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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

header {
    background: white;
    padding: 30px;
    border-radius: 15px;
    text-align: center;
    margin-bottom: 20px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
}

header h1 {
    color: #667eea;
    margin-bottom: 10px;
    font-size: 2.5em;
}

header p {
    color: #666;
    font-size: 1.1em;
}

.tabs {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.tab-btn {
    background: white;
    border: none;
    padding: 15px 25px;
    border-radius: 10px;
    cursor: pointer;
    font-size: 1em;
    font-weight: 600;
    transition: all 0.3s ease;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

.tab-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 12px rgba(0,0,0,0.15);
}

.tab-btn.active {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.tab-content {
    display: none;
    background: white;
    padding: 30px;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
    animation: fadeIn 0.3s ease;
}

.tab-content.active {
    display: block;
}

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

h2 {
    color: #667eea;
    margin-bottom: 20px;
    padding-bottom: 10px;
    border-bottom: 3px solid #667eea;
}

h3 {
    color: #764ba2;
    margin: 20px 0 10px 0;
}

/* Search Bar */
.search-bar {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

.search-bar input,
.search-bar select {
    flex: 1;
    padding: 12px;
    border: 2px solid #ddd;
    border-radius: 8px;
    font-size: 1em;
}

.search-bar input:focus,
.search-bar select:focus {
    outline: none;
    border-color: #667eea;
}

/* Card Grid for Books */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
}

.book-card {
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    border-radius: 10px;
    padding: 20px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: transform 0.3s ease;
}

.book-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 6px 12px rgba(0,0,0,0.15);
}

.book-card h3 {
    color: #667eea;
    margin: 0 0 10px 0;
    font-size: 1.2em;
}

.book-card .author {
    color: #764ba2;
    font-weight: 600;
    margin-bottom: 5px;
}

.book-card .details {
    font-size: 0.9em;
    color: #666;
    margin: 5px 0;
}

.book-card .copies {
    margin-top: 10px;
    padding: 8px;
    background: white;
    border-radius: 5px;
    text-align: center;
    font-weight: 600;
}

.book-card .copies.available {
    color: #4CAF50;
}

.book-card .copies.unavailable {
    color: #e74c3c;
}

/* Table Container */
.table-container {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 10px;
}

table th {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 12px;
    text-align: left;
    font-weight: 600;
}

table td {
    padding: 12px;
    border-bottom: 1px solid #ddd;
}

table tr:hover {
    background: #f5f7fa;
}

.status-badge {
    display: inline-block;
    padding: 5px 10px;
    border-radius: 15px;
    font-size: 0.85em;
    font-weight: 600;
}

.status-badge.prestado {
    background: #fff3cd;
    color: #856404;
}

.status-badge.devuelto {
    background: #d4edda;
    color: #155724;
}

.status-badge.atrasado {
    background: #f8d7da;
    color: #721c24;
}

/* Filter Buttons */
.filter-buttons {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 10px 20px;
    border: 2px solid #667eea;
    background: white;
    color: #667eea;
    border-radius: 8px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.3s ease;
}

.filter-btn:hover {
    background: #f0f4ff;
}

.filter-btn.active {
    background: #667eea;
    color: white;
}

/* Form Styles */
.form-container {
    max-width: 600px;
    margin: 0 auto;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 5px;
    color: #333;
    font-weight: 600;
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 12px;
    border: 2px solid #ddd;
    border-radius: 8px;
    font-size: 1em;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: #667eea;
}

.btn-primary {
    width: 100%;
    padding: 15px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1.1em;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 12px rgba(102, 126, 234, 0.4);
}

.btn-action {
    padding: 8px 15px;
    background: #4CAF50;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.3s ease;
}

.btn-action:hover {
    background: #45a049;
}

.btn-danger {
    padding: 8px 15px;
    background: #e74c3c;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.3s ease;
}

.btn-danger:hover {
    background: #c0392b;
}

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

.stat-card {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 25px;
    border-radius: 10px;
    text-align: center;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

.stat-card.warning {
    background: linear-gradient(135deg, #f5576c 0%, #e74c3c 100%);
}

.stat-icon {
    font-size: 3em;
    margin-bottom: 10px;
}

.stat-value {
    font-size: 2.5em;
    font-weight: bold;
    margin-bottom: 5px;
}

.stat-label {
    font-size: 1em;
    opacity: 0.9;
}

.chart-container {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 10px;
    margin-bottom: 20px;
}

.chart-item {
    display: flex;
    align-items: center;
    margin: 10px 0;
    padding: 10px;
    background: white;
    border-radius: 5px;
}

.chart-label {
    flex: 1;
    font-weight: 600;
    color: #333;
}

.chart-bar {
    flex: 2;
    height: 30px;
    background: linear-gradient(90deg, #667eea 0%, #764ba2 100%);
    border-radius: 5px;
    display: flex;
    align-items: center;
    padding-left: 10px;
    color: white;
    font-weight: 600;
}

/* Notification */
.notification {
    position: fixed;
    top: 20px;
    right: 20px;
    padding: 15px 25px;
    border-radius: 8px;
    color: white;
    font-weight: 600;
    opacity: 0;
    transform: translateX(400px);
    transition: all 0.3s ease;
    z-index: 1000;
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.notification.show {
    opacity: 1;
    transform: translateX(0);
}

.notification.success {
    background: #4CAF50;
}

.notification.error {
    background: #e74c3c;
}

.notification.info {
    background: #667eea;
}

/* Footer */
footer {
    text-align: center;
    color: white;
    padding: 20px;
    margin-top: 30px;
}

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.8em;
    }

    .tabs {
        flex-direction: column;
    }

    .tab-btn {
        width: 100%;
    }

    .tab-content {
        padding: 20px;
    }

    .stats-grid {
        grid-template-columns: 1fr;
    }

    .search-bar {
        flex-direction: column;
    }
}