:state()The :state() CSS pseudo-class matches custom elements based on their custom state, set through the ElementInternals.states API.custom-elementsCustom elementsnewly2024-05-17https://html.spec.whatwg.org/multipage/custom-elements.html#custom-state-pseudo-classhttps://developer.mozilla.org/docs/Web/API/CustomStateSetapi.CustomStateSetapi.CustomStateSet.@@iteratorapi.CustomStateSet.addapi.CustomStateSet.clearapi.CustomStateSet.deleteapi.CustomStateSet.entriesapi.CustomStateSet.forEachapi.CustomStateSet.hasapi.CustomStateSet.keysapi.CustomStateSet.sizeapi.CustomStateSet.valuesapi.ElementInternals.statescss.selectors.statehttps://nowyoucanuse.com/features--state.html