:root {
            /* Updated Color Scheme */
            --primary: #5e35b1;
            --primary-dark: #4527a0;
            --primary-light: #7e57c2;
            --primary-extra-light: #ede7f6;
            --accent: #ff7043;
            --accent-light: #ffab91;
            --success: #43a047;
            --warning: #ffb300;
            --danger: #e53935;
            --info: #039be5;
            
            /* Neutral Colors */
            --white: #ffffff;
            --gray-50: #fafafa;
            --gray-100: #f5f5f5;
            --gray-200: #eeeeee;
            --gray-300: #e0e0e0;
            --gray-400: #bdbdbd;
            --gray-500: #9e9e9e;
            --gray-600: #757575;
            --gray-700: #616161;
            --gray-800: #424242;
            --gray-900: #212121;
            --black: #000000;
            
            /* Text Colors */
            --text-primary: var(--gray-900);
            --text-secondary: var(--gray-600);
            --text-tertiary: var(--gray-400);
            --text-on-primary: var(--white);
            
            /* Shadows */
            --shadow-sm: 0 1px 3px rgba(0,0,0,0.12);
            --shadow-md: 0 4px 6px rgba(0,0,0,0.1);
            --shadow-lg: 0 10px 15px rgba(0,0,0,0.1);
            --shadow-xl: 0 20px 25px rgba(0,0,0,0.1);
            --shadow-inset: inset 0 2px 4px rgba(0,0,0,0.06);
            
            /* Border Radius */
            --radius-sm: 4px;
            --radius-md: 8px;
            --radius-lg: 12px;
            --radius-xl: 16px;
            --radius-full: 9999px;
            
            /* Spacing */
            --space-xs: 4px;
            --space-sm: 8px;
            --space-md: 16px;
            --space-lg: 24px;
            --space-xl: 32px;
            --space-2xl: 48px;
            --space-3xl: 64px;
            
            /* Typography */
            --text-xs: 0.75rem;
            --text-sm: 0.875rem;
            --text-base: 1rem;
            --text-lg: 1.125rem;
            --text-xl: 1.25rem;
            --text-2xl: 1.5rem;
            --text-3xl: 1.875rem;
            --text-4xl: 2.25rem;
            
            /* Layout */
            --sidebar-width: 280px;
            --sidebar-width-collapsed: 80px;
            --header-height: 64px;
            --transition-speed: 0.3s;
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
        }

        @font-face {
            font-family: 'Inter';
            font-style: normal;
            font-weight: 300 800;
            font-display: swap;
            src: url(https://fonts.gstatic.com/s/inter/v12/UcCO3FwrK3iLTeHuS_fvQtMwCp50KnMw2boKoduKmMEVuLyfAZ9hjg.woff2) format('woff2');
        }

        body {
            background-color: var(--gray-50);
            color: var(--text-primary);
            display: flex;
            min-height: 100vh;
            line-height: 1.5;
        }

        /* Improved Sidebar */
        .sidebar {
            width: var(--sidebar-width);
            height: 100vh;
            background-color: var(--white);
            position: fixed;
            left: 0;
            top: 0;
            display: flex;
            flex-direction: column;
            box-shadow: var(--shadow-md);
            transition: width var(--transition-speed) ease;
            z-index: 1000;
            overflow: hidden;
            border-right: 1px solid var(--gray-200);
        }

        .sidebar-header {
            padding: var(--space-md);
            display: flex;
            justify-content: space-between;
            align-items: center;
            height: var(--header-height);
            background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
        }

        .logo-container {
            display: flex;
            align-items: center;
            gap: var(--space-sm);
            min-width: calc(var(--sidebar-width) - 40px);
            color: var(--white);
        }

        .logo-icon {
            font-size: var(--text-xl);
            background-color: rgba(255, 255, 255, 0.15);
            width: 36px;
            height: 36px;
            border-radius: var(--radius-sm);
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .sidebar-title {
            font-size: var(--text-lg);
            font-weight: 600;
            white-space: nowrap;
            transition: opacity var(--transition-speed) ease;
        }

