Changes in the economy and society have led to a rethinking of the knowledge, skills, and competences that are key in the 21st century. A fundamental change has occurred in the redefinition of learning paradigms - from memorisation of facts to the acquisition of knowledge through meaningful learning through activities and problem solving. Through mathematics, we should formulate pupils' thinking in such a way that they can apply mathematical knowledge in other subjects and solve everyday problems outside the school. One of the main aims of teaching mathematics is to develop student's mathematical thinking, which can be supported by using different methodological tools. The novelty of the Poly-Universe geometric skill development game comes from the scale shift symmetry of the three basic shapes (triangle, square, circle) and the color combination system (red, blue, green and yellow). This game is universal for developing children's skills and abilities like problem solving, creativity, spatial seeing, algorithmic thinking, inductive and deductive thinking. It is also useful for increasing pupils’ motivation for learning and their creativity and innovativeness. In this paper we present selected mathematics tasks based on using the Poly-Universe game and methodological proposal for the formative assessment tools developed for them. The presented tasks are related to spatial geometry, combinatorics, physics and logical rule. Given that assessment is an essential part of the learning process, it is important that even when using non-traditional teaching methods, it is possible for the teacher to diagnose the student's learning outputs at least through formative assessment and at the same time for students to receive feedback on the achievement of the learning objectives.

Acknowledgements:
This paper includes research results gained as a part of the project KEGA no. 001UPJŠ-4/2023 "Implementation of formative assessment in primary school teaching with the focus on the digital form".

Keywords: Poly-Universe game, formative assessment, geometric skill.