Version tested: PlayStation 3
Who can remember when this was all just fields? Shiny, stripy, bright green fields, lying under fluffy white clouds and skies bluer than the liquid in an Always ad. All right, it wasn't all just fields; there were neon-lit casinos, crumbling ancient temples and cities in the clouds, too.
Yes, there were also giant industrial complexes so huge their purpose was probably something to do with chemical warfare and Iran. But these were fun to explore, so long as you could keep from drowning in the rivers of toxic waste.
And who inhabited these wondrous worlds? Not zombies, Nazis, mutants or drug dealers. Just a blue hedgehog, some small furry animals trapped inside robots and a fat man in a space helicopter. Good times.
But then it all went wrong. The Sonic series failed to make a successful transition into the brave new 3D world. Seeing our hero struggling round environments he wasn't designed to inhabit was painful, like watching your Grandma try to find a nice comfy pair of slippers in Urban Outfitters.
SEGA tried to paper over the cracks by introducing new characters, as if a slutty rabbit and a stupid crocodile would be enough to distract us from the truth. Then there were the experiments with role-playing and racing. Most recently, there was some ridiculous nonsense about werehogs and an attempt to shoehorn Sonic into the world of Arthurian legend. Inexplicable.
Even SEGA recognises things have gone wrong. The company is currently busy removing the worst of the Sonic games (all the ones produced this century, then) from shop shelves in an attempt to pretend they never happened, like Stalin airbrushing Trotsky out of photographs.
So it's a bit much, on booting up Sonic the Hedgehog 4: Episode I, to be greeted with old blueface grinning away on the menu screen, wagging his index finger as if admonishing us for some naughty misdemeanour. We're not the ones who have been rubbish for the last 15 years, mate.
But a few minutes later you'll be ready to forgive Sonic anything. Yes, even the hoverboarding incidents. That's because you'll be speeding, spinning and soaring around glorious 2D environments, across green fields and between fluffy clouds, pausing only to collect power-ups and bop robot fish on the head.
Sonic 4 isn't just a return to form; it's an apology for having been away so long. The differences between this and the old Sonic games are so few and far between that playing it involves existing in a constant state of deja vu. Which, if you were a fan back in the day, is a good thing.
Even the plot's familiar. Once again Sonic and Dr Eggman are fighting over the Chaos Emeralds, the most hotly contested artefacts since the Elgin Marbles. You start out in the Splash Hill Zone, which is basically the Green Hill Zone in HD.
Other zones are based on the classic casino, ruined temple and industrial zones. Before you accuse us of spoilering, they're all unlocked as soon as you complete the first, super-easy Splash Hill level, so you'd find out soon enough anyway.
Miserable old purists might complain about this. In ye olde Sonic games of yesteryear, death was final. Even if you'd made it to the last level you had to start again all the way from the beginning. This, the miserable old purists would say, taught children a valuable lesson, namely that life is nothing but a series of repetitive actions punctuated by crushing setbacks.
But times have changed, and you could no more convince 21st-century kids that starting from scratch is a good thing than you can make them understand that the Victorians didn't have mobile phones. Sonic 4 features new-fangled online leaderboards where you can compare your times and scores, so the option to select any level is essential. Plus, it means you don't have to keep hammering away at the same old section when you get stuck.
And you will get stuck. This is hard to believe at first. You'll sprint through Splash Hill without doing much more than pressing right on the d-pad. You'll zoom through the first Casino level just like old times, racking up points, bouncing off flippers, bumpers for goalposts etc.
'How disappointing,' you will think. 'They have dumbed Sonic down for the casual gamers and stupid children of today. As a veteran of the series, I find this experience to be enjoyable but unchallenging. I am therefore a superior being, even though my hobbies include making smug statements to myself in my head.'
Half an hour later you will be twisting your control pad in rage as if trying to wring its wretched plastic neck, swearing at gods you've even never heard of and vowing to spend the rest of your days stuffing towels in those holes at the side of country roads so no hedgehog may ever cross safely again. But you'll keep playing all the same.
That's because, just like the old games, Sonic 4 is brilliantly paced. The whizzy fast bits are punctuated by slow, tense sections, smart set-pieces and moments of seemingly impossible hardness. True, overall the game is easier to complete than its predecessors, especially since you can access all the levels in any order. But there are still tricky bits, and hardcore fans have plenty to be getting on with what with all the secret routes and hidden power-ups to discover.
Then there are the Special Stages, which once again are acccessed by completing levels with a minimum of 50 rings in Sonic's possession. They involve navigating around a floating maze to find the Chaos Emeralds. In the PS3 version, you can do this by tilting the Sixaxis controller instead of using the analogue stick. There is no-one living or dead who could explain why you would want to do this.
Perhaps the most obvious difference between Sonic 4 and the old games lies with the titular character. Sonic is presented here in his modern iteration, all droopy quills and long legs, looking a bit like a blue cartoon hedgehog version of Lenny Kravitz.
Along with old favourite the Spin Dash he has a new move, the Homing Attack. This allows Sonic to zoom in on enemies while in mid-air and bop rows of them in sequence. It's a fun addition which fits in well with the traditional move set.
Another key difference is less visible - in fact, it isn't visible at all. The music in Sonic 4, while decent enough and pleasingly retro, is entirely forgettable. It won't jangle around your brain at night when you're trying to sleep like good old Richard Jacques' tunes used to do.
Listen to the tune from the first level for an example. Like good drugs, a great Sonic track should make you want to run up walls and across ceilings with a giant smile on your face. This one is more likely to make you think about going for a coffee and buying some new blinds.
There may also be moans about the length of Episode I. It's comprised of 16 levels plus the Special Stages, and even with the tricky bits it won't take veterans too long to polish off the lot. But that's a decent amount of content for a tenner, and those who are bothered about collecting all the Chaos Emeralds, finding all the hidden bonuses and topping the online leaderboards will get even more bang for their buck.
Those who didn't play or enjoy the first games might argue Sonic 4 feels dated and derivative, and those are usually good reasons to condemn sequels. But this is a special case - it's the return to form of a much loved, much mucked-about series, and the fact it's so familiar has a lot do with why it's such glorious fun to play.
So if you fancy a happy afternoon spin-dashing down memory lane, Sonic 4 is well worth the money. There are no 3D environments, no isometric viewpoints, no sidekicks or hoverboards or knights of the round table. Just a blue hedgehog, a fat man in a space helicopter, a good selection of well-designed 2D environments and some of the greatest gameplay mechanics in history.
In short, this is the game SEGA should have made 15 years ago. It's just a shame that to be this good took ages.
Sonic the Hedgehog 4: Episode 1 is available now on iPhone and will be released tomorrow for PSN and XBLA. A WiiWare version follows on Friday.
9 / 10