body {
    font-family: "SimSun", "STSong", serif;
    background-color: #f8f9fa;
    color: #333;
    line-height: 1.6;
}
.book-title {
    font-size: 3rem;
    font-weight: bold;
    text-align: center;
    margin-bottom: 1.5rem;
    color: #f8f9fa;
}
.book-subtitle {
    font-size: 1.2rem;
    text-align: left;
    margin: 0 auto;
    line-height: 1.8;
}
.chapter-table {
    background-color: white;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    padding: .5rem 2rem;
    margin-bottom: 3rem;
}
.chapter-title {
    font-size: 1.8rem;
    color: #2c3e50;
    border-bottom: 3px solid #c19a6b;
    padding-bottom: 0.8rem;
    margin-bottom: 2rem;
    text-align: center;
}
.chapter-item {
    padding: 1rem 0.5rem;
    text-align: center;
    border: 1px solid #e9ecef;
    margin: 0.2rem;
    background-color: #f8f9fa;
    border-radius: 6px;
    transition: all 0.3s ease;
    display: block;
    text-decoration: none;
    color: #2c3e50;
}
.chapter-item:hover {
    background-color: #e9ecef;
    transform: translateY(-3px);
    box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
    color: #c19a6b;
    text-decoration: none;
}
.intro-section {
    background-color: white;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    padding: 2.5rem;
    margin-bottom: 3rem;
}
.intro-title {
    font-size: 1.8rem;
    color: #2c3e50;
    border-bottom: 3px solid #c19a6b;
    padding-bottom: 0.8rem;
    margin-bottom: 1.5rem;
}
.intro-content {
    font-size: 1.1rem;
    line-height: 1.8;
    text-align: justify;
}
.tools-section {
    background-color: white;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    padding: 2.5rem;
    margin-bottom: 3rem;
}
.tools-title {
    font-size: 1.8rem;
    color: #2c3e50;
    border-bottom: 3px solid #c19a6b;
    padding-bottom: 0.8rem;
    margin-bottom: 1.5rem;
}
.tool-item {
    padding: 1.2rem;
    text-align: center;
    background-color: #f8f9fa;
    border-radius: 8px;
    margin-bottom: 1rem;
    border: 1px solid #e9ecef;
    transition: all 0.3s ease;
    text-decoration: none;
    color: inherit;
    display: block;
}
.tool-item:hover {
    background-color: #e9ecef;
    transform: translateY(-3px);
    box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
    text-decoration: none;
    color: inherit;
}
.tool-name {
    font-weight: bold;
    color: #2c3e50;
    margin-bottom: 0.5rem;
}
.four-books-five-classics {
    font-size: 1.1rem;
    color: #c19a6b;
    font-style: italic;
    margin-top: 1rem;
    text-align: center;
}
.divider {
    height: 1px;
    background-color: #dee2e6;
    margin: 2rem 0;
}
.section-title {
    color: #2c3e50;
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
    padding-left: 0.5rem;
    border-left: 4px solid #c19a6b;
}
.content-box {
    background-color: white;
    border-radius: 8px;
    padding: 2rem;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
    margin-bottom: 2rem;
}
.copyright{
    margin-bottom: 20px;
}
@media (max-width: 768px) {
    .book-title {
        font-size: 2.2rem;
    }
    .chapter-item {
        padding: 0.8rem 0.3rem;
        font-size: 0.95rem;
    }
}
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    display: none;          /* 默认隐藏 */
    width: 50px;
    height: 50px;
    background-color: #2c3e50;
    color: white;
    border-radius: 50%;
    text-align: center;
    line-height: 50px;
    z-index: 999;
    transition: all 0.3s ease;
    box-shadow: 0 4px 10px rgba(0,0,0,0.2);
    text-decoration: none;
    opacity: 0.8;
}
.back-to-top:hover {
    background-color: #c19a6b;
    color: white;
    transform: translateY(-3px);
}
.back-to-top svg {
    width: 24px;
    height: 24px;
    vertical-align: middle;
    margin-top: -3px;
}
@media (max-width: 768px) {
    .back-to-top {
        bottom: 20px;
        right: 20px;
        width: 45px;
        height: 45px;
        line-height: 45px;
        opacity: 0.8;
    }
    .back-to-top svg {
        width: 20px;
        height: 20px;
    }
}