The common folder contains some text files, and three sub-folders with more text files. This is where we define the foundation of what we see ingame, and what we can modify the settings of. Here we can e.g. add a religion or a government type, add or modify a building type or change the types and effects of trade goods. In the subfolders we find some static information about each country defined in the game - like map colour on the political map, type of graphic representation (sprites) and historic information used to give historic colour to each country in a dynamic, generated reality - technologies and unit types. We will look much deeper into this below.