.books-nav {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 25px;
    padding: 20px 0;
}

.book-card {
    border-radius: 12px;
    background-color: var(--container-highlight);
    color: var(--text-color);
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
    display: flex;
    align-items: center;
    border: 1px solid transparent;
}

.book-card:hover {
    transform: translateY(-5px);
    background-color: #333;
    border-color: var(--primary-color);
}

.book-card img {
    border-radius: 8px;
    width: auto;
    height: 200px;
    object-fit: cover;
}

.book-card .book-info {
    flex: 1;
}

.book-number {
    font-size: 18px;
    font-weight: bold;
    color: var(--text-color);
    margin-bottom: 5px;
}

.book-title {
    font-size: 16px;
    font-weight: 500;
    color: var(--text-color-dark);
    margin-bottom: 5px;
}

.book-subtitle {
    font-size: 14px;
    margin-bottom: 15px;
    color: var(--text-color-dark);
}

.lesson-count {
    background: rgba(29, 185, 84, 0.1);
    padding: 6px 12px;
    border-radius: 20px;
    font-size: 12px;
    color: var(--primary-color);
    display: inline-block;
}

@media (max-width: 768px) {
    .books-nav {
        grid-template-columns: 1fr;
        gap: 20px;
    }
    .book-card {
        text-align: center;
    }
    .book-card img {
        margin: 15px;
        max-height: 35vw;
    }
    .book-card .book-info {
        text-align: center;
    }
}