Oh yeh of course, I knew about the extras but they're just extensions for completionists/achievements/trophies.
In that case, as I'm unable to find information, what is the criteria to unlock the super secret true final level + super sonic awesome? Special stages (which I've seen none), Chaos Emeralds, to ... buy it from the skill shop? lol
But overall, I personally don't think the game would be at all difficult and can be completed in one sitting (no 100% achievement), then backtrack to find the unlockables. But whether a straight rush (but an enjoyable one at that) to the very end would unlock the true final level or not I don't know lol!
EDIT: before anyone calls my bluff, I'm impatient and eager to get started to see if the game is challenging fun! =)
XI Wiki



