Could the answer be like a fractal, or something simpler? I'm really rusty at set theory already, and there are some symbols I don't fully understand :(

Thanks for the tips. As you point out, I already think I know the answer,

Somehow it isn't working :(

I know several people who would love to play something like this, unfortunately, none of them speak english :(

Oh right... That's what I was doing on my initial attempts, but somehow it didn't work... now it does, thanks!