The case notes
Follow a chain of black dots
Three black dots join these four cells. Each step doubles or halves a digit. Read the whole chain, not one dot at a time. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Four cells · three black dots
Three black dots join these four cells. Each step doubles or halves a digit. Read the whole chain, not one dot at a time.
1 → 2 → 4 → 8
Start with one. The next digit is two, then four, then eight. All four are different, so this works in a Sudoku row.
Only forward or reverse
Starting at eight simply reverses it: eight, four, two, one. Starting at three gets to six, but twelve is outside the grid. Turning back repeats three.
Ends: 1 or 8
So the ends can only be one or eight. Two and four belong in the middle. This deduction needs the full chain and the row rule together.
Read the transcript
Three black dots join these four cells. Each step doubles or halves a digit. Read the whole chain, not one dot at a time. Start with one. The next digit is two, then four, then eight. All four are different, so this works in a Sudoku row. Starting at eight simply reverses it: eight, four, two, one. Starting at three gets to six, but twelve is outside the grid. Turning back repeats three. So the ends can only be one or eight. Two and four belong in the middle. This deduction needs the full chain and the row rule together.
Keep following the clues
- Kropki Sudoku: How Kropki dots work →
- 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: Count even digits through V and white dots →
- Kropki Sudoku: Use a black dot to protect a box’s last one →