        .sidebar-toggle {
            background: none;
            border: none;
            color: var(--white);
            font-size: var(--text-lg);
            cursor: pointer;
            padding: var(--space-xs);
            margin-left: auto;
            transition: all 0.2s ease;
            background-color: rgba(255, 255, 255, 0.15);
            border-radius: var(--radius-sm);
            width: 32px;
            height: 32px;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .sidebar-toggle:hover {
            background-color: rgba(255, 255, 255, 0.25);
        }

        .sidebar-nav {
            flex: 1;
            overflow-y: auto;
            padding: var(--space-md) 0;
        }

        .sidebar-nav::-webkit-scrollbar {
            width: 6px;
        }

        .sidebar-nav::-webkit-scrollbar-thumb {
            background-color: rgba(94, 53, 177, 0.2);
            border-radius: 3px;
        }

        .sidebar-nav::-webkit-scrollbar-track {
            background-color: transparent;
        }

        .nav-item {
            margin: var(--space-xs) var(--space-sm);
            position: relative;
        }

        .nav-link {
            display: flex;
            align-items: center;
            justify-content: space-between;
            padding: var(--space-sm) var(--space-md);
            border-radius: var(--radius-sm);
            color: var(--text-secondary);
            text-decoration: none;
            transition: all 0.2s ease;
            white-space: nowrap;
        }

        .link-content {
            display: flex;
            align-items: center;
            gap: var(--space-md);
        }

        .link-icon {
            width: 24px;
            text-align: center;
            color: var(--primary);
            font-size: var(--text-base);
            flex-shrink: 0;
            transition: all 0.2s ease;
        }

        .link-text {
            font-size: var(--text-sm);
            font-weight: 500;
            transition: opacity var(--transition-speed) ease;
        }

        .nav-link:hover {
            background-color: var(--primary-extra-light);
            color: var(--primary-dark);
        }

        .nav-link:hover .link-icon {
            color: var(--primary-dark);
            transform: scale(1.05);
        }

        .nav-link.active {
            background-color: var(--primary-extra-light);
            color: var(--primary-dark);
            font-weight: 600;
            box-shadow: inset 3px 0 0 var(--primary);
        }

        .nav-link.active .link-icon {
            color: var(--primary-dark);
        }

        /* Dropdown styles */
        .dropdown-header {
            display: flex;
            align-items: center;
            justify-content: space-between;
            padding: var(--space-sm) var(--space-md);
            border-radius: var(--radius-sm);
            cursor: pointer;
            transition: all 0.2s ease;
            color: var(--text-secondary);
        }

        .dropdown-header:hover {
            background-color: var(--primary-extra-light);
            color: var(--primary-dark);
        }

        .dropdown-header:hover .link-icon {
            color: var(--primary-dark);
        }

        .dropdown-icon {
            font-size: var(--text-xs);
            transition: transform var(--transition-speed) ease;
            color: var(--primary);
        }

        .dropdown-menu {
            max-height: 0;
            overflow: hidden;
            padding-left: var(--space-md);
            transition: max-height var(--transition-speed) ease;
        }

        .dropdown-menu.open {
            max-height: 500px;
        }

        .dropdown-item {
            display: flex;
            align-items: center;
            gap: var(--space-sm);
            padding: var(--space-sm) var(--space-md);
            color: var(--text-secondary);
            text-decoration: none;
            font-size: var(--text-xs);
            border-radius: var(--radius-sm);
            transition: all 0.2s ease;
            white-space: nowrap;
        }

        .dropdown-item:hover {
            background-color: var(--primary-extra-light);
            padding-left: var(--space-lg);
            color: var(--primary-dark);
        }

        .dropdown-item i {
            font-size: var(--text-sm);
            width: 18px;
            text-align: center;
            color: var(--primary-light);
        }

