Cross Sudoku: How the 5-Grid Puzzle Works vs Samurai

Layout: Plus-Shape vs X-Shape

The most immediate visual distinction is the silhouette. In a Cross Sudoku, the five grids form a solid plus-sign (+) with four large empty corners in the 21x21 bounding box. The center grid is surrounded on all four sides, with each outer grid attached to the middle of a central grid edge.

In Samurai Sudoku, the grids form an X shape. The center grid sits in the middle, with an outer grid attached to each of its four corners. The empty spaces in the bounding box form a plus-shaped gap between the arms of the X. This diagonal arrangement is iconic.

Shared Boxes: Edge-Middle vs Corner Overlaps

How the grids connect is defined by their shared 3x3 boxes, which are critical to solving. In Cross Sudoku, each outer grid connects to the center grid along one full edge. Specifically, the middle 3x3 box on the inner edge of an outer grid is the same physical cells as the middle 3x3 box on the corresponding edge of the center grid. You have four of these overlapping edge boxes.

Samurai Sudoku connections happen at the corners. Each outer grid is positioned so that one of its corner 3x3 boxes overlaps perfectly with a corner 3x3 box of the center grid. This creates four overlapping corner boxes. In both puzzles, any digit placed in an overlapping box must satisfy the rules for both grids it belongs to simultaneously, creating powerful solving constraints.

Solving Approach and Strategy

The solving logic for both variants uses all classic Sudoku techniques like Naked Pairs and Pointing Pairs within each individual 9x9 grid. The real key is using the overlaps to transfer progress. A number placed in a shared box immediately gives you information in two grids. Most solvers start with the center grid, as it feeds clues to all four neighbors.

For Cross Sudoku, progress often spreads linearly from the center out along each arm. The shared edge boxes act as bridges. In Samurai Sudoku, the corner overlaps mean the center grid influences the corners of the outer grids first. Solving then progresses inward from those corners within each outer grid. Careful pencil marking across the entire structure is essential to manage the 369 cells that require a digit.

• Start in the center grid: It has the most connections.
• Track candidates diligently: Use pencil marks to avoid confusion across grids.
• Use the overlaps: Treat a shared box as a high-priority solving zone.

Difficulty and Complexity

Both puzzles are significantly harder than a single 9x9 Sudoku, but the primary challenge isn't new rules—it's scale and bookkeeping. Managing candidate notes across 369 cells and five interlocking logic spaces is demanding. The initial scarcity of givens can feel daunting.

Some solvers find Samurai Sudoku slightly more interconnected at the start because the center grid's corners are immediately active in the outer puzzles. Cross Sudoku might present a more segmented challenge initially, with work progressing down each 'arm.' However, the final solve for both requires synthesizing the entire puzzle. The difficulty is comparable, offering a deeply satisfying marathon for experienced players.

Where to Find These Puzzles

These multi-grid variants are popular in dedicated puzzle books and on advanced Sudoku websites. They are less common in daily newspapers but are a staple for enthusiasts seeking a longer challenge. When searching, use the precise names 'Cross Sudoku' and 'Samurai Sudoku' to find them. Many online platforms generate them with adjustable difficulty levels. They represent a fascinating branch of logic puzzles that build directly on classic Sudoku rules, much like the twisted regions of Jigsaw Sudoku.