Born in the recent past in school playgrounds and now a national sport, Nzango is a female-only game. The aim is to imitate, or more mysteriously, anticipate, the leg movements of the facing player. The pace is set by both teams singing and clapping in unison, faster and faster. Local variants thrive, ignoring the official rules. This, the girls’ own invention, involves “minus” and “times” signs, the first a mirror image – A’s right leg, B’s left leg – the second a crossed diagonal. And yet all the outsider perceives is a series of lightning confrontations, as pairs, then other formations, hop and kick ecstatically, advance and retreat according to an inapprehensible logic, telepathically improvised, perhaps. What geometry rules the final blur of legs?