I was going to centre this introductory paragraph around Sonic's epic shortcomings in the third dimension, but you've undoubtedly heard it all a thousand times before. So let's get straight down to business instead. Sonic 4: Episode 1 is the true successor to Sonic and Knuckles; the game that, after sixteen long and arduous years, sees Sonic return to his 2D throne. Of course there have been other 2D Sonic outings since then, Sonic Advance and Sonic Rush being two (actually quite good) examples, but they lack a certain inexplicable quality that ran through the original Sonic games. Sonic 4 looks to bring that charm back. It's the same retro experience that defined many a childhood re-branded with lovely HD visuals.

The game picks up fairly soon after Sonic and Knuckles, where after destroying Dr Robotnik's Death Egg, Sonic decides to get away from it all and check out some new and unexplored areas of Mobius. Unsurprisingly, Robotnik - or Eggman as he now likes to be known - survived his encounter with Sonic, and has re-created some of his all time favourite badniks (those being the original ones from the first games) in an attempt to defeat the pesky blue rodent once and for all. He might be criminally deluded, but you have to admire Eggman's persistence.

True to form, the first Zone of the game is set on a hill. Splash Hill Zone is the Sonic 4 equivalent of Green Hill and Emerald Hill - a gentle refresher course on the staple mechanics of a 2D Sonic game; the running, the jumping, the spin dashing, the homing attack. The homing attack!? Indeed, Sonic 4 adopts the homing attack introduced in Sonic Adventure. In case you've avoided every single Sonic game over the last sixteen years - the homing attack is achieved by pressing the jump button again whilst already in the air. If there's an enemy (or item you can target) nearby, Sonic will hurtle towards it in his deadly curled up form, killing the enemy and bouncing back up into the air. From here, you can use the attack again, chaining together numerous enemies to reach otherwise inaccessible areas.

This is the only fundamental change to the core mechanics of the game; everything else is pretty much how you'd remember it. Of course there are new features to make it worthy of the number four in its title, and the few I saw were fairly well sewn into the experience. The second act of the Lost Labyrinth Zone, for example, is completely bathed in darkness. Thankfully Sonic is sensible enough to have brought a torch with him, which illuminates the area immediately around him. It's also used to light candles, which open doors and raise platforms around the level. There was a particular puzzle late in the level that involved lighting candles in the right sequence so that the correct platforms are raised in the correct order to progress. This stumped me for some time, however, and I actually managed to reach the ten minute time limit that each level has in place. I've never quite understood why this would kill Sonic, but it does, and I died.

Structurally, Sonic 4 is very similar to its predecessors. Each of the four Zones has three acts and a boss, all separated with colourful and reassuringly familiar intro screens. If you complete a level with 50 rings or more, a giant ring portal will appear, transporting Sonic to the abstract and topsy-turvy world of the Special Stage. This time around though, players control the level itself and not Sonic. You rotate the level around the spinning Sonic, collecting rings to open gates and avoiding red balloons that threaten to boot Sonic from the stage. Like previous games, the object is to grab the chaos emerald before time runs out, with the ultimate intention of collecting all four so Sonic can (presumably) become Super Sonic on the next playthrough.

The one thing that struck me immediately after I started playing was that the camera was too close to Sonic. After playing for several minutes, I noticed that I'd moved back from the screen, desperately trying to catch a glimpse of my wider surroundings. Perhaps it was because I'd been playing Sonic Colours just beforehand (which uses a camera angle much further away from the action), but I felt all up in Sonic's personal space and wanted to distance myself somewhat. I suspect this could be a very personal criticism, but thought I'd raise the point anyway.

I'm slightly concerned that with Sonic 4, my judgment has been clouded somewhat by the mists of nostalgia. If I'm honest with myself, I think I enjoyed Sonic: Colours more than Sonic 4, which isn't at all what I would have predicted a few weeks back. Don't get me wrong, Sonic 4 is a very competent platformer, paying homage to the originals whilst bringing something new to the series at the same time. It looks great too, with gorgeous 2.5D visuals and slick new animations. Still, I couldn't help thinking it should have offered something slightly more, but quite what that 'more' might entail I have no idea. The only thing that will prove or soothe these worries is playing the full game, and despite a few reservations, I'm very much looking forward to doing so.

Sonic 4: Episode 1 will be available for XBLA, PSN and WiiWare in late 2010.