Making a Feathered Fade

[hoferchr]

I'm working on this Flash project for one of our instructors, and he would like to incorporate a yin yang symbol in the animation. Is there some way I could incorporate some kind of feathered fade animation (starting at the tips of the black and white) to gradually swap the colors? It would almost be like a gradual fill effect starting from the tip going to each of the circle parts of the yin yang...if that makes any sense.

[realMakc]

make yin yang parts into masks and slide gradients below in a tween.