Chapter 6 Rules and mechanics

Rules are at the core of many games. So how about generating them? This chapter discusses various ways to encode and generate game rules, and occasionally game entities that are strongly tied to rules. The first part discusses ways of generating rules for board games, including Ludi, perhaps the most successful example of automatically generated game rules. The second part discusses some more tentative attempts to generate rules for video games, in particular 2D games with graphical logic. Most approaches to generating game rules have used search-based methods such as evolution, but there are also some solver-based approaches. 6.1 Rules of the game So far in this book, we have seen a large number of methods for generating content for existing games. If you have a game already, that means you can now generate many things for it: maps, levels, terrain, vegetation, weapons, dungeons, racing tracks. But what if you don’t already have a game, and want to generate the game itself? What would you generate, and how? At the heart of many types of games is a system of game rules. This chapter will discuss representations for game rules of different kinds, along with methods to generate them, and evaluation functions and constraints that help us judge complete games rather than just isolated content artefacts. Our main focus here will be on methods for generating interesting, fun, and/or balanced game rules. However, an important perspective that will permeate the chapter is that game rule encodings and evaluation functions can encode game design expertise and style, and thus help us understand game design. By formalising aspects of the game rules, we define a space of possible rules more precisely than could be done through writing about rules in qualitative terms; and by choosing which aspects of the rules to formalise, we define what aspects of the game are interesting to explore and introduce variation in. In this way, each game generator