Windmill, Sohei, Flower and Gattai sudoku: the rare multi-grid family explained

First, the word: what "Gattai" means

Gattai (合体) is Japanese for "merged" or "combined" — the same word Japanese uses for robots combining into a bigger robot, which is honestly the right mental image. In puzzle publishing, Gattai-N means N overlapping 9×9 grids: Gattai-2 is two grids (often sold as Twodoku), Gattai-3 is three, and the world-famous Samurai layout is formally Gattai-5 — five grids, one central, four on the corners.

The rules are identical across the entire family and take one sentence: every grid must be a valid sudoku on its own, and every shared box must simultaneously satisfy all grids it belongs to. Rows and columns never extend between grids — only the shared boxes couple them. Everything else on this page is geometry: how many grids, and where they touch.

Windmill sudoku (Kazaguruma)

Layout: five grids — four arranged like the blades of a pinwheel around a fifth in the middle (kazaguruma is Japanese for windmill), overlapping in rotational symmetry. Rotate the whole puzzle a quarter turn and it looks the same; each blade plays an identical structural role. (Print collections sometimes vary the exact windmill arrangement, but the five-grid pinwheel is the shape you'll solve in Sudoku by Joseph.)

Rules: each of the five grids is a complete, valid 9×9 sudoku; shared boxes must work in both grids they belong to.

Solving notes: the symmetry is the challenge. In a Samurai puzzle the central grid is an obvious hub to organize around; a windmill has no center, so no grid is "the main one." Expect to keep four fronts open and rotate deliberately: when a grid stalls, move to the next blade, and treat every shared box as a message-passing channel — a resolved digit there immediately constrains a row or column in the neighboring grid. If you find yourself grinding one blade for ten minutes, you've almost certainly left cheap deductions sitting in another.

Sohei sudoku

Layout: four grids arranged in a cross — north, east, south, west — with a hole in the middle. This is the layout people mistake for Samurai at a glance, and the difference matters: there is no central grid. The four grids overlap each other directly at their corners, forming a closed ring around an empty center. The name refers to the sōhei, the warrior monks of feudal Japan — a fitting sibling to Samurai.

Rules: standard gattai rules — four valid sudokus, shared corner boxes valid in both adjoining grids.

Solving notes: the ring topology changes how information travels. In Samurai, the center grid connects everything, so deductions radiate outward from one crossroads. In Sohei, a deduction in the north grid can only reach the south grid the long way — through east or west. That makes Sohei feel like a relay race: you push each grid as far as it goes, hand off through a shared box, and count on the chain eventually looping back around with new information. Patience with the circuit is the whole skill.

Flower sudoku

Layout: five grids in a tight, flower-like arrangement — one central grid with four others overlapping it far more deeply than Samurai's corner-touch layout. The grids share large amounts of territory, petals around a core.

One disambiguation, because search results split two ways: this is the adult logic variant — not the "flower sudoku" printables for young children where you place flower pictures in a small grid. If you're after the kids' activity, this page isn't it.

Rules: standard gattai rules across five grids. Because the overlaps are so large, a substantial share of all cells belong to two grids at once.

Solving notes: Flower is the densest layout in the family. With this much shared territory, almost every placement echoes somewhere else — which cuts both ways. Openings can feel generous, since every deduction pays out twice; the endgame punishes sloppy pencil marks brutally, because a candidate you forgot to eliminate in one grid's context is still lying to you in the other's. Keep notes fastidiously synchronized in the shared regions, and when you're stuck, re-examine the doubly-constrained cells first: they're the most constrained cells on the board, and usually the crack in the wall.

Gattai-3 sudoku

Layout: three 9×9 grids sharing regions in a merged arrangement — the middle child of the family, between Twodoku's simple pair and the four- and five-grid spectaculars.

Rules: three valid sudokus; shared boxes valid in every grid they belong to.

Solving notes: Gattai-3 is the best training puzzle in the whole family, and we'd say that even if we didn't ship it. It's big enough that grids genuinely depend on each other — you cannot brute-force one grid in isolation and ignore the overlap — but small enough that a solve fits comfortably in one sitting. The skill it teaches is the one every larger layout demands: noticing the moment a grid stops yielding and switching fronts instead of grinding. If your ambition is Samurai or Flower, run a week of Gattai-3 first; the bigger puzzles will feel like more of the same rather than a cliff.

Where you can actually play these

Honest answer: barely anywhere, which is why you likely landed here. Samurai has books and a few apps; Windmill turns up occasionally in print gattai collections; Sohei and Flower are genuinely rare in any medium. Conceptis MultiSudoku — a polished app from a respected publisher — covers overlapping layouts with hand-made puzzles sold in per-volume packs, and it's a fine product, but it doesn't ship this full set of layouts. Sudoku by Joseph has all four (plus Twodoku, Tripledoku, Samurai and Cross) as premium variants with unlimited on-device generation at every difficulty from Easy to Diabolic, offline, with no lives or coins anywhere in the app. The full comparison of every option, including the ones we don't make, is in the multi-grid sudoku app guide.

How to try the rare multi-grid variants in Sudoku by Joseph

1. Install the app and start the 7-day trial

   All four variants on this page are premium. The trial unlocks everything, so you can tour the whole family before deciding; pricing varies by country — see the App Store or Google Play.

2. Warm up on Gattai-3 at Easy

   Learn the switch-fronts-early rhythm on the smallest layout here before taking on the four- and five-grid boards.

3. Then pick your geometry

   Kazaguruma for the symmetric pinwheel, Sohei for the ring with no center, Flower for maximum overlap density. Wrong entries never lock the board — there are no lives — so experiment freely.

Other options worth knowing

If these layouts appeal but you'd rather not use our app: Conceptis MultiSudoku is the best curated alternative for overlapping sudoku generally, with hand-crafted puzzle packs sold per volume. samurai-sudoku.com offers free browser Samurai if the five-grid classic is really what you want. For print, search gattai or samurai collections — though expect Sohei and Flower to be nearly absent. There is no pretty way to say it: for these four specific layouts on a phone, the options are extremely thin.

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