Sudoku X is a challenging variant of the traditional sudoku, which has the same rules plus a few more. Your job is to fill all the squares in the 9x9 grid with numbers from 1 to 9, but the numbers cannot be repeated in the rows, columns, diagonals, and in each subgroup of 3x3. A new game is generated every time you start, so there are hundreds of possibilities. The game is timed, so the faster you complete the grid, the more score you will get. When you start a game, there will be a few guiding numbers to help you and if you get stuck, you can use the unlimited hints, which will reveal a number on the grid. However, there is a time penalty for using the hints and many seconds will be added to the timer. Unfortunately, the games cannot be saved to continue them later, and there's only one difficulty level available.
The game features simple sounds and graphics, and suitable music. Your score can be published on multiple social sites and you can send it by email. The game can be played in full screen and directly from the web browser.
All in all, if you like sudokus, you may want to try this challenging variant.