Terrain types are associated with the cells, borders, connections, and coatings in a world.
Form: terrain-type
name properties...
This form defines a new type of terrain, named by name. Details are similar to those for unit types.
GlobalVariable: t*
This variable evaluates to a list of all terrain types, listed in the order that they were defined.
GlobalVariable: non-terrain
This variable has a value that is guaranteed not to be a terrain type.