Place the digits 0 to 8 exactly once each in every row, column and 3x3 box. The grid is partially covered in fog. Placing correct digits will clear the fog from surrounding cells, possibly revealing more clues. Digits separated by a V sum to 5. Digits separated by an X sum to 10. Not all Vs and Xs are necessarily given. Every horizontal domino which sums to 5 must have either the two cells directly above it summing to 1 or the two cells directly below it summing to 9 (it could have both, but it doesn't need both).