This is an excellent article in its own right, but I want to add: this is one of the very few grand strategy games I've played where you can keenly feel the difference between "I have the theoretical knowledge to build a thing," "I have the resources and industrial capacity to build the thing," and "I have the logistical network to support the thing in meaningful numbers." In one game, faced with a dwindling rare earth metal supply, I had to downgrade my tank designs to heavier and less efficient steel armor to ensure I could keep expanding my solar farms, which were my only source of power. In another, I tried to siege an enemy city with heavy artillery in the early game, only to find that I had neither the supply trucks nor the munitions factories to fire them more than once every five or six turns.