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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 resembles that of shogi; the two games are often compared though no evidence suggests the one developing from the other. Crazyhouse is similar to bughouse chess; however, a game of Crazyhouse involves only two players.
Crazyhouse
by Fergus Duniho, '' The Chess Variant Pages''
Scidb
a chess database supporting Crazyhouse
Rules
for the variant on '' Lichess''
Blog post
with introduction, theory and more resources {{Chess variants, state=collapsed Chess variants
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 resembles that of shogi; the two games are often compared though no evidence suggests the one developing from the other. Crazyhouse is similar to bughouse chess; however, a game of Crazyhouse involves only two players.
Rules
The rules of chess apply except for the addition of drops, as explained below. * A piece that is captured reverses color and goes to the capturing player's reserve, pocket or bank, where it is considered held or in hand. At any time, instead of making a move with a piece on the board, a player can ''drop'' one of their held pieces onto an empty square on the board. * A pawn may not be dropped on the 1st or 8th . * A pawn that is dropped on its 2nd rank may use its two-square initial advance; a pawn that is dropped on any other rank cannot. * When a piece that is promoted from a pawn is captured, it enters the opponent's reserve as a pawn. Unlike in shogi, dropping a pawn on a containing another pawn of the same color and dropping a pawn to deliver checkmate are both permissible.Notation
To extend the standard algebraic notation, a drop is notated by inserting anat sign
The at sign, , is normally read aloud as "at"; it is also commonly called the at symbol, commercial at, or address sign. It is used as an accounting and invoice abbreviation meaning "at a rate of" (e.g. 7 widgets @ £2 per widget = £14), but ...
between the piece type and the destination square. For example, N@d5 means "knight is dropped on d5."
FEN
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 implementation:r2qk3/pp2bqR1/2p5/8/3Pn3/3BPpB1/PPPp1PPP/RK1R4/PNNNbpp b - - 89 45In XBoard/Winboard's notation system, the reserve is given in square brackets following the board position:
r2qk3/pp2bqR1/2p5/8/3Pn3/3BPpB1/PPPp1PPP/RK1R4 NNNbppb - - 89 45In 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.
r2q1r1k/2p1ppb1/p2p2pp/3P1p2/B6B/2N2NPp/1PP2P1K/3Q3q w - - 0 26 NNBRpr h1
Variations
Crazyhouse has several related variants: * Loop Chess: A promoted piece keeps its rank when captured. * Chessgi (also known as Mad Mate or Neo Chess): A promoted piece keeps its rank when captured. A pawn may be dropped on its 1st rank.See also
* Hostage chess, a variant where a player can drop back into play their own previously captured piecesReferences
External links
Crazyhouse
by Fergus Duniho, '' The Chess Variant Pages''
Scidb
a chess database supporting Crazyhouse
Rules
for the variant on '' Lichess''
Blog post
with introduction, theory and more resources {{Chess variants, state=collapsed Chess variants