/* ===============================================
   HEADER & NAVIGATION
   =============================================== */
.site-header {
    position: sticky;
    top: 0;
    z-index: var(--z-sticky);
    background-color: var(--color-bg-secondary);
    border-bottom: 1px solid var(--color-border);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
}

.header-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: var(--header-height);
    max-width: var(--max-width-7xl);
    margin: 0 auto;
    padding: 0 var(--spacing-4);
    gap: var(--spacing-6);
}

.header-brand {
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
    text-decoration: none;
    font-weight: var(--font-weight-bold);
    font-size: var(--font-size-xl);
    color: var(--color-primary);
    transition: var(--transition-colors);
}

.header-brand:hover {
    color: var(--color-primary-light);
}

.header-brand-subtitle {
    font-size: var(--font-size-xs);
    color: var(--color-text-muted);
    font-weight: var(--font-weight-normal);
}

.main-nav {
    display: flex;
    align-items: center;
    gap: var(--spacing-6);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: var(--spacing-5);
}

.nav-link {
    color: var(--color-text-secondary);
    text-decoration: none;
    font-weight: var(--font-weight-medium);
    font-size: var(--font-size-sm);
    padding: var(--spacing-2) var(--spacing-3);
    border-radius: var(--radius-md);
    transition: var(--transition-colors);
}

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

.nav-link.active {
    color: var(--color-primary);
    background-color: rgba(161, 161, 161, 0.1);
}

/* Dropdown Navigation */
.dropdown {
    position: relative;
}

.dropdown-toggle {
    display: flex;
    align-items: center;
    gap: var(--spacing-1);
    cursor: pointer;
    user-select: none;
}

.dropdown-menu {
    position: absolute;
    top: calc(100% + var(--spacing-2));
    left: 0;
    background-color: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    min-width: 200px;
    z-index: var(--z-dropdown);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-8px);
    transition: all var(--transition-base);
    overflow: hidden;
}

.dropdown.open .dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.dropdown-item {
    display: block;
    padding: var(--spacing-3) var(--spacing-4);
    color: var(--color-text-secondary);
    text-decoration: none;
    font-size: var(--font-size-sm);
    transition: var(--transition-colors);
    border-bottom: 1px solid var(--color-border);
}

.dropdown-item:last-child {
    border-bottom: none;
}

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

/* Breadcrumb Navigation */
.breadcrumb {
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

.breadcrumb-item {
    color: var(--color-primary);
    text-decoration: none;
    transition: var(--transition-colors);
}

.breadcrumb-item:hover {
    color: var(--color-primary-light);
}

.breadcrumb-separator {
    color: var(--color-text-muted);
    margin: 0 var(--spacing-1);
}

.breadcrumb-current {
    color: var(--color-text-primary);
    font-weight: var(--font-weight-medium);
}

.breadcrumb-extension {
    display: inline-flex;
    align-items: center;
    margin-left: var(--spacing-3);
}

/* Theme Toggle Button */
.theme-toggle {
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    border: none;
    border-radius: var(--radius-full);
    background-color: var(--color-bg-elevated);
    border: 1px solid var(--color-border);
    cursor: pointer;
    transition: all var(--transition-base);
    overflow: hidden;
}

.theme-toggle:hover {
    background-color: var(--color-bg-card);
    border-color: var(--color-border-light);
    transform: scale(1.05);
}

.theme-toggle:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

.theme-toggle-icon {
    position: absolute;
    width: 20px;
    height: 20px;
    color: var(--color-text-primary);
    transition: all var(--transition-base);
    transform-origin: center;
}

.theme-toggle-sun {
    opacity: 0;
    transform: rotate(180deg) scale(0);
}

.theme-toggle-moon {
    opacity: 1;
    transform: rotate(0deg) scale(1);
}

[data-theme="light"] .theme-toggle-sun {
    opacity: 1;
    transform: rotate(0deg) scale(1);
}

[data-theme="light"] .theme-toggle-moon {
    opacity: 0;
    transform: rotate(-180deg) scale(0);
}

.theme-toggle-tooltip {
    position: absolute;
    top: calc(100% + var(--spacing-2));
    left: 50%;
    transform: translateX(-50%);
    background-color: var(--color-bg-elevated);
    color: var(--color-text-primary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-2) var(--spacing-3);
    font-size: var(--font-size-xs);
    white-space: nowrap;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-fast);
    z-index: var(--z-tooltip);
    pointer-events: none;
}

.theme-toggle:hover .theme-toggle-tooltip {
    opacity: 1;
    visibility: visible;
    transform: translateX(-50%) translateY(-2px);
}

