:root {
  --bg-primary: #0D1117;
  --bg-secondary: #161B22;
  --bg-tertiary: #1C2128;
  --bg-hover: #21262D;
  --border-color: #30363D;
  --text-primary: #E6EDF3;
  --text-secondary: #8B949E;
  --text-tertiary: #6E7681;
  --accent: #7C3AED;
  --accent-light: #A78BFA;
  --accent-dim: rgba(124, 58, 237, 0.15);
  --radius: 6px;
  --sidebar-width: 280px;
}

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

html, body {
  height: 100%;
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  font-size: 15px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

.app {
  display: flex;
  height: 100vh;
  overflow: hidden;
}

/* Sidebar */
.sidebar {
  width: var(--sidebar-width);
  min-width: var(--sidebar-width);
  background: var(--bg-secondary);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  transition: transform 0.3s ease;
  z-index: 100;
}

.sidebar-header {
  padding: 16px 18px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-shrink: 0;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
}

.logo-img {
  width: 28px;
  height: 28px;
  border-radius: 6px;
  object-fit: cover;
}

.logo-text {
  font-weight: 700;
  font-size: 15px;
  color: var(--text-primary);
  letter-spacing: -0.3px;
}

.sidebar-toggle {
  background: none;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  padding: 4px;
  border-radius: 4px;
  display: none;
}

.sidebar-toggle:hover {
  background: var(--bg-hover);
}

.sidebar-nav {
  flex: 1;
  overflow-y: auto;
  padding: 12px 8px 24px;
}

.sidebar-nav::-webkit-scrollbar {
  width: 6px;
}
.sidebar-nav::-webkit-scrollbar-track {
  background: transparent;
}
.sidebar-nav::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 3px;
}
.sidebar-nav::-webkit-scrollbar-thumb:hover {
  background: var(--text-tertiary);
}

.nav-section {
  margin-bottom: 4px;
}

.nav-section-title {
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--text-tertiary);
  padding: 12px 12px 6px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.nav-section-icon {
  font-size: 14px;
}

.nav-item {
  display: block;
  padding: 6px 12px 6px 24px;
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 13.5px;
  border-radius: 5px;
  cursor: pointer;
  transition: all 0.15s ease;
  margin: 1px 0;
}

.nav-item:hover {
  background: var(--bg-hover);
  color: var(--text-primary);
}

.nav-item.active {
  background: var(--accent-dim);
  color: var(--accent-light);
  font-weight: 500;
}

.nav-item.sub {
  padding-left: 40px;
  font-size: 13px;
}

/* Content */
.content-wrapper {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.content-header {
  padding: 14px 32px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
  background: var(--bg-primary);
}

.mobile-menu-btn {
  background: none;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  padding: 4px;
  border-radius: 4px;
  display: none;
}

.breadcrumb {
  font-size: 13px;
  color: var(--text-tertiary);
}

.breadcrumb span {
  color: var(--text-secondary);
}

.breadcrumb .sep {
  margin: 0 6px;
  color: var(--text-tertiary);
}

.content {
  flex: 1;
  overflow-y: auto;
  padding: 40px 48px 80px;
  max-width: 820px;
  width: 100%;
  margin: 0 auto;
}

.content::-webkit-scrollbar {
  width: 8px;
}
.content::-webkit-scrollbar-track {
  background: transparent;
}
.content::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 4px;
}
.content::-webkit-scrollbar-thumb:hover {
  background: var(--text-tertiary);
}

/* Typography */
.content h1 {
  font-size: 32px;
  font-weight: 700;
  letter-spacing: -0.5px;
  margin-bottom: 24px;
  color: var(--text-primary);
}

.content h2 {
  font-size: 22px;
  font-weight: 600;
  margin-top: 40px;
  margin-bottom: 16px;
  color: var(--text-primary);
  padding-top: 8px;
  border-top: 1px solid var(--border-color);
}

.content h3 {
  font-size: 17px;
  font-weight: 600;
  margin-top: 28px;
  margin-bottom: 12px;
  color: var(--text-primary);
}

.content p {
  margin-bottom: 14px;
  color: var(--text-secondary);
}

.content ol, .content ul {
  margin-bottom: 16px;
  padding-left: 24px;
}

.content li {
  margin-bottom: 8px;
  color: var(--text-secondary);
}

.content li::marker {
  color: var(--accent-light);
  font-weight: 600;
}

.content a {
  color: var(--accent-light);
  text-decoration: none;
  font-weight: 500;
}

.content a:hover {
  text-decoration: underline;
}

.content code {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 2px 8px;
  font-family: 'JetBrains Mono', 'Fira Code', monospace;
  font-size: 13px;
  color: var(--accent-light);
  display: inline-block;
  line-height: 1.5;
}

.content pre {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 16px 20px;
  overflow-x: auto;
  margin: 16px 0;
}

.content pre code {
  background: none;
  border: none;
  padding: 0;
  color: var(--text-primary);
  font-size: 13px;
}

.content img {
  max-width: 100%;
  border-radius: var(--radius);
  margin: 12px 0 20px;
  border: 1px solid var(--border-color);
  display: block;
  background: var(--bg-secondary);
}

.content .image-placeholder {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 40px;
  text-align: center;
  color: var(--text-tertiary);
  font-size: 13px;
  margin: 12px 0;
}

.content .image-placeholder svg {
  margin-bottom: 8px;
  opacity: 0.5;
}

/* Card links on overview pages */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
  margin-top: 24px;
}

.card-link {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 20px 24px;
  cursor: pointer;
  transition: all 0.2s ease;
  text-decoration: none;
  display: block;
}

.card-link:hover {
  border-color: var(--accent);
  background: var(--bg-hover);
  transform: translateY(-1px);
}

.card-link-title {
  font-size: 15px;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 4px;
}

.card-link-desc {
  font-size: 13px;
  color: var(--text-tertiary);
}

/* Footer navigation */
.content-footer {
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border-color);
}

.footer-meta {
  font-size: 12px;
  color: var(--text-tertiary);
  margin-bottom: 20px;
}

.nav-buttons {
  display: flex;
  justify-content: space-between;
  gap: 16px;
}

.nav-btn {
  flex: 1;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 14px 20px;
  cursor: pointer;
  transition: all 0.15s ease;
  text-decoration: none;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.nav-btn:hover {
  border-color: var(--accent);
  background: var(--bg-hover);
}

.nav-btn.prev {
  text-align: left;
}

.nav-btn.next {
  text-align: right;
}

.nav-btn-label {
  font-size: 11px;
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.nav-btn-title {
  font-size: 14px;
  font-weight: 500;
  color: var(--text-primary);
}

/* Mobile */
@media (max-width: 768px) {
  .sidebar {
    position: fixed;
    left: 0;
    top: 0;
    height: 100vh;
    transform: translateX(-100%);
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .sidebar-toggle {
    display: block;
  }

  .mobile-menu-btn {
    display: block;
  }

  .content {
    padding: 24px 20px 60px;
  }

  .content h1 {
    font-size: 26px;
  }

  .content h2 {
    font-size: 20px;
  }
}