Misinformation on social media undermines informed decision-making and public trust. Prebunking offers a proactive complement by helping users recognize manipulation tactics *before* they encounter them in the wild. We present *CritiSense*, a mobile media-literacy app that builds these skills through short, interactive challenges with instant feedback. It is the *first* multilingual (supporting nine languages) and modular platform, designed for rapid updates across topics and domains. We report a usability study with 93 users: 83.9% expressed overall satisfaction and 90.1% rated the app as easy to use. Qualitative feedback indicates that *CritiSense* helps improve digital literacy skills. Overall, it provides a multilingual prebunking platform and a testbed for measuring the impact of microlearning on misinformation resilience. Over 6 months, we have reached 500+ active users. It is freely available on the Apple [App Store](https://apps.apple.com/us/app/critisense/id6749675792) and Google [Play Store](https://play.google.com/store/apps/details?id=com.critisense hl=en).