Web Sudoku

Sudoku is a numbers game I've started playing recently. Here is the game on the web. The site has four different levels to choose from. From the site, "The rules of Sudoku are simple. Enter digits from 1 to 9 into the blank spaces. Every row must contain one of each digit. So must every column, as must every 3x3 square." Websudoku is clean and has a good ui.

The link address is: http://www.websudoku.com/