This is a scheme with n difficulty levels, starting from 1 ( in particular, we will use n = 3 ).
The user is initially having questions from category 1.
After he correctly responds to a certain number of questions over a certain period of time, he will be automatically switched to the next category.

So there will be actually 3 separate game sessions types, one for each category. Players from one category will interract only with the players in that current category.

Possible questions:

  • what if the user is alone in his category and everyone else is playing on others categories?
  • what if an user wants to switch his category ?
  • if he can, the game will be easy for him, he will accumulate points and frustrate other players

Maybe this information can be something the user can be proud of ( while his friends are still level 1, he is level 2, so this is kind of some achievement thing ).