Has there ever been a platformer in which you climb something, like a mountain, and that's the whole game?
I don't mean it's crumbling or demons are chasing you or anything else that sounds like Tall Infinity/Catherine and whatnot.
I mean a MASSIVE structure that starts on the ground and you have to go around and around it, ever upward, until the end of the game when you reach the top.
If not, I've always thought this would be a good experiment for a Mario game. You could design a giant beanstalk and give it the same amount of variation as your Mario Galaxies, but all contained within the same climbable structure. There would be checkpoints for when you fall or die, reasonable power-ups that don't let you cheat, and the same zany enemies you've come to expect from the series.