Objective / Rules - Eliminate numbers until there are no duplicates in any row or column. - Eliminate numbers by marking them in Black. - You are not allowed to have two Black squares touching horizontally or vertically (diagonally is ok). - Any White square can be reached from any other (i.e. they are connected).
Colour Key Grey = undecided. Black = eliminated. White = in final solution.
Mouse Usage Note: only when supported by your computer/device/browser/etc. If you know a square cannot be Black, then you can mark it in White. Left-click = Grey >> White >> Black >> Grey. Right-click = Grey >> Black >> White >> Grey.
Checking The objective is to find all of the Black squares. The system will check the grid when all of the squares are either Black or White. However, you can click 'Check' at any time to see if you've correctly found all of the Black squares or simply to check your progress so far. If 'Show mistakes when checking' is checked mistakes will be marked in red.
Uniqueness Each puzzle has exactly one solution, which can be found using logic alone and no guesses are ever required. If you think you've found another solution, then please double check the rules.