How does collision detection work in Sonic the Hedgehog?

Hi, I'm working with a free program "Unity 3d". I've done a lot trying to keep my character from "bouncing" when going downhill but I just thought I'd mention that since indeed sonic seems to have a very thorough collision system and I too would like to know more about it so I can borrow some techniques. I've still got no solution but I think the left edge of loops may be triggered when sonic crosses a certain point on the right side of the loop. By the way, I'm not seeking to "copy" anything, and definitely won't be using any loops, as that is a trademark of Sonic.