The paper describes the experiments carried out within the frame of action research. It illustrates pupils' cognitive processes in the geometrical environment Cube buildings.
The tool of the experiment is a geometrical problem involving 3D shapes and their 2D representations and also combinatorics. The strategy that a pupil developed to solve the problem is introduced and its impact on solving strategies of other solvers is described.
The generalization the pupil's strategy to more difficult situations is discussed.