With all this time-travel malarky, it would have been enough for Sega to have left the game at that, but there are also the traditional bonus levels to conquer. Set in Mega-CD's answer to SNES' Mode 7 technology, these pseudo-3D special stages are rock hard, requiring you to take down a set number of UFOs without letting your time run out. These days, they look uber-naff, but the challenge they pose isn't to be sniffed at.
Above: Back when 3D was 'suggested' by clever use of sprites. This is one of the better-looking stages. Eew!
While the graphics are untouched, the conversion does add one thing. Tails! Complete the game once and the furry fella appears. He doesn't have Sonic's Super Peel Out special move, but he CAN fly. This should make the time posts easier to find, at least.
Above: Looking like Sonic 2's sprite but playing like Sonic 3's (he can fly), Tails is a welcome surprise
Like I say, it's highly probable you haven't played Sonic CD as you'd really need to be a fan to have sought it out before now. Coming to it all these years later and seeing old-style Robotnik being chased down by 'old' Sonic makes me feel jubilantly happy and yet so sad at the same time. I once described Sonic CD's sprite as "the original Sonic sprite's final, most evolved state - and it's awesome". Looking at the visuals, it's clear that this was always meant to be 'next gen' Sonic, as it ramped up everything while retaining the stylised scenery of Sonic 1.
Above: Robotnik's super, thanks for asking! The 'good future' version of the first boss is hilarious
Basically, I love this game. And I love it in a way that both fans and Sonic CD newcomers should be able to love it too. Fans will love the care and attention given to the conversion of one of the all-time great Sonic games. Newbies will share the same journey I just had, discovering a gem of a platformer that's been buried in obscurity for far too long. It's still relevant and only the ultra-hardcore level design is likely to put gamers off. If it does, go back to Sonic 2 instead - it's far simpler.
Above: Chibi-Sonic! Shrunk by a shrink-ray and now far too cute to be taken seriously
One final note: This is a multi-platform review, and while all of the above (and the score) applies to all versions, the iPhone conversion in particular is incredible. Easily the best handheld Sonic game ever, and it pops from the retina display of an iPhone 4S. It's incredibly cheap, yet makes the emulated Mega Drive offerings from Sega look Mega Shabby. iPhone or iPad, 360 or PS3, this is how it's done.
Above: Sometimes, Sonic, you're just too fast for your own good