Learn a language the way the research actually says you should.
Sprachbau builds every sentence at your exact frontier — mostly words you already know, plus a few new ones — schedules them with FSRS spaced retrieval, and corrects your writing like a patient tutor. No streaks. No gamification. Just practice that compounds.
Comprehensible input
Sentences are generated at ~95% known vocabulary, introducing only 2–4 new words at a time — the level where acquisition actually happens.
Spaced retrieval, done right
FSRS-6 scheduling targeting 90% retention. You review cloze sentences, not flashcard word pairs — meaning in context, every time.
Feedback that teaches
Write freely and get corrections split into structure vs. surface errors. The grammar you get wrong becomes tomorrow's targeted practice.
Offline-first
The mobile app reviews entirely on your device — the same scheduler runs on phone and server, so a plane with no Wi-Fi is still a full study session.
Quality of practice over engagement metrics.
Sprachbau has no streaks to protect, no badges to chase, and nothing to sell your attention to. It exists to make each minute of practice count — and then get out of your way.