Bughouse Rules & How to Play

Bughouse (Exchange Chess, Tandem Chess, Double Chess) is a four-player team variant. Two chess games run at the same time on Board Alpha and Board Bravo. When you capture a piece, it goes to your partner's reserve (pocket). Your partner can later drop that piece onto their board instead of making a normal move.

Bughouse Arena validates every move and drop server-side against these official rules using a dedicated rules engine built on chess.js.

Bughouse uses exactly two physical boards. Both teams play on both boards — one player from each team sits at each board:

• Board A (Alpha) — Team 1 White vs Team 2 Black
• Board B (Bravo) — Team 2 White vs Team 1 Black

There are no separate Board C or Board D. Four players share these two boards. Each board has its own position, clocks, and reserves. Captures on one board feed your partner's reserve on the other board.

In the arena you see your board and your partner's board. Captures you make appear in your partner's pocket instantly.

All normal chess rules apply on each board, validated through chess.js:

• Legal piece movement, including castling and en passant
• Check, checkmate, and pawn promotion on the final rank
• On your turn you make one action: a normal move or a reserve drop — never both

When you capture an enemy piece:

1. The piece is removed from your board.
2. Its type is determined (see promoted-piece rule below).
3. That piece is added to your partner's reserve — not yours.

Promoted pieces are tracked by square. If a promoted pawn is captured — even if it became a queen, rook, bishop, or knight — your partner receives a pawn, not the promoted piece type.

Example: a pawn promotes to queen on e8. Later that queen is captured. Your partner's reserve gains P, not Q.

Instead of moving, play a piece from your reserve onto any empty square. Drop notation looks like N@f7 (knight on f7) or Q@h6# (queen drop delivering mate). A drop uses your entire turn.

Dropped pawns cannot move two squares on their first move. If a dropped pawn later reaches the final rank, it promotes normally under standard chess rules.

In Bughouse Arena: select a piece in your pocket, then click an empty square on your board.

A drop is legal only when all of the following hold:

• The target square is empty
• You own the piece in your reserve
• It is your turn on that board
• After the drop, your king is not in check

A dropped piece may give check (N@f7+) or checkmate (Q@h6#) to the opponent. That is legal and often decisive.

You may never move or drop while your own king remains in check. If you are in check, you must move the king, capture the attacker, block the line, or drop a piece that resolves the check — such as B@d2 blocking the queen on c3 in the diagram above.

One board stalemating does not draw the full match. The game continues on the active board unless both boards are drawn under tournament rules.

Official Bughouse uses independent clocks on each board: White Alpha Clock, Black Alpha Clock, White Bravo Clock, and Black Bravo Clock. When White moves, White's clock stops and Black's clock on that same board runs — independently on Alpha and Bravo.

If anyplayer's clock hits zero, that player's team loses immediately.

When the match begins, both boards start simultaneously— White's clock on Alpha and White's clock on Bravo begin running immediately. No first move is required to start the clocks. If a player delays their opening move, only their own clock continues to run.

The match ends immediately when any of these occur:

1. Checkmate on either board
2. Time forfeit — any player's clock reaches zero
3. Resignation by any player (forfeits the whole team)
4. Administrative forfeit

Built-in voice chat connects you to your partner at match start. Queue solo or party with a friend to guarantee partner pairing.