Computational thinking (CT) is an essential 21st century skill for people to succeed in the increasingly technological (and interconnected) world. Researchers have explored different interventions to teach students CT skills (e.g., Scratch and robotics), but digital game-based learning is relatively under-researched. A critical issue to address in game-based learning is how to scaffold students throughout gameplay so that the game can achieve its full potential to improve learning. Towards that end, in this dissertation study, I evaluated the effectiveness of learning supports used in a coding game called "Penguin Go" to foster middle school students' CT skills. In addition, I investigated how the learning supports influenced students' game enjoyment and cognitive load during gameplay. I conducted an experiment with 57 middle school students via online sessions. The control group played the original game version, whereas the experimental group played the revised game version with learning supports embedded. I designed the learning supports in the form of partial worked examples that illustrated the working of the key coding structures. The results showed that the difference in CT skills, measured from pretest to posttest, did not differ significantly across conditions, but tended to favor the experimental group. Moreover, students who received learning supports reported significantly higher game enjoyment than the control group students. There was no difference in terms of cognitive load between the two groups. Implications of the findings and suggestions for future research are discussed at the end of my dissertation. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]