I'd like to suggest a feature that hides the problem's topic.
If you had a problem and its topic is "Number Theory", you'll know you need to use theorems of numbers theory. If you can hide the topic, you need at first to think what and how you'll approach this problem.
I also would like to suggest that you can show what you should definitively NOT use, for instance it hides the topic and says that you shouldn't use Calculus, because you're supposed to find the area of an elementary geometry problem or find the maximum value of polonomial of an algebra problem.
I think with this somebody can more effectively train their problem solving skills.