Hah, thanks! I open-sourced the counter separately (although beware, it's a React component): https://github.com/joshwcomeau/react-retro-hit-counter

Also, for any folks who immediately scroll down to see it: the hit-counter only loads a few seconds after the page initializes. This was done intentionally to avoid adding yet another thing to the busy period of initial mount. It means visits of less than a few seconds aren't counted, but -shrugs-.