Catt

Nope, the text is correct.

not (x or y) <=> (not x) and (not y)
not (x and y) <=> (not x) or (not y)

Edit: The parenthesis on the right side if the equivalence are only there to make it easier to read. Without those, the expression would be the same in this case

Me using runit, I agree

Nice, and I rewatched it, after you made the meme

Definitely recommend to watch turning a sphere inside out. Is really satisfying and don’t worry, you don’t have to be good at math to understand it^^