Trade Chess

Rules

The rules are the same as standard FIDE chess, except as follows:

Both players collect the pieces they capture. When both players have captured a piece of the same type, they trade them. Instead of moving a piece, players can place a captured piece of their color they have. (Promoted pawns are treated as the piece they were promoted to when captured.)

Pieces can be placed anywhere on the board, except as follows:

Pieces cannot be placed on a square where they can attack an enemy piece, or on a square already occupied by a piece.

Pawns must be placed (any distance) behind a pawn of the same color. (Pawns on your 2nd rank can move 2 squares forwards. If you have no pawns on the board, you cannot place pawns.)

Notes

Dropping pieces gives games more options and potentially more strategic depth, but dropping captured enemy pieces makes comebacks and positional sacrifices more difficult, and games like "hostage chess" are unstable and extremely aggressive.