User guide

Everything you need to play CHIKARA Chess, from your first move to the Rules Lab. The board diagrams in this guide are drawn by the same game engine you play against, so every move they show is legal.

Start playing

Open the game and choose Play.
Pick your opponent: The engine (the computer) or Another person on the same device.
Against the engine, pick your colour and a level. Then choose Start game.
Tap one of your pieces. Dots show where it can go. Tap a dot to move.

White always moves first. If you play Black, the engine opens and the board turns so your pieces are at the bottom.

The board

The board has 64 squares. Files (columns) are the letters a to h, and ranks (rows) are the numbers 1 to 8. Every square has a name made of both, such as e4. White starts on ranks 1 and 2, Black on ranks 7 and 8. The bottom-left square, a1, is always dark.

The starting position. The small letters and numbers on the edge are the file and rank names. In the game you can always read a square's name from them.

What the colours on the board mean:

Selected piece Square it can move to Piece it can capture Last move King in check Hint

How the pieces move

Each side has 16 pieces: one king, one queen, two rooks, two bishops, two knights and eight pawns. A piece captures by moving onto a square held by an enemy piece, which removes it. You can never capture your own piece.

Pawn

A pawn moves straight forward one square, or two squares on its first move if both are empty. It captures one square diagonally forward, never straight. It never moves backward. Here the pawn on e2 can go to e3 or e4, or capture the pawn on d3.

Knight

A knight jumps in an L: two squares in one direction and one square sideways. It is the only piece that jumps over others.

Bishop

A bishop slides any distance along a diagonal until it meets a piece. It can capture the first enemy piece in its way (here the pawn on f6) but cannot pass it. A bishop always stays on squares of one colour.

Rook

A rook slides any distance along a rank or a file until it meets a piece.

Queen

The queen combines the rook and the bishop: any distance along a rank, file or diagonal.

King

The king moves one square in any direction. It can never move onto a square that an enemy piece attacks.

Castling, en passant, promotion

Castling

Once per game, the king can move two squares towards a rook, and that rook jumps to the other side of the king. You can castle only when all of these are true:

Neither the king nor that rook has moved before.
All squares between them are empty.
The king is not in check, does not pass through an attacked square, and does not land on one.

Before: the king can go to g1 (short castling) or c1 (long castling).

After short castling: king on g1, rook on f1. It is written O-O. Long castling is O-O-O.

To castle in the app, tap your king and tap the square two steps along. The rook moves by itself.

En passant

If an enemy pawn moves two squares from its start and lands next to your pawn, you may capture it as if it had moved only one square. You must do it on your very next move or the chance is gone.

Black has just moved the pawn from d7 to d5. White's pawn on e5 can capture it by moving to d6.

After the capture the black pawn is gone, even though White landed on an empty square.

Promotion

A pawn that reaches the far end of the board must become a queen, rook, bishop or knight of its own colour. In the app a small window asks you to choose, and the move is made when you pick. Most players choose a queen.

The pawn on a7 is one step from promotion. It moves to a8 and becomes the piece you choose.

Check, checkmate, stalemate

Check means a king is under attack. The player in check must get out of it straight away, in one of three ways: move the king to a safe square, block the attack, or capture the attacking piece. The app shows the king with a red glow and says so in the status line. You cannot make a move that leaves your own king in check, and a piece that stands between its king and an attacker is pinned: it cannot leave that line.

The white king is in check from the rook on e8. It can step to d1, f1, d2 or f2. It cannot stay on the e-file.

Checkmate means a king is in check and has no way out. The game ends and the player who delivered it wins.

The quickest checkmate: 1.f3 e5 2.g4 Qh4#. White's king cannot move, block or capture.

Stalemate means the player to move is not in check but has no legal move. It is a draw, not a win.

Black to move. The king on h8 is not attacked, but every square it could go to is covered. This is stalemate, a draw.

Draws

A game is a draw, and the app ends it for you, in these cases:

Stalemate	The player to move has no legal move and is not in check.
Not enough pieces	Neither side can possibly checkmate: king against king, king and one bishop or knight against king, or only bishops that all stand on the same colour of square.
Threefold repetition	The same position, with the same player to move and the same rights to castle and capture en passant, has happened three times.
Fifty moves	Fifty moves by each side (100 half-moves) pass with no pawn move and no capture.

Official chess lets a player claim the last two draws rather than ending the game automatically, and lets players agree a draw. This app does not offer draw by agreement yet.

Using the app

Home

Home has Play and Piece sets buttons, tiles for Play the engine, Pass & Play, Piece sets, Rules Lab and Record, and a line showing that the rules self-check passed on your device. While a game is in progress a Resume your game button appears.

The Halo and the logo menu

The round button at the bottom of the screen is the Halo. Tap it to open shortcuts to Home, Play, Sets, Lab and Record. Drag it anywhere you like. Tap the CHIKARA mark at the top left to open the logo menu: search (Ctrl+K or ⌘+K on a keyboard), Halo size and position, visual quality, light or dark theme, sound, ambience, reduced motion, piece sets, the Rules Lab, a replay of the tour, and About. If you lose the Halo, choose Reset Halo Position.

New game

Opponent	The engine or Another person (Pass & Play).
You play	White, Black, or Random.
Engine level	Beginner looks one move ahead and often misses things. Casual sees simple tactics but still makes plain mistakes. Club plays a sound game. Strong searches as deep as it can in about two seconds a move. Lower levels deliberately make human-like slips. No level is given a rating.
Board (Pass & Play)	Keep the board fixed, or turn it after each move so it faces the player to move.

