Taking advantage of our digital era commodities, a plethora of game-based learning activities and educational game genres have been introduced into numerous academic disciplines. However, research has shown that regarding mathematics the variety seems limited; especially for higher level topics, e.g. calculus, there is a lack of immersive games (Anagnostopoulou, 2021). In search of innovative ways for learning mathematics, this study presents an investigation into the use of the immersive features of role-playing games (RPGs) to introduce higher level mathematics to adult learners. As part of a PhD research, an RPG was designed and developed, in such a way that the abstract patterns and structures of mathematics were gradually introduced and intrinsically incorporated into six RPG mechanisms. An experiment was then carried out to examine whether learners can be enabled to gain higher mathematics skills solely by playing the game. Adult learners with a variety of mathematical background knowledge and gaming experience were recruited. The participants were asked to a) complete a pre-questionnaire and test, b) play the game, and finally c) complete a post-questionnaire and test. Data were collected via the questionnaires, observations, and interviews. The experiment yielded positive results regarding game usability, functionality, and effectiveness. This paper reports only on the quantitative analysis from the questionnaire data, whereas the qualitative analysis was published in a separate paper (Anagnostopoulou, 2023). The quantitative results suggest learning and understanding of mathematical processes concerning basic differentiation rules was significantly increased by playing the game. There was a statistically significant increase in mathematics scores after playing the game. The effect size was large for users with low to medium mathematical background skills, whilst the effect on those with high mathematical skills was small. Recommendations for future improvements as well as avenues for further research are proposed.