Complex sentence: Sonic Anniversary is a new Sonic the Hedgehog game scheduled for release in 2011 to celebrate Sonic the Hedgehog's 20th anniversary with new versions of classic levels from the original "Sonic the Hedgehog" to "Sonic Adventure 2".
Split into simpler sentences: Sonic Anniversary is a new Sonic the Hedgehog game scheduled for release in 2011 to celebrate Sonic the Hedgehog's 20th anniversary. It will contatin new versions of classic levels from the original "Sonic the Hedgehog" to "Sonic Adventure 2".