Normal sudoku rules apply, and four 3x3 magic squares appear in the puzzle (in a 3x3 magic square, the numbers 1-9 are used, and each row, column and diagonal adds up to the same number).
Normal sudoku rules apply, and four 3x3 magic squares appear in the puzzle (in a 3x3 magic square, the numbers 1-9 are used, and each row, column and diagonal adds up to the same number).