Lietner

Plain flashcard apps feel flat. Lietner makes the Leitner system visible: cards physically move between boxes, so progress shows on the desk. It is built for students studying on their own, mostly on phones, who should be able to start a deck on a laptop, review on the bus and lose nothing, with or without an account.

Five wooden boxes sit on a three.js desk. Each due card lifts out, flips to show its answer and files itself into the next box, or back into box 1 if you missed it. The same desk works on phones, tablets and desktops, fully offline as a guest; signing in syncs decks and progress between devices.

1. 01

   Classic Leitner schedule: boxes come due every 1, 2, 4, 8 and 16 days, with a mastered tray.

2. 02

   Phones and tablets get a portrait desk, tap to flip and swipe to grade; desktops get keyboard shortcuts and one-step undo.

3. 03

   Cards in any language or script, including right-to-left. Import CSV/TSV (including Anki's export) or paste JSON cards written by your own AI.

4. 04

   Installable PWA that works fully offline, with a text mode for browsers without WebGL.

5. 05

   Optional sign-in with Google or a 6-digit email code syncs decks between devices; guest data never leaves the browser.

6. 06

   JSON export and import of everything, and account deletion from Settings.

1. D-01

   Make IndexedDB on the device the source of truth, and the server a per-account mirror. Guests never download the Supabase SDK; it is loaded with import() only when someone signs in.

2. D-02

   Sync with last write wins per row, enforced by SQL triggers: updated_at is capped at the server clock so a device with a fast clock can't win every conflict, and deletions are final tombstones.

3. D-03

   Pull by a server-stamped server_at cursor with keyset paging and a 60-second lookback, so an offline edit pushed days later is still picked up by every device.

4. D-04

   Isolate accounts with Postgres row-level security, covered by pgTAP tests that run in CI against a local Supabase stack.

5. D-05

   Render the three.js scene on demand, cap the pixel ratio on phones and drop quality automatically when frames run slow.

6. D-06

   Keep the UI behind DeskView and CardView interfaces, so a plain-DOM text mode for browsers without WebGL runs the identical review flow.

7. D-07

   Never let card text reach telemetry: page views are cookieless, and Sentry events and breadcrumbs pass through a scrubber with its own tests.

8. D-08

   Keep scheduling as pure functions over integer calendar days, so time zones and daylight-saving shifts never move a card by a day.

• [pass]Row-level security limits every account to its own rows; pgTAP tests prove the isolation in CI.
• [pass]SQL triggers cap client timestamps at the server clock and make deletions final.
• [pass]Telemetry is cookieless page views plus Sentry crash reports with card text scrubbed out; no ads, no data sales.
• [pass]Synced data lives in the EU (Supabase, Ireland); grade history never leaves the device.
• [pass]Signing out flushes unsynced changes first, then wipes account data from the device.