however, now my imagination is now running, and thinking about how overkill "true" random might be for this application. something "random" like an orbital sander would probably be enough. you're just trying to get away from side-to-side, left-circle, right-circle, up/down patterns. you're doing this to 3 different surfaces, so they would grind out any slight patterns which is the point. seems like a try crypto random would be as "effecient" as my roomba appears not to be.