Hi, Matthew Trost (author) here. I'm actually a bit mortified that this found its way onto Hacker News, as now my admittedly bush-league JavaScript code is getting the brickbats. :-) In truth, I made it mainly as a practice exercise: code, UI, documentation .... So, please check out the links offered by others here, as many talented folks out there deserve attention for their far-more-sophisticated work!

In any case, I love this discussion. Programming is fun.