An example Parity Lines puzzle: the parity alternates along the line - odd, even, odd, even (1, 4, 7, 2).
Parity Lines Sudoku draws lines whose digits must alternate odd and even. Step along the line and the parity flips every cell: if one is odd, its neighbour is even, the next odd again, and so on. The digits themselves are free - only their odd/even pattern is fixed.
The rule: odd, even, odd, even
Pick any marked line and read it end to end. No two adjacent cells on it share a parity, so the line is a strict alternation of odd and even values, on top of all the usual Sudoku rules.
Solving strategy
- Fix one, fix them all. A single known parity on the line sets the odd/even pattern for the whole line.
- Halve the candidates. Each line cell is limited to {1,3,5,7,9} or {2,4,6,8} before any other clue.
- Combine with the grid. The parity pattern often collides with a row, column or box elimination to pin a digit exactly.
Common mistakes
- Reading it as all-odd or all-even. Parity alternates; it does not stay constant along the line.
- Forgetting parity has five odds, four evens. The odd cells draw from a larger pool than the even ones.
- Dropping the ordinary rules. Rows, columns and boxes still each need 1-9 once.
Can I play it here?
Not yet - Parity Lines Sudoku isn't one of the puzzle types SudokuStreak generates for now. But you can learn its rules above, and there's plenty here to sink your teeth into meanwhile:
- Browse all the Sudoku variants we do offer.
- Or print free puzzles from the printable PDF page.
Where to play it
Parity Lines Sudoku belongs to the constraint family and runs on 9×9. It is not one SudokuStreak generates yet - but the deduction it trains is the deduction every Sudoku runs on.
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. Expert Sudoku leaves 25 of the 81 cells filled, where the beginner tools dry up almost entirely; Evil Sudoku leaves 23, with no easy moves at all. Take it at the gentler end while the pattern is still new, and move up once it stops being a fight.