Kropki

Kropki adds white and black dots between cells on the grid.

White dot means that digits on the cells must be consecutive, and black dot means digits must be in 1:2 relation. E.g. if one cell is 3 the other must be 6 or if one cells is 4 the other must be 2 or 8.

When grid has three cell in the same house (box, column or row) joined with two black Kropki dots those cells must be either 124 or 248. If the same house contains another pair of cells with black kropki, that other pair must be 36.