https://toggles.oddbird.net/
CSS Toggles demo
css togglesdemo
https://lists.wikimedia.org/hyperkitty/list/wikitech-l@lists.wikimedia.org/thread/D4X4TLYXFQ5UQ25WVBALZZ5J7HIOXVPM/
Cookie-based CSS toggles for logged-out readers? - Wikitech-l - lists.wikimedia.org