2- The 9x9 chessboard
The board used in Chess 99 consists of 81 squares arranged in a 9x9 grid of alternating light and dark squares. The vertical columns of squares are called “files”, the horizontal rows of squares are called “ranks”, and the straight lines of squares of the same color running from one edge of the board to an adjacent edge are called “diagonals”.
The files are labelled from left to right by the letters a to i and the ranks are labelled from bottom to top by the numbers 1 to 9. Each and every square on the board can thus be referenced by its unique set of coordinates. For example, the dark square at the very center of the board is called ‘e5’.
The 9x9 board is noticeably larger (by 26%) than the standard chessboard but it differs in other ways from its counterpart. For one thing, it has both a central file (e) and a central rank (5). The two major diagonals – those running from corner to corner – are both dark from which it naturally follows that all four corner squares are also dark and that the board can never be oriented incorrectly.
Those already familiar with the game of chess will know that control of the board center is usually considered important since it allows for an easier development of one’s pieces as well as easier access to other parts of the board. On the standard 8x8 board, the so-called “center” is a 2x2 block of four squares; on the 9x9 board, it is defined as the 3x3 block of nine squares centered on e5.