I've made a game engine that replicates the old Sonic games as closely as I could do; Sonic reacts to terrain very fluidly, following it at every angle, and his speed and momentum changes realistically when traversing over slopes and inclines, especially when rolling. There's far more information about it in the description of the project itself but it's available for anyone to use in their platformers/Sonic games with no credit needed.

LINK:
https://scratch.mit.edu/projects/74711180/

Enjoy!

So Cool!