Normal sudoku rules apply. Entering correct digits may clear fog somewhere in the grid. No guessing is necessary. Digits along a beige 'hitline' do not repeat. The number on a blue circle (or two-digit pill reading downwards or from left to right) points to the first cell ('position 1') along a hitline, and indicates the total of any digits that equal their position number along that hitline. Eg: on a 4-cell hitline, if the sequence of digits reads 1694 starting from the cell being pointed at, then the blue total would be 5 (the sum of 1 and 4) because 1 is in the 1st position and 4 is in the 4th position, and these are the only digits which match their position numbers.