.main-content {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 1rem;
}

.page-header {
    text-align: center;
    margin-bottom: 3rem;
}

.page-header h1 {
    font-size: 2.5rem;
    color: #333;
    margin-bottom: 1rem;
}

.page-header p {
    font-size: 1.1rem;
    color: #666;
    max-width: 600px;
    margin: 0 auto;
}

.books-section {
    margin-bottom: 3rem;
}

.section-title {
    font-size: 1.8rem;
    color: #333;
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 3px solid #007bff;
    display: inline-block;
}

.subsection-title {
    font-size: 1.4rem;
    color: #444;
    margin: 2rem 0 1rem 0;
    padding-left: 1rem;
    border-left: 4px solid #28a745;
}

.books-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.book-card {
    background: #fff;
    border: 1px solid #e9ecef;
    border-radius: 8px;
    padding: 1.5rem;
    transition:
        transform 0.2s ease,
        box-shadow 0.2s ease;
    position: relative;
}

.book-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.book-title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    line-height: 1.4;
}

.book-title a {
    color: #333;
    text-decoration: none;
}

.book-title a:hover {
    color: #007bff;
    text-decoration: underline;
}

.book-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid #eee;
}

.book-size {
    background: #f8f9fa;
    color: #666;
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 0.85rem;
    font-weight: 500;
}

.book-year {
    color: #888;
    font-size: 0.9rem;
}

.book-language {
    background: #e7f3ff;
    color: #0066cc;
    padding: 0.2rem 0.6rem;
    border-radius: 10px;
    font-size: 0.8rem;
    font-weight: 500;
    text-transform: uppercase;
}

.book-authors {
    color: #666;
    font-size: 0.95rem;
    margin-bottom: 0.5rem;
    font-style: italic;
}

.subject-math {
    border-left: 4px solid #ff6b6b;
}
.subject-physics {
    border-left: 4px solid #4ecdc4;
}
.subject-geology {
    border-left: 4px solid #45b7d1;
}
.subject-literature {
    border-left: 4px solid #96ceb4;
}

.stats-bar {
    background: #f8f9fa;
    border-radius: 8px;
    padding: 1.5rem;
    margin-bottom: 2rem;
    display: flex;
    justify-content: space-around;
    text-align: center;
}

.stat-item {
    flex: 1;
}

.stat-number {
    font-size: 1.5rem;
    font-weight: bold;
    color: #007bff;
}

.stat-label {
    font-size: 0.9rem;
    color: #666;
    margin-top: 0.25rem;
}

.search-section {
    margin-bottom: 2rem;
}

.search-box {
    width: 100%;
    max-width: 400px;
    padding: 0.75rem 1rem;
    border: 2px solid #e9ecef;
    border-radius: 25px;
    font-size: 1rem;
    transition: border-color 0.3s ease;
}

.search-box:focus {
    outline: none;
    border-color: #007bff;
}

.search-container {
    text-align: center;
    margin-bottom: 2rem;
}

@media (max-width: 768px) {
    .page-header h1 {
        font-size: 2rem;
    }

    .books-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
    }

    .book-card {
        padding: 1rem;
    }

    .stats-bar {
        flex-direction: column;
        gap: 1rem;
    }

    .book-meta {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }

    .search-box {
        max-width: 100%;
    }
}

@media (max-width: 480px) {
    .section-title {
        font-size: 1.5rem;
    }

    .subsection-title {
        font-size: 1.2rem;
    }

    .book-title {
        font-size: 1rem;
    }
}