body {

    font-family:
        Arial,
        "Microsoft YaHei",
        sans-serif;

    margin: 0;

    background: #f5f5f5;

    color: #333;

}


header {

    background: #222;

    color: white;

    padding: 20px;

}


nav a {

    color: white;

    text-decoration: none;

    margin-right: 20px;

}


.container {

    width: 900px;

    margin: 40px auto;

    background: white;

    padding: 40px;

}


footer {

    text-align: center;

    padding: 30px;

    color: #777;

}

button {
    padding: 10px 20px;
    font-size: 16px;
    cursor: pointer;
}

#result {
    margin-top: 20px;
    padding: 15px;
    border: 1px solid #ccc;
    border-radius: 8px;
    min-height: 80px;
    background: #f9f9f9;
}