Mobile learning brings us more learning opportunities due to the characteristics of learning devices and wireless computing. Recently, game-based learning also provides promising benefits in children's leaning. Therefore, how to design a game-based learning environment in handheld devices by combining an existing game with different learning activities is a significant research issue. In this paper, we attempt to incorporate game elements with the learning environment design in the PDA for students. Three considerations for the learning environment design in the hand-held devices are discussed: game element design, small screen design, and learnercentered design. According to these three considerations, a pet-nurturing game environment in the PDA, My-Mini-Pet system, is developed, including three components: emotional attachment, learning guidance, and costume show. The design rationale behind the My-Mini-Pet system is that taking good care of the Mini-My-Pet is actually improving the learner's learning status.