Ever struggled to explain what it means to consider extra dimensions? We all used once or other the idea that we can´t visualise the fourth dimension but just imagine that 3D shapes could be considered shadows of four dimensional figures, just as (our regular) 2D shadows are of three dimensional objects. We also have probably seen the faces of the audience as a reaction to this, ranging from nonplussed to nodding faces, but always with the feeling that the explanation didn´t really stick.
This app is a great example of how to use the interactive potential of this medium to explain complex concepts in a hands-on way and in a manner that allows users to tailor the time spent on each step to their own pace.
The app is available from http://fourthdimensionapp.com/