Crazyhouse

In Crazyhouse, the board and basic piece movement begin like standard chess, but every capture also gives the capturer a new resource. The captured piece changes color and enters that player's personal reserve, often called a pocket.

On a later turn, the player may make a drop: instead of moving a piece already on the board, they choose a reserve piece and place it on an empty square. Pawns cannot be dropped on the first or eighth rank. If a pawn promotes and is later captured, it returns to the reserve as a pawn, not as the piece it had become.

Drops also change how check works. A reserve piece can block an attacking line, give check, or even deliver checkmate if the drop is legal. A captured piece therefore should not be treated as permanently removed: it can reappear in almost any part of the board and create attacks or defenses that standard chess does not allow.

Crazyhouse is closely related to Bughouse, but it removes the partner and second board. In Crazyhouse, the piece you capture becomes available to you personally.