I noticed that the mouseover effect of expanding and contracting was not happening with the arc gauge. I thought it was working before, and I don't know if it was taken out on purpose of left out during the refactoring of the arc portion of the code. Here is a fix that goes with the current code.

Update c3.js, getInterporate being used to fill interpolate value. ...porate vs ...polate

Shouldn't getInterporate be getInterpolate to match what it is being used for?

Added chart_arc_gauge.html as a sample/demo of functionality. Added c3.update function to update configurations in the demo.