For the unaware, games played through the first-person perspective always have an option to invert the Y-axis on your controller. Instead of pressing ‘up’ to look up, the directions are reversed.
It might seem counter-intuitive, but it’s a hangover from flight simulators, which were based on real-world physics. You push forward to tilt your plane (or head) forward, and thus go downwards, and vice versa. It wasn’t about what was ‘up’ on a television screen, it was about simulating how heads and planes actually work.
I know it’s dumb and irrational and pointless, but I can’t help but assume a friend is some kind of caveman if pushing up has to necessarily mean ‘up’.