@monorail i think this is sonic 3, when you play as tails in ice cap zone?
@Kat @monorail the tails thing was separate
sonic 3's collision detection had Problems™, where it failed to detect walls properly if you were running vertically
and there were various places in the game where you could embed yourself inside of walls and floors if you weren't careful because of that, i remember carnival night being particularly bad about it
@monorail @Kat the tails in ice cap thing is just, the trigger to set the vertical looping flag is in sonic's snowboarding section, which tails skips
so if you don't enter the big ring, you reach the "bottom" of the stage and the game kills you
the starpost and big ring both set the flag correctly so it works fine after