About Us
About samuraisudoku.app
We publish a free, modern browser version of Samurai Sudoku — five overlapping 9×9 grids, generated with a single guaranteed solution — with notes, hints, undo, and a printable version.
- Grids
- 5
- Cells
- 369
- Solution
- 1
Origins
Where Samurai Sudoku comes from
From Number Place to Sudoku
The puzzle behind Sudoku appeared as “Number Place” in Dell magazines in 1979. The Japanese publisher Nikoli popularised it under the name Sudoku from 1984, and it became a worldwide newspaper habit in the 2000s.
Why five grids
Once solvers had mastered one 9×9 grid, publishers went bigger. Samurai Sudoku overlaps five grids so that they share four 3×3 boxes: the same rule, a longer solve, and a puzzle where a breakthrough in one corner ripples across the whole shape.
This build
samuraisudoku.app is an independent, modern implementation. The rules are unchanged; what is new is a generator that guarantees unique solutions, difficulty graded by technique, notes that clean themselves up across grids, a phone-friendly zoom, and one-tap printing.
Principles
What we care about
Instant to start
Open the page, pick a level, and you are solving. No account wall, no download, no splash video — a fresh puzzle is generated in a fraction of a second.
Honest puzzles
Every puzzle has exactly one solution and can be solved by logic. If you are stuck there is a forced move somewhere; hints are there when you want a nudge, and they are labelled as such in your stats.
Yours to keep
Your puzzle in progress, best times, and streaks live on your device. We do not hold your record behind a login, because there is no login. A refresh resumes the puzzle exactly where you left it.
Free, for real
The whole game is free. No energy meters, no interstitial video ads between puzzles, no paywall on the printable version.
Mechanics
How every puzzle is made
Nothing is pre-written or downloaded. When you press Start, the page builds your puzzle locally in a few dozen milliseconds. The rules for playing it are in the how-to-play guide.
A full solution first
A backtracking solver fills all 369 cells of an empty Samurai shape with randomised digit order, producing a valid solved puzzle where every row, column, and box in all five grids is correct.
Clues removed in pairs
Clues are taken away in mirrored pairs so the finished puzzle has 180° rotational symmetry — the tidy look printed puzzles have. After each removal a solver counts solutions and the removal is undone if the answer would stop being unique.
Graded by technique
Easy puzzles must be solvable using only cells with a single candidate. Medium adds hidden singles. Hard keeps removing clues until uniqueness is the only limit, giving about 100 givens.
Design
Built for a board this big
One board, every device
The 21×21 lattice scales to the width of a phone with the number pad right beneath it. Zoom doubles the cell size and follows your selection when you want to place notes.
Overlaps you can see
The four shared boxes are tinted, and selecting a cell highlights its row, column, and box in every grid it belongs to, plus every matching digit. Conflicts turn red immediately.
Sound with a real mute
Small synthesized sounds confirm placements and finished grids. Press M or use the speaker button to mute; the choice is remembered.