I have the nav panel working well, and now I'm beginning to work on the code for selecting an individual feature and displaying its descriptive info. It's a bit slow going, because I'm trying to document as carefully as possible, and because I've made a couple of reversals in working out how to keep the nav panel checkboxes all in sync. Getting there, though. I now have a banner/toolbar across the top as well, and the CSS is a little better.