Ok, so the author thought it's a great idea to embed a little mini-game onto the page - in case two squares shot by the things in each bottom corner ever collide, your mouse cursor vanishes. Brilliant - tab closed.

PS. fix the origin of the projectile shooters - right now they are shooting from the "side" and it looks sloppy.

Oh so that's why my cursor randomly vanished. I ended up just putting it in the middle right at the bottom so the little squares wouldn't get in the way of me trying to read

I spent some time trying to disable those with uBlock but they kept hiding once I entered the picker.

And then I've realized that uBlock has an option to "disable all JS on that website" - and that worked wonderfully, and stopped vanishing cursor too.

Recommend everyone does the same.