html, body{
    width: 100%;
    height: 100%;
    color: #fff;
    background-color: #000;
    font-family: Arial, Helvetica, sans-serif;
    padding: 0;
    margin: 0;
}
body{
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
}
a{
    color: white;
}
a:visited{
    color: #00ff00;
}