The problem
Dictionary apps translate words; they don’t teach a language. I wanted one tool that could take input in English, Chinese, or misspelled German (“gehn” → “gehen”), give me the full grammatical picture — conjugation tables, cases, examples — and then actually drill me on it.
What I built
- An intelligent translation pipeline — auto language detection across three input languages, German typo correction, database-first lookup over a 70K+ word vocabulary with AI fallback for anything unknown;
- Learning that closes the loop — a spaced-repetition system for retention, AI-generated exams with auto-grading, favorites and progress tracking;
- An AI tutor layer — interactive chat with structured, example-rich answers, and image generation for visual vocabulary;
- Production discipline — JWT auth with refresh cycles, XSS/CSRF/rate-limit protection, multi-tab session sync. Built to be used daily, not demoed once.
What it proves
The same pattern as my other systems, pointed at a personal need: a curated knowledge base (the vocabulary DB), retrieval in front of generation (database-first, AI-fallback), and honest UX around what the machine knows. Also: living in a language is the best requirements document.