Kakuro.com

Kakuro is a cross-sum number puzzle, and this site lets you play it free in the browser. Fill the grid with digits from 1 to 9, never repeating a digit within the same run, so that each row or column adds up to the clue shown for it. Multiple difficulty levels are available, from beginner right up to master, so you can warm up with something gentle or dive into a proper brain workout with nothing to download.

Casual