Techniques
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 most useful habit a Hyper Sudoku solver can build is the four-unit scan: row, column, box, hyper region. For the 36 cells that sit inside a hyper region, the hyper region is a unit the same way a row is, and the same scanning instinct that finds hidden singles in rows finds them in hyper regions too.
The pattern most beginners miss
A solver coming to Hyper Sudoku from classic plays the first puzzles exactly as they would play a classic. They scan rows, columns, boxes, place the obvious digits, and stall in the same place a classic puzzle would have stalled. Then they reach for a more complex technique to break the stall — pairs, locked candidates, sometimes chains — and either solve the deduction the hard way or get stuck.
Often the puzzle isn't actually stuck. The hyper region containing the cell already eliminates the digit through one of the eight other cells in the region. The fix is just to include the hyper region in the scan when the cell sits inside one.
A worked pattern
Suppose you're trying to place 5 in box 5 (the centre box of the grid). You scan rows 4, 5, and 6 and columns 4, 5, and 6, and you find that 5 could go in either (4, 5) or (5, 4). Both cells are inside box 5. Both cells satisfy row and column constraints. Classic-style scanning ends here.
Now check the hyper regions. Cell (4, 5) sits outside any hyper region — it's in the + shaped gap. Cell (5, 4) sits inside the top-left hyper region. If that hyper region already contains a 5 anywhere — say at (2, 3) or (3, 4) — then (5, 4) is eliminated, and the 5 lands at (4, 5).
The deduction is identical in shape to a row-based hidden single. It just runs on a different unit.
Three patterns worth recognising
The first is the hyper-only cell: a cell where the hyper region's constraints alone identify the digit, even when the row, column, and box would have left multiple candidates. The hyper region is a complete 9-cell unit, so its uniqueness rule is just as strong as a row's.
The second is the hyper pair: two cells inside the same hyper region where only two specific digits are candidates. Like a regular naked pair, this eliminates those two digits from every other cell in the hyper region. Hyper pairs are common at the medium tier and above because the hyper regions overlap four standard boxes, which often means a hyper pair eliminates candidates in cells you wouldn't have associated otherwise.
The third is cross-region deduction: the move that's only possible because a hyper region overlaps standard boxes. If a digit is locked to a particular row inside a hyper region, that digit is also locked to that row inside every standard box that overlaps the region at that row. The eliminations ripple further than they would in classic.
How often it fires
In an easy Hyper Sudoku, hyper-only cells fire two or three times per puzzle. In a medium, three to five. In hard, five to seven, and hyper pairs and cross-region deductions start to appear regularly. At expert, the variant is constructed assuming you'll find these moves — without them, the puzzle stalls.
The fix, again, is mechanical. When you're working on a cell that sits inside a hyper region, the hyper region joins the unit list — row, column, box, hyper region. After your third or fourth puzzle, this becomes automatic, and the four-unit scan stops being something you remember to do and starts being something your eye does on the way to the next placement.
When to look first
If a classic Sudoku at the same tier would have solved by scanning, the corresponding Hyper Sudoku will also solve by scanning — you just need to include the hyper regions in the scan. If a classic at the same tier would have needed naked pairs or locked candidates, the Hyper version is sometimes faster because the hyper region offers a tighter constraint than the corresponding standard box would have. The variant rewards the habit; the habit is worth building.
If you'd like a refresher on where the regions sit and why, the four hyper regions walks through the geometry. Otherwise, medium Hyper Sudoku is the tier where the four-unit scan starts to feel useful in earnest.
Related reading
Variants
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.
4 min read
Rules & basics
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.
4 min read
Variants
Meet Hyper Sudoku
An introduction to Hyper Sudoku (also called Windoku) — what the four hyper regions add, why classic solvers tend to enjoy it, and how to know if it's for you.
3 min read
Glossary terms
- 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-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.
- 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.
- 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.