Core techniques
On a 6 × 6 grid each digit appears six times. These three techniques fill most of an easy or medium grid.
1. Cross-hatching
Pick a digit, say 3, and look at every row and column that already contains one. In a region still missing a 3, those rows and columns are off limits. If only one free cell is left, that is where the 3 goes.
Start with the digits that are already plentiful: the keypad shows how many copies are left to place, and the most advanced digits are the most constrained.
2. Two-region bands
The shape of the regions is what sets Sudolito apart. Rows 1 and 2 form a band of two regions side by side, as do rows 3-4 and 5-6. If a digit sits on row 1 in the left region, it must be on row 2 in the right region: only three cells are left for it, often narrowed to one by the columns.
The other way round, columns 1 to 3 stack three regions of two rows. Each column therefore crosses three regions, which makes scanning by column a little less direct.
3. The last digit
When a row, column or region has only one or two empty cells left, count the missing digits. A cell that already "sees" five different digits across its row, column and region has only one option left.
Techniques for the Sunday grid
On Sundays the grid gives only about 13 of its 36 digits. Scanning runs out of steam sooner, and these techniques take over.
4. Lock a digit to chain placements
A long press on a keypad digit (or the L key) locks it: every copy is highlighted, which makes visual scanning instant. Each empty cell you tap then receives that digit. The lock lifts once the digit is complete.
5. Pairs
If two cells in a region can only hold the same two digits, say 2 and 5, those digits are reserved for them. The other cells in the region, and in the row if the two cells are aligned, can strike them from their candidates.
6. Notes by dragging
Notes mode lets you pencil candidates without committing. Drag your finger across several empty cells, then tap a digit: it is noted wherever the rules allow, and the game refuses cells where it would be impossible. When a digit is placed, it vanishes automatically from the notes in its row, column and region.
Protecting your score
7. Choosing between a mistake and a joker
Every digit is checked instantly. A wrong digit turns red, locks the grid until you remove it with the undo button (labelled Annuler), and still counts as a mistake. Depending on how many cells were empty, a mistake costs roughly 20 to 35 points.
The Joker costs about 60 points. It reveals the digit of the selected cell if that cell is empty, so select the cell that is blocking you before tapping it, rather than letting the game pick which cell to reveal.
If you are torn between two candidates after exhausting your deductions, testing one costs at most one mistake, less than a joker, and gives you the answer either way. But every grid has a logical solution: one more look at the bands and columns is often enough.
The timer
The reference time is 3 minutes on easy, 5 on medium and 7 on hard. Finishing in half that time earns the maximum 20% bonus; past the reference time the penalty grows slowly and is capped at 25%. A clean grid therefore beats a fast grid with three mistakes.
To review the rules and a sample region, read how to play Sudolito. For a change of logic, try Binero, SIWA's Takuzu.