A parameter sweep altering light pulse time can be configured using the ISSF editor. Results of a parameter sweep of the step function’s phase parameter for the Leloup Neurospora model (Leloup et al., 1999), reproducing Figure 5 of Leloup et al. (1999). A pulse of light early in the cycle (gray trace, pulse at 260 h, filled arrow) causes phase advance relative to a no–light pulse control (magenta trace), while a pulse of light at 264 h, when the frq level is maximal, causes phase delay (black trace, pulse at 264 h, open arrow). Light pulses when frq levels are declining do not alter the phase. For the step function controlling the main cycles, 10 cycles of LD (Θ0 = 1.6, Θ1 = 0.4, TC = 24 h, TP = 12 h, T = 0.1 h, and ϕ = 0 h) were followed by constant dark (Θ1 = 0); for the pulse, Θ0 = 0, Θ1 = 0.4, TC = 360 h, TP = 12 h, T = 0.1 h, and ϕ = 0 h, with ϕ ranging from −260 to −276.