Some people practice chess on a train with no signal. Others have a slow connection, or would rather not stream a board. For AccelaStudy® AI Chess, which is in development, we wanted a puzzle library that works with no connection at all. This is how that library is put together and what it means for your storage and your privacy.
The library
The puzzles come from the Lichess puzzle database, which is released under CC0. We converted the full pinned snapshot: 6,193,530 puzzles, each keeping its original solution and its source fields. Lichess is an independent organization, and AccelaStudy AI Chess is not affiliated with or endorsed by Lichess.
All of those puzzles in one file would be useless on a phone, so the library is split into 3,102 packs that never change once published. Downloading every pack is about 1.71 GB, and the packs expand to about 12.98 GB before indexes and overhead.
What "verified" means
Converting a library is easy to get wrong in small ways, so we checked it mechanically instead of trusting it.
- Every pack was checked against its recorded size and hash, both compressed and expanded.
- Each pack's record count was checked.
- Puzzles were checked for legal moves.
- The web reader opened the first and last puzzle of every pack.
A download goes through the same kind of checks on your device. A pack is verified before it replaces anything, and a download that fails midway cannot damage a pack you already have.
That is a check of the data. It is not a claim that every puzzle has been explained. The library keeps the original solution for each puzzle, and explanations are being developed separately, so you should not expect an explanation or narration for every puzzle.
Choosing what to download
You do not have to take all of it. Both development clients let you browse the library and download packs, and you can pause a download and resume it later. The native app can also filter the catalog by rating range and queue several packs.
The plan is for the app to offer recommended packs for your chosen target, packs by theme, packs by rating range, and the whole library. It is also designed to show the download size and your free space before you commit, rather than failing halfway.
Why the browser and the phone differ
Storage works differently on the web and on a phone.
- In a browser, the browser decides how much a site may store, and the limit differs between browsers and devices. A computer with plenty of free disk can still be told no. The web app is designed to explain a refused download and to leave your existing puzzles and history alone.
- On iPhone® or iPad®, the limit is the free space on the device. Because the whole library is about 12.98 GB when expanded, most people will want to choose a focused set.
Background downloading on the native app, the kind that continues when you leave the app, is planned and not built yet. Today downloads run while the app is open.
What stays private
Your practice history is separate from your puzzle packs. In the development clients, your attempts are saved on your own device, they are not uploaded, and they do not depend on which packs are installed. Practice, hints, and solution review all work with no connection.
Sync is planned for people with an AccelaStudy AI account. It will move history only when you choose, and you can practice without an account.
What it adds up to
The library is already converted and verified, and the development clients can download packs and practice from them offline. What is still ahead is the learning around it: lessons, opening study, game review, recommendations, and requested narration. Those are planned, and we have announced no dates.
If you want to hear when there is news, join the waitlist on the home page.