The board is divided into 9 smaller 3x3 blocks. Each field has one of the digits from 1 to 9 assigned. The digit can not be repeated in the same column/row and in any of the 3x3 blocks. In other words, each of the digits 1-9 must appear in every row/column/block. The goal of the game is to guess all the digits. The boards are generated automatically. Unfortunately, the boards are not perfect yet, so sometimes generating a board (especially on less powerful computers) may exceed the time during which the script can possibly run. In such case you should ignore the message.