Sudoku variants: killer, samurai, diagonal and more

By Miguel Arechaga

Once you've mastered classic sudoku and want something new, you'll discover a whole universe of variants. They all share the same basic idea (no repeating numbers in rows, columns, and blocks), but each adds an extra rule that completely changes how you have to reason. Here's a rundown of the best-known ones so you know what to expect and which one might be worth trying.

Diagonal sudoku ("X-Sudoku")

This is the easiest variant to understand and a natural first step from the classic version. One extra rule is added to the usual ones: the two main diagonals of the board must also contain the numbers 1 through 9 with no repeats. That small addition provides very useful extra clues and forces you to watch two lines that don't count in normal sudoku. If you want to try variants, diagonal is the best place to start.

Killer sudoku

Killer is probably the most famous variant and one of the most addictive. It barely has any starting numbers; instead, the board is divided into "cages" marked with dotted lines, and each cage has a small number showing the sum of the cells inside it. Besides not repeating in rows, columns, and blocks, you also can't repeat within the same cage. It combines sudoku logic with a bit of mental arithmetic, which is exactly why it hooks people who enjoy numbers.

Samurai sudoku

Samurai is pure visual spectacle: five nine-by-nine boards overlapping in the shape of an X, sharing corners. Each board is solved with the normal rules, but the shared zones force you to coordinate several grids at once. It's long, demanding, and very satisfying to complete — ideal for a quiet afternoon when you want a long-haul challenge instead of a quick game.

Windoku (Hyper Sudoku)

Windoku, also called Hyper, adds four extra three-by-three blocks marked with shading inside the board, set apart from the usual grid. Those four groups must also contain 1 through 9 with no repeats. The result is a sudoku with more constraints and, therefore, more paths for deduction, which often turns out easier to manage than its busy appearance suggests.

Jigsaw (irregular) sudoku

In this variant the classic three-by-three blocks disappear and are replaced by irregularly shaped regions, like puzzle pieces, each with nine cells. Rows and columns still work the same way, but the twisted regions completely change how you scan the board. It's a refreshing way to relearn how to look at a sudoku once the classic version starts to feel too small.

Mini and maxi sizes

Not every variant changes the rules; some just change the size. Mini sudokus, four-by-four or six-by-six, are perfect for kids and beginners because they keep the same logic but fit in a single glance. At the other extreme are the sixteen-by-sixteen maxi sudokus, which use numbers and letters (0-9 and A-F) and pose a monumental concentration challenge. They're the same idea taken to its two extremes.

Where should you start?

If you're coming from classic sudoku, the most comfortable order is usually: diagonal first, to get used to having extra rules, then killer if you enjoy numbers or jigsaw if you prefer a purely visual challenge, and save samurai and maxi for when you want a long session. The good news is that everything you learn in regular sudoku carries over: the elimination and candidate techniques are the same, only the map you apply them to changes.

Before diving into the variants, it's worth having the classic solidly nailed down, since it's the common language of all of them. If you're still building your foundations, check out our advanced sudoku techniques and practice with regular games on MundoSudoku. Once those feel easy, jumping into any variant will be much more enjoyable.