IIRC, there is logic that is done server side, but it is more of a basic simulation of the cities in the same region you are currently in, but are not currently

IIRC, there is logic that is done server side, but it is more of a basic simulation of the cities in the same region you are currently in, but are not currently managing. For obvious reasons, the entire simulation couldn't be done server side. I've gotten numerous "trying to reconnect" messages and the game happily continues until it does reconnect to their servers.