I totally love the game! I have completed it on Dark and Neutral missions. I also have Sonic Heroes, which I completed, but the best bit about Sonic heroes is where you go to the last battle called 'LAST' and you get to fight Metal sonic who transforms in Metal Overlord! Yay! And you get to be super sonic then. I love that. And when you play the game as 'Team Rose' Its ridiculosly easy, so play that first!
What missions are you doing so far on Shadow the hedgehog?
Let them see your black heart baby ??