body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 20px;
}
header {
    background-color: #333;
    color: white;
    padding: 1rem;
    text-align: center;
}
main {
    max-width: 800px;
    margin: 0 auto;
    padding: 20px;
}