Techniques · sudoku

BUG+1

Every unsolved cell but one has exactly two candidates. The odd cell must take the digit that would otherwise leave the grid with two solutions.

In the walkthroughs, every BUG+1 step shades the cells of the pattern and names the cell and digit it proves, so you can see the move on the grid rather than read about it. Press “Skip to next hard step” to jump straight to it.

Worked examples

Puzzles from the books where BUG+1 is used. Each link opens the full step-by-step solution.

Extreme Sudoku 2 (3 of 150 puzzles)

• Puzzle 32 · Expert 7
• Puzzle 37 · Expert 7
• Puzzle 118 · Expert 7

Where it sits

See the whole ladder on hard sudoku techniques, or look a puzzle up by number under solutions.