The rules had changed, some for the better and some for the worse. There were more military units to keep track of, and even more options for city development. The gameplay and rules of the latest version are almost exactly the same as in Civilization II . The game's strengths lie in its city development. The options under your control are the food output of the city squares, the production output, and the trade output.
Every square has different outputs for the three levels.
Grasslands, for instance, give 2 food. Ocean squares give 1 food and two trades. Forest squares give two production and 1 food. Each square can also contain a special icon, which means an increase in one or more of the three types. My personal favorite is the whale, which appears on an ocean square.