How to Play Hyper / Windoku
Four extra shaded 3×3 boxes must each contain 1–9
Hyper Sudoku — Windoku, to fans of the four "window pane" regions — was popularised by the Dutch newspaper NRC Handelsblad, and it remains the thinking solver's extra-region variant. Four shaded 3×3 windows sit offset from the standard boxes, each one required to contain 1 to 9. What makes it deeper than it looks is geometry: the four windows interlock with the nine standard boxes so tightly that they secretly imply further regions — the cells between the windows inherit constraints nobody printed. Cells inside a window answer to five houses, and the grid carries thirteen box-type regions in total. It suits solvers who like density over novelty: there's no arithmetic, no lines, no symbols, just more uniqueness pressing on the same 81 cells. Easy hyper puzzles solve noticeably faster than easy classics — the windows shower you with eliminations — while hard ones demand that you track interactions between overlapping houses with real discipline. If diagonal Sudoku is the gateway variant, hyper is the second course.
The Rules
Standard Sudoku rules apply: fill every row, column, and 3×3 box with the digits 1–9, each appearing exactly once.
Hyper Sudoku (also called Windoku) adds four extra shaded 3×3 regions to the standard grid. These regions overlap with the normal boxes and must each contain every digit 1–9, just like the standard boxes. The extra constraint can dramatically reduce candidate counts and often makes puzzles easier than they first appear.
At a Glance
How to Solve Hyper / Windoku
Worked Example: Opening a Hyper / Windoku Puzzle
Take the top-left window, covering rows 2–4 and columns 2–4. Suppose a given 7 sits at r3c3, inside both the window and standard box 1. That 7 is now barred from the entire window — including r2c4 and r3c4 (cells of box 2), r4c2 and r4c3 (cells of box 4), and r4c4 (a cell of box 5). Follow the box-2 thread: box 2 still needs a 7, its row-3 cells are ruled out by the given itself, and the window has just killed r2c4 — leaving only r1c4, r1c5, r1c6, r2c5, and r2c6. If row 1 already holds a 7 further right, box 2's 7 is squeezed into r2c5 or r2c6: a pointing pair that bans 7 from the rest of row 2, including all three box-3 cells. One given digit, and the ripple has crossed half the grid before anything new was placed. That is the standard hyper opening: take any digit inside a window, push its elimination through every box the window overlaps, and harvest the hidden singles and pointing pairs that surface two boxes away.
Common Mistakes in Hyper / Windoku
| Mistake | How to fix it |
|---|---|
| Treating the windows as decoration and solving the classic grid first | The windows are where the information is. Scan all four for hidden singles before anything else — a digit confined to one window cell is the most common opening move in Windoku. |
| Forgetting that window eliminations spill into multiple standard boxes | Each window overlaps four standard boxes, so one window elimination can kill candidates in up to four boxes at once. After every window deduction, check each overlapped box for new singles. |
| Missing the implied regions between the windows | Because the four windows plus rows and columns lock 36 cells so tightly, the leftover cells (like row 1, row 5, row 9 and their column counterparts) inherit hidden structure — advanced Windoku setters hide their key deductions there. |
Common Questions
What is Hyper Sudoku? ▾
Hyper Sudoku (also called Windoku or Hyper-Sudoku) adds four shaded 3×3 regions to the standard 9×9 grid. Each shaded region, like a standard box, must contain the digits 1–9 exactly once. This gives a total of 13 uniqueness groups: 9 rows, 9 columns, 9 standard boxes, and 4 hyper regions — though many cells overlap between groups.
Where are the four hyper regions? ▾
The four hyper regions are positioned symmetrically, offset from the standard boxes. They occupy the 3×3 areas starting at rows 2–4/columns 2–4, rows 2–4/columns 6–8, rows 6–8/columns 2–4, and rows 6–8/columns 6–8. Each hyper region overlaps with four standard boxes, creating a dense web of mutual constraints.
How do the hyper regions help solving? ▾
Any cell inside a hyper region carries five constraints simultaneously: its row, column, standard box, and the hyper region. This extra constraint eliminates candidates faster than standard Sudoku. After every digit placement inside a hyper region, scan all five groups for new eliminations.
Is Hyper Sudoku harder than regular Sudoku? ▾
Easy Hyper Sudoku is often easier than equivalent classic Sudoku because the extra constraints resolve the grid more quickly. Hard and expert Hyper puzzles are comparable in difficulty to their classic equivalents — the additional constraints help but also create complex multi-group interactions that require careful tracking.
What is the best first move in Hyper Sudoku? ▾
Focus on cells inside hyper regions, especially those at the intersections of a hyper region and a standard box. These carry the most constraints and are the most likely to resolve immediately. Always scan all four hyper regions after every placement.
How long does Hyper Sudoku take to solve? ▾
Easy puzzles take 5–12 minutes — often faster than classic Sudoku of equivalent difficulty. Medium puzzles run 12–25 minutes. Hard and expert puzzles take 25–60 minutes. The extra regions speed up early solving but hard puzzles compensate with fewer given digits.