This document discusses level design for computer games. It covers the nature of level design, including the space, initial conditions, challenges, and aesthetics. It also discusses universal level design principles such as tutorial levels, varying progression, rewarding players, and punishing less. Genre-specific principles for different game types are also outlined. Common level layouts including linear, parallel, ring, network, hub-and-spoke, and combined are defined. Finally, the level design process from planning to testing is summarized.