A Theory of Fun for Game Design is a book written and illustrated by Raph Koster. It is based upon a presentation Koster gave at the Austin Game Conference in 2003, and the book reflects its origins by displaying text on one page and a cartoon/graphic from the talk on the other page. This means that the book is 50% cartoons, which some people complain makes the book rather low on content, while others find this makes the book "fun".