:root {
    --primary-color: #3498db;
    --secondary-color: #2ecc71;
    --accent-color: #e74c3c;
    --warning-color: #f39c12;
    --info-color: #9b59b6;
    --dark-color: #2c3e50;
    --light-color: #ecf0f1;
    --text-color: #333;
    --text-light: #7f8c8d;
    --bg-color: #f9f9f9;
    --card-bg: #ffffff;
    --border-color: #ddd;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    --hover-shadow: 0 8px 15px rgba(0, 0, 0, 0.2);
    --transition: all 0.3s ease;
}

.dark-theme {
    --primary-color: #2980b9;
    --secondary-color: #27ae60;
    --accent-color: #c0392b;
    --warning-color: #e67e22;
    --info-color: #8e44ad;
    --dark-color: #34495e;
    --light-color: #2c3e50;
    --text-color: #ecf0f1;
    --text-light: #bdc3c7;
    --bg-color: #1a1a1a;
    --card-bg: #2d2d2d;
    --border-color: #444;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.3);
    --hover-shadow: 0 8px 15px rgba(0, 0, 0, 0.4);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    transition: var(--transition);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 20px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 0;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 20px;
}

.logo h1 {
    color: var(--primary-color);
    font-size: 28px;
    margin-bottom: 5px;
}

.logo p {
    color: var(--text-light);
    font-size: 14px;
}

.header-controls {
    display: flex;
    gap: 15px;
}

.btn-theme, .btn-export, .btn-primary {
    padding: 10px 15px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 8px;
}

.btn-theme {
    background-color: var(--card-bg);
    color: var(--text-color);
    border: 1px solid var(--border-color);
}

.btn-export {
    background-color: var(--accent-color);
    color: white;
}

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

.btn-theme:hover, .btn-export:hover, .btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--hover-shadow);
}

.dashboard {
    display: grid;
    grid-template-columns: 250px 1fr;
    gap: 20px;
    flex: 1;
}

.sidebar {
    background-color: var(--card-bg);
    border-radius: 8px;
    padding: 20px;
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
}

.nav-menu {
    list-style: none;
    margin-bottom: 30px;
}

.nav-link {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 15px;
    text-decoration: none;
    color: var(--text-color);
    border-radius: 5px;
    margin-bottom: 5px;
    transition: var(--transition);
}

.nav-link:hover {
    background-color: var(--primary-color);
    color: white;
}

.nav-link.active {
    background-color: var(--primary-color);
    color: white;
}

.icon-dashboard::before { content: "📊"; }
.icon-master::before { content: "🗓️"; }
.icon-class::before { content: "👨‍🎓"; }
.icon-teacher::before { content: "👨‍🏫"; }
.icon-free::before { content: "⏰"; }
.icon-teacher-free::before { content: "🧘"; }

.ai-section {
    margin-top: auto;
}

.ai-section h3 {
    margin-bottom: 15px;
    color: var(--primary-color);
}

.ai-chat {
    background-color: var(--light-color);
    border-radius: 8px;
    padding: 15px;
}

.dark-theme .ai-chat {
    background-color: var(--dark-color);
}

.ai-message {
    margin-bottom: 15px;
    padding: 10px;
    background-color: var(--card-bg);
    border-radius: 5px;
    font-style: italic;
}

.ai-suggestions {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.ai-suggestion-btn {
    padding: 8px 12px;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    text-align: left;
    font-size: 14px;
}

.ai-suggestion-btn:hover {
    background-color: var(--secondary-color);
}

.main-content {
    background-color: var(--card-bg);
    border-radius: 8px;
    padding: 20px;
    box-shadow: var(--shadow);
    overflow: auto;
}

.content-section {
    display: none;
}

.content-section.active {
    display: block;
    animation: fadeIn 0.5s ease;
}

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

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 1px solid var(--border-color);
}

.section-header h2 {
    color: var(--primary-color);
}

.controls {
    display: flex;
    gap: 15px;
    align-items: center;
}

select {
    padding: 8px 12px;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    background-color: var(--card-bg);
    color: var(--text-color);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.stat-card {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border-radius: 8px;
    padding: 20px;
    display: flex;
    align-items: center;
    gap: 15px;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

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

.stat-icon {
    font-size: 30px;
}

.stat-info h3 {
    font-size: 14px;
    margin-bottom: 5px;
    opacity: 0.9;
}

.stat-value {
    font-size: 24px;
    font-weight: bold;
}

.ai-recommendations {
    background-color: var(--light-color);
    border-radius: 8px;
    padding: 20px;
    margin-top: 30px;
}

.dark-theme .ai-recommendations {
    background-color: var(--dark-color);
}

.ai-recommendations h3 {
    margin-bottom: 15px;
    color: var(--primary-color);
}

.recommendation-list {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.recommendation-item {
    background-color: var(--card-bg);
    border-radius: 5px;
    padding: 15px;
    display: flex;
    align-items: center;
    gap: 15px;
    box-shadow: var(--shadow);
}

.rec-badge {
    padding: 5px 10px;
    background-color: var(--info-color);
    color: white;
    border-radius: 20px;
    font-size: 12px;
    font-weight: bold;
}

.timetable-container {
    overflow: auto;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 15px;
}

.timetable {
    width: 100%;
    border-collapse: collapse;
    min-width: 800px;
}

.timetable th, .timetable td {
    border: 1px solid var(--border-color);
    padding: 12px;
    text-align: center;
}

.timetable th {
    background-color: var(--primary-color);
    color: white;
    font-weight: bold;
    position: sticky;
    top: 0;
}

.timetable tr:nth-child(even) {
    background-color: rgba(0, 0, 0, 0.03);
}

.dark-theme .timetable tr:nth-child(even) {
    background-color: rgba(255, 255, 255, 0.05);
}

.subject-cell {
    font-weight: bold;
    border-radius: 4px;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.subject-cell::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
    transition: left 0.5s;
}

.subject-cell:hover::before {
    left: 100%;
}

.subject-cell:hover {
    transform: scale(1.05);
    cursor: pointer;
    box-shadow: var(--shadow);
}

.free-period {
    background-color: var(--light-color);
    color: var(--text-light);
}

.dark-theme .free-period {
    background-color: #3a3a3a;
}

.teacher-free {
    background-color: rgba(46, 204, 113, 0.2);
    color: var(--secondary-color);
}

.dark-theme .teacher-free {
    background-color: rgba(46, 204, 113, 0.3);
}

footer {
    margin-top: 30px;
    padding-top: 15px;
    border-top: 1px solid var(--border-color);
    text-align: center;
    color: var(--text-light);
    font-size: 14px;
}

/* Responsive Design */
@media (max-width: 1024px) {
    .dashboard {
        grid-template-columns: 1fr;
    }
    
    .sidebar {
        order: 2;
    }
    
    .main-content {
        order: 1;
    }
    
    .section-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 15px;
    }
    
    .controls {
        width: 100%;
        justify-content: space-between;
    }
}

@media (max-width: 768px) {
    .container {
        padding: 10px;
    }
    
    header {
        flex-direction: column;
        gap: 15px;
        align-items: flex-start;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .timetable th, .timetable td {
        padding: 8px;
        font-size: 14px;
    }
}

/* Print Styles for Export */
@media print {
    body {
        background: white;
        color: black;
    }
    
    .sidebar, .header-controls, footer, .controls button:not(.btn-export) {
        display: none;
    }
    
    .dashboard {
        grid-template-columns: 1fr;
    }
    
    .timetable {
        border: 2px solid #000;
    }
    
    .timetable th {
        background: #333 !important;
        color: white !important;
        -webkit-print-color-adjust: exact;
    }
}