This study uses the language learning app Duolingo as an example to explore the impact of its gamified design on user motivation and engagement. To ensure the accuracy of the results, a mixed-method approach was adopted for cross-validation. This included a preliminary survey in questionnaire form to understand users'perceptions of gamification mechanisms, followed by diary studies to authentically record usage scenarios and semi-structured interviews to gain deeper insights into participants' experiences. Subsequently, a theoretical framework combining Nielsen's usability heuristics, Self-Determination Theory, and the Octalysis Octagon Model was used to conduct a novel analysis of the experimental results.

The results showed that Duolingo's encouragement mechanisms are mostly successful in motivating users to learn and promoting participation, but they also impose an emotional burden on users. However, penalty mechanisms are significantly associated with decreased motivation. Although they are believed to ensure answer accuracy, they also trigger noticeable anxiety and frustration among users.

These findings offer helpful information by understanding how gamification influences user learning experiences and emotional responses. By examining both the benefits and disadvantages of gamification through usability and psychological aspects of users' motivation in the widely used language learning application, this study can contribute valuable insights to future research and even practical guidance for designers and developers to create more effective and user-centred gamification systems for educational platforms.