This study developed a game-based formative assessment, called tic-tac-toe quiz for single-player version (TRIS-Q-SP), in an energy education e-learning system. This assessment game combined tic-tac-toe with online assessment, and revised the rule of tic-tac-toe for stimulating students to use online formative assessment actively. Additionally, to investigate which types of formative feedback were appropriate for use in this game-based formative assessment, immediate elaborated feedback (IEF) and no immediate elaborated feedback (NIEF) mechanisms were designed and incorporated in TRIS-Q-SP. The findings revealed that all participants improved their energy knowledge through the e-learning system, and expressed enjoyment and positive opinions toward the TRIS-Q-SP. However, the various statistical results suggested that providing IEF for each question answered in TRIS-Q-SP was the optimal design. This design facilitated the enhancement of energy knowledge acquisition when comparing it with NIEF condition, and did not affect all participants' enjoyment perceptions.