Windoku: play hyper sudoku online

Windoku, also known as hyper sudoku, adds four shaded 3×3 windows to the classic grid. Each window must contain 1 to 9 too. Play windoku online free here, at four ranks.

The windows overlap four boxes each, and they quietly create five more hidden regions that most players never notice. Once you see them, windoku gets a lot friendlier.

The rules

• Normal sudoku rules apply: 1 to 9 once in every row, column and 3×3 box.
• Each of the four shaded windows (rows 2–4 and 6–8, crossed with columns 2–4 and 6–8) contains 1 to 9 exactly once.

How to start

Scan the windows like boxes

Every window is a full house, so hidden singles work inside windows exactly as they do in boxes. Each window touches four boxes, which gives you new intersections to exploit.

Find the hidden regions

Columns 2–4 contain each digit three times. The two windows in those columns use up two of them, so the nine remaining cells (rows 1, 5 and 9 of columns 2–4) hold each digit exactly once. The same argument gives five hidden regions in all, including the nine cells where rows 1, 5 and 9 cross columns 1, 5 and 9.

Use the hidden regions like houses

The hidden regions follow every house rule: hidden singles, pairs, the lot. Together with the four windows and nine boxes, that is eighteen nine-cell regions besides the rows and columns.

Common mistakes

• Forgetting the windows during a scan.
• Missing the hidden regions altogether.
• Mixing up the windows with the boxes they overlap.

How the ranks scale difficulty

Every puzzle type on Hoot’s Puzzles comes in four ranks, named after the stages of a mathematical idea. Lemma is the warm-up: about a dozen more digits are given than logic strictly needs, and singles plus the variant’s own rule will carry you through. Proposition needs a real idea or two, typically pointing and claiming. Theorem is near-minimal, so almost every clue is load-bearing and you may need pairs. Conjecture gives the fewest digits and sparser rule clues: expect to think hard.

The windows are fixed, so rank is all about the givens: fewer digits and deeper logic as you climb from Lemma to Conjecture.

There are 99,999 puzzles per rank, each with its own number, so you can replay one or share it. Every type also has a 30-puzzle collection that climbs from Lemma to Conjecture. Every puzzle is checked to have exactly one solution that you can reach by logic alone, with no guessing.

Keep exploring

• Sudoku XBoth main diagonals are extra houses. Also called diagonal sudoku.
• Classic SudokuRows, columns and boxes, nothing else. Pure logic at its cleanest.
• Anti-Knight SudokuNo digit repeats a chess knight’s move away.
• Solving techniquesSingles, pairs, cage arithmetic, line logic and Latin squares, all in one guide.
• All puzzle guidesEvery puzzle type on Hoot’s Puzzles, with rules and tips.