So I'm old, but there's this NES game called Abadox that my brother and I played growing up. It was an insanely hard shooter that scrolled horizontally and vertically. You're inside some sort of alien body zooming around killing shit, but also some paths will dead end and you just die if you go the wrong way so you gotta memorize (or hand draw) the maps. One hit kills you and you lose all upgrades, so sometimes continuing becomes impossible because the enemies are too hard without upgrades.

I used to have nightmares about this game