Samurai Sudoku - Play Free Online

Samurai Sudoku - also known as Gattai-5 or 5-grid sudoku - is a challenging variant that combines five standard 9×9 Sudoku grids into one massive overlapping puzzle. The grids are arranged in a cross (plus-sign) pattern: four corner grids surround a center grid, with each corner grid sharing a 3×3 box with the center.

The overlapping structure creates a unique strategic depth: cells in the shared 3×3 boxes must satisfy the constraints of both parent grids simultaneously. This means solving one grid reveals information for adjacent grids, creating a satisfying cascade of deductions that spans the entire 369-cell puzzle.

All standard Sudoku rules apply to each of the five 9×9 grids independently: every row, column, and 3×3 box within each grid must contain the digits 1 through 9 exactly once.

The key additional rule: four pairs of grids overlap at a single 3×3 box. Cells in these overlapping boxes must satisfy the row, column, and box constraints of both parent grids. This shared constraint is what links the five grids into one unified puzzle.

Each Samurai Sudoku puzzle has exactly one solution. The overlapping regions provide the 'bridges' that connect the grids and ensure the puzzle can be solved logically without guessing.

Start with the center grid - it shares 3×3 boxes with all four corner grids, making it the most constrained region. Any digit you place in the center grid's overlap boxes immediately constrains two grids at once, giving you maximum information per move.

Work outward through the overlap regions. When you solve cells in a shared 3×3 box, those digits propagate constraints into the adjacent corner grid. Think of the overlapping boxes as 'bridges' - solving one side of the bridge reveals clues for the other side.

Use standard Sudoku techniques within each grid - scanning, crosshatching, naked singles, hidden singles. For advanced puzzles, look for cross-grid eliminations: if a digit is determined in one grid's overlap box, it's simultaneously determined in the neighboring grid, which may trigger a chain of deductions.

Prioritize the center grid: With four shared boxes, the center grid has the most constraints and is often the fastest to make progress in. Place digits here first whenever possible.

Use overlap boxes as leverage: Whenever you place a digit in a shared 3×3 box, immediately check the adjacent grid for new singles or eliminations. The back-and-forth between grids is the key to efficient solving.

Don't solve grids in isolation: Unlike solving five separate Sudoku puzzles, Samurai Sudoku rewards switching between grids frequently. A stuck position in one grid often becomes solvable after making progress in a neighboring grid through the overlap bridge.

Regular Sudoku has one 9×9 grid with 81 cells and three constraint types (row, column, box). Samurai Sudoku has five interconnected 9×9 grids totaling 369 active cells, with overlap constraints that link the grids together. The puzzle is physically much larger and takes significantly more time to complete.

Despite the larger scale, the fundamental logic is the same - you're still placing digits 1–9 using elimination and deduction. The overlap regions add strategic depth but not complexity: cells in shared boxes have more constraints (peers in two grids), which actually provides more information to work with. Many solvers find the cross-grid deductions deeply satisfying.