Best App for Sudoku
81 digits: Soduku can be tough, but its rules are simple. Fill a nine-by-nine grid with digits, making sure no column or row has the same number twice. The grid is subdivided into three-by-three blocks, and these also can't repeat a number. The game starts you with a few prefilled squares, and the rest is up to you. In Sudoku Unlimited, tap a square to select it, and the app highlights its row and column for easy scanning.
Skin in the game: The game includes four skins, including this notepad design. All work the same: Tap a square to conjure the number pad. Tap the pencil icon to switch to "notes" mode and jot down tiny numbers to note the square's possible answers. (Here, 4 and 5 are noted as possibilities.) Tap the Auto-Fill icon, and the app does the dirty work for you, filling every empty square with notes of its possible numbers.
Version reviewed: 1.05
The App Store is thick with Sudoku games, reflecting the popularity of these number-crunching logic puzzles. Among several strong contenders, Sudoku Unlimited is the best entry, with a functionally limitless supply of randomly generated puzzles, five difficulty levels, and four "skins" for changing the look of your puzzles. The interface is easy and efficient with simple note entry and hints when you're stumped.