Chess-Uno rules

1Setup

• Standard chessboard, classic starting position. The creator of a private game plays White; in quick match and against the computer, the army is drawn at random (or chosen against the computer).
• Reference deck of 108 cards: for each of the four colors (red, blue, green, yellow) one 0, two copies of each value from 1 to 9, two “Skip”, two “Reverse”, two “+2”; plus four Jokers and four “+4”. Each card has a unique id.
• The deck used in a game is filtered by the settings: highest number card (maxCardNumber, 5 by default, from 1 to 9; 5 removes the 6 to 9), whether 0 cards (includeZero) and Jokers (includeJokers) are included.
• The deck is shuffled on the server with cryptographic randomness. The order of the draw pile is never sent to the players.

2Playing a turn

A turn belongs to the army to move. The player controlling that army starts it. Phases:

1. Start of turn, then draw: the player automatically draws the top card and reveals it to everyone (the draw is recorded before any notification).
2. Immediate effect: the card’s effect applies at once (see section 4). For a +2 or a +4, a pawn placement phase comes before the moves.
3. Moves: the number of moves granted by the card.
4. End of turn: the move passes to the other army. The revealed card goes to the discard pile of the player who drew it.

A player with no legal move still reveals their card and applies its effect, then their turn ends.

3Draw pile and discard piles

• Each player has their own discard pile: it shows the cards they drew.
• When the draw pile is empty, both discard piles are shuffled together into a new draw pile.
• If the draw pile and discard piles are all empty, the player does not draw and plays one normal move.

4Card effects

Series rules (several moves):

• The first move is mandatory if one exists; the player may then end the series at any time.
• The same piece may move several times. No draw between moves.
• If no move is possible anymore, the series stops.
• Capturing the king ends the game immediately.

Pawn recovery (+2 / +4):

• Only pawns actually captured by the opponent are recovered (never more than the number captured).
• The player chooses the squares: free squares of their starting rank (2 for White, 7 for Black); if that rank is full, the next one (3 / 6) experimental.
• With no captured pawn or no free square, the card simply grants 1 normal move.

Reverse: since there are no hands, only the armies are swapped. A Reverse neither grants nor extends an en passant right.

5Capturing the king, checkmate

You win by capturing the enemy king. There is no checkmate in the classic sense: even when their king is trapped, the opponent always draws a card to try to escape (a Joker, a series of moves, recovered pawns or a Reverse can change everything).

• Check: when a king is attacked, “Check!” is shown to both players and the king’s square is highlighted. The player concerned can parry with their turn’s card.
• Checkmate: if, when you have the move (after your draw, or during your series of moves), one of your moves can capture the enemy king, the game stops at once and you win by checkmate, without having to play the capture. If your card gives you no move (a 0, a Skip), there is no mate: the king survives that turn.

• You may leave your king on an attacked square, expose your king, move a “pinned” piece, or place the kings side by side.
• Piece movements, obstacles, captures and promotions are unchanged.
• Nothing forces you to answer a threat to the king: check is information, it blocks no action.
• “Careful king” option (kingAvoidsAttackedSquares, off by default): as in classic chess, the king cannot move to a square attacked by the opponent, and so cannot capture a defended piece. This also applies to the Joker’s “queen” moves. Capturing the enemy king is always allowed. Other pieces are not affected.
• Capturing the king, like checkmate, ends the game immediately and takes precedence over the remaining moves. A pawn capturing the king on the last rank does not choose a promotion piece: the game is over. The win goes to the current owner of the winning army (important after a Reverse).

Castling: classic conditions (king and rook not moved, squares in between free); allowed from, through or into an attacked square.

En passant: after a double step, the capture is only possible on the very next move, by the opposing army. Any other move, a fully skipped turn or an extra move by the same army (series) makes it expire.

6Series safeguard experimental

Setting stopComboOnKingThreat = true by default. When on, after each non-final move of a series, if the enemy king is attacked, the series stops and the turn passes to the other army. The attack is determined by the board’s moves and obstacles alone. This setting can be turned off before the game; it is locked during the game.

7Draws, resignation and disconnection

• The classic automatic draws (repetition, insufficient material, 50 moves) are disabled.
• Draw agreed by both players; resignation; draw after 10 consecutive turns without a piece moving experimental (threshold drawAfterTurnsWithoutMove, reset by any move actually played).
• Disconnection: in a game between humans, a disconnected player has a reconnection window (server setting, 60 s by default, shown in the game’s rules). Past that window without coming back, they forfeit. This window only exists in the server’s memory: a crash or restart never causes a forfeit, the game resumes from its saved state. A game against the computer can be resumed without any limit.
• Reconnecting or reloading never triggers a new draw: the full state is saved after every accepted command.

8What players see

Everyone sees: the board, the turn’s revealed card, the draw pile (count), each player’s discard pile, each army’s recoverable captured pawns, the armies controlled, pending effects, the player allowed to act, the remaining moves, the public log and connection states. The order of the draw pile and the server’s randomness are never sent. The computer only receives this same observation.

9Ranking

• Only finished games between two accounts are ranked; games against the computer do not count.
• Elo rating: 1000 at the start; a win against a higher-rated player earns more. The first 10 games count more (K = 40, then 24) to place a new player quickly.
• Tiers: 🥉 Bronze, 🥈 Silver (950+), 🥇 Gold (1050+), 🏆 Platinum (1200+), 💎 Diamond (1400+).
• Resignations and forfeits count as losses; a draw brings both ratings closer.
• For each pair of players, the head-to-head record (wins, losses, draws, recent form) is public.

10Configurable settings (default values)