body {
    font-family: Arial, sans-serif;
    margin: 20px;
    line-height: 1.6;
    background-color: #f5f5f5;
    color: #333;
}
a {
    color: #0066cc;
    text-decoration: none;
}
a:hover {
    text-decoration: underline;
}
nav {
    margin-bottom: 20px;
    padding: 10px;
    background-color: #fff;
    border: 1px solid #ddd;
    border-radius: 4px;
}
nav a {
    margin-right: 15px;
    font-weight: bold;
}
article {
    background-color: #fff;
    padding: 20px;
    border: 1px solid #ddd;
    border-radius: 4px;
}
header h1 {
    font-size: 28px;
    margin-bottom: 10px;
}
.header-title {
    text-align: center;
    margin-top: 0;
}
.chapter-title {
    font-size: 24px;
    margin-top: 0;
}