Norska comes with the .if and the .then_* classes,
allowing to change the display of an element if a specific checkbox/radio
button is checked.
This can be used to simulate the opening of a menu without needing JavaScript, as can be seen on this very website.
Note that it requires the .if element to either be a direct
sibling or the sibling of one of the .then_* element(s) parents. When in
doubt, place the .if element at the root of your body and
trigger its checking through a linked label