Game-based learning (GBL) has long been recognized as an effective way to engage students in learning through games, but little emphasis has been placed on scaffolding support for students, which hinders their learning. Therefore, our design of Space Adventure GBL ties games closely to scaffolds at every stage and investigates what role games and scaffolds play and whether greater exposure to games and scaffolds can boost learning. Six classes of 152 8th graders were randomly assigned to unlimited gaming and scaffolding group, limited scaffolding group, and limited gaming group. Students' learning outcomes in physics are optimized when they have unlimited access to GBL's gaming and scaffolding. All three groups perceived similar levels of engagement, engrossment, and total immersion. According to regression, time spent mastering the scaffolds on their first attempt is the most determinant predictor of physics concept learning and engagement, whereas winning the games for the first-time predicts mental model construction, engrossment, and total immersion the most. This study sheds light on future GBL studies that closely tying scaffolds and games challenges could motivate and facilitate students to master scaffolds and win games on their first attempts, resulting in better physics learning performance and more game immersion.