Gattai

Gattai is the English transliteration of the Japanese word 合体, which means “union” or “fused.” Like the giant robot from my childhood, Voltes V. In Sudoku, it describes the combination of multiple grids into a single larger puzzles.

Crosscurrents

The challenges in creating these larger puzzles are multiple. I could have created more than four single-grid puzzles in less time than it took to create this one, in part because each change required me to re-solve the puzzle from the start, to be sure I hadn’t broken anything unexpectedly. Still, the satisfaction of a working gattai that also follows the rules I’ve set for myself, it’s worth spending the extra time on one out of every dozen puzzles or so.

High and Tight

Overlapping grids are interesting, but I thought: why always align on thick region borders? What if I split them offset? The answer is: it is a much more difficult puzzle to set, but makes solving more interesting. Trivia: When I set my normal logical auto-solver to the settings I like to use for testing, it gets “stuck” at one particular step. So if you solve the puzzle without using the walkthrough, you’ve done a better job than my logical auto-solver! Even more trivial: The renban lines are almost perfectly symmetrical, but there are two differences.

DoubleDoku ][: Electric Boogaloo

It could have been named “Son of DoubleDoku” or “2 Double 2 Doku” or even “DoubleDoku: Folie à Deux,” but whatever it’s called, it’s a sequel to DoubleDoku.

Event Horizon

It’s a big one, and it’s anchored by Gravity Cages at the bottom. While these cages don’t directly affect anything else in the puzzle, I like to imagine they’ll combine to form a black hole, pulling everything in all four grids into a single cell.

Chips, Rice, and Curry

Irish pub cuisine, or a Gattai-3 Sudoku puzzle? You decide!

Double-Wide

Can I interest you in a fine manufactured home? It’s so wide! Almost, but not quite, twice as wide as a single-wide. In fact, it’s 1.67 times as wide, and 1.33 times as tall as a normal 9x9 Sudoku.

DoubleDoku

It’s t-t-t-two puzzles in one! For the low, low price of nothing, you get not one, not two, but 1.55 puzzles! It would be two puzzles, but four of the nine boxes are shared, so they probably shouldn’t count twice. One of the two grids is outlined in a shade lighter than the other.

Yojimbo

It may seem like a lot of constraints, but it's a Samurai Sudoku, so you should only have deal with one or two at a time.