There comes a point in working opus vermiculata that the lines start to intersect and overlap. The question becomes, which portion takes precedence, of any as they start bumping into each other. If you've done is right, the design forms some nice geometric-type shape—odd lumpy square or triangle. If you've done it like I obviously have to this point, you've gotten one area grown beyond where it should be at this point and it kind of overlaps the other side. Hopefully this will create a pleasing effect. In all events, I may be the only person who even notices the problem.