This is a logic puzzle game.
A correctly solved puzzle will have all of the numbers from 1-9 in each row, column, and block.
Here is a solved sample to show you the rows, columns, and blocks.
The difficulty setting will determine how many of the numbers are blank that you need to fill in.
Here are the difficulty breakdowns:
Easy
Medium
Hard
Impossible
Your score is the time, in seconds, it takes you to complete a puzzle.
The scores are broken down by difficulty.
Once you start a game, you cannot change the difficulty.
Although, you can start a new game with the same difficulty.
If you want to change the difficulty, just click the "Give up this puzzle" button.
