Sudoku
Fill the grid so every row, column and box holds each digit once. Every puzzle here is checked before it is dealt, so it has one answer and can be reasoned out without ever guessing.
Every row, column and three-by-three box holds each digit from 1 to 9 exactly once. Tap a cell, then a number. Notes writes small pencil marks instead — useful for holding the possibilities in a cell while you work out which is right. Clashing digits are marked in red, but a grid with no clashes can still be wrong. Every puzzle here can be solved by reasoning alone, so you never have to guess. Undo is unlimited within the last 80 actions.
Free play
Every deal here is randomly generated, and you can play as many as you like. Your game saves itself as you go, so you can close the tab mid-deal and pick it up later.
New to Sudoku? Read the rules.