Fill some white cells using digits 1-9, such that the sum of each block of digits equals the clues in the grey cells. A clue above a diagonal applies to the block of digits to its right. A clue beneath a diagonal applies to the block of digits below it. Within a block all digits are different. Some cells remain empty. All empty cells are traversed by a single closed loop that travels horizontally and vertically and doesn’t cross or overlap itself.