sudokUI › Sudoku techniques › Fireworks
Fireworks in sudoku
Three digits missing from a row and a column whose candidates in those two units, outside the box where they cross, all sit in one wing cell of each.
Why it works
Each digit sits in a wing, or else inside the box for both the row and the column, which can only be the cell where they cross. Three digits therefore fill these three cells, which lose all candidates except those three digits.
How to spot it
Scan a row and column that cross in a box for digits whose candidates outside that box sit in a single cell of each.
Worked example
Fireworks: digits 1/4/8 each must land on one of r8c6 (cross), r8c3 (row wing) or r2c6 (column wing), locking those three cells, so all other candidates there are removed.
Practise it on a real puzzle. sudokUI generates a puzzle that needs Fireworks and takes you straight to the position where it applies. Hints draw the pattern on the board and explain the step.
In a puzzle's rating
Each time the solver needs Fireworks, the puzzle's difficulty rating grows by 400. Its class is Extreme. It is needed in 1 in 120,000 puzzles that sudokUI generates. How the rating works.