Sudoku set
Free sudoku — 6x6 expert Set 1. Fun and challenging. Download and print today.
Solve 6x6 expert sudoku Set 1. Fun and challenging.
Windoku, also known as Window Sudoku or NRC Sudoku, adds four fixed 3×3 window regions to the standard 9×9 grid. The windows are positioned symmetrically: top-left at rows 2-4, columns 2-4; top-right at rows 2-4, columns 6-8; bottom-left at rows 6-8, columns 2-4; bottom-right at rows 6-8, columns 6-8. Every window must contain digits 1-9 without repetition, in addition to standard row, column, and box constraints. The overlapping nature of windows and standard boxes creates rich constraint chains that experienced solvers find deeply satisfying.
The 6×6 grid strikes a balance between accessibility and depth. With 36 cells in 2×3 boxes, puzzles take 3 to 10 minutes depending on difficulty. The 6×6 is large enough to showcase variant rules meaningfully — Killer cages have room to create genuine arithmetic puzzles, Windoku windows overlap in interesting ways — while remaining completable in a single sitting. Many players find the 6×6 their "daily driver" format: challenging enough to be satisfying, short enough to fit into a break. Variant rules interact more visibly at this size than the 4×4.
Expert difficulty requires advanced solving techniques beyond basic elimination. Expect to use X-wing patterns (where a candidate appears in exactly two cells across two rows that align in the same two columns), swordfish (three-row X-wing extension), and XY-wing (three-cell chain eliminations). For Killer Expert, complex cage arithmetic with 3-4 possible combinations must be narrowed through cross-cage deduction. Most expert solvers use full candidate notation. Average time: 40-60 minutes for 9×9. Not recommended as a first attempt at any variant.
Best for logic practice, print-and-solve puzzle books, classroom challenges, and variant Sudoku exploration.
Answer support is available for review after a real attempt; printable answer-key behavior depends on the activity type.
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