From publisher blurb:
Although originally part of the Center Space Basic Rules, in a effort to revise and simplify, a GM Supplement has been created as a seperate pdf. This pdf has been revised and expanded from the information given in the previous version of Center Space 2nd Edition, and contains everything a GM needs to start playing Center Space, including:
Creatures: Including the horrid living constructions of the Thahazi.
Descriptions of the various worlds of the Center Space Universe; icluding a detailed description of Post-Occupation Earth.
Alien artifacts of the Thahazi and Old Alliance.
The Prophecy: an Introductory adventure to the Center Space world.
Nim Traveling: rules for telepathic interface with computer networks.