.books-nav {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    grid-auto-rows: 1fr;
    gap: 100px;
    padding: 100px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
}

.book-card {
    border-radius: 12px;
    background-color: #222222;
    color: #ffffff;
    text-align: center;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
    cursor: pointer;
    transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    position: relative;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
}

.book-card img {
    border-radius: 12px;
    width: 50%;
    height: 50%;
    object-fit: cover;
}

.book-card .book-info {
    flex: 1;
    padding: 0 10px;
}

.book-card:hover {
    transform: translateY(-10px) scale(1.02);
    box-shadow: 0 30px 60px rgba(0, 0, 0, 0.15);
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
}

.book-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.4), transparent);
    transition: left 0.5s;
}

.book-card:hover::before {
    left: 100%;
}


.book-number {
    margin-top: 10px;
    font-size: 20px;
    font-weight: bold;
    margin-bottom: 10px;
    background: white;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    flex: 1;
}

.book-card:hover .book-number {
    background: white;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.book-title {
    font-size: 15px;
    font-weight: bold;
    margin-bottom: 10px;
    color: #888888;
}

.book-subtitle {
    font-size: 12px;
    margin-bottom: 10px;
    color: #888888;
}

.lesson-count {
    background: rgba(102, 126, 234, 0.1);
    padding: 8px 16px;
    border-radius: 25px;
    font-size: 10px;
    margin-bottom: 10px;
    color: #667eea;
}

.book-card:hover .lesson-count {
    background: rgba(255, 255, 255, 0.2);
    color: white;
}

/* SEO 优化新增样式 */
.subtitle {
    font-size: 14px;
    color: #cccccc;
    margin-top: 10px;
    text-align: center;
}

.description {
    font-size: 14px;
    color: #888888;
    text-align: center;
    margin-bottom: 15px;
}

/* 学习资源样式 */
.learning-resources {
    padding: 30px;
    background-color: #111111;
    border-radius: 20px;
    margin-top: 30px;
}

.learning-resources h3 {
    text-align: center;
    color: #ffffff;
    font-size: 24px;
    margin-bottom: 25px;
}

.resource-links {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 20px;
}

.resource-card {
    display: flex;
    align-items: center;
    padding: 20px;
    background: linear-gradient(135deg, #2d3748, #4a5568);
    border-radius: 12px;
    text-decoration: none;
    transition: all 0.3s ease;
    border: 1px solid #4a5568;
}

.resource-card:hover {
    background: linear-gradient(135deg, #667eea, #764ba2);
    transform: translateY(-3px);
    box-shadow: 0 10px 25px rgba(102, 126, 234, 0.3);
}

.resource-icon {
    font-size: 32px;
    margin-right: 15px;
}

.resource-info h4 {
    color: #ffffff;
    margin: 0 0 5px 0;
    font-size: 18px;
}

.resource-info p {
    color: #cccccc;
    margin: 0;
    font-size: 14px;
    line-height: 1.4;
}

.resource-card:hover .resource-info h4 {
    color: white;
}

.resource-card:hover .resource-info p {
    color: #f0f0f0;
}

@media (max-width: 768px) {
    .books-nav {
        grid-template-columns: 1fr;
        gap: 40px;
        padding: 40px;
    }

    .subtitle {
        font-size: 12px;
    }

    .description {
        font-size: 12px;
    }

    .learning-resources {
        padding: 20px;
        margin-top: 20px;
    }

    .learning-resources h3 {
        font-size: 20px;
    }

    .resource-links {
        grid-template-columns: 1fr;
        gap: 15px;
    }

    .resource-card {
        padding: 15px;
    }

    .resource-icon {
        font-size: 28px;
        margin-right: 12px;
    }

    .resource-info h4 {
        font-size: 16px;
    }

    .resource-info p {
        font-size: 13px;
    }
}

/* 课程详细介绍样式 */
.course-details {
    padding: 40px 30px;
    background-color: #0a0a0a;
    border-radius: 20px;
    margin-top: 30px;
}

.course-details h3 {
    text-align: center;
    color: #ffffff;
    font-size: 24px;
    margin-bottom: 30px;
}

.course-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(500px, 1fr));
    gap: 25px;
}

.course-detail-card {
    background: linear-gradient(135deg, #1a1a2e, #16213e);
    border-radius: 15px;
    padding: 25px;
    border: 1px solid #333;
    transition: all 0.3s ease;
}

.course-detail-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 30px rgba(102, 126, 234, 0.2);
    border-color: #667eea;
}

.course-header {
    display: flex;
    align-items: center;
    margin-bottom: 15px;
}

.course-icon {
    font-size: 32px;
    margin-right: 15px;
}

.course-header h4 {
    color: #ffffff;
    margin: 0 0 5px 0;
    font-size: 18px;
}

.course-target {
    color: #667eea;
    margin: 0;
    font-size: 14px;
    font-weight: 500;
}

.course-info p {
    color: #cccccc;
    margin: 8px 0;
    font-size: 14px;
    line-height: 1.5;
}

.course-info strong {
    color: #ffffff;
}

/* 学习路径样式 */
.learning-path {
    padding: 40px 30px;
    background-color: #111111;
    border-radius: 20px;
    margin-top: 30px;
}

.learning-path h3 {
    text-align: center;
    color: #ffffff;
    font-size: 24px;
    margin-bottom: 30px;
}

.path-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 20px;
    margin-bottom: 30px;
}

.path-step {
    flex: 1;
    min-width: 200px;
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
}

.step-number {
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, #667eea, #764ba2);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 20px;
    font-weight: bold;
    margin-bottom: 15px;
}

.step-content h4 {
    color: #ffffff;
    margin: 0 0 8px 0;
    font-size: 16px;
}

.step-content p {
    color: #cccccc;
    margin: 0;
    font-size: 13px;
    line-height: 1.4;
}

.path-arrow {
    color: #667eea;
    font-size: 24px;
    font-weight: bold;
}

.learning-quote {
    text-align: center;
    margin-top: 30px;
}

.learning-quote blockquote {
    background: linear-gradient(135deg, #2d3748, #4a5568);
    padding: 20px 30px;
    border-radius: 12px;
    margin: 0;
    border-left: 4px solid #667eea;
}

.learning-quote p {
    color: #ffffff;
    font-style: italic;
    margin: 0;
    font-size: 16px;
    line-height: 1.6;
}

/* 移动端适配 */
@media (max-width: 768px) {
    .course-details {
        padding: 25px 15px;
        margin-top: 20px;
    }

    .course-details h3 {
        font-size: 20px;
        margin-bottom: 20px;
    }

    .course-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }

    .course-detail-card {
        padding: 20px;
    }

    .course-icon {
        font-size: 28px;
        margin-right: 12px;
    }

    .course-header h4 {
        font-size: 16px;
    }

    .course-info p {
        font-size: 13px;
    }

    .learning-path {
        padding: 25px 15px;
        margin-top: 20px;
    }

    .learning-path h3 {
        font-size: 20px;
    }

    .path-container {
        flex-direction: column;
        gap: 15px;
    }

    .path-arrow {
        transform: rotate(90deg);
        font-size: 20px;
    }

    .path-step {
        min-width: auto;
        width: 100%;
    }

    .step-number {
        width: 40px;
        height: 40px;
        font-size: 18px;
    }

    .step-content h4 {
        font-size: 15px;
    }

    .step-content p {
        font-size: 12px;
    }

    .learning-quote blockquote {
        padding: 15px 20px;
    }

    .learning-quote p {
        font-size: 14px;
    }
}