Proven Sudoku
Techniques / Exotic and rank-zero
Fireworks
Also called Firework, Firework Subsets, Hanabi.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
A number is trapped so that it can only sit in one row, one column, or the square where they cross. It looks like a firework going off from that square. Stack a few together and they clear a lot.
The exact rule, for stronger players
The rule, stated exactly: A digit confined within a box to one row and one column, forming a cross whose centre cell is a candidate for a triple placement. Combining several such crosses on different digits yields eliminations.
What it removes: Remove non-participating candidates from the shared cells once enough fireworks overlap.
Why it works: Each firework restricts a digit to the union of one row segment, one column segment, and their intersection. Combining enough of them saturates the available cells.
Worked examples
None yet. This pattern does not turn up in our daily boards, so there is no real example to show. We would rather wait than draw a fake one.
Learn these first
- Locked Candidates (general form)Sometimes all the spots for a digit inside one group also sit inside a second group.
- Rank TheoryA way to count a pattern.
Related exotic and rank-zero
- Gurth's Symmetrical PlacementSome puzzles are built with a mirror pattern.
- Homogeneous ChainsA chain where every link is the same kind.
- Junior ExocetTwo squares act as a launcher and two more as the target.
- Multi-Sector Locked SetsCount several rows, columns and boxes at once.
- Pattern Overlay MethodEvery digit has to land in one of a fixed set of shapes across the grid.
How often does it come up?
Our rough estimate: rare. Firework Subsets are the combining forms, and Appendix A omits them.