255,255,255,0.1);
}

.brand strong {
  display: block;
  font-size: 1.4rem;
  color: #fff;
}

.brand small {
  color: #94a3b8;
  font-size: 0.85rem;
}

nav ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

nav a {
  display: block;
  padding: 12px 24px;
  color: var(--sidebar-fg);
  text-decoration: none;
  border-left: 4px solid transparent;
}

nav a:hover,
nav a.active {
  background: rgba(255,255,255,0.05);
  border-left-color: var(--accent);
}

.sidebar-footer {
  margin-top: auto;
  padding: 16px 24px;
  font-size: 0.8rem;
  color: #94a3b8;
}

.content {
  flex: 1;
  margin-left: 280px;
  padding: 32px;
  max-width: 900px;
}

.page-header {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 24px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--border);
}

.page-header h1 {
  margin: 0;
  font-size: 1.8rem;
}

.menu-toggle {
  display: none;
  background: var(--accent);
  color: var(--accent-fg);
  border: none;
  padding: 8px 12px;
  font-size: 1.2rem;
  border-radius: 4px;
  cursor: pointer;
}

.markdown-body h1 { font-size: 2rem; margin-top: 0; }
.markdown-body h2 { font-size: 1.5rem; margin-top: 32px; border-bottom: 1px solid var(--border); padding-bottom: 8px; }
.markdown-body h3 { font-size: 1.2rem; margin-top: 24px; }
.markdown-body p { margin: 12px 0; }
.markdown-body table { width: 100%; border-collapse: collapse; margin: 16px 0; background: var(--card-bg); }
.markdown-body th, .markdown-body td { border: 1px solid var(--border); padding: 10px; text-align: left; }
.markdown-body th { background: #f1f5f9; }
.markdown-body code { background: var(--code-bg); padding: 2px 6px; border-radius: 4px; font-family: Consolas, monospace; }
.markdown-body pre { background: var(--code-bg); padding: 16px; border-radius: 6px; overflow-x: auto; }
.markdown-body ul, .markdown-body ol { margin: 12px 0; padding-left: 24px; }
.markdown-body a { color: var(--accent); }

.lead { font-size: 1.15rem; color: #475569; }

.grid-2 {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 20px;
  margin-top: 24px;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 20px;
  text-decoration: none;
  color: var(--fg);
  transition: box-shadow 0.2s;
}

.card:hover {
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
  border-color: var(--accent);
}

.card h3 { margin: 0 0 8px; color: var(--accent); }
.card p { margin: 0; color: #64748b; }

.manual-footer {
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  color: #64748b;
  font-size: 0.9rem;
}

.chapter {
  page-break-before: always;
}

.chapter:first-child {
  page-break-before: auto;
}

.chapter.cover {
  min-height: 80vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  text-align: center;
}

.chapter.cover h1 {
  font-size: 2.8rem;
  margin-bottom: 24px;
}

.chapter.cover .lead {
  font-size: 1.4rem;
  margin-bottom: 32px;
}

@media (max-width: 768px) {
  .sidebar {
    transform: translateX(-100%);
    transition: transform 0.2s;
  }
  .sidebar.open {
    transform: translateX(0);
  }
  .content {
    margin-left: 0;
    padding: 20px;
  }
  .menu-toggle {
    display: inline-block;
  }
}

@media print {
  .sidebar, .page-header, .manual-footer, .menu-toggle {
    display: none !important;
  }
  .content {
    margin-left: 0;
    padding: 0;
    max-width: none;
  }
  .chapter {
    page-break-before: always;
  }
}