Game rules

This page tells about game rules (e.g. how to move pieces). For what users and website may and may not do see website rules.

In brief

• Rules of Chess apply.
• You may "cheat" (do not confuse with cheating as playing unfairly) by performing an illegal move. Try not to get caught.
• Try to catch your opponent cheating. Use "claim illegal move" button for that. Capturing the king will also claim.
• Being caught cheating will drain your HP. If it reaches zero, you lose. "Expensive" pieces hurt more.
• To win, checkmate your opponent, and then capture the king.

Controls

To make a move, highlight (click) a square, and then click destination square. You may also drag the piece. Clicking highlighted square will deselect it.

To confirm a move, press "confirm". Press "cancel" to "cancel". If there's a "special" move variant available (e.g. castling), a separate button will appear. If not, pressing Enter or NumpadEnter will confirm the move.

To claim opponent's illegal move:

• Press "claim illegal move"
• Select a square where that move ended.
• Confirm.
• Check results below the board.

Notation

The following notation applies:

• + — check
• # — checkmate
• – (en dash) — illegal move
• E — checkmate escape
• * — "special" move (e.g. castle or en passant)

This is a chess variant

The rules are the same as normal chess, except for the stated changes.

Illegal moves and claims

Any move, which is possible, but not allowed by regular chess rules, is considered illegal. You may perform an illegal move instead of normal move. Moving opponent's pieces, capturing friendly pieces and putting king under check is also considered an illegal move.

Before your turn, you may claim opponent's move. If the claim is correct, the opponent loses HP, the position is rolled back and the opponent should make a move. If the claim is not correct, you lose HP. Then you can make another claim or a move.

Claim depends on square. You need to select correct target square of the opponent's move. If you selected a wrong square, or the previous move was legal, the claim is considered not correct.

You are not forced to claim. If you want, you may continue playing after opponent's illegal move.

If you perform a move, it "confirms" a position. You cn no longer claim a move that you have confirmed.

Castling is king's move. Claiming a rook will be incorrect.

Capturing opponent's king with a legal move is also a claim. It will never be incorrect, but could not be sent if the position is confirmed. It will also deal extra damage. This is called a capture‑claim

Note that by website rules you are not allowed to view recording of the match until the game is over. The game relies on player's memory.

HP

Each player starts with 100 HP (health points). If player's HP reaches zero, that player loses.

If you perform a correct claim, your opponents loses some HP. The more "expensive" was the moved (or captured) piece, the more HP is lost. There's an extra penalty for leaving king endangered or moving opponent's pieces.

If you preform an incorrect claim, you will lose some HP (but less than for moving illegally).

Move variants

Castling

"Legal" castling is allowed like normal. There are some other variants which can be performed on the website:

• You can castle illegally even after losing castling rights.
• You can move the king 2 squares illegally without castling.
• You can castle through pieces illegally. If a king or a rook lands on other pieces, it will capture them.
• You can castle from/through/into check illegally. Your opponent may capture your king en passant to capture‑claim.

Castling is king's move. Claiming a rook after an illegal castling will be incorrect.

En passant

"Legal" en passants are allowed like normal. There are some other variants which can be performed on the website:

• Any piece can en passant a pawn illegally.
• If a pawn moves (illegally) 2 squares in the center of the board, it can be captured en passant legally by another pawn (or illegally by a piece).
• You can illegally move a pawn diagonally without capturing en passant.

Pawn's special moves

You can move a pawn any number of squares illegally. If it is moved 2 squares (even illegally, i.e. in the center of the board), it can be captured en passant legally by another pawn (or illegally by a piece).

If a pawn is returned to its home rank, it can move 2 squares legally.

Pawn can not be moved to the farthest row without promoting. It can however be moved illegally several squares at once to promote.

Checkmate

If a king is checked and can not escape with a legal move, it is considered checkmate. However, it does not end the game instantly.

Checkmated player can:

• Try to escape with an illegal move. This move could be claimed.
• Try to escape with a legal move (which however still keeps the king in danger). This move is called a checkmate escape and is notated with a letter 'E'. Checkmate escape is considered a legal move — claiming it will be considered incorrect.

If the king is captured after an escape attempt, it is called a fatal capture. Performing a fatal capture wins a game.

If the king is not captured after an escape attempt, it is considered a successful escape, and the position is no longer a checkmate, until checkmated again.

Automatic game termination

Threefold repetition results in an automatic draw.

Ending the game on time does not account for insufficient material.

Insufficient material is: bare kings, knight only, or bishop only.

Some of these rules might change later.

Stalemate occurs if a player has no available legal moves. It results in a draw.

50-move rule

After 50 reversible moves any player can claim draw at any time (until an irreversible move is played). After 75 such moves the game results in a draw automatically.

Illegally moving a pawn backwards (with slight sideways movement) does not reset the counter, since it could potentially be revered by a series of legal moves.