InZeDoku takes the rule everybody knows — never the same symbol twice in one group — and runs it on five geometries, three ways of filling a cell and sizes from 2 × 2 all the way up to 26 × 26. Alone, for the pleasure of an evening grid; in class, to learn arithmetic on the very grid the whole class shares. Every grid is built on the device, offline, with a unique solution proven before you get to play.
Android app in a free version and a full version, plus a web demo. The same game code gives exactly the same grid everywhere.
A single engine solves and builds every grid, and it knows nothing of a row or a column: it is given groups of cells that must all differ. Changing the mode means changing what a cell contains.
A cell holds a digit — or a letter beyond nine cells a side. All the deduction comes from the groups: rows, columns, regions… and, on the other boards, three-direction rows or zones. It is played on all five shapes, from 2×2 to 26×26.
The grid is cut into cages that each announce a calculation: 20+, 32×, 3−, 3:. No blocks, ever. It is the only mode whose arithmetic is set independently of the sudoku difficulty — operations, numbers, fractions, cage size.
A cell holds a colour, a cage announces a colour, and the only operation is mixing. CMY — black target, like ink — or RGB — white target, like light: a complete row makes exactly the target. From three to eight colours.
A cage is no longer a sum but a recipe: place the right pieces and they compose the thing asked for. Science — Chemdoku, Phydoku, Biodoku, Astrodoku. Kids — Pictoku, Whodoku and Geodoku, playable before knowing how to count.
Changing the shape means declaring other groups to the engine. That is why a hexagon, a triangle or a completely irregular tiling are not three different games — and why, when in doubt, you only need to touch a cell: everything linked to it lights up.
From a four-cell toy to a 676-cell marathon. Blocks follow the size — 2×3 at 6×6, 4×4 at 16×16; a prime side gives a Latin square. Beyond nine, Sudoku switches to letters.
19, 37 or 61 cells, and lines in three directions — no regions at all, because those numbers are prime. A Latin square with three families of lines.
The densest board in the game: regions of nine triangles, rows in three directions, and two triangles that touch always carry different symbols.
A triangle where some rosettes of six cells melt into a hexagon — the most constrained cell on the board. Regular layout, or a “Surprise” one drawn from the seed.
No hidden lattice: the tiling is drawn from the seed, and no two games ever share a board. Families of zones replace rows and columns; square, hexagonal, octagonal or triangular outline.
The grids overlap on a single board, each with its own coloured frame. Samurai, butterfly, windmill… rather than a catalogue, the layout is drawn from the seed: every game is a new map, and resuming rebuilds exactly the same one.
Extra all-different groups, shaded on the board: there too, never the same value twice. Diagonals, windows, block centres, asterisk, girandola — the pattern is drawn at random for every game.
The level — Easy, Medium, Hard, Expert — only sets the deduction. The arithmetic is set elsewhere. A five-by-five board can carry a nine-year-old's multiplication tables as well as a seven-year-old's halves.
Every cage is a product of two numbers between 1 and 10: a multiplication table laid over a sudoku small enough not to get in the way. And since the grid remains a real sudoku, the child checks the products against rows and columns — with nobody having to mark anything.
Fully playable in the free version. Facing 15× over two cells, the child does not compute 3 × 5: they look for which factors give 15 — the table read backwards, the one used for division.
G2CS51BL100OTAV2S31-bg7jl8-U4A sudoku that draws a random grid is useless in class. InZeDoku does not store its grids: it builds them from a number, and the same number always gives back the same grid, on any device. So a grid is designated by a short string instead of being carried around.
The full version adds two pages when printing. The first says how the grid could be solved; the second, how the pupil actually solved it. In front of a projected grid that will not budge and twenty-five pairs of eyes waiting, the first is the way out: read the next step, show it, move on, without losing the class or the time. With a pupil's work, the second is the marking: you see where the reasoning slipped, and from where. To get unstuck on a single cell, the game's light bulb 💡 is free.
