Path of the Warrior Chess

Each chess piece has a rubber ink stamp on the bottom. Each side has its own color, naturally. Using a dry-erase board, and dry-erase ink, the game is played in the usual fashion... except that no piece may ever occupy a space that has formerly been occupied by a different type member of its own side. So, any pawn can occupy space that has your color's pawn mark on it. But a knight must find a different space. Eventually, every space will be filled with colored unit identifiers. Knights can only land on spaces with your color's knight identifiers on them. The same goes for every piece. You can move them over other identifiers to reach your destination, but cannot stop on one. Kings and queens are exempt from this rule, and can move at will as usual.