The goal of this research is to implement a prototype online game learning management platform with high usability via a formative design approach. Two stages of usability evaluations, namely, cognitive walkthrough and heuristic evaluation, are applied to assess the prototype system, followed by a small-scale survey. A total of 15 suggestions are obtained; In general, the students adequately perceived the incremental functionalities on real estate transactions and the learning concepts intended by this research. As a learning game, its design earned recognitions and raised user intention to use this platform as a learning tool. The overall user satisfaction on both the game and the class management platform ranges from neutral to slightly positive, thereby implying a positive general user attitude with more expectations for improvements. With this initial formative evaluation, the outcomes provide valuable input to subsequent formative design stages, as well as a foundation for high usability, closer to actual game scenarios, and a pioneering platform for informal game learning in higher education applications.