body {
    background-color: #F1F1F1;
    color: #333333;
}
div {
    border: 1px solid #000;
    width: 75%;
    margin: 0px auto;
    padding:0px 10px;
}
@media (prefers-color-scheme: dark) {
    body {
        background-color: #121212;
        color: #e3e3e3;
    }
    div {
        border-color: #353535;
    }
}
@media (prefers-color-scheme: light) {
    body {
        background-color: #F1F1F1;
        color: #333333;
    }
    div {
        border-color: #a1a1a1;
    }
}