Since I hand rolled my physics, now I can start to do some fun stuff, like walking over uneven (bitmap-based) terrain. Basic collision detection with arbitrary sprites (happens to be a simple ground here but could also easily have had a floating irregularly shaped sprite to interact with as well) where the movement code will properly step you up - within a certain limit of height. Also implemented a Dinorun-esque steepness penalty which I think you can see in this video - you slow down as you climb up a hill, proportional to its steepness.