What's new
Materials
Five strategic materials lie in the land's special tiles: iron in the mountains, coal or copper in the hills, oil or salt in the desert, oil in the wetland.
You hold a material when one of your cities works its tile, or when you keep a camp on it. Camps can be built anywhere, far outside your borders, and a rival's camp changes hands when your unit stands on it.
Without the material, anything that needs it costs half again as much. Copper gates the bronze age and the wire age, from the Phalanx to the Neural Lab; coal gates the Factory; oil gates armour, aircraft and the modern navy. Salt feeds the Granary, and holding it calms one citizen in every city you own.
The rivals know this too, and they send settlers to camp the deposits they lack. See Strategic Resources.