Abstract
End-User Development (EUD) is a topic that finds application in varied domains but so far it has only been marginally considered in digital games research. However, there are several games that would benefit from a EUD approach, in particular for those games designed for a purpose other than entertainment, such as learning or training. These processes are permeated by large individual variation; as a consequence, the teacher must have a control over the game to use it like any other educational resource. In this chapter we present the state of the art in research on EUD for serious games from academic and industrial perspectives. We discuss a case study investigating the design process and evaluation of the Actors' Programming Environment (APE), a EUD tool for modelling the behaviour of Non-Player Characters (NPCs). Starting from the literature review and empirical experience gathered over a time span of two years, the chapter provides a set of guidelines for the design of EUD tools for serious games, reflecting on their importance and complexity. It concludes with a set of heuristics that may advance research in the topic.