[data-theme="dark"] {
    --bg-primary: var(--gray-900);
    --bg-secondary: var(--gray-800);
    --bg-tertiary: var(--gray-700);
    --text-primary: var(--gray-100);
    --text-secondary: var(--gray-300);
    --text-tertiary: var(--gray-400);
    --border-primary: var(--gray-700);
    --border-secondary: var(--gray-600);

    /* Dark mode shadows */
    --shadow-xs: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.4), 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -2px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.4), 0 10px 10px -5px rgba(0, 0, 0, 0.3);
    --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.6);
}

[data-theme="dark"] body {
    background: linear-gradient(135deg, #1e293b 0%, #334155 100%);
}

[data-theme="dark"] .sidebar {
    background: #1e293b;
    border-right: 1px solid var(--border-primary);
}

[data-theme="dark"] .sidebar::before {
    background: rgba(0, 0, 0, 0.2);
}

[data-theme="dark"] .sidebar-header {
    border-bottom: 1px solid var(--border-primary);
    background: rgba(0, 0, 0, 0.2);
}

[data-theme="dark"] .sidebar-header::before {
    background: linear-gradient(135deg, rgba(0, 0, 0, 0.1) 0%, rgba(0, 0, 0, 0.05) 100%);
}

[data-theme="dark"] .department-selector {
    border-bottom: 1px solid var(--border-primary);
    background: rgba(0, 0, 0, 0.1);
}

[data-theme="dark"] .department-selector select {
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 1px solid var(--border-primary);
}

[data-theme="dark"] .department-selector select:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

[data-theme="dark"] .nav-profile {
    border-top: 1px solid var(--border-primary);
    background: rgba(0, 0, 0, 0.3);
}

[data-theme="dark"] .mobile-menu-toggle {
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 1px solid var(--border-primary);
}

[data-theme="dark"] .mobile-menu-toggle:hover {
    background: var(--bg-tertiary);
}

[data-theme="dark"] .action-btn:hover {
    background: var(--gray-700);
    color: var(--primary-light);
}

[data-theme="dark"] .action-btn#darkModeBtn:hover {
    background: var(--warning);
    color: var(--gray-900);
}

[data-theme="dark"] .search-input:focus {
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

[data-theme="dark"] .bookmark-btn:hover {
    background: var(--gray-700);
    color: var(--primary-light);
}

[data-theme="dark"] .toast {
    background: var(--gray-800);
    border: 1px solid var(--border-primary);
}