Using chess sets to play mini-sukoku (6x6)

Mini-sudoku with chess pieces

This is not an original game, nor does it really have anything to do with chess, beyond using the pieces. It is just a way to use two chess sets to play the existing game mini-sudoku.

Mini-sudoku is played on a 6-by-6 board using six numbers instead of nine. The board is arranged in six groups of six squares. (See the setup section for a diagram.) The goal is to fill in the missing numbers so that each row, column and 2x3 subsection contains exactly one of each number.

You can get mini-sudoku puzzles several places on the Internet, including sudokuplace.com and sudoku.org.uk. You can turn these puzzles into a nice solitaire board game by using a chessboard and two sets of chess pieces. I will also describe a way to play independently, without relying on previously created starting positions.

Setup

The playing space will be six sections of the chessboard, with blank rows and columns between them (Xs represent the playing area):

x x x . . x x x
x x x . . x x x
. . . . . . . . 
x x x . . x x x
x x x . . x x x
. . . . . . . .
x x x . . x x x
x x x . . x x x

If you are using a previously-created opening position, follow the puzzle diagram to arrange the given pieces on the board, interpreting a 1 as king, 2 as queen, 3 as bishop, 4 as knight, 5 as rook, and 6 as pawn. Once the given pieces are in place, you don't have to remember which piece represents which number.

If you are playing independently, take the eleven black pieces from the first chess set (king, queen, 2 bishops, 2 knights, 2 rooks and 3 pawns) and arrange them at random on the playing area. Make sure that each subsection of the board has at least one piece, and no more than three. Also make sure that no row or column or 2x3 subsection contains more than one of any kind of piece.

Pieces

To play you need six of each piece (K,Q,B,Kt,R,P), three of each color. If you use three chess sets, you will have enough. If you use two chess sets, you will have four of each color except for the king and queen. You need an extra king and queen of each color. Take one bishop of each color from the second chess set and mark them some way (with rubber bands or stickers or paper collars etc,) and think of them as kings. Take one rook of each color from the second chess set and mark them to make them into queens. Set aside the two extra knights from the second set. Also set aside all the extra pawns, keeping three of each color.

Rules

Once the black pieces of the first chess set are in place, try to place the other pieces so that each row, column and subsection contains exactly one of each kind of piece. If you are using a previously-created setup, this should be possible in only one way. If you are playing independently, one of three things will happen:

1. There will be only one solution. This is unlikely, but it does happen sometimes.
2. There will be more than one solution. When you see that this is the case, choose one of the possibilities and continue playing.
3. There will be no solution. When you reach an impasse, move one of the original pieces in such a way that it doesn't make a duplicate in any row, column or section. You may have to move more than one piece. Try to do this in as few moves as possible. Then continue playing. This can make for a very challenging puzzle. However, often one or two simple moves will fix the problem.

Notes

In practice I've found that most of the time I'm able to bring the game to a successful completion without too much trouble. I find that if I've narrowed the position of piece to one of two adjacent squares, it helps to place the piece on the boundary between the squares. Then later when I've eliminated one of the squares, it makes it easy to place the piece.

When you have finished, you may want to write down where the black pieces from the first set are. If you had more than one solution, you may also want to write down where you put the extra piece you chose so that you could continue playing. Congratulations! You have created your own puzzle that you can play again later. You can start with more or fewer than eleven pieces, but that will make it more difficult to record your successful starting position when you are done.