Instructions & Guide
1. Sudoku Rules
Fill the 9x9 grid so every row, column, and 3x3 subgrid contains all digits from 1 to 9 without repeating any number.
2. Note Taking & Pencil Marks
Toggle "Notes Mode" to annotate candidate digits in empty cells. Notes automatically clear as confirmed numbers are entered.
3. Smart Hints & Validation
Stuck on an expert board? Click "Hint" for logic-based clues, or enable "Highlight Duplicates" for instant conflict alerts.
4. Four Difficulty Tiers
Choose from Easy, Medium, Hard, and Expert. Puzzle layouts are generated uniquely with guaranteed single-solution validity.