Sonic the Hedgehog 4: Episode 2 probably wasn't intended for as inauspicious a venue as the Xbox Live Marketplace, but here we are with a whole mess of new screens and several new details about the game itself. A-dorable.
Anyway, according to the Xbox Live Marketplace listing, Sonic 4 Episode 2 will feature online and offline co-op play with Tails, all set in an "all new game engine" with updated physics. The blurb further promises "four brand new Zones" and a "new special stage." From the shots that were released thus far, it's looking like Sonic and Tails should pack an extra pair of snow boots!