Poly-Puff - Practice English translation, get instant AI feedback

I started building Poly-Puff for my own students - I wanted them to be able to conveniently practice English outside of class, with great exercises all in one place instead of scattered across a dozen apps and worksheets. Most language apps either drill vocab in isolation or lean entirely on an LLM for corrections - which means the grammar feedback can be inconsistent or just wrong. Poly-Puff cross-checks every correction against a database of 340 grammar rules across 35 categories before it ever calls the AI, so the feedback is accurate, not just plausible-sounding. Students translate sentences from their own native language into English and get instant, rule-backed feedback - plus pronunciation coaching and CEFR-leveled exercises from A0 to C2. It's Android-first right now, and I'm looking for closed testers to help me stress-test it before a wider launch. Drop a comment (or DM me) with the Gmail address you'd like invited on, and I'll add you to the tester list. Would love your feedback, especially if you're learning English or teach ESL yourself.