How to play Sudoku: rules, notes and how to start a hard puzzle

Sudoku is a number puzzle, but there is no maths in it, only logic. On ComCom Games it is a solo friendly: just you and a fresh puzzle at Easy, Medium or Hard, from Friendlies.

What are the rules?

• The grid is 9 by 9, split into nine 3 by 3 boxes. Some numbers are given at the start.
• Fill every row, every column and every 3 by 3 box with the numbers 1 to 9, each once.
• Every puzzle is new, made for you when you start, with exactly one solution. Easy gives you more numbers to start with, Hard gives you fewer.

How does it work on ComCom Games?

• Tap a square, then a number, or type it on a keyboard.
• A wrong number is not placed and counts as a mistake. Three mistakes and the puzzle is over.
• You have 30 minutes, and the clock starts when the puzzle opens. Solve it in time and it counts as a win.
• Notes mode lets you pencil small numbers into a square while you work it out. A note disappears once its number is placed in the same row, column or box.

How do you start?

• Pick a number, say 5, and look at one box. Cross off the rows and columns that already have a 5. If only one square in the box is left, the 5 goes there.
• Look for a row, column or box with only one or two empty squares. They are the quickest to finish.
• Tap a placed number to light up every copy of it on the grid. It makes the step above much easier.
• On Medium and Hard, use notes: pencil in every number a square could be. When a square is down to one note, that is its number.

Does it pay ComCom Coins?

Yes. Every Sudoku you solve earns ComCom Coins, up to a daily limit, like every friendly win, and counts on the Friendlies tab of the Leaderboard.