Cell by cell, in the order they can be found, each with the rule that unlocks it. The sheet says so at the top: it is one path among others — several techniques may apply at every step, and a pupil who proposes another one is not wrong. On a grid that logic alone cannot finish, it stops and says how many cells remain.
As printed by the app, cell by cell, with the rule that unlocks each one.
The game replays the pupil's moves in order and names the rule that applied to each. It only says “error” under one strict condition: the value placed makes the grid impossible to finish. Here, a game in progress — seven moves, an error on the seventh, the grid unfinished. The faulty move is set aside and what follows is judged without it: a pupil often slips in one place and reasons perfectly on the rest.
1 error. A move flagged as an error is set aside for what follows: everything after it is judged without it.
Taken from the teaching dossier. In the app: Code → Scan a QR, aim at the screen, and the grid opens — the configuration is shown in plain words before you play.
The pencil, the torch and the colours know nothing: they tidy your reasoning, they don't do it for you. The light bulb does know the answer — and says only as much of it as you ask for.
Not a promise but a property: the published package is checked for the absence of any internet access permission, and a package declaring one would not be published. Everything else follows from that absence.
An advertising library needs the network and profiles you. There is none, and there cannot be one.
No usage statistics tool, no identifier, no profiling. The game does not know who you are — a logic game has no need to.
Nothing is sent anywhere. To report something, the ✉️ Feedback entry prepares a message of which you see and edit every line — and it is your mail app that sends it.
No sign-up, no e-mail address. A game travels from one device to another by a code, a QR or a sheet of paper — by your gesture, and nothing else.
The full version is paid on Google Play — €2 a year, or €10 for life. The store takes the payment: the game never sees any payment data, and there is nothing else to buy, ever.
Ongoing games, home-screen configuration and settings are saved locally. The flip side is worth knowing: uninstall the game and your games go with it — copy the state code of the ones that matter.
The camera is only requested when you scan a QR, and the image is decoded on the device by an embedded decoder. The printed document is built locally and handed to the print service.
The InZeMobile name in the About box, and ✉️ Feedback. In both cases the game hands over to the browser or the mail app: that app is the one accessing the network, not the game.
A game with no ads, no data collection and no server still has to be funded — and the two usual ways of doing so are exactly the ones it refuses. So there are simply two apps — one free, the other €2 a year or €10 for life — and a web demo.
The free version forbids nothing. What it limits is finishing: outside its range, a grid only fills up to the share shown, and beyond that the keypad places nothing more.
| Board and mode | Free up to | Beyond |
|---|---|---|
| Square · Sudoku | 9×9 | 25% |
| Square · Calcudoku | 5×5 | 25% |
| Square · Colodoku | 4×4 | 35% |
| Square · Pictoku, Geodoku… | 5×5 | 50% |
| Square · science sets | 5×5 | 30% |
| Hexagonal | radius 2 | 35% |
| Triangular | side 6 | 35% |
| Voronoi | 5 symbols | 35% |
| Mosaic | — | 25% |
When several reasons apply, the lowest share wins. Nothing is forbidden: only placing a value is refused past the wall — erasing, correcting, undoing, the pencil, the preview, the timer and the code keep working.
Two books — to read as PDF in the browser, or to take along as EPUB — plus the guide built into the app, 📖 Game guide, in sixteen sections and all seven languages, readable offline like everything else. The screenshots are not mock-ups, and every grid shown carries its code: reopen it in the game and play what you are reading.
Everything the game can do, mode by mode, setting by setting: the three base modes, the sixteen themed sets, the five boards, the generation options, the helpers, the keyboard, the game code letter by letter, and the two versions.
Twenty-five pupils, fifty minutes, and the same grid for everyone: a lesson in four stages — on the board, in groups, alone, as homework — and sheets sorted by notion, from first additions to fractions and decimals. None of it is an instruction: you are in charge of your classroom.
