body {
    margin: 0;
    font-family: "Segoe UI", "Microsoft YaHei", Arial, sans-serif;
    color: #222;
    background: #f7f7f7;
}

main {
    max-width: 900px;
    margin: 80px auto;
    padding: 40px;
    background: white;
}

h1 {
    font-size: 42px;
    margin-bottom: 5px;
}

h2 {
    font-weight: normal;
    color: #555;
}

h3 {
    margin-top: 40px;
}

p {
    line-height: 1.8;
    font-size: 17px;
}