Hitori is a small logic puzzle in a similar vein to the more popular Sudoku. In the game, the player starts with a square board of numbers, and has to paint out cells until there are no duplicate numbers in each row and column. The following rules apply:
There must only be one of each number in the unpainted cells in each row and column.
No painted cell may be adjacent to another, vertically or horizontally.
All the unpainted cells must be joined together vertically and horizontally in one group.
These are the only three rules of the game, and so there may well be multiple solutions to a Hitori puzzle board.