Sonic & Knuckles, sequel/counterpart to Sonic 3 for SEGA Genesis, will emulate the “lock-on” technology available in the original. This means that it will work with previous XBLA releases of Sonic the Hedgehog, Sonic the Hedgehog 2, and Sonic 3.

Here’s how it works: If you have any of the previous XBLA Sonic games (1, 2, or 3) , Sonic and Knuckles will detect this and unlock additional options for play. Here’s what you can get:

• 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!

Sonic & Knuckles will be available on Xbox Live Arcade Sept. 9, 2009.