Box Brain Sudoku
Rules › Kropki
How to play Kropki sudoku
Kropki sudoku marks the edges between neighbouring cells with white and black dots. Few or no digits are given; the dots do the work.
Dots between neighbours.
The rules
- Classic rules apply: every row, column and 3×3 box holds the digits 1 to 9 once each.
- A white dot joins two consecutive digits, like 4 and 5.
- A black dot joins two digits where one is double the other, like 3 and 6.
- Every such pair is marked. Neighbours without a dot are neither.
Where to start
- A cell with dots on every side has few options. A black dot can only use 1, 2, 3, 4, 6 and 8.
- A missing dot is a clue too: those two neighbours are not consecutive, and neither is double the other.
Play Kropki in Box Brain Sudoku
Every Kropki puzzle in the app has exactly one solution and can be solved by logic alone, from Easy to Expert. Stuck? A hint first nudges you towards the right area, then names the technique and shows the move.