The study concerns a mathematical game Tandemat based on the Activity game. The research questions are: What are the benefits and limits of Tandemat for the development of pupils' mathematical knowledge? What knowledge does the game bring to the teacher? Does the game have any benefits outside the field of mathematics? A qualitative analysis of experiments with five groups of pupils has shown that the game has potential to diagnose pupils' understanding, to develop and consolidate their mathematical knowledge, and to develop some non-mathematical abilities.
Examples of the game playing are given to support results.