Twenty years ago, Sonic the Hedgehog made his first appearance on the Genesis. To celebrate, Sega has released a demo for its upcoming platforming throwback, Sonic Generations. However, it'll only be available for the next twenty days.
Xbox Live Gold subscribers can grab the 652MB demo from the Xbox Live Marketplace now. The demo's also available on the PlayStation Network in Europe, and will presumably also launch in North America today. Sony wouldn't want to miss the little blue fellow's birthday, right? (Update: The demo should be available later today.)
Sonic Generations features both the 'chubby' original Sonic and his modern counterpart, letting you play it as a traditional side-scroller or a fancy modern 3D-o-rama. It's headed to Xbox 360, PlayStation 3 and Nintendo 3DS in "late 2011."
The demo contains the first act of the Green Hill Zone, which is the section we got to play in our E3 preview. You're only able to play as the old Sonic, though. According to Sega, the demo will only be available for 20 days, so make like a hedgehog and hurry!