Hit the "play" button to start playing. Your controls are the arrow keys.
I've tested this on Windows using Mozilla and Opera so it should work on Netscape too. It does not work on IE5 because that browser doesn't capture keystrokes in the same way. IE6 is untested.
I think it's pretty good. There are a couple small bugs, but it's playable and if you download the source, you can customize the levels pretty easily. Just give me credit for the code.