Digital interactive games are more than tools for entertainment and can be used as learning and training environments. This approach is giving rise to what is known as serious games. "YouVerify!" European project has developed a serious game called "BotBusters" to help young people cultivate the know-how to identify manipulated visual news. The game has been used as a distance learning tool in three different languages, French, Spanish and English, and has been applied to a large and open audience. Contributing to the literature body in the emerging field of online visual disinformation, this article aims to provide an analysis of the players' behavior and to assess to what extent the game has been able to attract their attention and achieve the objectives of therefore mentioned distance training tool. A quantitative methodology based on in-game post-play data will be used to study game engagement rate evolution. A detailed study of the inoculative strategies of the game determined which ones were more useful to avoid the drop-out of the tool. The findings of this analysis determine that this gamified intervention keeps high the level of users' engagement with the educational content and facilitate the inoculation of critical thinking to verify news and to avoid visual disinformation. Those findings will provide a better understanding of how young users reflect on media literacy and which is the best methodology to use on distance learning tools to motivate them to move from a simple opinion to constant and thorough verification.