A prototype which you learned what not wanted users. See this article about experimentation as an approach for changing Tjepkema geniux (2010). And read more about prototyping as a way for instructional design (Naveen, 1999). For the tough questions that occupy you, try to find "all vooruitstruikelend" solutions? The question was asked me at the beginning of the lecture encouraged me to detect a "big mistake". My brains blocked because I could not find the right drawer. With me is the description.