Beginner Tips & Simple Patterns
Short answer: to solve a sudoku, scan each row, column and 3×3 box to find a spot where only one shape can go — then place it and scan again. No maths, no guessing. Below are the two patterns that do most of the work on an easy puzzle.
The one rule
Fill the grid so every row, every column, and every 3×3 box contains all nine shapes exactly once. In form9 the symbols are a circle, square, triangle, slash, diamond, star, plus, ring and heart instead of the digits 1–9 — but the logic is identical to number sudoku, and so is every technique on this site.
Pattern 1 — scanning a box (cross-hatching)
Pick a shape and a box, then ask: where in this box could the shape actually go? Every row and column that already contains that shape blocks a whole line of cells. Cross those off and you're often left with a single legal square.
This is the single most useful beginner habit: run one shape at a time through each box and watch the options collapse.
Pattern 2 — the last free cell
When a row, column or box has only one empty cell left, there's nothing to work out: the one missing shape simply goes in the gap. Always sweep for these first — they're free moves.
A beginner's solving routine
Put the two patterns together and work in this loop:
- Start where the grid is fullest. Look for the row, column, box, or shape that already appears most often. The more that is placed, the fewer options remain — and the easier the next deduction.
- Scan one shape across the grid. Pick a shape and check each 3×3 box. Because that shape can appear only once per row, column and box, its existing copies rule out most cells — a technique called cross-hatching.
- Place a shape when only one cell is left. If a box (or row or column) has just one cell where a shape can legally go, place it there.
- Fill any cell that has only one option. If a single cell can hold only one shape — because its row, column and box already contain the other eight — write it in.
- Rescan after every placement. Each shape you place removes options elsewhere. Go back and scan again; easy puzzles unravel one forced move at a time.
Where to go next
Once scanning stops finding moves, two named techniques take over — and they're still easy:
- Hidden singles — a shape that fits only one cell in a unit (this is scanning, formalised).
- Naked singles — a cell that can hold only one shape.
Frequently asked questions
What is the best way to start a sudoku puzzle?
Begin with the shape or unit that is already the most complete. Scanning the fullest rows, columns and boxes first gives you the quickest forced placements, which in turn open up the rest of the grid.
What is cross-hatching in sudoku?
Cross-hatching is scanning a single shape across a 3×3 box: you mentally trace the rows and columns that already contain that shape, cross off the cells they pass through, and see which cell in the box is left. If only one remains, that shape goes there.
Do beginners need to write pencil marks?
Not for easy puzzles. Scanning and the "last free cell" pattern solve most beginner grids without any candidate notes. Pencil marks become useful later, for naked singles and harder techniques.
Is it ever okay to guess?
No. A proper sudoku always has one logical solution. If you're tempted to guess, there's a placement you've missed — rescan the fullest units rather than risk breaking the grid.