Origin of Doppelganger Chess: Many years ago I saw a Twilight Zone episode about a lady who was waiting at a desolate bus station. In the dim light and silence she eventually got a glimpse of someone someone who looked just like her and who was there to take her place in the world she had seen her doppelganger. On the morning of May 1st, 2004 I awoke with Doppelganger Chess in my head. It is based on the presence of Doppelgangers (shadow walkers). Doppelgangers are indistinguishable from normal earthly chess pieces.
How to play: Standard 8x8 board western chess setup and movement apply, with the exception of what happens after a piece is captured and what happens after a pawn is promoted. The object is to checkmate your opponent.
Captures: The captures are based on the existence of Doppelgangers. The person making the capture removes the captured piece and its counterpart (a Doppelganger). Thus, if a Bishop is captured both enemy Bishops are removed from the board. If a pawn is captured, the player making the capture removes it plus any one other enemy pawn (capturers choice). If the removal of the second piece (or pawn) causes check to your opponent, that is fine. But you cannot capture a piece (or pawn) if removal of its counter part would put your King in check. Queens have no Doppelganger, so capturing a Queen results in only in removal of that Queen.
Promotions: A pawn promotion is always a Doppelganger Promotion and must result in adding 2 Rooks, 2 Knights, or 2 Bishops. You can end up with 4 rooks, 6 rooks, etc. You cannot promote a pawn to a Queen. To promote a pawn: (1) move it to the last rank, (2) replace it with a Bishop, Knight, or Rook, (3) remove one of your other pawns (4) replace it with the second Bishop, Knight, or Rook. If either piece is captured now (or later) both it and its counterpart are removed. Note: You can end up with two light or two dark-squared Bishops as a result of promotion, depending on where the second pawn is.
A Note in Closing: In the original game (the one that I awoke with) black pieces were doppelgangers relative to white pieces and visa versa. When you captured a piece both it and a matching one of yours was removed. Even promotions resulted in a promotion for your opponent. Material balance was maintained throughout the game, and it was very difficult to achieve victory. That game is a real workout and can be very frustrating. I changed the game so that each side had its own doppelgangers and by doing so created great opportunity for dynamic imbalance. Based on games played, the game submitted here is much more fun than the subconsciously created version, but should there be any interest in the original game, I will gladly submit the rules.
Gary K. Gifford 5/16/2004