Nabner Sudoku
A Nabner board: the marked line already holds 1, 5 and 7. Its two empty cells can only be 3 and 9 - a five-cell Nabner line is always 1·3·5·7·9.
Nabner Sudoku is Classic with a marked line drawn across the grid. On that line no digit may repeat, and no two digits may be consecutive. Everything else is unchanged.
The rule
- All the Classic rules apply - 1-9 exactly once in every row, column and 3×3 box.
- No digit repeats anywhere on the line.
- No two digits on the line are consecutive. If a 3 sits on the line, neither 2 nor 4 can appear anywhere else on it.
- Crucially, this applies to every pair on the line, not only to cells that touch. Two line cells at opposite ends still constrain each other.
Both halves of the rule are the same test in disguise: any two digits on the line must be at least two apart. A repeat is a difference of zero, a consecutive pair is a difference of one - both fail it.
Why a Nabner line can never exceed five cells
Pick digits that are pairwise two or more apart and count how many you can fit into 1-9. Start at 1, and the next has to be 3, then 5, then 7, then 9 - five digits, and there is no room for a sixth: anything you add is either already used or sits next to one of them.
So a five-cell Nabner line is always 1, 3, 5, 7 and 9, in some order. That is the single most useful deduction in this variant, and it is worth checking for first: the moment you spot a five-cell line, every digit on it is odd and every even digit is eliminated from those five cells at once.
How to play, step by step
- Count the line. Five cells means 1·3·5·7·9 immediately. Four cells is nearly as strong - the options are few and every one of them skips at least two digits.
- Pencil out from one known digit. A single given on the line removes three digits from every other cell on it: itself and its two neighbours. One clue does a lot of work here.
- Cross-check with the boxes. A line usually crosses several 3×3 boxes, so a digit eliminated by the line is also eliminated from its box - which often opens up cells nowhere near the line.
- Then solve normally. Away from the line it is plain Classic Sudoku.
Nabner and Renban
The name is Renban spelled backwards, and the rule is its mirror image. A Renban line holds a set of consecutive digits in any order - 4·6·5·7 is a valid Renban. A Nabner line forbids consecutive digits outright, so that same set would be illegal several times over. It is why Nabner is sometimes called an anti-Renban line.
Common mistakes
- Treating it like a whisper line. On a German or Dutch Whispers line only neighbouring cells are compared. On a Nabner line every pair counts, however far apart the cells are. This is the mistake that costs the most time.
- Forgetting that repeats are banned too. A line can wander through several boxes, and two cells on it may sit in different rows, columns and boxes - the ordinary rules would allow them to match, but the line does not.
- Missing the five-cell shortcut. If the line has five cells and you are still weighing even digits, you are solving a harder puzzle than the one in front of you.
Difficulties & scoring
This type can be played on all five difficulties. The score multiplier for Nabner Sudoku is ×1.2 - so every point counts for more on this variant. The "normal time" below is tuned for this type.
| Difficulty | Base score | Max (×1.2) | Normal time | Hints |
|---|---|---|---|---|
| easy | 150 | 360 | 6 min | 5 |
| medium | 300 | 720 | 11 min | 4 |
| hard | 600 | 1440 | 17 min | 3 |
| expert | 1000 | 2400 | 22 min | 2 |
| evil | 1500 | 3600 | 34 min | 1 |
How the score is calculated
Your score builds up from 0 as you place correct numbers, up to the full base when the board is finished. Then two bonuses are added:
base × your progress × (1 + combo bonus + time bonus) × 1.2
- Progress: the live score climbs from 0 to the base as the grid fills with correct numbers.
- Combo bonus (up to +50%): keep a clean run for the full bonus. Each error or hint is a combo break that shrinks the bonus - but it never takes Sparks away below the base.
- Time bonus (up to +50%): beat the normal time and you earn extra, proportional to how much faster you were. Finishing slower than normal costs nothing - there is no time penalty.
- The total is multiplied by ×1.2 and never drops below 0.
Coins
The coins you earn reflect your score - the more Sparks, the more coins (about 1 coin for every 45 Sparks, minimum 1). Spend coins in the Shop on hints and Jokers.
Tip: a clean, hint-free solve under the normal time scores the highest. The Daily Challenge is always Classic and fully scored.
Where to play it
Nabner Sudoku scores at 1.20× here, because the extra rule is real work on top of classic logic: A line where every pair of digits is at least two apart - the opposite of a Renban run.
Difficulty and type are two separate dials here: the type sets the extra rule, the level sets how much of the grid you start with. Hard Sudoku leaves 26 of the 81 cells filled, where scanning gets you started and then leaves you stranded; Expert Sudoku leaves 25, where the beginner tools dry up almost entirely. Take Nabner at the gentler end while the pattern is still new, and move up once it stops being a fight.