Measuring and providing efficiency of educational applications is a serious, open problem, which impacts the future of this expanding industry greatly. Reaching player engagement is a complex challenge, as it also depends on the given task and the mental state of the player. Researches answer this by using adaptive educational games. To reach the goal, however, knowledge about more parameters is required about the game tasks, the abilities of the player, his actual physiological state and performance as well. In this paper we present our results, which use a biofeedback based adaptive algorithm, and based on this, an innovative psychometric model to take a step towards maximizing user engagement.