About the Author Ernest Adams is an American game design consultant and trainer currently work- ing in England with the International Hobo game design group. In addition to his consulting work, he gives game design workshops and is a popular speaker at con- ferences and on college campuses. He has worked in the interactive entertainment industry since 1989, and he founded the International Game Developers' Association in 1994. He was most recently employed as a lead designer at Bullfrog Productions, and for several years before that he was the audio/video producer on the Madden NFL line of football games at Electronic Arts. In his early career, he was a software engineer, and he has developed online, computer, and console games for machines from the IBM 360 mainframe to the present day. He is the author of three other books and the "Designer's Notebook" series of columns on the Gamasutra developers' webzine. His professional web site is at www.designersnotebook.com. About the Technical Editor Christopher Weaver founded Bethesda Softworks, the software entertainment com- pany credited with the development of physics-based sports sims, including the original John Madden Football for Electronic Arts, as well as the Elder Scrolls role- playing series. A former member of the Architecture Machine Group and Fellow of the MIT Communications and Policy Program, he is currently a Board Member of the Communications Technology Roadmap and Visiting Scientist in MIT's Microphotonics Center. Weaver is CEO of Media Technology, Ltd. and teaches part time in the Comparative Media Studies Program at MIT. In 2005, he was inducted into the Cosmos Club for Excellence in Engineering.