Ultimate Games: 25,000 Sudoku

Ultimate Games: 25,000 Sudoku is, as the name implies, a collection of twenty-five thousand Sudoku puzzles.

The game installs these puzzles into ten books each containing two-thousand five hundred puzzles and within each book the puzzles are further divided by difficulty. The puzzles can be played either by the keyboard, the mouse or a combination of the two. Answers may be entered in pen - used when the player is sure of a cell's contents, and in pencil - used to indicate potential answers.

The game has a help function which basically explain the rules, a cheat function and a 'check answers' function which tells the player 'you have entered x numbers and y are incorrect' without saying which are incorrect.