The areas of Science, Technology, Engineering and Mathematics (STEM) careers, are important areas of knowledge for contemporary society. Among the basics subjects of these careers is Mathematics, but many young students present difficulty to understand basic mathematical concepts. This learning process is complex and demands a lot of motivation by part of the students. In this sense, educational games can act as a stimulating helping tool for them. In Brazil, the levels of proficiency on rational numbers in their fractional representation presented by students aged between 9 and 12 years, in general, are low. We present such a game, called Fracpotion, developed as an Open Educational Resource to teach about fractions to children guided by Didactic Situation theory. This game has been tested by a group of students in an elementary school at São Paulo city, Brazil, and the preliminary results were positive.