/* ============================================================================
   NAVIGATION & HEADER STYLES
   Premium sticky navigation, mega-menu, mobile drawer
   ============================================================================ */

/* ============================================================================
   HEADER
   ============================================================================ */

header {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  background-color: var(--bg-primary);
  border-bottom: var(--border-width) solid var(--border-primary);
  backdrop-filter: blur(10px);
  background-color: rgba(255, 255, 255, 0.8);
  transition: all var(--transition-base);
}

[data-theme="dark"] header {
  background-color: rgba(11, 15, 20, 0.8);
}

header.scrolled {
  box-shadow: var(--shadow-sm);
  background-color: rgba(255, 255, 255, 0.95);
}

[data-theme="dark"] header.scrolled {
  background-color: rgba(11, 15, 20, 0.95);
}

/* ========== NAV CONTAINER ========== */

nav.navbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-4) 0;
  max-width: 1440px;
  margin: 0 auto;
  padding-left: var(--space-8);
  padding-right: var(--space-8);
}

@media (max-width: 768px) {
  nav.navbar {
    padding-left: var(--space-6);
    padding-right: var(--space-6);
  }
}

@media (max-width: 480px) {
  nav.navbar {
    padding-left: var(--space-4);
    padding-right: var(--space-4);
  }
}

/* ========== LOGO / BRAND ========== */

.navbar-brand {
  font-size: var(--font-size-xl);
  font-weight: var(--font-weight-bold);
  color: var(--text-primary);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: var(--space-2);
  transition: color var(--transition-fast);
  margin-right: auto;
}

.navbar-brand:hover {
  color: var(--accent-primary);
}

.navbar-brand span {
  display: inline-block;
  width: 32px;
  height: 32px;
  border-radius: var(--radius-lg);
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: var(--font-weight-bold);
  color: var(--color-obsidian);
  font-size: var(--font-size-sm);
}

/* ========== MAIN NAVIGATION MENU ========== */

.navbar-menu {
  display: flex;
  list-style: none;
  gap: var(--space-8);
  align-items: center;
  margin: 0;
  padding: 0;
}

.navbar-menu li {
  margin: 0;
  position: relative;
}

.navbar-menu > li > a {
  color: var(--text-primary);
  font-weight: var(--font-weight-medium);
  padding: var(--space-3) var(--space-2);
  transition: color var(--transition-fast);
  position: relative;
  display: block;
}

.navbar-menu > li > a::after {
  content: '';
  position: absolute;
  bottom: -6px;
  left: 0;
  right: 0;
  height: 2px;
  background-color: var(--accent-primary);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--transition-fast);
}

.navbar-menu > li > a:hover {
  color: var(--accent-primary);
}

.navbar-menu > li > a:hover::after {
  transform: scaleX(1);
}

.navbar-menu > li > a.active {
  color: var(--accent-primary);
}

.navbar-menu > li > a.active::after {
  transform: scaleX(1);
}

/* ========== DROPDOWN MENUS ========== */

.navbar-submenu {
  position: absolute;
  top: 100%;
  left: 0;
  background-color: var(--bg-primary);
  border: var(--border-width) solid var(--border-primary);
  border-radius: var(--radius-lg);
  margin-top: var(--space-2);
  min-width: 200px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: all var(--transition-fast);
  z-index: var(--z-dropdown);
  box-shadow: var(--shadow-md);
  padding: var(--space-2) 0;
  list-style: none;
}

.navbar-menu > li:hover > .navbar-submenu {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.navbar-submenu li {
  margin: 0;
}

.navbar-submenu a {
  display: block;
  padding: var(--space-3) var(--space-6);
  color: var(--text-primary);
  font-weight: var(--font-weight-regular);
  font-size: var(--font-size-sm);
  transition: all var(--transition-fast);
}

.navbar-submenu a:hover {
  background-color: var(--bg-secondary);
  color: var(--accent-primary);
  padding-left: var(--space-8);
}

/* ========== THEME TOGGLE ========== */

.theme-toggle {
  background: none;
  border: none;
  font-size: var(--font-size-xl);
  cursor: pointer;
  padding: var(--space-2);
  color: var(--text-primary);
  transition: transform var(--transition-fast);
  margin-left: var(--space-4);
}

.theme-toggle:hover {
  transform: rotate(20deg);
}

/* ========== MOBILE MENU BUTTON ========== */

.mobile-menu-button {
  display: none;
  background: none;
  border: none;
  font-size: var(--font-size-2xl);
  cursor: pointer;
  color: var(--text-primary);
  padding: var(--space-2);
}

@media (max-width: 768px) {
  .mobile-menu-button {
    display: flex;
    align-items: center;
    justify-content: center;
  }
}

/* ========== MOBILE DRAWER ========== */

.navbar-drawer {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--bg-primary);
  z-index: var(--z-fixed);
  transform: translateX(-100%);
  transition: transform var(--transition-base);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
}

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

.navbar-drawer-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.5);
  z-index: var(--z-modal-bg);
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-base);
}

