Sonic has always been about the speed. It's what made SEGA's iconic platforming series so popular in the first place. So, after a series of missteps for the blue hedgehog, it came as a great relief when SEGA announced Sonic Unleashed would see a return of 2D gameplay, albeit with a suitably next-gen coat. Sat in a demo room at the Leipzig Games Convention last month we saw for the first time exactly what SEGA meant when it said Sonic Unleashed would deliver an "immersive 3D experience whilst keeping alive the 2D gameplay elements and fantastic worlds that Sonic fans know and love".

The stories in Sonic titles are always good for a laugh and Sonic Unleashed is no different. The world has been broken apart by Dr Eggman and it's up to Sonic to make things right by retrieving the power of the chaos emeralds. To do so he'll have to travel to seven broken continents and face new challenges when the sun goes down - Sonic will turn into a Werehog, but more on that later.

Our demo began on a European stage with the design taking inspiration from the likes of Paris and Rome. First impressions were positive with SEGA's promise of speed seemingly being delivered in spades. Indeed, SEGA has implemented a host of new moves for Sonic designed to aid the new focus on speed. These include the Quick Step to dodge obstacles and enemies without losing speed, Sonic Boost to accelerate to supersonic speed by collecting rings, and Speed Drift which allows Sonic to manoeuvre around corners at high speed.

After blitzing through the European Stage the demo moved to China with the level on show featuring an impressive Dragon theme park ride that winds through the stage. We also saw Sonic use his speed to run on water, although a pesky enemy got in the way resulting in Sonic coming to a standstill and sinking. Each of the two stages shown featured multiple paths plus a mix of side-on 2D and 3D (behind Sonic and dynamic camera) sections. It was all seamless and a quick hands-on confirmed what we'd been thinking - it was great fun.

And so we moved onto one of the new Werehog stages. Here Sonic has transformed into a much larger beast and the gameplay also takes a dramatic change of pace. Forget about burning through a stage in the blink of an eye, as the Werehog it's all about fighting off much larger numbers of enemies, traversing the environment and solving basic puzzles. A whole new move set is at the player's disposal including double jumps, grabs, throws, dash and a range of attacks. The stage shown saw Sonic smashing up enemies before using his stretchy arms to climb up the side of a building and swing across some poles in Prince of Persia fashion.

It all seemed perfectly serviceable, but why Sonic Team sees a reason to slow the game down to a crawl is a mystery. We want to be hurtling through stages, collecting rings and jumping on enemies. We don't particularly want to be breaking through doors, traversing buildings and smashing up Dr Eggman's minions in a sub-par mix of Prince of Persia and God of War.

The Werehog sections need more work

Sonic The Hedgehog, Sonic Team's first Sonic title for the Xbox 360 and PS3, wasn't exactly a visual tour de force, suffering from slowdown, pop-up and poor detail. Thankfully things have improved somewhat in Unleashed, with the new 'Hedgehog Engine' delivering a Sonic that looks the part. Motion blur and depth of field effects are all over the shop, helping to bring a believable sense of speed, and the environments are full of detail - although this is something you're only likely to appreciate if you slow down and take a look around.

It's not all rosy though, with the frame rate in the Sonic sections not able to hold steady. The Werehog sections - currently farthest from completion - are the biggest concern though. The section we were demoed struggled to reach a frame rate in double figures and without the blistering speed looked rather plain and uninspired. SEGA says the game engine has been in development for three years, but with a November release only around the corner there still appears to be plenty of work left to do. We only saw the Xbox 360 version, but it's absolutely vital that all four versions (Xbox 360, PS3, Wii and PS2) are shipped with a solid frame rate. Anything less will hurt Unleashed's biggest draw... speed.

We're convinced the traditional Sonic sections will be a blast, but without any hands-on time with the Werehog we were left with mixed feelings. Sonic is and always has been about speed and we just hope Sonic Team hasn't spoiled Unleashed's party with an unwelcome guest.

Sonic Unleashed is scheduled for release in November 2008 for Xbox 360, PS3, Wii and PS2.