Template:If dark/styles.css - Wikipedia

/* this should be the fallback */
html:not(.skin-theme-clientpref-night) .ifdark > .dark {
    display: none;
}

html.skin-theme-clientpref-night .ifdark > .nodark {
    display: none;
}

@media screen and (prefers-color-scheme: dark) {
	html.skin-theme-clientpref-os .ifdark > .nodark {
	    display: none;
	}
}

@media screen and (prefers-color-scheme: light) {
	html.skin-theme-clientpref-os .ifdark > .dark {
	    display: none !important;
	}
}