Nothing. Every mode, every geometry, every size, every level, every setting opens and plays, and any game code works. What it limits is finishing: outside its range — Sudoku beyond 9×9, Calcudoku beyond 5×5, Hard and Expert levels, mosaic, Mystery, values beyond 10 — a grid only fills up to a share of its cells. You can try a Voronoi, a 26×26, an eight-colour Colodoku, play a good part of them; you simply won't be able to finish them.
The game warns you three times: when closing a selector as soon as the share changes, when opening the game by naming every reason, and when the wall is reached.
€2 a year, or €10 for life, your choice, on Google Play. The game refuses the two usual ways of funding a free app — advertising and data collection — and has neither account nor server: it is funded by the people who keep it, and by nothing else. The free version lets you try everything, with no time limit; the full one lifts the filling limits and adds the solving list and the player's path to printing. The store handles the payment, never the game: it sees no payment data.
On the device, and nowhere else: nothing is sent, nothing is saved online, nothing follows an account. The flip side: if you uninstall the game, your games disappear with it, and there is nowhere to restore from. If a game matters to you, copy its state code — the string carrying the grid and everything you wrote in it — and keep it wherever you like.
Yes. The code does not carry the grid but what is needed to rebuild it, and it starts with the version of the generator that made it — G1, G2… Since earlier generators are kept, a code never stops working: the one you hand out this year will open the same grid in five years. A check key at the end catches any typo and any swap of two neighbouring characters.
Through the game code — a pill under the tools, one tap copies it — which the other person types, pastes or scans as a QR from the Code button on the home screen. To pass on a game in progress, with your values and pencil marks, the button marked with a grid copies the state code. And when there is neither screen nor phone, paper: the printed grid carries its code and its QR.
Entirely. The app declares no network permission: once installed, it never needs the internet again, and a school has nothing to open in its firewall. The web demo only needs the network to load the page the first time.
Today the game exists in two forms: the Android app — phone or tablet, free or full version — and the web demo, which opens in a browser on any computer, with nothing to install, at inzedoku.inzemobile.com. Both give the same grid for the same code — measured grid by grid, not assumed.
A keyboard and mouse plugged into a phone or tablet work too: nothing is reserved for the desktop.
Yes, both ways, and without an account: the web demo at inzedoku.inzemobile.com has every geometry, every mode and every level. From the computer to the phone, the QR button on the game screen shows the grid — or the game as it stands, values and pencil marks included, if you flip the switch — and the phone scans it with Code → Scan a QR. From the phone to the computer, the grid button copies the game's state code, to paste into the browser with Code → Paste a game: eleven characters without pencil marks, one more per value placed.
The same code gives exactly the same grid on both sides — measured grid by grid, not assumed. So you pick up right where you were, and you can go back the other way as often as you like.
Two-finger zoom and panning work everywhere, but a 16×16 does not fit comfortably on a phone. The first time you go past nine a side, the game tells you itself: those sizes play better in the browser, on a large screen, with a mouse and keyboard. Hand it the game, as explained above, and carry on on the other side.
It can flag conflicts — placing a value that contradicts an already-filled cell — but that setting is off by default. On the other hand, it never tells you a value is wrong with respect to the solution as long as it contradicts nothing: that would be playing in your place. The preview shows everything — but that is a gesture you ask for explicitly.
Yes. The Colour blindness setting is chosen by type — deuteranopia, protanopia, tritanopia, achromatopsia — because the different forms are not compensated the same way. In Colodoku, a symbol is added over the colour; in multidoku, the frames switch to an axis your type distinguishes, or to stroke patterns when no colour is perceived. And some of the game's marks rely on colour in no setting at all: the full badge of a correct cage, the red cross of a duplicated colour, the black dot of a given value.
Seven: English, French, Spanish, Portuguese, Italian, German, Dutch — and decimal notation follows the language, point or comma. The language is changed from the ☰ menu on the home screen, not buried in the settings: it is the first setting anyone needs.
Nothing to install to give it a try: the web demo is at inzedoku.inzemobile.com. On Android, the free version lets you try every mode, every geometry and every size — for as long as you like.