        /* Sidebar footer */
        .sidebar-footer {
            padding: var(--space-md);
            border-top: 1px solid var(--gray-200);
            background-color: var(--white);
        }

        .user-profile {
            display: flex;
            align-items: center;
            gap: var(--space-sm);
            margin-bottom: var(--space-md);
        }

        .avatar {
            width: 40px;
            height: 40px;
            border-radius: var(--radius-full);
            background-color: var(--primary-light);
            display: flex;
            align-items: center;
            justify-content: center;
            flex-shrink: 0;
            overflow: hidden;
            border: 2px solid var(--primary-extra-light);
        }

        .avatar i {
            font-size: var(--text-lg);
            color: var(--white);
        }

        .avatar img {
            width: 100%;
            height: 100%;
            object-fit: cover;
        }

        .user-info {
            display: flex;
            flex-direction: column;
            min-width: calc(var(--sidebar-width) - 80px);
            overflow: hidden;
        }

        .username {
            font-size: var(--text-sm);
            font-weight: 600;
            white-space: nowrap;
            overflow: hidden;
            text-overflow: ellipsis;
        }

        .user-role {
            font-size: var(--text-xs);
            color: var(--primary-light);
            white-space: nowrap;
            overflow: hidden;
            text-overflow: ellipsis;
        }

        .logout-btn {
            display: flex;
            align-items: center;
            gap: var(--space-sm);
            padding: var(--space-sm) var(--space-md);
            color: var(--primary-dark);
            text-decoration: none;
            font-size: var(--text-sm);
            font-weight: 500;
            border-radius: var(--radius-sm);
            transition: all 0.2s ease;
            background-color: var(--primary-extra-light);
        }

        .logout-btn:hover {
            background-color: var(--primary-light);
            color: var(--white);
        }

        .logout-btn i {
            font-size: var(--text-base);
        }

        /* Collapsed state */
        .sidebar.collapsed {
            width: var(--sidebar-width-collapsed);
        }

        .sidebar.collapsed .sidebar-title,
        .sidebar.collapsed .link-text,
        .sidebar.collapsed .dropdown-icon,
        .sidebar.collapsed .username,
        .sidebar.collapsed .user-role,
        .sidebar.collapsed .dropdown-item span,
        .sidebar.collapsed .logout-btn span {
            opacity: 0;
            width: 0;
            height: 0;
            overflow: hidden;
            display: inline-block;
        }

        .sidebar.collapsed .logo-container {
            justify-content: center;
            min-width: auto;
        }

        .sidebar.collapsed .sidebar-nav {
            overflow-x: hidden;
        }

        .sidebar.collapsed .dropdown-menu {
            position: absolute;
            left: var(--sidebar-width-collapsed);
            background-color: var(--white);
            min-width: 200px;
            border-radius: 0 var(--radius-md) var(--radius-md) 0;
            box-shadow: var(--shadow-lg);
            z-index: 1001;
            padding-left: 0;
            max-height: 0;
        }

        .sidebar.collapsed .dropdown:hover .dropdown-menu {
            max-height: 500px;
            display: block;
        }

        .sidebar.collapsed .logout-btn {
            justify-content: center;
            padding: var(--space-sm);
        }

        .sidebar.collapsed .nav-link {
            justify-content: center;
        }

        .sidebar.collapsed .dropdown-header {
            justify-content: center;
        }

        /* Main Content Area */
        .main-content {
            flex: 1;
            margin-left: var(--sidebar-width);
            transition: margin-left var(--transition-speed) ease;
            padding: var(--space-xl);
            min-height: 100vh;
        }

        .sidebar.collapsed ~ .main-content {
            margin-left: var(--sidebar-width-collapsed);
        }

        /* Header Styles */
        .page-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: var(--space-xl);
            flex-wrap: wrap;
            gap: var(--space-md);
        }

        .page-title {
            font-size: var(--text-2xl);
            font-weight: 700;
            color: var(--text-primary);
            line-height: 1.2;
        }

