Domain Analysis (DA) plays an important role in Model Driven Development (MDD) and Domain-Specific Modeling (DSM). However, most formal DA methods are heavy weight and not practical sometimes. For instance, when computer games are developed, the problem domain (game design) is decided gradually within numerous iterations. It is not practical to fit a heavy-weight DA in such an agile process. In this research, we propose a light-weight DA which can be embedded in the original game development process. The DA process is based on a game ontology which serves for both game design and domain analysis. In this paper, we introduce the ontology and demonstrate how to use it in the domain analysis process. We discuss the quality and evaluate the ontology with a user acceptance survey. The test result shows that most potential users considered the ontology useful and easy to use.