In-Game Problems as Advertisement Locks
An AdLock ("Advertisement Lock") would be a fun game element, supported by most 3D-Game Engines, that locks the gamer from moving through a path, if it is not unlocked. An AdLock allows game developers to easily add various problems into a variety of existing games, without having to think of the problems themselves. An AdLock automatically chooses the best problems, just like AdWords with Google Display Networks on a web-page automatically chooses the best ads to show based on context.
Examples of an AdLock:
-- a virtual Rubik's cube -- a door with a question, and an entry field.
This would allow schools and universities to add homework problems and some more complex problems as barriers in the games that their students like to play. For companies, it would allow to include R&D questions.