I love to see this sort of thing. In fact, nothing makes me happier on the web than seeing something simplified and improved because of that simplification. This article demonstrates that beautifully and teaches you how to write some pretty dang solid CSS that is battle tested in the real world. What also makes me happy is accessibility was simplified because of the use of semantic lists. Superb stuff.
I’ve historically grabbed a charting library to do even simple charts, but that will no longer be the case. Move over heavy duty charting libraries because for simple charts, HTML and CSS is ready to go!