Its not perfect but I've taken it as far as I can understand.
I'm going to release the source to see where other people can go with it.
its main problems currently are,
boxing in extra blue spheres with red spheres to make extra rings is not implemented (I just don't understand how to make that work)
although you can make a map of any size, theres a limit I can't fix, you can go out side the level but thats not the problem, once out side you can't turn any more, this is because your outside it the trun grid object, this controlls when you can turn, so sonic follows the grid properly, I've tried to replace this object with a calculation, but I couldn't get it to work right that way.
Rings work
Blue spheres to Red spheres works
Springs work... Jumping too.
The ending squence works too, you may replace the emerald sprite with anything you see fit.
Now that example map you just saw! was created through my engine by this
this is 4x normal size
the offscreen layout object, (this ones 16x16)
over all I hope this helps you.
download source here MMF2 only