Variants

How to Solve Samurai Sudoku

A Samurai is five ordinary Sudoku grids woven into one giant puzzle, and the trick to solving it is not raw patience but knowing where the five grids touch. Here is how to read the overlaps and keep a big board moving.

What a Samurai is

Samurai Sudoku — also called Gattai-5 or Five-Grid Sudoku — arranges five standard 9×9 grids in the shape of an X. Four sit in the corners and one sits in the middle, and where they meet they share a complete 3×3 box. Each of the five grids must obey the ordinary Sudoku rule on its own: every row, column and box holds 1 to 9 once. It is not five separate puzzles printed close together; the shared boxes link them into a single connected board.

Start with the overlaps

The four shared boxes are the key to the whole puzzle. Because each one belongs to two grids at the same time, it carries twice the constraints of an ordinary box, so it usually resolves first and gives you the most to work with. Every number you fix in a shared box is instantly a clue in two grids at once. Begin there, and let the information flow outward from the centre into the corners.

Work the fullest grid

At any moment one of the five grids will be closer to complete than the others. Spend your effort there: finishing nearly-full rows, columns and boxes is the same quick win it is in a classic game, and in a Samurai each completed overlap box feeds the neighbouring grid as a bonus. When a grid stalls, do not grind at it — switch to a different one, because progress elsewhere almost always loosens the shared box that had you stuck.

Pace a bigger puzzle

A Samurai is a longer sit than a single grid, and the solvers who enjoy it most treat it that way. There is no prize for racing; a careful placement early saves far more time later than a hasty guess. Because the board saves automatically, you can fill the centre and one corner over a coffee, close the tab, and return to the far corners tomorrow. Patience and a steady eye on the four overlaps beat speed every time.

A sample ripple

Suppose the centre grid places a 6 in its top-left box, and that box is the overlap shared with the upper-left corner grid. The 6 is now a given for the corner grid too, which may complete a row there, which closes a column, which resolves that corner's own overlap — and so the ripple carries on. Watching a single placement travel across two grids is the particular pleasure of the Samurai.

On phones, and the tools

The board is large, so on a small screen you will scroll it sideways or pinch to zoom; it is most comfortable on a tablet or desktop where the whole X fits at once. Everything you rely on is here — undo, erase, a one-cell hint and conflict highlighting across all five grids — so a big board never feels unwieldy.

Why five grids beat one big one

At first glance a Samurai can look like five ordinary puzzles printed close together, but the overlaps change everything. Each shared box does two jobs at once, so the number of genuine deductions available to you is higher than in a single grid — and the satisfaction of watching a placement in the centre cascade out into a corner is something a lone 9×9 cannot offer. It is the same logic you already know, scaled up into something that feels more like an unfolding landscape than a single test, which is exactly why solvers who like a long sit keep coming back to it.

Ready for the big board? Play Samurai Sudoku. If you like an extra layer of logic, Killer Sudoku adds arithmetic cages, and the classic grid is always waiting at Sudoku AZ.