Evaluating the subjective playing experience and engagement in learning is important in the design of advanced learning technologies (ALTs) that respond to the learners' cognitive and emotional states. This article addresses students' attitudes toward an educational game, Heroes of Math Island, and their responses to the emotional agent, an animated monkey. Fifteen students (seven boys and eight girls) from grades six and seven participated in this quasi-experimental study (pretest, intervention, post-test, followed by post-questionnaire and interview). This research presents a detailed analysis of students' subjective reactions with respect to Heroes of Math Island and to the underlying mathematics content, their learning gains and emotions triggered during gameplay, and design issues resulting from the evaluation of the game and of its emotional agent. The findings from this study inform how ALTs and educational games can be designed in order to be effective and provide emotional engagement, enjoyment, and learning.