I've been working on PlugBrain, an open-source Android app that helps reduce screen time by blocking distracting apps. Instead of simply locking you out, PlugBrain makes you solve math puzzles to regain access. PlugBrain uses math challenges as a barrier. The difficulty increases as you use distracting apps more often, and decreases if you stay away. The app is GPL3-licensed and available on GitHub. Still early, so I'd love feedback on the code, usability, and whether the idea feels useful or annoying in practice.