During a game

Above the board is your opponent, below it is you. Beside each name are the pieces that player has captured and, when ahead, the material lead in pawns (a pawn is worth 1, a knight or bishop 3, a rook 5, a queen 9). The status line says whose turn it is. Moves are listed underneath in standard notation, such as Nf3 or exd5.

Undo	Against the engine, takes back your last move and the engine's reply. In Pass & Play it takes back one move. It also works if the engine is still thinking.
Hint	The engine looks for a good move for you, highlights it in green for a few seconds and shows it in notation.
Flip board	Turns the board around.
Resign	Asks you to confirm, then ends the game as a loss.
New game	Takes you to the New game screen. Starting a new game ends the old one.

When a game ends a window tells you the result and offers Play again (same settings) or Home.

Good to know. A game in progress stays available while you move around the app, but it is not saved if you reload or close the page. Finish it or accept that it will be lost.

Piece sets

Open Piece sets to change the material of the board and pieces: Marble, Gold and Obsidian, Verdite, Amethyst and Quartz, or Copper and Slate. The change applies at once, even to a game in progress, and is remembered. The sets are artwork inspired by materials. They never change the rules or the engine.

Each set tells the two sides apart by more than colour: dark pieces have a double notch on the base and light pieces a single pip, so the sides stay clear in low light or for colour-blind players.

The Rules Lab

The Rules Lab is a sandbox for learning and checking. Nothing in it is saved or counted.

Open Rules Lab from the Halo or the logo menu. The start position is loaded.
Tap any piece of the side to move. Its legal destinations are listed under the board.
Tap a destination to play the move, or tap an illegal square to get the reason, for example "That move would leave your king in check" or "Another piece is in the way."
To study a position, paste it into the box in FEN notation and choose Load position. A position that cannot exist is rejected with the reason.

Start position	Resets the board.
Undo	Takes back the last move you made in the Lab.
Validate	Checks the position in the box and lists every legal move.
Count moves (perft 3)	Counts every position reachable in one, two and three moves. Handy for checking the engine against published numbers.
Run self-check	Runs 56 rule tests and 14 move-count checks on your device and reports how many passed.

In the Lab a pawn that reaches the last rank is always promoted to a queen.

Your record and privacy

Your record (games, wins, draws and losses, by level), your piece set and your settings are stored in your browser on this device and nowhere else. There is no account, no sign-in and no tracking in the game. The computer opponent is a search program that runs on your device; the game never contacts an online AI service. The only thing the app requests from the internet is its typefaces, and it falls back to your device's fonts when offline.

To erase your record open Record and choose Clear my record. Clearing your browser's site data for this address removes everything.

Install and offline

Open the game while online, once. Your browser keeps a copy.
Choose 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 new icon. After that it works with no connection, including the computer opponent.

When the game is updated, your device fetches the new version in the background. Close the app completely and open it again to use it.

Accessibility

Every square on the board is a button with a spoken name, for example "e4, white pawn, legal move".
The status line announces whose turn it is, check and the result.
You can reach the squares with Tab and select with Enter or Space. Arrow-key movement across the board is not available yet.
Sides differ by shape marks as well as colour, and every piece has at least 3:1 contrast against every square in every set.
Turn on Reduce motion in the logo menu to stop sliding animations. The game also follows your device's own setting.
This has been built with accessibility in mind but has not yet been tested with a screen reader. If something does not work for you, please tell us.

If something goes wrong

The game looks old after an update

Close every tab or window of the game, then open it again. If it still looks old, reload the page twice, or clear the site data for this address in your browser settings. Clearing site data also erases your record.

The page is blank, or the game will not install

The game must be opened from its web address. Opening the file straight from a folder on your device cannot install it or keep it offline. If you host it yourself, serve it over https.

The engine takes a long time on my phone

Choose a lower level on the New game screen. Beginner and Casual answer almost instantly. Strong uses up to two seconds a move on a fast device and may be slower on an old one.

I cannot find the round Halo button

Open the logo menu (the CHIKARA mark, top left) and choose Reset Halo Position. Reset Halo size puts it back to 75.

I tapped a piece and nothing is highlighted

It is either not your turn, the engine is still thinking, or that piece has no legal move (for example, it is pinned or your king is in check). The status line says which. In the Rules Lab you can tap the piece and see the reason.

My game disappeared

Games are not saved if you reload or close the page. Only your record and settings are saved.

Text looks plain when offline

The game's typefaces come from the internet. Offline it uses your device's fonts. Everything else is unchanged.

The rules self-check shows a number lower than 56

That should never happen. Reload the page once; if it persists, send the failing item shown in the Rules Lab to the contact below.

Words used in chess

Rank, file	A row (1 to 8) and a column (a to h) of the board.
Check	A king is under attack.
Checkmate	A king is in check with no escape. The game is won.
Stalemate	No legal move and not in check. A draw.
Pin	A piece that cannot move because it would expose its king.
Fork	One piece attacking two or more enemy pieces at once.
Notation (SAN)	The way moves are written: a letter for the piece (K, Q, R, B, N; none for pawns), then the destination square, with x for a capture, + for check and # for checkmate.
FEN	A line of text that describes a whole position, used in the Rules Lab.
Perft	A count of every position reachable in a number of moves, used to test that a game engine knows the rules exactly.