Extreme technique · Technique Academy

BUG+1

BUG+1 arises when every unsolved cell has exactly two candidates except one cell that has three. A board of only pairs would have two solutions, a state called a Bivalue Universal Grave, and a proper puzzle cannot allow that.

Professor Cryptic, the owl who teaches in the app
Professor Cryptic is thinking

The reasoning

Why does the BUG+1 work?

To avoid the grave, the odd cell must take the candidate that appears three times in its row, column and box. That digit goes in.

A worked example

What does the BUG+1 look like on a real board?

BUG+1 worked exampleA sudoku board with pencil marks. The BUG+1 uses R5C7 and digit 3 (R5C7). The move places 3 in R5C7.4635971282154683939789712345673685124958937423361142637937853957123756869462891457339574378566912
The move places 3 in R5C7. Digit 3, R5C7.
  • The cell that decides

Make it stick

How can you practise the BUG+1?

The Technique Academy in Cryptic gives every technique its own lesson and 5 practice boards that need exactly this move.

Get it onGoogle PlayPlay Cryptic on the web

Further reading: HoDoKu's page on this family of techniques.

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