Sonic the Hedgehog 4 Episode: II

[Vipershark]

Uhhh
honestly i don't think it's really that hard to fathom
the game uses the same engine
In the -years- between the games, they easily had enough time to tweak features and add in new things
It's not like "hey guys let's make a sonic game that mixes old stuff with new stuff" is some kind of revolutionary concept that could only be conceived in the year 2011