body {
    background-color: black;
    color: white;
    font-family: monospace;
}
header {
    text-align: center;
    font-size: 16pt;
}
a.nav {
    color: white;
    text-decoration: none;
}
a.nav:hover {
    background-color: white;
    color: black;
    cursor: pointer;
}
a.nav.active::before {
    content: "■ ";
}