After looking at several options, I think I found a way to regulate game flow. I'll be using the cck, the quiz and workflow_ng modules to change the permissions on the different nodes of content type "persoon", "object" and "gesprek". I've now managed to add an event to the quiz module as described here. The "quiz passed" event is launched when the user successfully passed a quiz. The workflow_ng module is quite powerfull, btw.
