I m building KasusKnacker, a German practice app focused on drills (not lessons).

Which topics cause you the most pain: der/die/das, cases, prepositions, conjugation, pronouns ?

I m prioritizing based on real pain points.

Many apps force you through a fixed flow of screens/levels. I personally dislike that.

KasusKnacker is designed for open practice immediately close .

Which style do you prefer and why?