Everydoku12×12 and 16×16 sudoku
Once 9×9 feels comfortable, bigger boards are waiting. The rule is the same and so are the techniques, but with 144 or 256 cells, choosing where to look matters far more. Here is how to finish boards that take anywhere from twenty minutes to over an hour.
What the boards look like
| 12×12 | 16×16 | |
|---|---|---|
| Boxes | 3 rows × 4 columns, 12 of them | 4×4, 16 of them |
| Symbols | 1–9, A (10), B (11), C (12) | 1–9, A (10) … G (16) |
| Cells each cell touches | 28 | 39 |
| Difficulties | Normal, Hard | Normal, Hard, Master |
Digits above 9 are written as the letters A to G so each fits in one character. If letters feel awkward, turn on “Numbers above nine” in settings to see 10 to 16 instead. The 1–9C button on the play screen switches it on the spot.
An order of attack
- Sweep the board one digit at a time. On a big board, counting thirty-odd neighbours of a single cell is slow. Picking one digit and looking for its hidden single in each box is much faster. Start with the digits that already appear most.
- Go after nearly full boxes. A box with two or three empty cells has only a few digits left, so their places settle quickly.
- Take notes only when stuck. Pencilling all 256 cells from the start will wear you out. Write candidates only for the boxes and lines where you are stuck.
- Use auto notes wisely. Everydoku's big boards have auto notes, which fill in the current candidates of the selected cell. It does not fill the whole board; use it to check a confusing cell precisely.
- Take breaks. Pause stops the clock and covers the board. Every move is saved, so you can close the window and carry on the next day.
Techniques that get stronger on big boards
- Locked candidates: on 16×16 a box and a line overlap in four cells, so candidates line up far more often than on 9×9. It is the key technique for Hard boards.
- Naked pairs: in a line with many empty cells, one pair can clear many candidates.
- Hidden pairs and the X-Wing: for getting past the sticking points of 16×16 Master boards.
Big boards on a phone
On a phone screen the cells of a 16×16 board are small. Everydoku draws notes inside cells as dots and shows the selected cell's notes large in the notes bar below the board. In landscape, on a tablet or on a computer, the board gets bigger and the number pad moves to the side. On a computer you can type with the arrow keys, the number keys and the letter keys A to G.
Prefer paper? Use the printable 12×12 and printable 16×16 pages.