Longtime Sonic the Hedgehog fans can look forward to a key piece of series history surfacing in the upcoming remastered iOS and Android versions of the classic 16-bit platformer Sonic the Hedgehog 2, as the new mobile ports will include a finished, playable version of the game's long-lost Hidden Palace Zone.

Originally planned as a bonus level showcasing Sonic's transformation into Super Sonic after collecting the game's seven Chaos Emeralds, the Hidden Palace Zone was scrapped midway through Sonic 2's development. The level's remnants later surfaced in a prototype version distributed as a downloadable ROM file, sparking fan discussion and speculation for years afterward.

The mobile version of Sonic the Hedgehog 2 is developed by Christian Whitehead, creator of the "Retro Engine" that powered the multiplatform Sonic CD port released for Xbox Live Arcade, the PlayStation Network, PC and mobile platforms in 2011. Whitehead is known to incorporate cut content in his modern-day Sonic ports; the recent Sonic the Hedgehog remake for iOS and Android featured an expanded debug mode giving access to items scrapped from the original game, and his Sonic CD adaptation hinted at a revival for Sonic 2's lost Dust Hill Zone.

The Hidden Palace Zone is featured in Sonic the Hedgehog 2's upcoming Android release, and is included in a free update replacing Sonic the Hedgehog 2's previous port on iOS. Both the new Android version and the iOS update are launching tomorrow.