In the last decade, more and more games have been developed for handheld devices. Furthermore, the popularity of handheld devices and increase of wireless computing can be taken advantage of to provide students with more learning opportunities. Games also could bring promising benefits--specifically, motivating students to learn/play, sustaining their interest, reflecting their learning/playing status, and facilitating the learning/playing progress. However, most of these have been designed for entertainment rather than education. Hence, in this study we incorporate game elements into a learning environment. The My-Mini-Pet system is a handheld pet-nurturing game environment, in which students learn with an animal learning companion, their My-Mini-Pet. Three design strategies are adopted. First, the pet-nurturing strategy, which simulates the relationship between the pet and its owner, the My-Mini-Pet becomes a motivator/sustainer of learning. Second, the pet appearance-changing strategy, which externalizes the learning status of the student. In other words, the My-Mini-Pet plays the role of a reflector. Third, the pet feedback strategy, which links the behaviours of the student and his/her pet, the My-Mini-Pet acts as a facilitator of learning. A pilot study was also conducted to preliminarily investigate the effectiveness and experiences of the strategies on allowing the student to understand arithmetic practices. The results showed that the strategy was effective, encouraging the students to engage in learning activities. Furthermore, the game attracted the students' attention and stimulated discussion between peers. Some implications about the further developments are also discussed. (Contains 7 tables.)