It's a simple game -- just click the squares to rearrange them into numerical order. The number 1 should be at the top left, running left-to-right, then row-by-row.
All the graphics (rubbish as they are!) were made using The GIMP, along with its built-in patterns. If you have any questions about implementation, then please leave a comment and I'd be happy to answer them. I might even post some of the source code at some point. :)