Sudoku in brief
Sudoku as we know it is credited to Howard Garns, an American architect whose puzzle appeared in 1979 in a Dell puzzle magazine under the name Number Place. The Japanese publisher Nikoli printed it from 1984 and gave it the name Sudoku. The game conquered Europe after it appeared in The Times, in London, in November 2004.
The rules fit in one sentence: fill a 9×9 grid so that each digit from 1 to 9 appears once in every row, every column and every 3×3 box. A few digits are given at the start, and a good grid has only one solution, reachable by logic alone.
What Sudoku lovers enjoy
- Pure deduction: no luck, no trivia, nothing but logic.
- Momentum: every digit you place unlocks others, right up to the final cascade.
- Techniques: pairs, scanning, single candidates, which make hard grids manageable.
- The ritual: a grid with your morning coffee, in the paper or on your phone.
The first two games in the selection are Sudoku in the strict sense. The other two are different grid puzzles that call on the same way of reasoning.
Comparison: what each SIWA game shares with Sudoku
| SIWA game | In common with Sudoku | What changes |
|---|---|---|
| Sudoko | The same rules, in 9×9 | Each digit is checked as soon as it is placed |
| Sudolito | The same rules | 6×6 grid, 2×3 boxes, digits 1 to 6 |
| Binero | Row and column constraints | Two symbols instead of nine digits |
| Bouclo | Pure deduction from number clues | You draw a loop instead of filling cells |
Sudoko and Sudolito: Sudoku every day
Sudoko is a classic 9×9 Sudoku, with a fresh grid every day. The difficulty varies between easy, medium and hard according to the number of starting digits; on Sundays the grid is always hard. Allow 5 to 12 minutes. Each grid is generated by an algorithm and then checked by a solver: it has a single solution, with about 36 given digits on easy and as few as 22 on hard.
One difference is worth knowing for purists: each digit is checked as soon as it is placed. A wrong digit shows in red, blocks input until you undo it, and still counts as a mistake in your score. The game also offers a notes mode, multi-cell selection with a swipe, and a long press that locks a digit to highlight it across the grid. If you get stuck, a joker reveals a cell, for a few points.
Sudolito follows exactly the same rules on a 6×6 grid divided into boxes of 2 rows by 3 columns, with digits 1 to 6. The deductions are the same, in half the time: allow 3 to 7 minutes.
Binero and Bouclo: the same logic, different rules
Binero replaces the nine digits with two symbols, ○ and ●. Three rules: never more than two identical symbols in a row, as many ○ as ● in every row and column, and no duplicate row or column. The grid, 6×6 or 8×8, is judged only once it is full: with just two symbols, flagging a wrong cell would give away the answer. Our guide to games like Takuzu covers this binary cousin of Sudoku in detail.
Bouclo changes the gesture. You draw a single closed loop along the edges, between the dots of the grid; the number in a cell tells you how many of its four sides belong to the loop. Like Sudoku, it is a puzzle of pure deduction, where every segment you place forces others. On Sundays the grid is bigger and harder; a joker reveals a correct segment if you get stuck.
One grid a day, the same for everyone
Each grid changes at midnight, in your local time, and it is the same for everyone that day. The daily leaderboard compares everyone's score, calculated out of 1000 points from mistakes, jokers and time.
Everything is free, in the browser, with nothing to download and no sign-up. A free account keeps your streaks and opens the archives so you can catch up on a missed grid. A simple routine: Sudolito as a warm-up, then Sudoko, and Binero or Bouclo when you want to change rules.