We examined the use and effectiveness of an incentive system--one of the five elements of a theory-based motivational architecture in educational games that we proposed--in a computer-based physics game on students' learning and performance. The incentive system's purpose was to motivate students to access learning supports designed to facilitate content knowledge acquisition (i.e., content-related supports) and minimize the use of solution videos (i.e., game-related supports). Students (n = 199) could earn game money by accessing content-related supports but had to pay to watch solution videos. Results indicated that the incentive system effectively increased how often students viewed content-related supports and decreased their reliance on solution videos. Furthermore, students who viewed more content-related supports showed higher posttest scores and solved more game levels compared to those who watched fewer supports, controlling for pretest scores. Solution videos, however, appeared to have no effect on either posttest scores or number of levels solved. Finally, our analysis of students' behavioral data, extracted from log files, confirmed that students did not abuse solution videos. We conclude by proposing areas of interest for future research.