Bartle actually expands on this paradigm in the book Designing Virtual Worlds, where he introduces another axis for the four types (bringing it to eight) and also specifies two progressions between the types as players grow.
http://www.amazon.com/Designing-Virtual-Worlds-Richard-Bartl...
Bartle actually expands on this paradigm in the book Designing Virtual Worlds, where he introduces another axis for the four types (bringing it to eight) and also specifies two progressions between the types as players grow.
http://www.amazon.com/Designing-Virtual-Worlds-Richard-Bartl...