McLuhan described the possibilities of man to expand the world by means of media: Parts of the human body may be amputated and replaced with extensions like wheels, cameras or permanent clothing. The most radical extensions so far are games which manage to work practically self-sufficiently: (Game-) Worlds which may remind us of Dr. Daniel Schreber's "Aufzeichnungen eines Nervenkranken" (Recordings of a nerve patient). But what is it we neglect to see or displace in those media systems? How can we render those magic borders visible which surround each game and medium, how can we capture their rules and make them even playable?