:root {
    --primary: #3b82f6;
    --primary-dark: #2563eb;
    --success: #10b981;
    --danger: #ef4444;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-600: #4b5563;
    --gray-800: #1f2937;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, sans-serif;
    line-height: 1.6;
    color: var(--gray-800);
    background-color: var(--gray-100);
    padding: 20px;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    background-color: white;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    padding: 20px;
}

header {
    text-align: center;
    margin-bottom: 30px;
}

h1 {
    color: var(--primary);
    margin-bottom: 10px;
}

.attendance-summary {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin: 15px 0;
    flex-wrap: wrap;
}

.summary-card {
    padding: 15px;
    border-radius: 8px;
    background-color: var(--gray-100);
    text-align: center;
    min-width: 120px;
}

.summary-card h3 {
    font-size: 24px;
    margin-bottom: 5px;
}

.controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin: 20px 0;
    flex-wrap: wrap;
    gap: 15px;
}

.search-box {
    padding: 10px 15px;
    border: 1px solid var(--gray-200);
    border-radius: 4px;
    flex-grow: 1;
    max-width: 150px;
}

.date-selector {
    display: flex;
    align-items: center;
    gap: 10px;
}

.date-display {
    font-weight: bold;
    min-width: 120px;
    text-align: center;
}

.btn {
    padding: 8px 16px;
    background-color: var(--primary);
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    transition: background-color 0.2s;
}

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

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

.btn-danger:hover {
    background-color: #dc2626;
}

.students-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 15px;
    margin-top: 20px;
}

.student-card {
    border: 1px solid var(--gray-200);
    border-radius: 8px;
    padding: 15px;
    display: flex;
    align-items: center;
    gap: 15px;
    background-color: white;
    transition: transform 0.2s, box-shadow 0.2s;
}

.student-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.student-info {
    flex-grow: 1;
}

.student-name {
    font-weight: bold;
    margin-bottom: 4px;
}

.student-id {
    color: var(--gray-600);
    font-size: 14px;
}

.attendance-toggle {
    display: flex;
    gap: 5px;
}

.toggle-btn {
    padding: 6px 12px;
    border: 1px solid var(--gray-200);
    background-color: white;
    cursor: pointer;
    border-radius: 4px;
    transition: all 0.2s;
}

.toggle-btn.active {
    background-color: var(--success);
    color: white;
    border-color: var(--success);
}

.toggle-btn.absent {
    background-color: var(--danger);
    color: white;
    border-color: var(--danger);
}

.export-controls {
    margin-top: 30px;
    display: flex;
    justify-content: center;
    gap: 15px;
}

@media (max-width: 768px) {
    .controls {
        flex-direction: column;
        align-items: stretch;
    }
    
    .search-box {
        max-width: 100%;
    }
    
    .date-selector {
        justify-content: center;
    }
    
    .students-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .attendance-summary {
        flex-direction: column;
        align-items: center;
    }
    
    .summary-card {
        width: 100%;
        max-width: 200px;
    }
    
    .export-controls {
        flex-direction: column;
    }
}