Game-based learning has been a popular development and recommended as an effective pedagogy in educating new generations of learners. Few studies, however, have demonstrated the efficacy of game-based learning on learners' academic performance with empirical data. The described learning outcomes of game-based pedagogy within the limited available research are diverse. One prominent explanation is the lack of established guidelines. This paper addresses the issues of game design guidelines through a qualitative phenomenographic perspective of the experience of a group of students designing an educational game utilizing an adapted instructional design (ID) model--the gentry model. The results revealed the participants benefited from the process primarily in two capacities: a significant growth in their knowledge of game design and content knowledge; and great enjoyment and high motivation in the learning process. We conclude ID models with proper adaption and adjustment are effective to provide guidance and improve the efficacy of game-based learning if more ID models will be examined. (Contains 2 figures.)