This is a fun Sudoku game. Right now, the system will turn sqares red to let you know if there is an error. Errors include if the character in the square is not a number from 1-9, if there are duplicate numbers in a subsquare, and if there are duplicates numbers in a row or column.

I have the script fairly efficient, but it's still only javascript, so if the browser says the script is taking too long, give it a little while longer and it will most likely finish what it was doing. If you do kill the script running though, no worries, the game still continues, some squares may just not be colored right from your last play.