You can argue that all of the city-building games now popular on Facebook descend from Will Wright's SimCity, but none of them resemble that game quite as strongly as CityZen does. CityZen incorporates classic SimCity play mechanics like disasters and keeping your townsfolk happy by carefully arranging roads and public amenities. Where other city-builders might have you level up by attracting citizens, CityZen progresses in a more SimCity-like manner. You level up simply by making your city bigger and bigger, keeping your citizens as happy as you can.