Box Brain Sudoku
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Easy · technique 5 of 18
Arrow Sums
The digits on an arrow add up to its circle.
A Arrow sudoku technique.
How it works
The circle is at least the smallest possible sum of its arrow and at most the largest, which trims both ends.
A worked example
Arrow: the digits on the arrow add up to the digit in its circle, so the cell in row 5, column 2 cannot be 2.
- The cells that make the pattern
- Candidates it rules out
A real position from a puzzle in the app. Small digits are the candidates the step looks at; coloured digits are already solved.
Practise it in Box Brain Sudoku
The app teaches Arrow Sums on this same board, then hands you puzzles that need it. When you are stuck mid-game, a hint first points you to the right area, then names the technique and shows the move.