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