Earlier quoted context omitted.
No repro here (Chrome 99 on Windows): right-clicking the button works the same as left-clicking it (yes, there's my browser's context-menu, but it doesn't seem to interfere with the webpage's logic at my end).
On Chrome on Mac I get the same, and right clicking outside the button makes it stick in the (idle, down) state, hovering makes it move between (hover, pressed) and (idle, down). Still a crazy cool demo though. Having worked on ui for my hobby games, I always knew it was more complex than just onClick, but this makes me understand it perfectly. I'm probably going to implement a model based on this in my current proje…
I can make it do this on Firefox on Ubuntu; the key is to hit Escape to dismiss the context menu, instead of clicking away. Closing it by clicking away makes it act correctly.