Sakubun is intended to be a tool to help people practice kanji and improve their Japanese vocabulary. The main target audience is people who are learning kanji, but don't yet know enough to practice efficiently using real-world material like news articles, manga, or light novels.

The way sakubun solves the problem of too many unknown kanji is by storing a list of what kanji you've learnt so far, so that it can give you practice sentences that use only those kanji.

The backend is written in rust, and the web server is powered by rocket. The scripts directory has some scripts that were used to fetch data and stuff, but isn't used by the actual web app.

There's a collection of over 130K sentences (with English translations) taken from the tatoeba project you can practice with. Kuroshiro is used to generate kana readings and evaluate user responses, and WanaKana is used to provide a rudimentary IME to type the answers.

You can copy-paste Japanese text from anywhere, to get furigana over just the words that have kanji you don't know yet. The furigana is again generated with kuroshiro, like the kana readings in the quiz.