Fluencia

Fluency isn’t vocabulary — it’s sentences you can produce under pressure. Fluencia is a sentence-mining app built on the boring truth that real fluency comes from one to two hours of active daily practice: flashcards, cloze, listening, and full production, with an AI conversation partner waiting at the other end.

The idea

Most language apps optimise for the dopamine of a streak, then leave you unable to actually speak. They reward recognition — “do you know this word?” — over production, so the practice never transfers to a real conversation. Fluencia keeps the streak but forces active recall in every mode, including typing full sentences and holding an actual dialogue. The goal isn’t to feel productive; it’s to be able to talk to someone.

It’s also built to be entirely self-hosted and free — a local database, browser-native speech, and an AI layer that’s optional rather than load-bearing.

How it works

Everything centres on a custom spaced-repetition scheduler. New cards step through three learning stages — one minute, ten minutes, a day — before graduating into review, where each interval multiplies by an ease factor that starts at 2.5 and tightens as you struggle. Cards you miss drop into relearning; cards you find easy space out. The queue always fronts due reviews, then learning cards, then a configurable number of new cards per day.

Four study modes each pull on a different muscle:

• Flashcard — see the Spanish, self-rate from Again to Easy.
• Cloze — type the missing word. Active recall, not recognition.
• Listening — hear it spoken, type what you heard.
• Production — see the English, type the Spanish. The hardest mode, and the one that actually matters.

On top of that, a conversation mode drops you into scenarios — a restaurant, a market, asking directions, the doctor — with an AI partner that speaks at your level, sticks mostly to vocabulary you’ve already studied, and corrects your grammar inline. When a sentence is worth keeping, one tap mines it straight into your decks. A dashboard tracks streaks, accuracy, and the cards most at risk of being forgotten, with a weekly streak freeze for the days life gets in the way. Three optional AI tools build on that history: a generator that writes new sentences on the i+1 principle, a weak-points analysis of where you struggle, and an auto-built practice deck that targets exactly those gaps. A stats page charts thirty days of reviews, an activity heatmap, and accuracy trends, so you can watch the work compound.

Under the hood

• Custom SM-2 scheduler tuned for sentence mining — ease adjustments, relearning steps, and per-day caps on new cards and total reviews.
• Four starter decks seeded on first run — 500 words and 236 sentences across Essential Words, Getting Started, Daily Life, and Express Yourself, so day one is never empty.
• SQLite as the single store — words, sentences, the many-to-many links between them, decks, SRS cards, and a full review-history log, all local with no account required.
• AI that’s an enhancement, not a dependency — sentence generation on the i+1 principle (mostly known words plus one new element), grammar explanations, weak-point analysis, and conversation all run through Gemini, but the app works fully without a key.
• Free audio everywhere via the Web Speech API, and keyboard-first study — Space to flip, 1–4 to rate.
• Export and own your data — JSON backup and restore, because progress this hard-won shouldn’t be locked in someone else’s database.

Fluencia is the kind of product I build for myself first — because the best way to know something works is to need it every day.