by Jeff Caruso
January 2004 (updated November 2014)
This note describes a chess variant that was known as "hyper-chess" around MIT in the 1970s. I wish to thank people who have read this and sent me comments, especially Jerry Leichter who gave me a link to a copy of Robert Abbot's article in Recreational Mathematics (August 1962) describing an early version of the game.
Hyper Chess is a chess variant played with a standard board and pieces, though the pieces are named differently. Unlike chess, where all the pieces move differently but have the same basic method of capturing, in Hyper Chess the pieces move mostly the same way but capture all different ways.
The "king" is actually called a King, and moves (and captures!) like an ordinary chess king, though he has greater significance, as you will see.
The "pawns" are called Straddlers and move like an ordinary chess rook, though they don't capture like rooks. (see below)
The other pieces are named as follows:
All of these move like queens in ordinary chess (but of course they don't capture like chess queens). Each piece has its own special power, usually a special way of capturing.
There is no castling, no promotion, and no capturing en passant. On the other hand, all the capture rules might remind you of capturing en passant.
The object of the game, as in ordinary chess, is checkmate. That is, place the enemy King in a situation where he could be captured on the next move, and has no legal move that would get him out of it. The presence of pieces like Coordinators and Immobilizers gives us more ways to threaten such a capture, and more meanings to having no moves. But the ideas are the same.
As in ordinary chess, stalemate is the situation where the King is NOT threatened with immediate capture, but his side has no legal moves, and is a draw. This is sometimes the last resort in an otherwise lost position, and one way of attempting it is unique to Hyper Chess. (See below)
The Springer (N) captures by jumping over a lone enemy piece on the same rank, file, or diagonal. There must be no pieces between it and the enemy piece, and it leaps to a square immediately next to the enemy piece on the opposite side, which must be empty. The enemy piece is then removed from the board.
The Retractor (Q) can only capture a piece next to it, by moving one square in the exact opposite direction, but that square must be empty.
Straddlers (P) capture a piece by moving one on either side of it on a rank or file. The second straddler must make a move to do this. If there is an empty space between two straddlers an enemy piece can move there without ill effect, though one of the straddlers can move away and come back again to make the capture.
The Coordinator (R) captures by setting up two "death squares." Think of the rectangle described by the Coordinator and its own King. The squares at the other corners (if any) are death squares that swallow up any enemy pieces that try to stand on them. Friendly pieces can sit on such a square without ill effect.
If the King and Coordinator are on the same rank or file then they don't make any death squares. They can move to shift the death squares around (like underneath an enemy piece) and capture pieces this way. Unlike the empty space between two straddlers, the death squares remain deadly as long as the King and Coordinator are in their positions. An enemy piece can move to such a square, but vanishes immediately.
(Note: this interpretation might be specific to our crowd at MIT in the 1970s. Most other people I've talked to followed a different rule, namely that the death squares only come into effect at the end of the move of the coordinator (or a piece acting as a coordinator, see below), and do not persist. This would eliminate most of the "complexities" and "mysteries" described below.
A King is not allowed to move to a death square, in the same way that it isn't allowed to move into check. If a Springer or Retractor moves to a death square as part of a capture, it captures itself as well as the enemy piece! But a Straddler or Coordinator (or King!) dies before using its special power on the new square. I would say in a game with ordinary chess pieces against the hyperpieces, an ordinary chess piece could capture an enemy piece sitting on a death square, though it would vanish too.
Example: A White King sitting on the same file as the Black King, is IN CHECK if the Black Coordinator could move to a square on the White King's rank. Any square! If White can't stop the Coordinator and can't move his King off the file, he is checkmated!
The Immobilizer (U = Upside-down Rook) can't capture anything, but is actually the most powerful piece because no enemy piece next to it can move. This is even better than a pin in ordinary chess; an immobilized piece is so paralyzed that it cannot even give check! This can be a good way to get out of check--move the immobilizer next to the checking piece!
Two Immobilizers next to each other are BOTH immobilized, and still immobilize other enemy pieces. An immobilized King or Coordinator can still create death squares. But an immobilized King is in real trouble since it cannot move out of check, and the enemy King can move right up next to it to give checkmate!
However, it is possible in the endgame to try to move all your pieces next to the enemy immobilizer to try to get stalemate.
This is perhaps the oddest piece in this odd game. The Chameleon (B) exerts power on another piece by pretending to be the same kind of piece.
It can jump a Springer, or retract a Retractor, capturing it.
It can give check to a King by moving to a square one king-move away from him.
It can combine with its own King to create a "death square" for the enemy Coordinator. (This is a favorite trap!)
The Chameleon can immobilize an Immobilizer that is next to it, though then it is immobilized too. (In this situation, remember that the Chameleon doesn't immobilize anything else besides the Immobilizer!)
A Straddler can be captured by a Chameleon and a Straddler (or two Chameleons; why not?), but if the Chameleon is the piece moving to make the capture, it must do so by a Straddler's move (non-diagonal, that is) or it isn't a capture!
The Chameleons of opposing armies have no effect on each other.
It's not simple. Remember the example of the Coordinator and the enemy King. Well, a Coordinator and a Chameleon also set up death squares for the enemy King. It is check if he's on the same file as the Chameleon, if the Coordinator can move up to his rank. Similarly, if the enemy King is on the same rank as our Coordinator, he is in check if our Chameleon could make a King's move to any square on his file! Lots of checkmates happen this way, but often neither player notices!
But what if the Chameleon were further away? What if the enemy King is on the same rank as our Coordinator, and the Chameleon makes a long move (not a King move) to the file of the enemy King? I would say that the enemy King is not captured, but he is now in check, and must get out of check somehow. He must either move away, or capture the Chameleon or the Coordinator. Even immobilizing both of them at once won't save him!
The following position took me a long time to come to any conclusion about. Say the enemy King is immobilized, and I move my King up next to his. Checkmate, right? Not always--perhaps he can immobilize my King. But what about the following situation, where he places his Chameleon and Coordinator like so:
I can take his King, but I land on a death square for my King (from the Chameleon and the Coordinator), and so my King is lost instantly. I'm not sure what to call this! An immobilized piece can't give check. A pinned piece can give check, because intuitively his own King is merely in check when the other King is captured. This is an in-between case: a King moving to a death square to capture the other King.
I would argue that this is checkmate anyway, because my King lasts an instant longer than his. But it's a good example of the strange situations that arise in this strange game.