Smartphone-based mobile AR solves challenges that past AR systems had, including inconvenience of head-mounted displays and computer backpacks as well as requirement of external data processing infrastructure. We described two versions of Calory Battle AR exergame that utilizes mobile AR as a means of visualization and interaction. In Calory Battle AR, the player’s role is to find and defuse virtual calory bombs in a real world environment. First prototype of the game was created without a third party rendering or game engine. This led to many challenges related to 3D data processing and presentation. To solve these challenges, we designed a new version of game with the Unity3D game engine. The game development process was significantly faster and required far less programming than the first prototype development. Usability evaluation indicated that the Unity version outperformed the first prototype especially in aspects of interaction with AR content and user interface clarity. One of aspect that improved user experience is virtual buttons. They made it possible for players to have more realistic interaction by using their fingers directly. Graphical expression was also enhanced by using Unity’s built-in shaders.