Features: 1) 2 games selection: 6x6,6x8,2000 preset puzzles plus over 1,000,000 computer generated puzzles. 2) Save and resume the puzzles to play, alert sound for incorrect input(optional function). 3) Demo play function. 4) Help function to show you all possible numbers and /or number combination. 5) Timer to keep track of how long you take to solve a puzzle, you can compete with your friends on the same puzzle. 6) Create your own puzzle and the unit can provide hint. 7) Display correct number one by one in auto solve mode. 8) Place unconfirmed numbers on the grids to be finished later.