Contains a new puzzle variation: Kropki, implementation of Kropki
Works similiar to the Adjacent mode, with these rules:
- A black circle indicates that one number is double to its neighbour.
- A white circle indicates that one number is adjacent (one higher / lower) to its neighbour.
- No circle means both numbers must not be double or adjacent.
- The numbers 1 and 2 are both double and adjacent to each other. In this case, the circle color is chosen randomly.