Sudoku.com, reviewed

Our take

Sudoku needs no introduction: fill the grid so every row, column and box holds the numbers one to nine once. This site does the plain version well, with levels from easy to extreme, a killer mode with sums, pencil notes, undo and hints that explain the logic instead of simply filling a square.

It also has a three-mistakes rule, which we like because it rewards checking over guessing. The puzzles load quickly and the grid is clear on a phone.

The catch is adverts. There are banners, video adverts and full-screen adverts between puzzles, and we rank it lower for that, along with tournaments, events and streaks that are there to bring you back. The puzzles are the good part; you can enjoy them and ignore the rest.

A first sitting

Start at medium rather than easy, use notes freely, and try one puzzle without a single hint.

Where to stop

One puzzle is a natural stop. The site offers another straight away and runs timed events; one or two puzzles and close the tab.

Worth knowing

Its licence terms set a minimum age of 16. Expect full-screen adverts between puzzles.