I'm working in SDL and have bounding rectangles for collisions set up for each frame of the sprite's animation. However, I recently stumbled upon the issue of putting together collisions for characters walking up and down hills/slopes with irregularly curved or rocky terrain - what's a good way to do collisions for that type of situation? Per-pixel? Loading up the points of the incline and doing player-line collision checking? Should I use bounding rectangles in general or circle collision detection?