I think it is excellent as well—that it also demonstrates aperture and shutter priority is a bonus.

I do feel (image nerding now) that its shutter/ISO visual for showing the image over/under-exposed is not quite correct. It appears they show incorrect exposure by taking the "correct" image and blend (multiply) with either white or blend with black (on the other end of the exposure spectrum) to produce the resulting image.

I suppose I am expecting something more like "levels" that pushes all the pixels to white (or black) until they are forced to clip. (But maybe I am too trained in photo-editing tools and expect the film to behave in the same way.)