/* Layout Grid & Shell: Header (64px) + Left Sidebar (280px) + Main Viewport (Max 920px) + Right TOC (240px) */

#app-container {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* ==========================================================================
   1. TOP NAVIGATION BAR (64px sticky)
   ========================================================================== */
.top-nav {
  height: 64px;
  width: 100%;
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg-surface-glass);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--space-6);
  transition: background var(--transition-normal), border-color var(--transition-normal);
}

.top-nav-left {
  display: flex;
  align-items: center;
  gap: var(--space-4);
}

.brand-cluster {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  text-decoration: none;
  cursor: pointer;
}

.brand-logo-icon {
  width: 34px;
  height: 34px;
  background: linear-gradient(135deg, var(--color-primary-600), var(--color-accent-500));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #ffffff;
  font-weight: 700;
  font-size: 17px;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-fast);
}

.brand-cluster:hover .brand-logo-icon {
  transform: scale(1.05);
}

.brand-titles {
  display: flex;
  flex-direction: column;
}

.brand-main {
  font-size: 15px;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.2;
  letter-spacing: -0.01em;
}

.brand-sub {
  font-size: 11px;
  font-weight: 500;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* Search Trigger Button (Cmd+K) */
.search-trigger {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  height: 36px;
  padding: 0 var(--space-3);
  border-radius: var(--radius-md);
  background: var(--bg-surface-subtle);
  border: 1px solid var(--border-subtle);
  color: var(--text-muted);
  font-size: 13px;
  cursor: pointer;
  transition: all var(--transition-fast);
  min-width: 200px;
}

.search-trigger:hover {
  background: var(--bg-surface);
  border-color: var(--color-primary-500);
  color: var(--text-primary);
  box-shadow: var(--shadow-sm);
}

.search-trigger kbd {
  margin-left: auto;
  font-size: 11px;
  padding: 2px 6px;
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-xs);
  color: var(--text-secondary);
}

/* Nav Menu Items */
.top-nav-center {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.nav-link-item {
  font-size: 14px;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 6px var(--space-3);
  border-radius: var(--radius-sm);
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: all var(--transition-fast);
  position: relative;
}

.nav-link-item:hover {
  color: var(--color-primary-600);
  background: var(--bg-surface-subtle);
}

.nav-link-item.active {
  color: var(--color-primary-700);
  font-weight: 600;
  background: var(--color-primary-50);
}

[data-theme="dark"] .nav-link-item.active {
  color: var(--color-primary-300);
  background: var(--color-primary-950);
}

/* Top Nav Controls (Theme Toggle & Mobile Menu) */
.top-nav-right {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.theme-toggle-btn, .mobile-menu-btn {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  background: var(--bg-surface-subtle);
  border: 1px solid var(--border-subtle);
  transition: all var(--transition-fast);
}

.theme-toggle-btn:hover, .mobile-menu-btn:hover {
  color: var(--text-primary);
  border-color: var(--border-strong);
  background: var(--bg-surface);
}

.mobile-menu-btn {
  display: none;
}

/* ==========================================================================
   2. MAIN 3-COLUMN LAYOUT CONTAINER
   ========================================================================== */
.layout-body {
  display: flex;
  flex: 1;
  width: 100%;
  max-width: 1540px;
  margin: 0 auto;
  position: relative;
}

/* Left Sidebar (280px) */
.left-sidebar {
  width: 280px;
  min-width: 280px;
  height: calc(100vh - 64px);
  position: sticky;
  top: 64px;
  overflow-y: auto;
  overflow-x: hidden;
  border-right: 1px solid var(--border-subtle);
  padding: var(--space-4) var(--space-3);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  background: var(--bg-app);
}

.sidebar-group {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.sidebar-group-title {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  padding: var(--space-2) var(--space-3);
  margin-bottom: 2px;
}

.sidebar-subgroup-label {
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-primary-600);
  padding: 6px var(--space-3) 2px;
  opacity: 0.85;
}

.sidebar-item {
  font-size: 13.5px;
  color: var(--text-secondary);
  padding: 7px var(--space-3);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: space-between;
  transition: all var(--transition-fast);
  cursor: pointer;
}

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

.sidebar-item.active {
  background: var(--color-primary-50);
  color: var(--color-primary-700);
  font-weight: 600;
  border-left: 3px solid var(--color-primary-600);
}

[data-theme="dark"] .sidebar-item.active {
  background: var(--color-primary-950);
  color: var(--color-primary-300);
}

/* Collapsible Sidebar Tree Menu */
.sidebar-tree {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.sidebar-tree-node {
  display: flex;
  flex-direction: column;
}

.sidebar-tree-header {
  font-size: 13.5px;
  color: var(--text-secondary);
  padding: 7px var(--space-3);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: space-between;
  transition: all var(--transition-fast);
  cursor: pointer;
}

.sidebar-tree-header:hover {
  background: var(--bg-surface-subtle);
  color: var(--text-primary);
}

