Normal sudoku rules apply. The cells in the grid are numbered from 1 to 81 in normal reading order ie 1 at the upper left, ..., 9 at the upper right until 81 at the bottom right. The digit in a cell with a square number is itself a square (1,4,9) while the digit in a cell with prime number is a prime (2,3,5,7). In addition, any vertical or horizontal straight line of three cells never contains a consecutive set of digits.