Hi I'm trying to make a mod that allows cities connected by trade route or just roads to exchange population. So in the case of two cities A and B which share a trade route or road. I was thinking something like City A: tourism/City B: culture is the percent chance every turn that a citizen from City B goes to City A. I was thinking to make this mod I need kind_route, PSEUDOYIELD_CITY_POPULATION, YIELD_CULTURE, and PSEUDOYIELD_TOURISM. I really have no clue from here how to start this mod. Any help would be appreciated.