.sidebar-tree-header.active {
  background: var(--color-primary-50);
  color: var(--color-primary-700);
  font-weight: 600;
  border-left: 3px solid var(--color-primary-600);
}

[data-theme="dark"] .sidebar-tree-header.active {
  background: var(--color-primary-950);
  color: var(--color-primary-300);
}

.tree-caret {
  font-size: 11px;
  color: var(--text-muted);
  transition: transform 0.2s ease;
}

.sidebar-tree-children {
  display: flex;
  flex-direction: column;
  gap: 1px;
  padding-left: var(--space-4);
  margin-left: var(--space-2);
  border-left: 1px solid var(--border-subtle);
  margin-top: 2px;
  margin-bottom: 4px;
}

.sidebar-sub-item {
  font-size: 12.5px;
  color: var(--text-muted);
  padding: 5px var(--space-2);
  border-radius: var(--radius-xs);
  display: flex;
  align-items: center;
  gap: 6px;
  transition: all var(--transition-fast);
}

.sidebar-sub-item:hover {
  color: var(--color-primary-600);
  background: var(--bg-surface-subtle);
}

.sidebar-item .tag-badge {
  font-size: 10px;
  padding: 1px 6px;
  border-radius: var(--radius-full);
  font-weight: 600;
}

/* Center Content Viewport (Max 920px) */
.main-viewport {
  flex: 1;
  min-width: 0;
  padding: var(--space-8) var(--space-8) var(--space-16);
  max-width: 960px;
}

/* Breadcrumb Header */
.breadcrumb-nav {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: var(--space-6);
}

.breadcrumb-nav a:hover {
  color: var(--color-primary-600);
  text-decoration: underline;
}

.breadcrumb-sep {
  color: var(--border-strong);
}

/* Right TOC Aside (240px) */
.right-aside {
  width: 240px;
  min-width: 240px;
  height: calc(100vh - 64px);
  position: sticky;
  top: 64px;
  padding: var(--space-8) var(--space-4);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  border-left: 1px solid var(--border-subtle);
}

.toc-title {
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
}

.toc-list {
  display: flex;
  flex-direction: column;
  gap: 6px;
  list-style: none;
  font-size: 13px;
}

.toc-link {
  color: var(--text-secondary);
  transition: color var(--transition-fast);
  padding: 3px 0;
  display: block;
  line-height: 1.4;
}

.toc-link:hover {
  color: var(--color-primary-600);
}

.toc-link.active {
  color: var(--color-primary-700);
  font-weight: 600;
}

[data-theme="dark"] .toc-link.active {
  color: var(--color-primary-400);
}

.back-to-top {
  margin-top: auto;
  font-size: 12px;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 4px;
  padding-top: var(--space-4);
  border-top: 1px dashed var(--border-subtle);
  cursor: pointer;
}

.back-to-top:hover {
  color: var(--color-primary-600);
}

/* ==========================================================================
   3. MEGA MENU DROPDOWN
   ========================================================================== */
.mega-menu-wrapper {
  position: relative;
}

.mega-menu-panel {
  position: absolute;
  top: calc(100% + 8px);
  left: 50%;
  transform: translateX(-50%) translateY(-10px);
  width: 780px;
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-xl);
  padding: var(--space-6);
  opacity: 0;
  pointer-events: none;
  transition: all var(--transition-normal);
  z-index: 110;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-6);
}

.mega-menu-wrapper:hover .mega-menu-panel,
.mega-menu-panel:hover {
  opacity: 1;
  pointer-events: auto;
  transform: translateX(-50%) translateY(0);
}

.mega-group-title {
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-primary-600);
  margin-bottom: var(--space-3);
  display: flex;
  align-items: center;
  gap: 6px;
}

.mega-item-link {
  display: block;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
  margin-bottom: 4px;
}

.mega-item-link:hover {
  background: var(--bg-surface-subtle);
}

.mega-item-name {
  font-size: 13.5px;
  font-weight: 600;
  color: var(--text-primary);
}

.mega-item-desc {
  font-size: 11.5px;
  color: var(--text-muted);
  line-height: 1.3;
  margin-top: 2px;
}

/* ==========================================================================
   4. RESPONSIVE BREAKPOINTS
   ========================================================================== */
@media (max-width: 1200px) {
  .right-aside {
    display: none;
  }
  .main-viewport {
    max-width: 100%;
  }
}

@media (max-width: 900px) {
  .left-sidebar {
    position: fixed;
    top: 64px;
    left: 0;
    bottom: 0;
    z-index: 90;
    transform: translateX(-100%);
    transition: transform var(--transition-normal);
    box-shadow: var(--shadow-xl);
  }

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

  .top-nav-center {
    display: none;
  }

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

  .main-viewport {
    padding: var(--space-6) var(--space-4) var(--space-12);
  }

  .search-trigger {
    min-width: 140px;
  }
}