There are five difficulty levels and 14 different backgrounds, but not all of them are available right away. The difficulty is measured by the amount of givens (numbers already entered) and the amount of coins. Coins can be exchanged for hints. Hint A gives some possible numbers for the current cell, Hint B provides the correct number for the current cell, and Hint C scans the whole board and marks cells as right or wrong. While playing, you can also erase numbers or enter up to four small numbers into a single cell when you want to keep track of the possibilities. Scores are based on the completion time and the amount of mistakes made.
In the Solver mode, you can design your own puzzles and have the computer solve them, which is especially useful when you are unable to complete a paper puzzle. In the Custom mode, you can create and save your own puzzle, and have the game check if they are valid. The most difficult mode is called Sudoku X. All regular apply there, but it requires that you do not replicate any digit in the two diagonals as well.