Advances in technology have led to continuous innovation in teaching and learning methods. For instance, the use of tablet PCs (TPCs) in classroom instruction has been shown to be effective in attracting and motivating students' interest and increasing their desire to participate in learning activities. In this paper, we used a TPCs game--an iPad app called "Motion Math: Hungry Fish"--to help young students learn to theoretically understand and practically implement the mathematical concepts of addition and subtraction. Based on findings from a pilot study, we categorized the game's 18 levels of difficulty into "challenging" (experimental group) and "matching" (control group) games. We aimed to investigate whether challenging games were more able than matching games to improve the students' motivation, flow experience, self-efficacy for technology, self-efficacy for science, feelings about the TPC game, and satisfaction with the learning approach. The findings showed that the students in the experimental group achieved better flow experience, learning performance, and satisfaction.