The case notes
How Kropki dots work
White dots join consecutive digits. Black dots join digits in a one-to-two ratio. Pairs without dots are free. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Two dots. Two rules.
These little dots sit between neighbouring Sudoku cells. White and black dots tell two different stories.
White: one apart
A white dot joins consecutive digits. Next to eight, that means seven or nine. The dot does not tell us which one yet.
The column chooses 9
There is already a seven in this column. Cross out seven here. Nine is the only neighbour left for eight.
Black: one is double
A black dot means one digit is double the other. Half of six is three. Double six would be twelve, so this cell is three.
Read the dots, not the gaps
White means one apart. Black means double. An empty gap says nothing unless the puzzle specifically gives a negative-dot rule.
Read the transcript
These little dots sit between neighbouring Sudoku cells. White and black dots tell two different stories. A white dot joins consecutive digits. Next to eight, that means seven or nine. The dot does not tell us which one yet. There is already a seven in this column. Cross out seven here. Nine is the only neighbour left for eight. A black dot means one digit is double the other. Half of six is three. Double six would be twelve, so this cell is three. White means one apart. Black means double. An empty gap says nothing unless the puzzle specifically gives a negative-dot rule.
Keep following the clues
- Kropki Sudoku: Find the partner across a dot or marker →
- Kropki Sudoku: Read two dots together →
- Kropki Sudoku: Carry a Whisper’s side through a black dot →
- Kropki Sudoku: Let a Whisper choose between dot-chain options →
- Kropki Sudoku: Follow a chain of black dots →
- Kropki Sudoku: Count even digits through V and white dots →
- Kropki Sudoku: Use a black dot to protect a box’s last one →
