Since a large variety of digital games have been used in many fields for educational purposes, their real functions in learning have caught much attention as well. This study aims to explore learning characteristics of problem-solving digital games and their corresponding cognitive levels. this research aims to design and develop a problem-solving game in which story context the tasks are inter-related to each other. Learners' task analysis are performance to observe two elementary learners' gaming paths, behaviors and cognitive activities. System documentation, video recording, researcher observation, and interviews are conducted to analyze learners' learning strategies and their cognitive performance during the gaming process. This research chooses to use in-depth case study to investigate learners' cognitive performance in problem-solving game not only want to understand learners' internal psychological activities, but also hope to provide references for future research in terms of the instructional design of games.