I wrote this over the course of a few evenings because I wanted a neat-looking metronome more than I wanted to continue practicing some basic cello piece that I've already forgotten.
Also, it was a nice exercise in JS and CSS features I never really had the opportunity to use back when I had to do frontend web development that would work reliably in browsers such as IE6. I don't actually use this one, because the CSS animations and gradients are actually taxing enough that the metronome itself suffers.
Not included: files for the tick/tock sound effects.