* { box-sizing: border-box; }
body {
    margin: 0;
    font-family: Arial, sans-serif;
    background: #f5f7fa;
    color: #222;
}
main {
    max-width: 900px;
    margin: 60px auto;
    padding: 30px;
    background: white;
    border-radius: 10px;
    box-shadow: 0 4px 20px rgba(0,0,0,.08);
}
a { color: #1769aa; }
nav { margin-bottom: 30px; }