Look take the 2 shapes below and add them in for a footwork matrix !? Good stuff eh.
Look there is no north south line. One of the things I regret is learnining to step forwards and backwards in a line mechanically. No doubt it has its place but the 'V' and '^' angles of stepping are really useful and worth in-graining early on in someone. Backwards steps are a bad habit to rely on to get out of 100% pressure. In a confrontation in public if someone is blocking your path a step diagonally forward or away would move you around - or away - from their colleague who may be behind you unbeknown to you.
The is a place for forwards and backwards lines but maybe their practice should not be moving me away from these other angles.