Rules: Enter a single digit from 1 to 9 into some cells so that the sum of digits in each Across entry equals the value given to the left of the entry, and the sum of digits in each Down entry equals the value given above the entry. No digit may be repeated within a single sum. Some cells may remain empty, and empty cells cannot be adjacent.
Background: It is one of my inventions. I made first time for 19th WPC in Poland. However, this idea wasn’t used in 19th WPC. After that I made this type for many different places like Raetsel Portal 1, 2, 3; Best of LMI Test, Puzzle Jackpot, 11th 24 HPC.