Thanks, man! I'll look into it some more later on. I'll definitely make it open source, but not on Github, because I don't trust them to not nuke me from orbit like they did with youtube-dl. (Gitlab, maybe?)

Wikimedia commons is good. I intend(ed) on using maps from there and then manipulating them with javascript.

I was thinking about having a slider, yes. There are really a whole bunch of controls, and those probably wouldn't be much of an issue after I get everything set up.

The only problem is I don't think javascript behaves correctly on static websites, so I'll need to move hosting providers first. I think gitlab will let me host my projects there, though I've never used it before. If so, I'll just link to it from my main website.