9×9 · 9 cats · par 3:23
Meowdoku 9×9 — a sudoku grid, a different question
Eighty-one cells, nine cats, nine colored regions. The grid will look familiar; almost nothing you do on it will.
The same grid, asking something else
A sudoku fills all eighty-one cells with digits. Meowdoku places nine cats and leaves the rest empty, and the constraint that does the work — no two cats may touch, not even diagonally — has no sudoku equivalent at all. What carries over is the habit of reading a row, a column and a box as three views of the same cell; what does not is everything about pencil marks. The full guide works a board end to end, and Meowdoku vs Queens covers the other puzzle people arrive here from.
The regions replace the boxes, and unlike boxes they are not 3×3 and not the same shape twice. The generator will run one up to 17 cells. Region colour is the only thing marking where one ends — there are no borders — which is a real constraint on legibility and is measured in the region-colors study.
Two free regions, and why that helps more than it sounds
From size 8 up the generator hands out two gift regions rather than one, so two of its 9 regions are single cells. Two decided cats do not just remove two cells; they remove two rows, two columns, and up to sixteen neighbours, and on a board where cats sit far apart those exclusions rarely overlap.
That makes the 9×9 open faster than the 7×7 despite being half again as large — the one place on this site where the bigger board is the friendlier start.
Where to go next
Extreme is one row and one column larger and takes a gift back, which is a bigger jump than the size suggests. The daily puzzle is also 10×10 but keeps both gifts, so it sits between the two.
Questions
Is Meowdoku 9×9 the same as sudoku?
Only the grid. Sudoku fills every cell with a digit; Meowdoku places nine cats and adds a rule sudoku has no version of — no two cats may touch, including diagonally.
How many cats on a 9×9?
Nine. One per row, one per column, one per colored region — and no two of them adjacent in any direction.
What is a good 9×9 time?
Par is 3:23. Beating it with no mistakes and no hints is what an S rating asks for.