I don’t know about mathematical, but I’ve always thought of it as a vertical vs horizontal motion with the front foot used as as kind of rotation axis for an impossible…
Yeah for sure, the way the foot wraps with the board is the visual cue. It has led me and friends to some fun debates in a game of skate i.e. "that wasn't an impossible", so I was hoping to be able to point to some ridiculous mathematical definition the next time it comes up.