Data

Should be in some format (e.g. CSV) that is accessible by spreadsheet applications to facilitate easy editing of data, copying/pasting and data generation through calculations (e.g. you may wish a tank to be twice as fast as infantry, but you can just tweak the infantry speed and the tank speed automatically adjusts [obviously any spreadsheet with calculations would need to be maintain separately from the data file and the data would need to be exported each time after editing {unless a format such as open office calc is used}]).