Ed's Big Plans

Computing for Science and Awesome

A Chess Post – S-Chess and Omega Chess

with 2 comments

Update: A link for Omega Chess, and a link for Seirawan Chess.

This is the first of a few posts I’d like to make about chess. In particular, this post is about two chess variants. Seirawan Chess (S-Chess) and Omega Chess. These two variants feature the familiar FIDE chess pieces along with two new pieces each. I’ll introduce each variant on their own first.

In Seirawan Chess, one starts with the familiar eight-by-eight board and opening array with the addition of two pieces set aside in reserve. These pieces are the Hawk and the Elephant. The Hawk is a Bishop and Knight compound while the Elephant is a Rook and Knight compound (a compound is a combination of pieces– a Queen is a Rook and Bishop compound). The two pieces that are set aside are placed onto the board when a player moves a piece from the back rank. The piece being dropped onto the board thus occupies the square in the back rank that has just been vacated. One can only place a single reserved piece in a given move. During a castle if the player so chooses, a reserved piece may be dropped on either the King’s or the Rook’s original square; it is not permitted to drop both reserved pieces during a castle.

In Omega Chess, one starts with a ten-by-ten board and an opening array that is flanked by the addition of a Champion and the Champion’s Pawn. The board is also extended diagonally by a single square in each of the four corners– these corner squares are occupied by a Wizard each. In the opening array, each piece is placed behind a Pawn with the exception of the Wizard. The Champion may move one step orthogonally, leap two steps orthogonally or leap two steps diagonally. The Wizard may move one step diagonally or leap (1, 3) — whereas a Knight leaps (1, 2). The Wizard is hence colour bound. The special corner Wizard squares are not actually special– they are just part of the board topology and can be used by all other pieces (except the Rook which cannot leap or slide diagonally into those spots).

For the fun of it, I have been playing Omega Chess with Seirawan Chess dropped pieces and it’s worked quite well so far. The size of the board accommodates well the Seirawan compounds. Additionally, I have been considering a house rule about dropping the Seirawan pieces– perhaps it shouldn’t be allowed that a dropped piece immediately defend the piece that dropped it. For instance, a Bishop dropping a Hawk makes for a very tough defense. A Wizard dropping a Hawk should be allowed however if the Wizard made its oblong (1, 3) leap.

If you see me walking around with a big black tube, I’m probably carrying this chess set. Challenge me to a game 😀

I’ll post some photos and such soon. The design of all the pieces from both sets is remarkably soothing and fits very well into the Staunton style. I was very lucky to discover that the Seirawan pieces are each appropriately tall compared to the Queen of the Omega Chess set I purchased.

One final thing– I decided to score the pieces in this combined game based on the mobility of each of the pieces on the ten-by-ten board. Here are my findings…

Score Piece Remark
29.40 Queen FIDE
23.76 Elephant Seirawan
18.00 Rook FIDE
17.16 Hawk Seirawan
11.40 Bishop FIDE
9.36 Champion Omega
8.28 Wizard Omega
6.84 King FIDE
5.76 Knight FIDE

The score is proportional to the total number of squares controlled by a piece calculated for every square it can occupy in the ten-by-ten grid. Aside from giving a general impression of how one would rank a piece against other pieces, there’s not really a lot that one can tell from this scheme. In this scheme, the Seirawan pieces rank high, and the Omega pieces rank low but only due to their finite ranges. Leapers’ attacks have the distinct advantage of being immune to blocking.

That’s all for now, back to work.

Eddie Ma

June 2nd, 2010 at 10:47 pm

E.Cho says...

there are 10×10 chess boards ? that’s awesome

i may try s-chess sometime

Eddie Ma says...

Wow, what an oversight! I should put links up to both of these items.