Game design is the act of deciding what a game should be. Decisions about rules, look and feel, timing, pacing, risk-taking, rewards, punishments, and everything else the player experiences are the responsibility of the game designer. Why 'A book of Lenses'? Jesse Schell has gathered together the best principles and rules of game design for new game designers to study, consider, make use of, and see how others have used them. He refers to these principles as lenses, because each one is a different way of viewing a design.