Population-based simulation. Sequential observation of a simulated growing population. The surface on which the cells are growing in contains the inputs with both inputs present in the left half (input logic “1”, established at 1.5 nM for this simulation, as before) and neither input present in the right half (input logic “0”, fixed at 0.0 nM, as before). The output Out is represented as if it were a green fluorescent protein: high expression corresponds to a bright green colour of the cells. The high mobility of cells after 50 and 95 hours (due to there being plenty of free space available) lets us see the graphical pattern produced by the predictive behaviour of the circuit. When the population is very crowded (after 180 hours) the behaviour of the circuit is directly proportional to the surface features. Red circled region: wrong predictions being resolved by changing the direction of the switch. Generation time of cells = 12h.