[Challenge] Urban Growth simulation

I've been thinking about a sketch lately but it's way out of my league right now, since I'm only just starting with programming. Maybe you would find it interesting. I'm trying to think of a simulation for "spontaneous"/ "organic" human settlements, like we'd see in Medieval cities or modern-day slums. I think this would make for a cool subject to tackle with an agent-based model. I've got some material on Brazilian favelas if you're interested.