1.N@e7+ Kh8 2.Bxg7# (@ notation)
1.N@e7+ Kh8 2.Bxg7# (@ notation)

Crazyhouse (also known as drop chess, mad chess, reinforcement chess, turnabout chess and schizo-chess) is a chess variant in which captured enemy pieces can be reintroduced, or dropped, into the game as one's own. The drop rule is based on that of shogi. Crazyhouse is similar to bughouse chess; however, a game of Crazyhouse involves only two players.


The rules of chess apply except for the addition of drops, as explained below.

Unlike in shogi, dropping a pawn on a file containing another pawn of the same color and dropping a pawn to deliver checkmate are both permissible.[2]


To extend the standard algebraic notation, a drop is notated by inserting an at sign between the piece type and the destination square. For example, N@d5 means "knight is dropped on d5."[1]


There is no standard FEN specification for Crazyhouse. Lichess uses an extended version of FEN, adding a 9th rank as a reserve. Here is an example of Lichess's FEN implemention:[3]

r2qk3/pp2bqR1/2p5/8/3Pn3/3BPpB1/PPPp1PPP/RK1R4/PNNNbpp b - - 89 45

In Xboard/Winboard's notation system, the reserve is given in square brackets following the board position:

r2qk3/pp2bqR1/2p5/8/3Pn3/3BPpB1/PPPp1PPP/RK1R4[PNNNbpp] b - - 89 45

In Chess.com's notation system, the reserve is located after the full-move number.

To keep track of which pieces are promoted, Lichess and Xboard/Winboard use "~" after the letter designation. Chess.com uses the coordinates of the pieces.[4][failed verification]

r2q1r1k/2p1ppb1/p2p2pp/3P1p2/B6B/2N2NPp/1PP2P1K/3Q3q w - - 0 26 NNBRpr h1


Crazyhouse has several related variants:

See also


  1. ^ a b "crazyhouse". FICS Help. Free Internet Chess Server. 2008-02-28. Archived from the original on 2014-04-16. Retrieved 2014-04-17.
  2. ^ a b c "crazyhouse". ICC Help. Internet Chess Club. Archived from the original on 2012-05-02. Retrieved 2014-04-17.
  3. ^ ""IM opperwezen vs LM JannLee in T6Q3tMva : Analysis board • lichess.org"". Lichess. Archived from the original on 2018-05-26. Retrieved 2018-05-26.
  4. ^ ""Chess: liviu78ro vs JannLeeCrazyhouse - 3367504566 - Chess.com"". Chess.com. Archived from the original on 2019-01-17. Retrieved 2019-01-17.
  5. ^ "Game rules (Loop Chess)". BrainKing. Retrieved 2014-04-17.
  6. ^ "Chessgi". ChessVariants.org. 2001-03-20. Archived from the original on 2014-03-27. Retrieved 2014-04-17.