Sonic the Hedgehog running on Super NES - see the tech demo in action

What if Sonic the Hedgehog was ported to Super NES? What would it look like? How would it play? Could an engine designed specifically for the Sega Mega Drive/Genesis transfer gracefully to Nintendo's 16-bit machine - even without Blast Processing? After 29 years, we finally have some answers and we've seen and played a convincing SNES port of one of Sonic the Hedgehog's levels.

On the NesDev forums, noted Mega Drive programmer TiagoSC posted a tech demo, showcasing the third stage of the Green Hill Zone, and it's a fascinating piece of work. Of course, we've seen fan-made attempts to bring rival platform mascot characters to other consoles before, but what sets TiagoSC's work apart is that the work carried out is actually based on original Sonic code (courtesy of SonicRetro's disassemblies of the engine), then embellished with SNES-specific customisations for more optimal performance.

Two key aspects define a Sonic game - first of all the speed of the scrolling and the range of the tiles that define the landscape. Secondly, and crucially, there's the physics of Sonic himself. This is a game about speed and momentum and getting the way Sonic acts and reacts to the gradients and loop-the-loops is a make-or-break factor in delivering a good Sonic experience. TiagoSC's tech demo is one of the few efforts that gets it right (bar very, very slight changes) as you can see in this playthrough, where I tested it on original Super NES hardware - on a CRT, of course.

It's a convincing facsimile in many ways but obviously quite different too - mainly because the Super NES was a very, very different machine to its Sega rival, something we've seen emphasised by multi-platform projects of the era like Pitfall: The Mayan Adventure, a game I've looked at in depth in a prior DF Retro episode. At the most basic level, the two systems operate at different resolutions. The Sega machine typically ran at 320x224, though it supports lower resolutions as well, whereas the Super NES standardised at 256x224. In the case of this Sonic port, there is a fundamental change to the presentation simply because you see significantly less of the play area. However, the Nintendo machine had advantages of its own including a wider colour gamut - and again, this is taken advantage of in TiagoSC's port.

There are other changes too - while objects are still loaded into screen area with a 128 pixel border or buffer area, variations in the SNES hardware design mean that the sprites are half the size, meaning more are required, filling up the sprite list faster and hitting CPU harder. TiagoSC estimates that the Motorola 68000 processor in the Sega hardware carries out select tasks 40 to 70 per cent faster than the SNES CPU (though it's not that cut and dried) and while the demo is generally solid, you do have to wonder whether an actual port of the era would have required the use of a 'mapper' - essentially co-processor silicon built into every cart.

It's worth stressing that this is a tech demo, with TiagoSC building it as part of the process in making his own game engine for the Super NES for a concept that has similar speed gameplay to Sonic the Hedgehog. It's unlikely to ever become a full port, but as a proof of concept, it is a fascinating 'what if' - and clearly a lot of time and effort has gone into it, right down to an improved sky colour gradient that woould have proven difficcult on the Mega Drive/Genesis and a change in the way parallax scrolling functions. This was in the Sega original, but only in the slightly more refined Japanese version of Sonic the Hedgehog.

As for the notion of Sonic the Hedgehog running on a console that didn't possess Blast Processing - well, as we've explained in the past, while the technique was real it was never a part of Sonic's technical make-up and in actual fact, it was never implemented in any shipping title for the Sega platform. The chances are that Sega's marketing team chanced upon the term in a technical presentation, thought it sounded cool and co-opted it for Sonic PR, disregarding what the technology is and where it could be applied.

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