I'm a little fuzzy on how planetary tiles work since I have not had a chance to play the game yet. When you build something on a tile, does it act like a single building which is finite in it's value, or does it act like the DEAs in MOO3, where you can add to it to increase it's overall value? For example, (using terminology from MOO series as I haven't played GC at all) do you build automated factories on one tile, and robotic fatories on another, or do you build an Industry tile, and add automated and robotic components?