The sixteen.

Each creature is four genes. The crown of spines is its ask band: one spine per cell of width, lifted off the body when its gap gene is set. The fringe below is its bid band. A creature is scored on its own turns only; its score is its fitness summed over its turns, divided by its turns plus six, so a newcomer counts as average until it has a record. A genome is written A10 / B6g: an ask 10 cells wide, a bid 6 cells wide, and a g where a band keeps one cell away from the price. A cell is 400 ticks, about 4% of price.