.navbar-drawer.open ~ .navbar-drawer-overlay {
  opacity: 1;
  visibility: visible;
}

.navbar-drawer-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-6);
  border-bottom: var(--border-width) solid var(--border-primary);
}

.navbar-drawer-close {
  background: none;
  border: none;
  font-size: var(--font-size-2xl);
  cursor: pointer;
  color: var(--text-primary);
  padding: 0;
}

.navbar-drawer-menu {
  display: flex;
  flex-direction: column;
  list-style: none;
  padding: var(--space-6);
  margin: 0;
  gap: 0;
}

.navbar-drawer-menu li {
  margin: 0;
  border-bottom: var(--border-width) solid var(--border-primary);
}

.navbar-drawer-menu li:last-child {
  border-bottom: none;
}

.navbar-drawer-menu a {
  display: block;
  padding: var(--space-4) 0;
  color: var(--text-primary);
  font-weight: var(--font-weight-medium);
  transition: color var(--transition-fast);
}

.navbar-drawer-menu a:hover {
  color: var(--accent-primary);
}

.navbar-drawer-menu a.active {
  color: var(--accent-primary);
  font-weight: var(--font-weight-bold);
}

/* ========== MOBILE SUBMENU ========== */

.navbar-drawer-submenu {
  display: none;
  list-style: none;
  padding: 0;
  margin: 0;
  margin-top: var(--space-2);
  border-left: 2px solid var(--accent-primary);
  padding-left: var(--space-4);
}

.navbar-drawer-submenu.open {
  display: block;
}

.navbar-drawer-submenu li {
  border: none;
  margin: 0;
}

.navbar-drawer-submenu a {
  padding: var(--space-2) 0;
  font-size: var(--font-size-sm);
  color: var(--text-secondary);
}

.navbar-drawer-submenu a:hover {
  color: var(--accent-primary);
}

/* ============================================================================
   BREADCRUMB NAVIGATION
   ============================================================================ */

nav.breadcrumb {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--font-size-sm);
  margin-bottom: var(--space-6);
}

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

.breadcrumb-item a {
  color: var(--accent-primary);
}

.breadcrumb-item::after {
  content: '/';
  margin-left: var(--space-2);
  color: var(--text-tertiary);
}

.breadcrumb-item:last-child::after {
  display: none;
}

.breadcrumb-item.active {
  color: var(--text-primary);
  font-weight: var(--font-weight-semibold);
}

/* ============================================================================
   PAGINATION
   ============================================================================ */

nav.pagination {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  justify-content: center;
  margin-top: var(--space-12);
}

.pagination-item {
  min-width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-lg);
  border: var(--border-width) solid var(--border-primary);
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  text-decoration: none;
  font-weight: var(--font-weight-medium);
  transition: all var(--transition-fast);
}

.pagination-item:hover {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
}

.pagination-item.active {
  background-color: var(--accent-primary);
  border-color: var(--accent-primary);
  color: var(--color-obsidian);
  font-weight: var(--font-weight-bold);
}

.pagination-item.disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* ============================================================================
   SIDEBAR NAVIGATION (for project/article pages)
   ============================================================================ */

.sidebar-nav {
  position: sticky;
  top: var(--space-24);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.sidebar-nav h5 {
  font-size: var(--font-size-sm);
  text-transform: uppercase;
  color: var(--text-secondary);
  margin-bottom: var(--space-4);
}

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

.sidebar-nav li {
  margin: 0;
}

.sidebar-nav a {
  display: block;
  padding: var(--space-3) var(--space-4);
  color: var(--text-secondary);
  font-size: var(--font-size-sm);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  position: relative;
  padding-left: var(--space-6);
}

.sidebar-nav a::before {
  content: '';
  position: absolute;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 3px;
  height: 3px;
  background-color: var(--text-tertiary);
  border-radius: 50%;
}

.sidebar-nav a:hover {
  background-color: var(--bg-secondary);
  color: var(--accent-primary);
}

.sidebar-nav a.active {
  color: var(--accent-primary);
  font-weight: var(--font-weight-semibold);
  background-color: rgba(34, 211, 238, 0.1);
}

.sidebar-nav a.active::before {
  background-color: var(--accent-primary);
  width: 6px;
  height: 6px;
  left: -3px;
}

/* ============================================================================
   RESPONSIVE NAVIGATION
   ============================================================================ */

@media (max-width: 1024px) {
  .navbar-menu {
    gap: var(--space-6);
  }

  .navbar-submenu {
    min-width: 180px;
  }
}

@media (max-width: 768px) {
  .navbar-menu {
    display: none;
  }

  .theme-toggle {
    margin-left: var(--space-2);
  }

  .sidebar-nav {
    display: none;
  }
}

@media (max-width: 480px) {
  nav.navbar {
    padding: var(--space-3) 0;
  }

  .navbar-brand {
    font-size: var(--font-size-lg);
  }

  .navbar-brand span {
    width: 28px;
    height: 28px;
    font-size: var(--font-size-xs);
  }
}