Self-evaluation of one's competences is considered a core factor in various domains of human functioning, including learning and instruction, as well as academic and vocational choices. Researchers from the fields of metacognition and learning, as well as motivation and learning have thus intensively investigated issues related to the self-evaluation of competences. Insights from both lines of research have been used in the serious game project SERENA to inform the selection and design of technical tasks and tutorial feedback strategies. The main goal of the SERENA project was to develop a serious game for adolescent females that fosters their self-evaluation of competence regarding technical tasks. This paper describes how insights from metacognition, motivation and feedback research were integrated to inform the game design. Furthermore, it reports two evaluation studies conducted with 93 students in real school settings. The findings reveal that girls' self-evaluation of competences assessed in terms of perceived technical competences and self-concept of technical abilities, as well as intrinsic motivation regarding technical tasks can be strengthened with the serious game Serena Supergreen. The log-file analyses indicate that seeking feedback and help within the game is associated with an increase in perceived competences. The challenges encountered within this applied research field are discussed.