Remember the Lock-On function of Sonic & Knuckles on the Mega Drive? It's making a resurgence in Sonic the Hedgehog 4: Episode 2, as the trailer below shows.

Anyone who owns Sonic the Hedgehog 4: Episode I and the follow-up will be able to access four exclusive Metal Sonic levels that span the gap between Sonic CD and Sonic 4, explaining how and why everyone's favourite robotic hedgehog came back.

The PS3 download reaches North America on 15th May; a European release the next day looks likely.