Poly-Puff

Poly-Puff is an AI English learning app that combines translation exercises, grammar correction, and pronunciation coaching for ESL learners worldwide. It is built around a database-first approach: 340+ grammar rules are checked before any AI model call, so hard rules always win (for example, "a university" is graded correct regardless of what the model predicts). The app supports 52 languages, ships 10 learning modules, and uses 100% rule-based grading for consistent feedback. Its Dual Audio Feedback plays a native-speaker version at 0.9x speed for clarity, then plays your own translation back so you can spot flow issues, and an Accuracy Heatmap shows visual progress rings that shift from red to emerald as your score improves. Positioned as more than a flashcard app, Poly-Puff targets ESL students and teachers who want reliable, real-time grammar and pronunciation feedback grounded in explicit rules rather than model guesswork. Separate teacher and student sign-ups suggest a classroom-friendly setup, and the product notes GDPR and COPPA compliance for global use.

Best for ESL students and teachers who want rule-based grammar grading plus pronunciation feedback rather than a flashcard app.