This text provides a comprehensive treatment of virtual world design from one of its pioneers. It spans the literary, economic, sociological, psychological, physical, technological and ethical underpinnings of design, while providing the reader with a deep, well-grounded understanding of VW design principles. It covers everything from MUDs to MOOs to MMORPGs, from text-based to graphical VWs. It brings a rich, well-developed approach to the design concepts behind virtual worlds. It is grounded in the earliest approaches to such designs, but the examples discussed in the book run the gamut from the earliest MUDs to the present-day MMORPG games mentioned above. It teaches the reader the actual, underlying design principles that many designers do not understand when they borrow or build from previous games.