IGNDC has released info and movies on Green Forest:
When you start off the Green Forest level, you have eight minutes to complete the stage before it blows up! Yeah, we don’t know who the heck would decimate a forest (well, besides corporations like Exxon), but if Sonic has to run, no problemo! The Green Forest level is a pretty dangerous level as one bad jump will send Sonic down to the watery depths… and as we all know, hedgehogs can’t swim. The level design of the Green Forest is fantastic as it follows the true principle of any Sonic level; while you can get through the game carefully, there’s always a faster path that allows you to zoom by the level even faster… so long as you have the skill to do it! I really implore you dear readers to check out the movies as they really demonstrate how the level design of the Green Forest is made for our favorite turbo-charged hedgehog. Also, The Green Forest is the two-player battle level for Sonic and Shadow where both characters are trying to out race each other to the Goal Ring!
You can check out the new screens and movies here.
Source: IGNDC