(It might not work on touch screens.)
the capability is there, your local hardware determines how seamless it would be.
Mental framing of a tech is weird.
But seriously, the parent comment isn't saying the technical fact a browser can see your cursor's coordinate is unnerving. They're saying the experience of being reminded of this fact is unnerving.
Technically, every time you take a bus ride the driver can just decide to crash the vehicle and kill the passengers and himself. This fact itself isn't unnerving -- it's just how buses work. But if there were a poster on the bus reminding passengers of that, that'd be quite unnerving.
It’s unnerving because people don’t like being watched.
In my case, though, after carefully enabling only scripts from the site and the Cloudflare CDN, but not enabling XHR/websockets back to the source page, or any cookies, the only thing that happens for me is:
1. I see a button and an exhortation to click the button.
2. I click the button.
3. The site goes "Subject has clicked the button."
4. The site goes "...".
...and then nothing else happens, no matter where I click or move my mouse. In the background I can see attempted websocket connections, but I'm blocking those so they can't happen.
If the aim of the game is to open people's eyes to the dangers of online tracking, it feels like there should be a reward mechanism if such tracking is blocked!