The Perfect Dark RPG uses a modified version of the RPG rules used in the James Bond 007 RPG from the early 80's. The rules have been modified to move the game along quicker, ignore things that don't pertain to the Perfect Dark universe, and to add elements that were not in the original rules set. If you are at all interested in The Perfect Dark RPG I would suggest you purchase the 007 RPG also (Which is out of print though some places still carry it.)