Hyper-only cell
A Hyper Sudoku (Windoku) deduction: a cell where row, column, and standard box together leave multiple candidates, and the hyper region alone forces the digit.
A hyper-only cell is a Hyper Sudoku deduction in which row, column, and standard 3×3 box together leave two or more candidates for a cell, and the hyper region the cell sits inside narrows the candidate set to one. The deduction has no analogue in classic Sudoku because classic Sudoku doesn't have a hyper region as a fourth unit.
Interactive example
Step 0 / 7
When it fires
Imagine a cell at row 3, column 3 — the corner of the top-left hyper region. The row contains three given digits already; the column contains three more; the standard 3×3 box (the top-left corner box) contains two. Between row, column, and box, the cell still admits two candidates. In a classic Sudoku, the solver would need to find a naked pair or chain elsewhere to break the symmetry.
In Hyper Sudoku, the hyper region containing the cell may already include one of those two candidates somewhere else, instantly eliminating it. The remaining candidate lands as a forced digit.
How common it is
Hyper-only cells fire two or three times per easy puzzle, three to five times at medium, and five to seven times at hard. By the expert tier, the variant's puzzles are constructed assuming hyper-only deductions; without them, the puzzle stalls.
The deduction is structurally identical to a classic hidden single — it's just that the unit doing the work is a hyper region. The visual cue on Sudoku Mountain's board is the coral outline marking the four hyper regions; when working on a cell inside one of them, the hyper region joins the unit list alongside row, column, and box.
For the practical scan habit, see when hyper regions narrow it down.
See also
- Hyper Sudoku— A Sudoku variant with four extra 3×3 regions overlaid on the standard grid, each obeying the uniqueness rule. Also called Windoku in continental European communities.
- Hyper region— One of the four extra 3×3 regions in a Hyper Sudoku (Windoku). Each region carries the same digit-uniqueness rule as a row, column, or standard 3×3 box.
- Hyper pair— A naked pair where both cells lie in the same hyper region of a Hyper Sudoku (Windoku). Eliminates the two pair digits from every other cell of that region.
- Cross-region deduction— A Hyper Sudoku move using the overlap between a hyper region and a standard 3×3 box: locking a digit to a shared sub-region eliminates it from the rest of both units.
- Naked single— A cell on the Sudoku grid that has only one legal candidate left — the simplest deduction in the game, and the one that solves most of an easy puzzle.
- Hidden single— A digit with only one possible cell within a unit (row, column, or 3×3 box) — even if that cell could legally hold other digits. The unit-first sibling of the naked single.
Read more
- When hyper regions narrow it down
A practical tactic for Hyper Sudoku and Windoku: scan the hyper region as a fourth unit when row, column, and box reasoning runs out. Worked patterns and where they fire.
- The four hyper regions
Where the four extra 3×3 regions sit inside a Hyper Sudoku (Windoku) board, why they're positioned that way, and how to spot them while solving.
- The rules of Hyper Sudoku
Hyper Sudoku — also known as Windoku — is classic Sudoku with four extra 3×3 regions overlaid on the grid. Each of the four hyper regions obeys the uniqueness rule.