Normal sudoku rules apply. Digits along the blue 'negative' diagonal may not repeat; this diagonal begins in row 1 column 1 and crosses the grid to row 9 column 9. Some of the grid is covered in fog; placing a correct digit will remove the fog surrounding that digit. No guessing is required. A cell with a blue square contains an even digit. Digits in cells joined by an X sum to 10; NOT all X clues are given. Digits in cells joined by a V sum to 5; ALL V clues are given and visible from the outset of the puzzle. If two digits are joined by a black dot then one of those digits is double the other. Not all black dots are given.