Together with the passing and dropping of pieces, this can make the game look chaotic to the casual onlooker, hence the name bughouse, which is slang for mental hospital.

There are references to a bughouse-like game in the 1930's, perhaps evolved by players like Alekhine, who visited Japan and witnessed Shogi.

[6] When used, it applies to pieces in reserve as well; they are considered dropped after contact has been made with an empty square.

Bughouse can be played without a clock, but then there is usually a rule preventing a player waiting for pieces (stalling or sitting) indefinitely.

A game is won when one player gets checkmated, resigns, runs out of time, or makes an illegal move.

The match can be drawn by agreement or when two players on opposite teams run out of time or are checkmated simultaneously.

In three-board bughouse chess, the middle player is the key since they get material from two boards, but have to decide how to divide the captured pieces.

In standard chess, a pawn equals one unit, a bishop or knight is worth three, a rook five and a queen nine.

Long-range pieces like the queen or the rook lose relative value, due to the constantly changing pawn structure.

[15] Another common situation in the interplay between the two boards is a player not moving, a strategy known as sitting or stalling.

[17] Apart from active communication, a good bughouse player tries to coordinate silently by keeping an eye on the other board and adapting moves accordingly.

From a player's perspective, attacking the king has important advantages as opposed to defending or attempting to win material:[19] Partner communication is essential in a good defense.

[22] Bughouse openings are generally geared towards dominating vital squares and fast development.

[28][30][31][32][33][34] One of the strongest matches on record (in terms of chess players' ratings) took place following the 2014 Sinquefield Cup, with Magnus Carlsen and Maxime Vachier-Lagrave teaming up against Fabiano Caruana and Levon Aronian – all four being among the top ten chess players in the world at the time.

Examples include: Other tournaments are organized privately: Since 1995, Bughouse has been available online at chess servers such as FICS and ICC and, as of 2016, at Chess.com.

[44] FICS was historically the most active server for bughouse, attracting the world's best players like Levon Aronian,[45] but it is much more likely to find a game more quickly at chess.com.

In games over the board, communication is heard by all players, while in online bughouse it is usually done via private messages between two partners.

They have the ability to display both boards at the same time and store played or observed games; they also have partner communication buttons and a lag indicator.

[48][49][50] Although much faster than humans, they lack in positional understanding and especially in coordination and communication, an essential skill in this team game.

While some instructors find beneficial learning outcomes for bughouse, most do not consider it to have a positive effect, especially for novice chess players.

"[55] Arguments supporting a negative view of bughouse include that it distorts typical chess pattern recognition[56] and that it too heavily emphasizes tactical play at the expense of positional strategy.

[57] For example, in bughouse, one can just drop a pawn to compensate for a weakness created by moving one, unlike normal chess.

It also lacks endgame play due to pieces being recycled, thereby reducing the need for precise moves.

In addition, the lack of control over teammates' boards introduces randomness that is not encountered in normal chess.

Further, many claim that since there is no set order of moves between the two boards, normal calculation ability is diminished.

I started to play bug when I was already at master level, [you] see, and I think bughouse is good for the imagination, to develop new ideas.

"[57] For Joel Benjamin, bughouse trains players to pay closer attention to empty squares on the board.