Prince of Persia

I have suspicion that the screen direction will be reset when entering the next level, because it resets on character death.
I didn't try that myself though. I guess the simplest option would be to turn screen over with xrandr right after taking the potion, which would make playing in that mode as easy as in regular mode.

Yes, in PoP 1 the upside down mode resets when prince dies or advances to the next level.

In PoP 2 the screen stays upside for 90 seconds even if prince dies or goes to the next level. And it gets reset by the blue/purple poison potion.

Indeed, you are right. I have tried that, and used which allowed me to play normally. Then screen was turned over back to normal, when I got to next level.