equations, balance scales, didactic e-application, isolated models, generalization, generic model, constructivism

We are currently collaborating on the development of a didactic application by EDIacademy, in which we guarantee the mathematical and didactic content. The application will consist of key environments for teaching mathematics at primary schools, in order to cover complete mathematics curriculum. Individual environments are created according to the textbooks and other study materials by professor Milan Hejný and his team, which are currently used to teach mathematics at roughly a quarter of Czech schools. This constitutes the first comprehensive teaching system of mathematics in the Czech Republic, which consistently makes use of a constructivist teaching style. The application will supplement the printed teaching materials of this series.The first completed environment of the e-application is Scales (balance scales). This environment was tested at the end of school year 2015/16 with second grade primary school pupils. Each pupil worked individually with the experimenter. After a structured interview concerning computer literacy, the pupil independently spent 20 minutes with the application, allowed to solve any available exercises. The interview was recorded on a camera, the work with the application was recorded by an external camera (face and hands) together with an internal camera (cursor movement on the screen) - we used Screencast-O-Matic. In this paper, we introduce the mathematical and didactic content of the e-application, focusing particularly on 1) the large potential of series of individual exercises leading to transition from an isolated model to generic model, 2) individualization of the difficulty level of exercises. We summarize the results of the test analysis with focus on selected parameters.