For debugging purposes, you can the see the curve that's been placed through the level. I've put a bunch of test wiggles and curves in it to make sure the physics works ok. The curve is used to define a vertical plane, so the player can roam up and down above and below the curve (allowing you to jump up onto platforms or fall down through holes).
Apologies in advance for the poor encoding on the moovie, I should have cranked up the quality a bit.
Right now I'm still just using my little cow, but he's just a placeholder (as he's staying in my main game).
The next step is to add a dedicated camera model for the side scrolling that automatically orients the camera to the tangent of the curve. Unfortunately, this set me on a collision course with a very ugly bit of camera code I'd hacked in years ago. You see, while everything else in the game is controlled with a generic Behaviour/Controller class you attach to it, the camera was a honking big switch statement with a bunch of modes (like MOUSE_PUSH_SCROLL, THIRD_PERSON, STATIC). I'd been wanting to clean this up for a while anyway, so I'm currently in the middle of pulling the control code out of the Camera class so you can just dump a whole bunch of different controls on the camera. This will allow the initialisation for the scrolling game to put in totally different camera code than the iso one uses. It should also allow me to write camera effects (like camera shake) and much more easily do temporary camera overrides (like mini cut scenes, or moving the camera over to highlight a door or enemy the player should be aware of).