In our attempt to support Object-Oriented Programming (OOP) learning for beginners, we designed a novel microworld called PrOgO. It is based on a three-dimensional (3D) constructive game metaphor for describing OOP basic concepts and their implementation. In this paper, we describe a study about the use of PrOgO by beginners to investigate their behaviours when interacting with the programming microworld. The study is based on the collection, analysis and reporting of data about players (playing analytics). The data analysis allows the identification and the characterisation of different behaviours. From an educational perspective, the expected behaviour has been confirmed for a limited number of students. This enabled us to conclude that the design of the game needs to be improved. In addition, behaviours triggered by most students might have other educational values, which could be confirmed by other similar studies.