A computer-vision-based method is widely employed to support the development of a variety of applications. In this vein, this study uses a computer-vision-based method to develop a playful learning system, which is a robot-based learning companion named RobotTell. Unlike existing playful learning systems, a user-centered design (UCD) approach is applied to assess the interface design of the RobotTell System so that the human-robot interaction can be enhanced during the design process. More specifically, the interface of the RobotTell system is assessed based on Nielsen's heuristics. Based on the results of Nielsen's heuristic evaluation, three versions of the RobotTell system were produced. The implications for the design of these three versions of the RobotTell system are discussed.