body {
    background-color: #000;
    color: #fff;
    font-family: Arial, sans-serif;
}
header {
    background-color: #111;
    padding: 10px;
}
nav a {
    color: #fff;
    margin: 0 10px;
    text-decoration: none;
}
nav a:hover {
    text-decoration: underline;
}
.categories a {
    display: block;
    margin: 10px 0;
    color: #fff;
}