Any ideas on how to implement a strategic resource based on a civ advance dependent process? For example, bronze, requires copper & tin resources and the kiln smelting civ advance. I should then be able to trade bronze as a strategic resource with other civs and bronze should be the required resource. Also, an either / or resource dependency would be desireable also. For example, units requiring iron can be build if either iron ore or bog iron is available. Can I create another resource having the identical name, i.e., 'iron', and if either (or both) sources of 'iron' are available I can build units that require iron? That'd be great if that works in that both resources could be dependent upon different civ advances, be located in different terrain types and have differing disappearance probability values.