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As you'd imagine, a lot of challenges come into such a task. You must locate cities so as to make use of food, construction and trade resources, which can be later improved by constructing irrigation, roads, mines, railroads, and farmland. Each city can construct one item at a time - civilian and military units, buildings or Wonders of the World (there are 28 of these across the different eras of the game, and each can be possessed by only one city). The buildings and wonders have different effects - most buildings and some wonders improve defenses, scientific research, trade or food output, but most wonders offer unique advantages that can be used to great strategic effect.

Combat can occur in cities or in the open terrain - things like forests and mountains give the defense an advantage. Unlike in other games, fights aren't always won outright - most times the winning unit will be damaged, reducing its movement speed and attacking prowess until it's repaired, but the losing unit always disappears from game. If multiple units are in a square that comes under attack, the strongest unit fights - unless it is a city or Fortress, all units will be lost if the fight is lost. Once a city has no defensive units left, it can be captured. Certain units have the ability to cover all squares as fast as if they were roads, only a few can see submarines, and air units require re-fueling in a friendly city.