Logic Masters Deutschland e.V.

If you'd like a somewhat easier introduction to these rules, check out Moduloops!

Place the digits 1-9 once into each row, column, and 3x3 box.

XV and Kropki dots work modulo 9:

• Two digits separated by an X must sum to 10.
• Two digits separated by a V must sum to either 5 or 14.
• Two digits separated by a white dot must be consecutive; 1 and 9 are consecutive.
• Two digits separated by a black dot must be in a 1:2 ratio modulo 9, meaning that one digit multiplied by 2 must be equal to either the other digit or the other digit plus 9. For example, 5 and 1 can be separated by a black dot, because 5 x 2 = 10 = 1 + 9.

Online solver: SudokuPad