.back{
    position: fixed;
    bottom: 10px;
    left: 10px;
    z-index: 99999;
    font-size: 2.5em;
    background-color: white;
    padding: 10px;
}

a {
    color:deeppink;
}

a:hover{
    color: aquamarine;
}

@media (prefers-color-scheme: dark) {
    body, .back{
        background-color: black;
    }
}