Through the looking glass: The Sonic the Hedgehog 3 prototype ROM was likely created in October 1993 and contains a lot of leftover data. It's likely that there are plenty of assets here that haven't yet been uncovered so there's a lot for data miners to dig through still.

A piece of Sonic the Hedgehog history has made its way online after more than 25 years.

Sega Technical Institute (STI) started work on the sequel to Sonic the Hedgehog 2 in 1993. The title was originally intended to be an isometric 3D game like what Sonic 3D Blast ended up being but those plans were scrapped due to time constraints. Specifically, the Sega Virtual Processor (SVP) chip needed to enable the 3D gameplay wouldn’t be ready before Sega’s February 1994 deadline.

Sega shifted gears and restarted work on Sonic the Hedgehog 3 as a traditional 2D platformer that more resembled its predecessor. What some may not have realized is that the games we eventually got – Sonic the Hedgehog 3 and Sonic & Knuckles – were originally being developed as a single game until time and financial issues forced a project split.

At the time, Sega was overly concerned with the types of leaks that had plagued Sonic the Hedgehog 2 during its development and wanted to keep them at a minimum. They also wanted to mask the game’s issues – some of which weren’t fixed until the very final days of development.

To do this, they put some serious restrictions in place to prevent media outlets from seeing or commenting on the game during development. They even went so far as to fly media in to play the game instead of sending early samples and insisted they only use supplied screenshots in their stories.

This meant that very few publications had an early preview of Sonic 3 in 1993 but there is one famous exception.

The January 1994 issue of Sega Magazine (UK) went on sale on December 10, 1993, with an extensive preview of Sonic the Hedgehog 3 covering lots of features, levels and artwork that didn’t make it into the final cut. It was based on an early prototype of the game and miraculously enough, the Internet has managed to track down that prototype and put it online for all to enjoy.