Here is an interesting article on how embusen were designed in Southern China. There is a progression from square angles to flanking and then turns to eight directions and corners, signified by the kanji for ten 十, wood 木 and rice 米.
That system isn't perfect. It leaves out the common pattern for work 工, for example. (Which is functionally equivalent to the first.)
I find the system helpful for classifying a kata's content concerning footwork by and large. Which I find particularly interesting anyway.