The board has a magnetic surface, which is also dry-erase. Two sets of magnetic numbered tiles is included, one black and white and the other coloured with each number a different colour. A black and white number is placed in the positions of the "given" numbers. The dry-erase pen (also included) is then used to test out and write in numbers, which may be used in the other squares. As the trial numbers are eliminated they are easily removed using the duster supplied. Once a number is finally determined a coloured magnetic number is placed in that position. And so on until the puzzle is completed.