:root {
    /* Color Palette - Premium Blue */
    --primary-color: #2563eb;
    --primary-light: #3b82f6;
    --primary-dark: #1d4ed8;
    --secondary-color: #64748b;
    --accent-color: #0ea5e9;
    
    /* Semantic Colors */
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --info: #3b82f6;
    
    /* Backgrounds */
    --bg-main: #f8fafc;
    --bg-card: #ffffff;
    --bg-sidebar: #ffffff;
    --bg-glass: rgba(255, 255, 255, 0.7);
    
    /* Text */
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --text-on-primary: #ffffff;
    
    /* Effects */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 1rem;
    --radius-xl: 1.5rem;
    --glass-blur: blur(12px);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Dark Mode Variables */
[data-theme="dark"] {
    --bg-main: #0f172a;
    --bg-card: #1e293b;
    --bg-sidebar: #1e293b;
    --bg-glass: rgba(30, 41, 59, 0.7);
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.3);
}

/* Reset & Base */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
}

body {
    background-color: var(--bg-main);
    color: var(--text-primary);
    line-height: 1.5;
    overflow-x: hidden;
    transition: background-color 0.3s ease;
}

button {
    cursor: pointer;
    border: none;
    outline: none;
    background: none;
    transition: var(--transition);
}

a {
    text-decoration: none;
    color: inherit;
}

ul {
    list-style: none;
}

/* Layout Structure */
.app-container {
    display: flex;
    min-height: 100vh;
}

/* Sidebar */
.sidebar {
    width: 260px;
    background-color: var(--bg-sidebar);
    border-right: 1px solid rgba(0, 0, 0, 0.05);
    display: flex;
    flex-direction: column;
    padding: 2rem 1.5rem;
    position: fixed;
    height: 100vh;
    z-index: 100;
    transition: var(--transition);
}

.logo-container {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 3rem;
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: bold;
    font-size: 1.25rem;
    box-shadow: var(--shadow-md);
}

.logo-text {
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.025em;
}

.nav-links {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.nav-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.875rem 1rem;
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-weight: 500;
    transition: var(--transition);
}

.nav-item:hover {
    background-color: rgba(37, 99, 235, 0.05);
    color: var(--primary-color);
}

.nav-item.active {
    background-color: var(--primary-color);
    color: white;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.2);
}

.nav-item i {
    font-size: 1.25rem;
}

/* Main Content */
.main-content {
    flex: 1;
    margin-left: 260px;
    padding: 2rem;
    transition: var(--transition);
}

/* Header */
.top-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2.5rem;
}

.welcome-text h1 {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--text-primary);
}

.welcome-text p {
    color: var(--text-secondary);
}

.user-profile {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 0.5rem 1rem;
    background: var(--bg-card);
    border-radius: var(--radius-full);
    box-shadow: var(--shadow-sm);
}

.user-info {
    text-align: right;
}

.user-name {
    font-weight: 600;
    font-size: 0.9rem;
}

.user-role {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.user-avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: #e2e8f0;
    object-fit: cover;
}

/* Dashboard Grid */
.dashboard-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2.5rem;
}

.stat-card {
    background: var(--bg-card);
    padding: 1.5rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    position: relative;
    overflow: hidden;
    transition: var(--transition);
}

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

.stat-card::after {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    width: 100px;
    height: 100px;
    background: var(--primary-color);
    opacity: 0.03;
    border-radius: 50%;
    transform: translate(30%, -30%);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.stat-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
}

.stat-trend {
    font-size: 0.75rem;
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.trend-up { color: var(--success); }
.trend-down { color: var(--danger); }

/* Subject Cards */
.subjects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
}

.subject-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
    border-left: 5px solid var(--primary-color);
}

.subject-card.warning { border-left-color: var(--warning); }
.subject-card.danger { border-left-color: var(--danger); }
.subject-card.success { border-left-color: var(--success); }

.subject-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
}

.subject-info h3 {
    font-size: 1.1rem;
    font-weight: 600;
}

.subject-info p {
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.attendance-badge {
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
}

.progress-container {
    margin: 1.25rem 0;
}

.progress-bar {
    height: 8px;
    background: #e2e8f0;
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--primary-color);
    border-radius: 4px;
    transition: width 1s ease-out;
}

.subject-footer {
    display: flex;
    justify-content: space-between;
    font-size: 0.8rem;
    color: var(--text-secondary);
}

/* Section Controls */
.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    box-shadow: 0 4px 10px rgba(37, 99, 235, 0.2);
}

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
}

/* Modal Overlay */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.modal-overlay.active {
    display: flex;
    opacity: 1;
}

.modal-content {
    background: var(--bg-card);
    width: 100%;
    max-width: 500px;
    border-radius: var(--radius-lg);
    padding: 2rem;
    box-shadow: var(--shadow-lg);
    transform: scale(0.9);
    transition: transform 0.3s ease;
}

.modal-overlay.active .modal-content {
    transform: scale(1);
}

/* Animations */
@keyframes slideIn {
    from { opacity: 0; transform: translateX(20px); }
    to { opacity: 1; transform: translateX(0); }
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes scaleIn {
    from { opacity: 0; transform: scale(0.95); }
    to { opacity: 1; transform: scale(1); }
}

.content-section {
    animation: fadeIn 0.4s ease-out;
}

.stat-card {
    animation: scaleIn 0.3s ease-out backwards;
}

.stat-card:nth-child(1) { animation-delay: 0.1s; }
.stat-card:nth-child(2) { animation-delay: 0.15s; }
.stat-card:nth-child(3) { animation-delay: 0.2s; }
.stat-card:nth-child(4) { animation-delay: 0.25s; }

/* Glassmorphism Classes */
.glass {
    background: var(--bg-glass);
    backdrop-filter: var(--glass-blur);
    border: 1px solid rgba(255, 255, 255, 0.1);
    box-shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.07);
}

.glass-dark {
    background: rgba(15, 23, 42, 0.6);
    backdrop-filter: blur(12px);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

/* Responsive */
@media (max-width: 1024px) {
    .sidebar {
        width: 80px;
        padding: 2rem 0.5rem;
    }
    .logo-text, .nav-item span {
        display: none;
    }
    .main-content {
        margin-left: 80px;
    }
}

@media (max-width: 768px) {
    .sidebar {
        bottom: 0;
        height: auto;
        width: 100%;
        flex-direction: row;
        padding: 0.75rem;
        justify-content: space-around;
        border-right: none;
        border-top: 1px solid rgba(0, 0, 0, 0.05);
    }
    .main-content {
        margin-left: 0;
        margin-bottom: 80px;
        padding: 1.5rem;
    }
    .logo-container {
        display: none;
    }
    .nav-links {
        flex-direction: row;
        width: 100%;
        justify-content: space-around;
    }
}