The 3D sudoku cube

The sudoku cube puts a 9×9 grid on each of the six faces of a cube. Turn it with your mouse or your finger, then select a face: it lies flat, full size, and plays like a regular sudoku. A face filled in without errors turns gold; when all six faces are gold, the cube is won. Sudoku-Land's three cubes are free to play in your browser, with no sign-up, on desktop and mobile alike.

Each face is an ordinary 9×9 sudoku: each number from 1 to 9 once in each row, each column and each box. What the cube mainly adds is a way of getting around:

• Turn the cube: drag across it, with the mouse or your finger. The cube-shaped button, next to the face buttons, turns it back to a three-quarter view.
• Lay a face flat: select it, or its button (1 to 6). It lies flat in front of you, ready to play; the golden ring around each button shows how far along its face is.
• Move to the next face: the arrows on the edges of the flat face bring up the face next to it, without going back to the overview.
• Finish a face: filled in without errors, it turns gold and locks. You can finish the faces in any order you like.

Your cube is saved automatically on your device: you can pick up a long game right where you left it.

Imagine a Rubik's Cube where each small cube on the surface carries a digit. A small cube in the middle of a face only shows on that face; an edge cube shows on two faces, a corner cube on three. Each face is still a normal 9×9 sudoku, but its borders are also those of its neighbours: a digit placed on an edge shows on both faces, and it must be correct for both. In all, the cube has 386 cells, not 6 × 81 = 486.

A face on its own does not have enough digits to be solved: its neighbours bring it more. So you do not fill in six grids one after the other; you work your way around the cube, moving from one face to another. A finished face also locks its borders, including the cells it shares with its neighbours.

• Who it's for: 9×9 players who want a real three-dimensional challenge, with no new rule to learn.
• The right reflex: when a face gets stuck, move to its neighbour. The digits found on the shared edge often unlock the first one.

Over to you: play the Classic Cube.

Each face carries a sudoku variant, always in the same place: Sudoku X on face 1, Hyper Sudoku on face 2, Even-Odd Sudoku on face 3, Jigsaw Sudoku on face 4, Greater Than Sudoku on the top and Killer Sudoku on the bottom. When a face lies flat, its rule is shown above the number pad, and each face's button shows the symbol of its variant. On the Killer face, the combinations of the selected cage show in place of the rule.

The faces are separate: each one can be solved on its own, like a puzzle from the site's variant pages. The whole point is to change rules without changing games, moving from one face to the next.

• Who it's for: players who want to discover all six variants in one go, or who already know them and are looking for a long game.
• The right reflex: read the face's rule before you play. The markings change from one face to the next: a diagonal only counts on the X face, a shaded cell only on the even-odd face.

Each variant is explained on the sudoku variants page. To play them all at once: play the Variant Cube.

The Ultimate Cube brings both ideas together: the six variants, in the same places as on the Variant Cube, on a cube with shared edges like the Classic Cube. A border cell belongs to two faces, so to two rules: on the border between the even-odd face and the Killer face, a digit must both match the shading of its cell and fit the sum of its cage.

The Killer and greater than faces start with few digits, or none at all: their edges fill in as you make progress on their neighbours. It is the most demanding of the three cubes; plan for a long game, autosave will keep it for you.

• Who it's for: players who have finished the Classic Cube or the Variant Cube and want more.
• The right reflex: start with the fullest faces, then use their edges to tackle the almost empty ones.

The big challenge: play the Ultimate Cube.

All three cubes have 3 levels, Easy, Medium and Hard. Start with Easy: even there, a cube takes far longer than a single grid.

In short: the Classic Cube to discover sudoku in 3D, the Variant Cube to tour the variants, the Ultimate Cube for both at once.

The cubes keep everything that makes classic sudoku comfortable on Sudoku-Land:

• ✏️ Notes mode (Space key, right-click or long press), and in the ⚙️ Settings menu, automatic notes for the face in play, which take its variant into account. The “Cleaned candidates” option costs a hint.
• ⊙ The ring of digits around the selected cell, for faster input.
• 💡 Six hints for the whole cube, to use on the face of your choice. A hint reveals the digit of the selected cell.
• ⏸ Pause and the timer, which also stops when you leave the page.
• Automatic saving of the whole cube, on your device.
• Separate statistics for each cube (cubes started, solved, without hints, best times), stored in your browser and never sent to a server.
• Reading comfort: dark theme and large print.

What is a sudoku cube?

It is a three-dimensional sudoku: six 9×9 grids, one on each face of a cube that you turn. Each face is solved with the usual rules (each number once in each row, each column and each box), and the cube is won when all six faces are filled in. On the Classic Cube and the Ultimate Cube, the faces also share the cells along their borders.

What does “shared edges” mean?

Think of the cube as a Rubik's Cube where each small cube carries a single digit. A cell on the border of a face is also on the border of the neighbouring face: the digit you place there shows on both faces, and it must be correct for both. A corner cell even belongs to three faces.

Do you have to finish the faces in order?

No. Play the faces in any order you like, and switch faces as often as you need. On the cubes with shared edges, it is even essential: a face on its own does not have enough digits to be solved, and its neighbours bring it more.

Can you play the sudoku cube on a phone?

Yes. Tap a face: it lies flat and takes up almost the full width of the screen. A long press on a cell switches to notes mode, and the buttons 1 to 6 below the cube let you change faces without turning it.

Is the cube harder than classic sudoku?

Each cube has 3 levels. At the Easy level, the faces can be solved with basic techniques; the difficulty comes mostly from the length of the game and, on the cubes with shared edges, from going back and forth between the faces. The Hard level calls for more advanced techniques, such as locked candidates.

Are my statistics separate for each cube?

Yes. Each cube has its own save and its own statistics, separate from those of the 9×9 puzzles and the variants. They are stored in your browser and never sent to a server.