CHIKARA ChessThe Stone
Board
Chess with pieces cut from marble, gold and mineral.
The standard rules, a computer opponent at four levels, and a Rules Lab that tells you why a move is not allowed. It all runs on your device, so it works with no signal.
What you can do
Play the computer
Four levels, from Beginner, which often misses things, to Strong, which thinks for up to two seconds a move. Play White, Black or let the app choose.
Pass the device
Two people, one phone. The board can turn to face whoever is moving.
Learn from mistakes
Take a move back, ask for a hint, or open the Rules Lab and try any move to see the exact reason it is or is not legal.
Choose your material
Five piece sets. The rules never change, only the stone does. Dark pieces carry a double notch on the base, so the sides differ by more than colour.
Keep playing offline
After the first visit the whole game, including the computer opponent, works without a connection.
Keep your data to yourself
No account. Your record stays on your device. The opponent is a search program on your phone, not an online AI service.
Five materials, one game
The sets are artwork inspired by materials. They show how a game can look. They are not a guide to the stones, and they never change how the game is played.
Checked, not just claimed
| Check | What it covers |
|---|---|
| 30 move-count checks | The move generator is compared against published reference counts for six standard test positions, to as deep as 4.8 million positions from the start. |
| 56 rule cases | Castling, en passant, promotion, check, pins, checkmate, stalemate and the draw rules, each with a named test. They run again on your device in the Rules Lab. |
| Full games in a real browser | Complete games played through the screen with every piece on the board matching the game state, plus restarts and undo while the computer is thinking. |
| Contrast of 3.04:1 or better | The edge of every piece against every square, for all five sets and both sides. |
What is not yet measured: how strong the computer opponent is. It is not given a rating. Games are not saved if you reload the page, and moving a piece by dragging is not available yet.
Put it on your home screen
- Open the game once while you are online.That lets your browser keep a copy for offline play.
- Use your browser's install option.In Chrome on Android, open the menu and choose Install app. In Safari on iPhone, tap Share, then Add to Home Screen. Menus differ between versions.
- Open it from the icon.It opens full screen, like any other app.