What does pencil mode do?

It lets you write small candidate numbers in a cell without committing to them — useful for tracking possibilities when a cell could hold multiple values.

Is every puzzle guaranteed to have one unique solution?

Yes — properly generated Sudoku puzzles have exactly one valid solution achievable through logic alone.

What is the difference between difficulty levels?

Easier levels provide more starting numbers and require only basic elimination; harder levels require advanced techniques like X-Wing or hidden pairs.

Sudoku

Puzzle Games

Sudoku is the classic 9×9 number puzzle where every row, column, and 3×3 box must contain each digit from 1 to 9 exactly once. This version adds auto-highlighting — when you select a cell, all cells sharing the same row, column, and box are shaded, making conflicts immediately visible.

Fill cells by tapping a number, use the pencil mode to leave candidates when you're not sure. The puzzle generates errors when you place a duplicate and shows them in red. Difficulty levels range from Easy (many givens, simple elimination) to Expert (requires bifurcation — guessing a value and following the chain). One Sudoku puzzle typically takes 5-30 minutes depending on difficulty.

Suited for players who enjoy slow, methodical logic puzzles — there's no time pressure unless you turn on the timer yourself. Great for daily mental exercise. Tip: start by scanning for numbers that appear most frequently in the given cells — 7s and 8s are often easier to place early because they appear less frequently.

FAQ

What does pencil mode do?: It lets you write small candidate numbers in a cell without committing to them — useful for tracking possibilities when a cell could hold multiple values.
Is every puzzle guaranteed to have one unique solution?: Yes — properly generated Sudoku puzzles have exactly one valid solution achievable through logic alone.
What is the difference between difficulty levels?: Easier levels provide more starting numbers and require only basic elimination; harder levels require advanced techniques like X-Wing or hidden pairs.