Mode
Three difficulties
About 40, 32, or 26 givens.
01 — Story
The brief
Sudoku asks you to fill a nine-by-nine grid with the digits 1 to 9 so every row, every column, and every 3×3 box contains each digit once. There is no arithmetic.
A new puzzle is generated in the browser and checked so it has exactly one solution. Tap a cell and then a number, or type it. Arrows move. Conflicts turn red as you go. Hint fills the selected cell. Check tells you whether any entry is wrong. Backspace or the eraser clears a cell.
Easy shows about 40 givens, medium about 32, and hard about 26. Scan for a digit that is already common, then for the one cell in a group where it can still go. Harder grids need pairs: two cells that share the same two candidates, which removes those digits from the rest of the group. A timer runs. Accuracy beats speed.
How to enter a digit
Select a cell, then tap a pad number or press a key. If it clashes with a row, column, or box, it turns red.
