In this sudoku solver you have the option of solving the puzzle in two different ways. If you just use the "Solve !" option, each number change in the board will take place only after a 25 millisecond delay. This is done so that it will be easier to visualize the recursion and backtracking that takes place.

However if the sudoku puzzle entered in is difficult, the "Solve !" option can take quite a lot of time to solve it.

To overcome this problem I have also added in a "Speed Solve !" option in which the 25 millisecond delay is taken away and the puzzle gets solved almost instantly.