figure > img {
    height: 300px;  /* resize figures so they aren't too big */
}

@media (prefers-color-scheme: dark) {
    body:not([data-theme="light"]) figure > img {  /* auto and dark is dark mode */
        filter: invert(92%);
    }
}

@media (prefers-color-scheme: light) {
    body[data-theme="dark"] figure > img {  /* auto and light is light mode */
        filter: invert(92%);
    }
}