Full pipeline: teach the app which words you already know, upload a hard book, choose how much difficulty to keep, translate it with Gemini, then read online with hover translations or download a PDF.
Upload books you have already read (PDF/TXT — words used 2+ times count as known) or a plain word list (one word per line).
Upload the target book (PDF/TXT), then check the coverage: a random 30 of its unknown words and per-page difficulty.
The level = how much of the unknown TEXT stays. The most frequent unknown words are kept until they cover that share of the unknown word occurrences — so the four levels feel evenly spaced while reading. Only these four options exist, so every translated page is cached and never paid for twice.
Pick a page range and start. Pages are sent to the Gemini API one by one (free tier, cached pages are skipped for free).
page from to