Despite their strong potential, most learning games are found to be poorly designed, ineffective in enhancing learning, and not grounded in theory. Studying the effects of different instructional features on learning is a key area of game-based learning research. In this regard, “narrative” as an instructional feature in games can potentially enhance learning by situating mathematical problem solving in context but there is little evidence to support this. This project focuses on creating a theory-based digital game aimed at enhancing adolescents’ understanding of geometry. The Van Hiele Model of Geometry Learning  (Hiele, 1999) and the Learning Mechanic - Game Mechanic Framework (Arnab et al., 2015) are applied to design a game for building adolescents' understanding of geometry. Two versions of the game are created, one with "narrative" feature and one without it. Using a multi-group, experimental design, we study the impact and effectiveness of “narrative” feature in games on geometry acquisition. Learning is evaluated based on the performance of participants in a standardized knowledge test and through log-file data collected during gameplay.