Sudoku variant · rules and tips

German Whisper

On a German Whisper line, any two neighbouring cells must differ by at least 5. The line is forced to leap between low digits and high ones, like a conversation between people who never agree.

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Professor Cryptic, the owl who teaches in the app
Professor Cryptic explains the rule

The Professor's tips

How do you solve German Whisper?

01 / Warm up

Start on a 4 by 4 grid

  • A gap of 5 is a large demand. Before you look at any line, ask which pairs on this grid could possibly be that far apart.
  • Reason from one cell outwards. Place a digit and the gap of 5 tells you at once what may stand beside it.
  • A whisper line zigzags between the extremes: low, high, low. Settle one digit and the rest of the line narrows quickly.
02 / Level up

Then try a 6 by 6 grid

  • With digits 1 to 6, a difference of 5 admits only the pair 1 and 6. That is the whole constraint, and it is a severe one.
  • Since only one pair qualifies, a whisper line of three or more cells would have to alternate 1, 6, 1, 6, which the row and column rules will usually forbid.
  • Use the line as a wedge rather than a puzzle in itself. Wherever it touches a cell, it eliminates almost every candidate.
  • Where a line offers few valid sequences, simply list them. Enumeration is not beneath you. It is frequently faster than brilliance.
03 / Full size

Move on to a 9 by 9 grid

  • With digits 1 to 9, a difference of at least 5 means every cell on the line is either low, 1 to 4, or high, 6 to 9. The digit 5 cannot appear on a whisper line at all, because nothing is 5 away from it in either direction. Poor 5. Always in the middle, never invited.
  • The line must therefore alternate: low, high, low, high. Settle one cell and the pattern of the whole line follows.
  • The extremes are the most sociable. A 1 may sit beside 6, 7, 8 or 9, whereas a 4 may sit beside 9 alone.
  • Where a whisper line crosses a box boundary, apply the alternation and the box rule together. The candidates thin out very quickly.
  • Treat the line as a wedge into the rest of the grid. Banishing 5 from a string of cells is often worth more than anything the line itself says.

The rule, drawn

What does German Whisper look like?

  1. German Whisper rule illustration, step 1 of 2
  2. German Whisper rule illustration, step 2 of 2

Start with a single square

Where can you play German Whisper?

German Whisper is one of the 17 variants in Cryptic, each with a lesson and unlimited puzzles.

Get it onGoogle PlayPlay on the web