Share solution with something new

The instructions are:

Share a new solution but with using specific function or keyword Less... You haven’t used one element of the language yet, so in this quest you must try it out! Choose a suitable mission (even from the already solved ones), then create and publish a solution in which this keyword or function will be applied.

I have tried several times to share solutions, last time I picked capitalize() off the list of unused functions but the quest is still unsolved.

What am I doing wrong?