### Source Peer feedback, collected in #167. Quote (translated): it would be nice to gray out the options that lead to an empty result, for example difficulty H. ### Problem A visitor can choose a filter combination that gives no results (for example a difficulty that the chosen apparatus does not have) and only finds out after the search. ### What to do - [ ] Decide how to know which choices are empty. Either from the structure that is already fetched (which difficulties and groups exist for an apparatus), or with counts from the API. Prefer the structure if it is enough, because it needs no extra request. - [ ] Show an empty choice as disabled, with the reason available to a screen reader (as the difficulty sort already does with its reason), and not by color alone (WCAG 1.4.1). - [ ] Test the filter menus with the keyboard and a screen reader name. ### Done when - [ ] A choice that can give no result is shown as unavailable and says why. _Comment made with Claude Code in discussion with Ronja_