Advances are scientific, economic, social, or any other type of general accomplishment. They can enable the construction of particular types of units.
No more than 126 types of advances may be defined.
advance-type symbol properties...
This form defines a new type of advance, named by symbol. Details are similar to those for unit types.
This variable evaluates to a list of all advance types, listed in the same order as they were defined.
This variable has a value that is never an advance type.
This property is the number of research points necessary to achieve the
advance. Defaults to