how to play ninefold
Ninefold is our free take on sudoku, the classic nine by nine number placement puzzle. Fill the grid so every row, every column and every three by three box holds the numbers 1 to 9 exactly once. Every puzzle has exactly one answer and can be solved by logic alone, and the levels are graded by the techniques a solve actually needs.
- Tap an empty square, then tap a number (or type it) to place it.
- Turn on notes to pencil in the numbers a square could still be. Placing a number clears it from the notes in its row, column and box.
- A number that clashes with another in its row, column or box turns red. Fix it before you finish.
- Stuck? Hint lights up the next square you can fill and says why, for 20 seconds on the clock. If you placed a wrong number, it finds that first.
- Fill every square without a clash to stop the clock. Undo is always there.
Keyboard: Arrow keys move around the grid, 1 to 9 place a number, Shift with a number writes a note, N switches notes on and off, Backspace or 0 erases, H asks for a hint, Z undoes, and Esc goes back to the menu.
tips
- Scan one number at a time: where can the 5 still go in this box?
- A square with only one candidate left in its notes is ready to fill.
- If a number in a box can only sit in one row, it can't sit anywhere else in that row. That's the pointing trick normal puzzles need.
faq
Is there always one solution?
Yes. Our solver finishes every puzzle step by step without guessing before you see it, which proves the answer is unique.
What do the levels mean?
Easy needs only singles: the one spot left for a number, or the one number left for a spot. Normal also needs pointing, claiming, pairs or triples. Hard needs at least one x-wing, swordfish, xy-wing or xyz-wing. The daily is normal and the same for everyone.
How is it scored?
By time, plus 20 seconds for each hint. Mistakes don't cost anything, but the clock keeps running while you fix them. It stops while the tab is in the background.
Is there a mistake limit?
No. A clash turns red so you can spot it, and you can keep going. Nothing ends the game but a full, clean grid.