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).
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 project.
I added a `#button:active` style to see if it was actually leaving it activated after dismissing the context menu, but apparently no. Not sure what the cause is.