This is a screen shot of my Sudoku game. The small numbers indicate numbers that are valid candidates for that square.
To get started you must enter a puzzle using the on-screen keyboard and save it using "Save Puzzle" and then reload it using "Load Puzzle"
"Save Pen" and "Load Pen" allow you to save intermediate results for a given puzzle.
"Save Pencil" and "Load Pencil" allow you to save guesses.