How to play Sudoku Zen
Fill the 9 by 9 grid so every row, every column and every 3 by 3 box holds the numbers 1 to 9 exactly once. Tap a square, then tap a number on the pad. On a keyboard use the arrow keys and the number keys.
Difficulty, notes and hints
Easy starts with 40 filled squares, Medium with 32 and Hard with 25. Every puzzle has exactly one answer. Daily gives everyone the same 30-square puzzle for that calendar day, and clearing it on back-to-back days builds a streak.
Turn on Notes to pencil in small candidate numbers. Undo steps back through your moves. Hint picks the empty or wrong square with the fewest possible numbers and fills it for you. The mistake counter and the red highlight can be switched off with the box under the board.
Stars and best times
A clean solve with no mistakes and no hints earns 3 stars. A few slips or one hint earns 2, and heavy help earns 1. A best time is only saved when you used no hints and made fewer than 3 mistakes. Your best times, daily streak and the puzzle you are in the middle of are saved in this browser, so you can close the tab and carry on later.