A couple of weeks ago on the Training forum, a few posters made the argument that Hsing-i Chuan was a linear art. I and several others pointed out that although it looks linear, internally, there are quite a few spirals and twistings happening that aren't apparent in the solo forms.
They responded with the opinion that what made Hsing-i linear was the "fact" that stepping patterns "went in a straight line." I put those assumptions in quotes because that's true of only about a third of the footwork when you include the 12 animals.
Anyhow, for the interested, here is a clip of a basic Hsing-i drill using the most "linear" techniques in Hsing-i.
http://www.youtube.com/watch?v=Rc89q6urFwI
Perhaps you'll be interested to observe how the tiny twisting and spiralling movements on an internal level can produce big obvious circles when you put another person into the mix.