A dedicated Note Mode allows users to pencil in multiple possibilities per cell, which can be set to update automatically as you fill in the grid . Performance and Interface

The most common form of protection involves an algorithm embedded within the application executable. When a user enters a key, the software runs the input through a mathematical algorithm to verify its validity.

: You can download the official version of Sudoku Up directly from the developer, Solitaire City / TreeCardGames . They often offer free trials or demo versions.