Sega’s clasic hits Sonic 3 and Sonic & Knuckles is coming to the Xbox Live Arcade Septemeber 9. In addition, Sega is including a few unlockables for the game, provided you own the XBLA ports of the first three Sonics.

Sonic the Hedgehog: Unlocks the game “Blue Sphere,” the bonus/Chaos Emerald level from Sonic the Hedgehog 3

Sonic the Hedgehog 2: Lets you play as Knuckles, complete with the ability to get to previously inaccessible areas of the game, and new power-ups added for playingas Knuckles

Sonic the Hedgehog 3: Play as Knuckles in Sonic 3, and also changes the flow of the game and connects it directly to Sonic & Knuckles, so that you can play the two seamlessly!

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