Most modern graphics-based computer games entertain the player in part by presenting him or her with a simulated space, an imaginary two- or threedimensional region whose visual appearance is mapped onto the twodimensional surface of the video screen. The player observes this space and sometimes virtually explores or moves through it in the course of playing the game. As an imaginary space, it is necessarily constructed by human beings, and therefore may be thought of as the product of architectural design processes. In this paper I discuss the psychosensory limitations of perceiving ludic space compared with real-world architectural space, and the primary and secondary functions of ludic space. The primary function is to support the gameplay by providing a context for challenges, and I discuss how this occurs; secondarily, the space informs and entertains in its own right by a variety of means: Familiarity, Allusion, Novelty, Atmosphere, and others, which I illustrate by example. Key...