        .header-actions {
            display: flex;
            gap: var(--space-md);
            flex-wrap: wrap;
        }

        /* Button Styles */
        .btn {
            padding: var(--space-sm) var(--space-md);
            border-radius: var(--radius-sm);
            font-weight: 500;
            font-size: var(--text-sm);
            cursor: pointer;
            border: none;
            transition: all 0.2s ease;
            display: flex;
            align-items: center;
            gap: var(--space-sm);
            white-space: nowrap;
        }

        .btn-primary {
            background-color: var(--primary);
            color: var(--white);
            box-shadow: var(--shadow-sm);
        }

        .btn-primary:hover {
            background-color: var(--primary-dark);
            box-shadow: var(--shadow-md);
            transform: translateY(-1px);
        }

        .btn-outline {
            background-color: transparent;
            border: 1px solid var(--gray-300);
            color: var(--text-secondary);
            transition: all 0.2s ease;
        }

        .btn-outline:hover {
            background-color: var(--primary-extra-light);
            color: var(--primary-dark);
            border-color: var(--primary-light);
            transform: translateY(-1px);
        }

        .btn-icon {
            padding: var(--space-sm);
            border-radius: var(--radius-sm);
            min-width: 36px;
            min-height: 36px;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        /* Stats Cards */
        .stats-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
            gap: var(--space-md);
            margin-bottom: var(--space-xl);
        }

        .stat-card {
            background-color: var(--white);
            border-radius: var(--radius-md);
            padding: var(--space-lg);
            box-shadow: var(--shadow-sm);
            transition: transform 0.3s ease, box-shadow 0.3s ease;
            border: 1px solid var(--gray-200);
            position: relative;
            overflow: hidden;
        }

        .stat-card:hover {
            transform: translateY(-5px);
            box-shadow: var(--shadow-md);
        }

        .stat-card::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            width: 4px;
            height: 100%;
            background-color: var(--primary);
        }

        .stat-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: var(--space-md);
        }

        .stat-title {
            font-size: var(--text-sm);
            color: var(--text-secondary);
            font-weight: 500;
            text-transform: uppercase;
            letter-spacing: 0.5px;
        }

        .stat-icon {
            width: 44px;
            height: 44px;
            border-radius: var(--radius-md);
            display: flex;
            align-items: center;
            justify-content: center;
            color: var(--white);
            font-size: var(--text-lg);
            box-shadow: var(--shadow-sm);
        }

        .stat-icon.students {
            background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
        }

        .stat-icon.assessment {
            background: linear-gradient(135deg, var(--success) 0%, #66bb6a 100%);
        }

        .stat-icon.messages {
            background: linear-gradient(135deg, var(--info) 0%, #29b6f6 100%);
        }

        .stat-icon.pending {
            background: linear-gradient(135deg, var(--warning) 0%, #ffca28 100%);
        }

        .stat-value {
            font-size: var(--text-2xl);
            font-weight: 700;
            color: var(--text-primary);
            margin-bottom: var(--space-xs);
        }

        .stat-change {
            font-size: var(--text-xs);
            display: flex;
            align-items: center;
            gap: var(--space-xs);
        }

        .stat-change.positive {
            color: var(--success);
        }

        .stat-change.negative {
            color: var(--danger);
        }

        /* Charts Section */
        .charts-row {
            display: grid;
            grid-template-columns: 2fr 1fr;
            gap: var(--space-md);
            margin-bottom: var(--space-xl);
        }

        @media (max-width: 1200px) {
            .charts-row {
                grid-template-columns: 1fr;
            }
        }

        .chart-card {
            background-color: var(--white);
            border-radius: var(--radius-md);
            padding: var(--space-lg);
            box-shadow: var(--shadow-sm);
            border: 1px solid var(--gray-200);
        }

        .chart-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: var(--space-lg);
            flex-wrap: wrap;
            gap: var(--space-sm);
        }

