Nice! I've always thought I should check out TeX and LaTeX sometime... but... don't really do enough typesetting stuff, let alone math-specific typesetting, for it to have gotten me past a cursory glance. (I dug much deeper into both n/troff and postscript at different points, for various reasons, but never this, really.) Cool to see such nice online tools for getting folks started these days. Who knows, perhaps I'll actually try it out at some point!