I have done some more work to my ProSonic engine. Now you can wrap levels vertically as done in Metropolis Zone, Marble Garden, and other classic Sonic levels.
This trick is more advanced in ProSonic because it's more flexible. Sonic 1 and 2 allowed wrapping at 2048 pixels, while Sonic 3 and Sonic & Knuckles wrapped at 8192 pixels. ProSonic will allow designers to set a variable for each level that tells the game where to wrap. ProSonic allows wrapping between 256 and 32768 pixels. That's also a hint that ProSonic will support levels that are much larger than those found in all the original Sonic games.