How to make a spherical robot, with three degrees of freedom, tumble in a straight line due to center of gravity displacement?

To continue are State Machine discussion…

GOAL: Goal objective exists? (Move!)NAV: Navigation objective exists? (Forward!)SYS: System objective exists and is amenable to bot movement? (Plenty of battery!)OO: Orientation objective exists?Current OO?Roll X:Forward 1 revolution.

In order to accomplish this…

Current BO: Bot orientation (where we are now, angle ...