        .chart-title {
            font-size: var(--text-lg);
            font-weight: 600;
            color: var(--text-primary);
        }

        .chart-actions {
            display: flex;
            gap: var(--space-sm);
            flex-wrap: wrap;
        }

        .chart-container {
            height: 300px;
            position: relative;
            background-color: var(--white);
            border-radius: var(--radius-sm);
            overflow: hidden;
        }

        /* Activity Section */
        .recent-activity {
            background-color: var(--white);
            border-radius: var(--radius-md);
            padding: var(--space-lg);
            box-shadow: var(--shadow-sm);
            margin-bottom: var(--space-xl);
            border: 1px solid var(--gray-200);
        }

        .activity-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: var(--space-lg);
            flex-wrap: wrap;
            gap: var(--space-sm);
        }

        .activity-title {
            font-size: var(--text-lg);
            font-weight: 600;
            color: var(--text-primary);
        }

        .activity-list {
            list-style: none;
        }

        .activity-item {
            display: flex;
            padding: var(--space-md) 0;
            border-bottom: 1px solid var(--gray-200);
        }

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

        .activity-icon {
            width: 40px;
            height: 40px;
            border-radius: var(--radius-full);
            background-color: var(--primary-extra-light);
            display: flex;
            align-items: center;
            justify-content: center;
            margin-right: var(--space-md);
            flex-shrink: 0;
            color: var(--primary);
        }

        .activity-content {
            flex: 1;
        }

        .activity-message {
            font-size: var(--text-base);
            margin-bottom: var(--space-xs);
            color: var(--text-primary);
        }

        .activity-meta {
            display: flex;
            justify-content: space-between;
            font-size: var(--text-xs);
            color: var(--text-secondary);
            flex-wrap: wrap;
            gap: var(--space-sm);
        }

        .activity-time {
            color: var(--primary-light);
            font-weight: 500;
        }

        /* Tasks Section */
        .upcoming-tasks {
            background-color: var(--white);
            border-radius: var(--radius-md);
            padding: var(--space-lg);
            box-shadow: var(--shadow-sm);
            border: 1px solid var(--gray-200);
        }

        .tasks-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: var(--space-lg);
            flex-wrap: wrap;
            gap: var(--space-sm);
        }

        .tasks-title {
            font-size: var(--text-lg);
            font-weight: 600;
            color: var(--text-primary);
        }

        .task-list {
            list-style: none;
        }

        .task-item {
            display: flex;
            align-items: center;
            padding: var(--space-sm) 0;
            border-bottom: 1px solid var(--gray-200);
        }

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

        .task-checkbox {
            margin-right: var(--space-md);
            width: 18px;
            height: 18px;
            accent-color: var(--primary);
            cursor: pointer;
        }

        .task-content {
            flex: 1;
        }

        .task-name {
            font-size: var(--text-base);
            margin-bottom: var(--space-xs);
            color: var(--text-primary);
        }

        .task-meta {
            display: flex;
            gap: var(--space-md);
            font-size: var(--text-xs);
            color: var(--text-secondary);
            flex-wrap: wrap;
        }

        .task-priority {
            display: inline-block;
            padding: 2px 8px;
            border-radius: var(--radius-full);
            font-size: var(--text-xs);
            font-weight: 600;
            text-transform: uppercase;
        }

        .priority-high {
            background-color: rgba(229, 57, 53, 0.1);
            color: var(--danger);
        }

        .priority-medium {
            background-color: rgba(255, 179, 0, 0.1);
            color: var(--warning);
        }

        .priority-low {
            background-color: rgba(67, 160, 71, 0.1);
            color: var(--success);
        }

        /* Calendar Modal */
        .calendar-container {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background-color: rgba(0, 0, 0, 0.5);
            z-index: 2000;
            justify-content: center;
            align-items: center;
        }