/* Mobile Navigation */
.mobile-nav-toggle {
    display: none;
    flex-direction: column;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-2);
    border-radius: var(--radius-md);
    transition: background-color var(--transition-fast);
}

.mobile-nav-toggle:hover {
    background-color: var(--color-bg-elevated);
}

.mobile-nav-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background-color: var(--color-text-primary);
    margin: 3px 0;
    transition: all var(--transition-fast);
    border-radius: 1px;
}

.mobile-nav-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(6px, 6px);
}

.mobile-nav-toggle.active span:nth-child(2) {
    opacity: 0;
}

.mobile-nav-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(6px, -6px);
}

/* Mobile Navigation Overlay */
.mobile-nav-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    z-index: var(--z-overlay);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
}

.mobile-nav-overlay.active {
    opacity: 1;
    visibility: visible;
}

.mobile-nav-menu {
    position: fixed;
    top: 0;
    right: -300px;
    width: 280px;
    height: 100%;
    background-color: var(--color-bg-elevated);
    border-left: 1px solid var(--color-border);
    padding: var(--spacing-6) 0;
    z-index: var(--z-modal);
    transition: right var(--transition-base);
    overflow-y: auto;
}

.mobile-nav-menu.active {
    right: 0;
}

.mobile-nav-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--spacing-6) var(--spacing-6);
    border-bottom: 1px solid var(--color-border);
    margin-bottom: var(--spacing-4);
}

.mobile-nav-brand {
    font-size: var(--font-size-lg);
    font-weight: var(--font-weight-bold);
    color: var(--color-primary);
}

.mobile-nav-close {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    background: none;
    border: none;
    cursor: pointer;
    color: var(--color-text-secondary);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

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

.mobile-nav-links {
    padding: 0 var(--spacing-4);
}

.mobile-nav-link {
    display: block;
    padding: var(--spacing-3) var(--spacing-4);
    color: var(--color-text-secondary);
    text-decoration: none;
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-medium);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-1);
    transition: all var(--transition-fast);
}

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

.mobile-dropdown {
    margin-bottom: var(--spacing-1);
}

.mobile-dropdown-toggle {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    padding: var(--spacing-3) var(--spacing-4);
    background: none;
    border: none;
    color: var(--color-text-secondary);
    text-align: left;
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-medium);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.mobile-dropdown-toggle:hover {
    background-color: var(--color-bg-card);
    color: var(--color-text-primary);
}

.mobile-dropdown-icon {
    width: 16px;
    height: 16px;
    transition: transform var(--transition-fast);
}

.mobile-dropdown.active .mobile-dropdown-icon {
    transform: rotate(180deg);
}

.mobile-dropdown-menu {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-base);
    background-color: var(--color-bg-secondary);
    border-radius: var(--radius-md);
    margin: var(--spacing-1) var(--spacing-2) 0;
}

.mobile-dropdown.active .mobile-dropdown-menu {
    max-height: 300px;
}

.mobile-dropdown-item {
    display: block;
    padding: var(--spacing-2) var(--spacing-4);
    color: var(--color-text-muted);
    text-decoration: none;
    font-size: var(--font-size-sm);
    transition: all var(--transition-fast);
    border-radius: var(--radius-sm);
    margin: var(--spacing-1);
}

.mobile-dropdown-item:hover {
    background-color: var(--color-bg-card);
    color: var(--color-text-secondary);
}

.mobile-theme-toggle {
    margin: var(--spacing-6) var(--spacing-4) 0;
    padding-top: var(--spacing-4);
    border-top: 1px solid var(--color-border);
}

/* Responsive Header */
@media (max-width: 768px) {
    .main-nav .nav-links {
        display: none;
    }
    
    .mobile-nav-toggle {
        display: flex;
    }
    
    .header-container {
        padding: var(--spacing-4);
    }
    
    .header-brand {
        font-size: var(--font-size-lg);
    }
    
    .theme-toggle {
        width: 36px;
        height: 36px;
    }
    
    .theme-toggle-icon {
        width: 18px;
        height: 18px;
    }
    
    .theme-toggle-tooltip {
        display: none;
    }
    
    .breadcrumb {
        flex-wrap: wrap;
        gap: var(--spacing-1);
        font-size: var(--font-size-xs);
    }
    
    .breadcrumb-separator {
        margin: 0 var(--spacing-1);
    }
}

@media (max-width: 480px) {
    .header-container {
        padding: var(--spacing-3);
    }
    
    .header-brand {
        font-size: var(--font-size-base);
    }
    
    .header-brand-subtitle {
        font-size: var(--font-size-xs);
    }
}