In 1961 François Jacob and Jacques Monod worked out how E. coli decides whether to digest lactose: a repressor sits on the operator and silences the genes until an inducer derived from lactose pulls it off. It was the first gene-regulatory circuit ever mapped.
The twist is a positive feedback loop. One of the genes builds permease, the pump that imports lactose. More permease means more inducer inside, which frees more promoter, which builds still more permease. Below a threshold the loop can't catch; above it, it latches. Because an already-lit cell keeps its own inducer flooding in, the operon stays ON well below the level that first tripped it — a bistable switch with memory (hysteresis).
Glucose overrules everything through an AND gate: the promoter also needs cAMP-CAP, and glucose strips cAMP away. So the circuit fires only when lactose is present and glucose is scarce — the founding example of a cell computing a logic function on its inputs.
The simulation stopped unexpectedly — the lesson continues without it. You can move on; nothing you did was wrong.