        .calendar-container.open {
            display: flex;
        }

        .calendar {
            background-color: var(--white);
            border-radius: var(--radius-lg);
            box-shadow: var(--shadow-xl);
            width: 90%;
            max-width: 400px;
            overflow: hidden;
            animation: fadeInUp 0.3s ease;
        }

        @keyframes fadeInUp {
            from {
                opacity: 0;
                transform: translateY(20px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        .calendar-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: var(--space-md);
            background-color: var(--primary);
            color: var(--white);
        }

        .calendar-title {
            font-size: var(--text-base);
            font-weight: 600;
        }

        .calendar-close {
            background: none;
            border: none;
            color: var(--white);
            font-size: var(--text-lg);
            cursor: pointer;
            transition: transform 0.2s ease;
        }

        .calendar-close:hover {
            transform: scale(1.1);
        }

        .calendar-body {
            padding: var(--space-md);
        }

        .calendar-grid {
            display: grid;
            grid-template-columns: repeat(7, 1fr);
            gap: var(--space-sm);
        }

        .calendar-day-header {
            text-align: center;
            font-size: var(--text-xs);
            font-weight: 600;
            color: var(--text-secondary);
            padding: var(--space-sm);
        }

        .calendar-day {
            text-align: center;
            padding: var(--space-sm);
            border-radius: var(--radius-full);
            cursor: pointer;
            transition: all 0.2s ease;
            font-size: var(--text-sm);
            aspect-ratio: 1/1;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .calendar-day:hover {
            background-color: var(--primary-extra-light);
            color: var(--primary-dark);
        }

        .calendar-day.today {
            background-color: var(--primary-light);
            color: var(--white);
            font-weight: 600;
        }

        .calendar-day.selected {
            background-color: var(--primary);
            color: var(--white);
            font-weight: 600;
        }

        .calendar-day.other-month {
            color: var(--gray-400);
        }

        .calendar-nav {
            display: flex;
            justify-content: space-between;
            margin-bottom: var(--space-md);
            align-items: center;
        }

        .calendar-nav-btn {
            background: none;
            border: none;
            font-size: var(--text-base);
            cursor: pointer;
            color: var(--primary);
            padding: var(--space-xs) var(--space-sm);
            border-radius: var(--radius-sm);
            transition: all 0.2s ease;
        }

        .calendar-nav-btn:hover {
            background-color: var(--primary-extra-light);
        }

        .calendar-month-year {
            font-weight: 600;
            color: var(--text-primary);
            font-size: var(--text-base);
        }

        /* Empty State Styles */
        .empty-state {
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            padding: var(--space-xl) var(--space-md);
            text-align: center;
            color: var(--text-secondary);
        }

        .empty-state-icon {
            font-size: var(--text-3xl);
            color: var(--gray-300);
            margin-bottom: var(--space-md);
        }

        .empty-state-text {
            font-size: var(--text-base);
            max-width: 400px;
            margin-bottom: var(--space-md);
        }

        /* Responsive Adjustments */
        @media (max-width: 768px) {
            .sidebar {
                transform: translateX(-100%);
                width: var(--sidebar-width);
            }
            
            .sidebar.collapsed {
                transform: translateX(0);
                width: var(--sidebar-width-collapsed);
            }
            
            .main-content {
                margin-left: 0;
                padding: var(--space-lg);
            }
            
            .sidebar.collapsed ~ .main-content {
                margin-left: var(--sidebar-width-collapsed);
            }

            .header-actions {
                width: 100%;
            }

            .btn {
                flex: 1;
                justify-content: center;
            }
        }

        @media (max-width: 480px) {
            .stats-grid {
                grid-template-columns: 1fr;
            }

            .chart-actions .btn {
                padding: var(--space-xs) var(--space-sm);
                font-size: var(--text-xs);
            }
            
            .main-content {
                padding: var(--space-md);
            }
        }

        /* Animations */
        @keyframes fadeIn {
            from { opacity: 0; }
            to { opacity: 1; }
        }

        .fade-in {
            animation: fadeIn 0.5s ease;
        }