vail/static/dark.css

@media (prefers-color-scheme: dark) {
    html {
        background-color: black;
        color: white;
    }

    .box {
        color: #eee; /* Make this darker to make the on-screen lighter. I don't know why. */
    }

    .button.is-primary {
        background-color: #096;
    }

    input[type=range] {
        accent-color: #096;
    }
}