Fill every row, column and 3×3 box with the digits 1–9. Every puzzle is generated fresh and verified to have exactly one solution — plus a new daily puzzle every day.
Every puzzle starts from a randomly generated, fully solved grid. Cells are then removed one by one, and after each removal a solution-counting solver confirms the puzzle still has exactly one answer — so harder levels mean genuinely fewer clues, never a broken or ambiguous board. Generation runs in a background thread, so even Master puzzles never freeze the page.
The hint looks for a real logical step first — a naked single (a cell with only one possible digit) or a hidden single (a digit that fits in only one place in a row, column or box) — highlights the cells involved and explains why. Only when no simple step exists does it reveal a cell directly.
Notes are small pencil marks for digits you're still considering. Turn Notes on (or hold Shift while typing a digit) to add or remove them. Auto-notes fills every empty cell with all digits that are currently legal there, which is a great starting point for harder puzzles.
Once a day a new puzzle is created from the date itself, so everyone who plays today gets exactly the same grid — handy for comparing times with friends.
Yes. Your current puzzle, notes, time and mistakes are saved automatically in this browser, along with your stats for each difficulty.