Go! Sudoku

The addictive game comes to the PSP.
Those of you in the know know exactly what Sudoku is about. It's an ancient numbers game created to challenge and feed the brain.
You are supplied a Square Grid with 9 small squares from Left to Right and 9 squares from top to bottom.
The aim is to get the numbers '1 to 9' within the grid without repeating a number in any Box, Row or Column.
It's sounds complicated but it's not. It's just hard to explain with words.

There are 1000 grids available. Rangings from Easy, Mild, Hard and Fiendish. More are available to Download online.

Unfortunatly though you can't lose. Whenever you enter a wrong number the number turns Red which means that it's placed wrong. Also if you use up all the 9s for example the option to place a 9 disappears.
Another thing that bugs me is that you never feel rewarded for passing a grid simply because the game practically tells you the answers. It is true that you get a time...