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Crazyhouse is a chess variant. The main difference between it and regular chess is that in Crazyhouse chess, captured pieces reverse color and can be put back (or "dropped") onto the board by the capturing player. The variant is often compared to Shogi (Japanese chess), whose "drop" rule is largely the same as the one in Crazyhouse chess.


The rules of Crazyhouse are the same as those of regular chess, with the following additions:

  • Every time a piece is captured, it reverses color and goes into the capturing player's "reserve".
  • A player may use their turn to "drop" a piece from their reserve onto any vacant square on the board, in lieu of making a move.
    • A pawn may not be dropped onto the first or eighth rank.
    • A pawn dropped onto the player's second rank may advance one or two squares on its first move; a pawn dropped onto any other rank may not.
    • When a promoted piece is captured, it enters the capturing player's reserve as a pawn.


Crazyhouse notation is an extension of the standard algebraic notation. Drops are notated with the abbreviation of the piece's name (pawns are abbreviated as P), followed by an at sign (@) and the square on which the piece is dropped. For example, dropping a bishop on the square g4 would be notated as "B@g4", and dropping a pawn on the square h2 would be notated as "P@h2".