To clear the puzzle, click on 

Enter your puzzle here, then click on 
This will copy your puzzle into the grid below.

There are a few puzzles ready to try. Click a button to load one of them instead of writing your own.

Beware of bugs
I started to write this program ages ago and never finished it. It almost works, but you will find that it does not always do what you would expect!

First, load a puzzle as above.

There are a couple of rules for the program to follow in trying to solve the puzzle. You just keep applying them until it is complete.

The first rule is to check each position in turn to see what could be in it. It can be any number unless that number already appears in the same row, column or box. Click to apply the rule

The next rule is to look look for any new positions which now have only one possible number - and mark them green .

Now repeat Rule 1 and Rule 2 until the puzzle is complete.

You may notice that sometimes single digits are left unmarked when they should be green. This is because of a bug in the program which I have not yet found.

These two rules allow you to solve the Supereasy and Easy puzzles, but they get stuck on more difficult ones. This is partly due to the bug mentioned, but also because the rules above will not solve all puzzles.