combines the elements of three logic puzzles: , and . It consists of a square grid with white and black cells. The goal is to fill in the white cells, one number in each, so that each column and row contains the numbers 1 through 9 exactly once. Black cells contain a diagonal slash from top left to bottom right with numbers in them, called "the clues". Such number tells the sum of numbers in consecutive cells at its right or downward. If absolute difference between two numbers in neighboring cells equals 1, then they are separated by a dot. If a dot is absent between two white cells, the difference between the numbers in these cells is more than 1.