Logic Masters Deutschland e.V.

This is a variant of a kropki sudoku, in which each dot gives information about 4 adjacent cells, not 2.

Standard sudoku rules apply: Fill the grid with numbers from 1 to 9, so that every row, column, and 3x3 box contains each of the 9 numbers exactly once.

For each group of 4 cells that forms a 2x2 square, a black dot in the middle means that the numbers can be divided into 2 pairs (A,B) and (C,D) with A/B=2 and C/D=2. A white dot means that they can be divided so that A‑B=1 and C‑D=1. A grey dot means that they can be divided so that A‑B=1 and C/D=2.

In case 2 different dots could be used, the darkest possible dot will be shown. For example, the numbers 1, 2, 3, and 6 would have a black dot, since 2/1=2 and 6/3=2, not a grey dot (2‑1=1 and 6/3=2). The numbers 3, 4, 5, and 6 would have a grey dot, since 5‑4=1 and 6/3=2, not a white dot (4‑3=1 and 6‑5=1).

Digits can be repeated within a 2x2 square if they're not in the same row, column, or box.

All possible dots are given.

The puzzle is available on Penpa.