Flashcards

A simple personal flashcard app (Expo / React Native, Android). Create decks, add cards manually or via CSV import, and practice with lightweight spaced repetition. All data is stored locally on the device in SQLite — no accounts, no internet required.

Features

• Multiple named decks.
• Add cards manually (front / back), or add many at once on the Add cards in bulk screen — paste a list (one card per line) or import a CSV file, with a configurable front/back separator.
• Practice mode: up to 10 due cards per batch, flip to reveal, then rate it — Hard / Good / Easy (the middle rating is stored internally as 'fine' for data compatibility). Each card carries a Familiarity level (a Leitner "box"); the rating moves that level, which sets how long the card is put away.
  • Hard → forgot: reset to level 0, stays due now.
  • Good → recalled: climb one level (longer interval).
  • Easy → easy: climb two levels.
  • Intervals grow along the ladder 1 → 3 → 7 → 14 → 30 → 60 days (capped at 60), so a card you keep getting right returns less and less often.
  • When a card's timer passes, it automatically becomes due again.
  • Swipe (or arrow keys on web) to move between cards without rating them — Familiarity is left untouched, so a skipped card stays in the set for later. Swiping forward past the last card skips it and ends the session.
• Session summary after each batch, with the option to practice the next 10.
• Progress screen (chart icon on the home screen): current/best practice streak, total reviews, a 14-day activity chart, an upcoming-due forecast, and each deck's familiarity-level breakdown. Backed by a local reviews history table — one row per rating. Deleting cards or decks (or restoring a backup) keeps the history; it is deliberately not included in the backup file (the backup format is unchanged).

Bulk add / CSV import format

On the Add cards in bulk screen (deck "⋯" menu) you set a front/back separator (defaults to -), then either paste lines or import a CSV/text file. One card per line, no header row:

hola - hello
gato - cat
buenos días - good morning

• Each line is split on the first occurrence of the separator, so the back may itself contain the separator (e.g. set it to ; for hola;hello files).
• Surrounding whitespace (around the separator and at line ends) is stripped.
• Blank lines and lines without the separator are skipped.

Run it during development

bun install            # first time only (Bun is the package manager)
npx expo start         # then scan the QR code with the Expo Go app on your Android phone

Press a to open in an Android emulator if you have Android Studio set up.

Build a standalone APK (install permanently, no PC needed)

Uses EAS Build (free tier, builds in the cloud):

bun add -g eas-cli
eas login              # create / sign in to a free Expo account
eas build -p android --profile preview

When the build finishes, EAS gives you a download link for an .apk. Open that link on your phone and install it. Data persists across restarts.

Project layout

src/
  app/                         expo-router screens
    _layout.tsx                root Stack navigator
    index.tsx                  decks list (create deck, see due counts)
    deck/[id]/index.tsx        deck detail (stats, practice, add card, bulk add, rename/delete)
    deck/[id]/card.tsx         add / edit a single card (?cardId=... to edit)
    deck/[id]/bulk.tsx         add many cards at once (paste or CSV file, custom separator)
    deck/[id]/practice.tsx     practice batch + session summary
    stats.tsx                  Progress screen (streaks, activity, forecast, deck levels)
  db/
    database.ts                opens SQLite, creates schema
    decks.ts                   deck queries
    cards.ts                   card queries + spaced-repetition rules (due_at)
    reviews.ts                 review history: day counts + streak math
    stats.ts                   per-deck level breakdown + due forecast
  lib/csv.ts                   delimited line parser (custom separator)
  lib/haptics.ts               haptic vocabulary (no-op on web)
  components/                  shared UI (Button, PressableScale, OverflowMenu,
                               ModalCard, EmptyState, Icon, Screen, ...)
  theme.ts                     colors / type scale / spacing / press feedback

How "learned vs. due" works

Each card has a due_at timestamp (epoch ms) and a familiarity level (a Leitner box, 0 = new/lapsed). A card is due / unlearned when due_at <= now. New and imported cards start at familiarity = 0, due_at = 0 (immediately due). Rating a card runs nextReview (src/db/cards.ts): the rating moves its familiarity level, and the new level indexes the interval ladder INTERVAL_DAYS = [0, 1, 3, 7, 14, 30, 60] (days) to set the next due_at. Hard keeps the card due now (it stays in the practice set); Good and Easy push it out along the ladder. These two fields drive both the practice filter and the automatic return of expired cards — no background job is needed.

Review history

Every rating also inserts a row into the reviews table (rating, level_before, level_after, reviewed_at, plus nullable card_id/deck_id references that are SET NULL on delete, so pruning decks never erases your streak). The Progress screen buckets timestamps by the device's local calendar day in JS (src/db/reviews.ts); a streak survives overnight as long as no full day passes without practice.