I haven't actually played Deltarune in quite a long time, but this community needs some more posts, and I'd like to do my part for that.

For Deltarune's teacup rides, the left key makes you go clockwise and the right key makes you go counterclockwise. This way, when you press left/right from the starting position (bottom), you go in that direction.

But I was more used to pressing left to go counterclockwise and pressing right to go clockwise, the same as the controls for Super Hexagon (and its predecessor Hexagon, which is how I got used to those controls). This way, you go left/right when you press left/right from the top instead of the bottom.

So in my latest playthrough, I swapped the left and right controls in the settings whenever there was a teacup section. Actually made those sections quite a bit easier for me.