Cones (fovea cluster)
Rods (periphery)
After a bright flash bleaches your visual pigment, your eyes take many minutes to recover full night vision — and they do it in two distinct stages. This simulator models the photochemistry directly: a bleaching flash sets an initial bleached fraction in both rod and cone photopigment, each pool regenerates on its own numerically-integrated exponential-recovery ODE, and Rushton's photochemical relation converts remaining bleach into a threshold-elevation curve for each system. Because cones regenerate fast but have a small sensitivity range while rods regenerate slowly but reach far greater sensitivity, the overall visible threshold follows the lower of the two curves — producing the classic biphasic dark-adaptation curve with its "rod-cone break". A 2D patch of cone- and rod-shaped photoreceptor dots brightens on the flash and visibly dims back to baseline as pigment regenerates, alongside a live-plotted sensitivity graph, a bisection-found analytic crossover marker, and readouts for elapsed dark time, threshold elevation, dominant system and the measured break time.