1991 was a pretty amazing year in video gaming history.

Sid Meier came up with Civilization, EA gave us Road Rash, Capcom fought back with Street Fighter II, Nintendo started shipping the Super Nintendo Entertainment System, and Sega decided to take a punt with a blue hedgehog called Sonic. You might think they were joking, but after fifty million sales even fat Italian plumbers weren't laughing.

Recent Sonic titles have been a bit hit-and-miss, and this latest contender is no different. Let's start by using a terrible sporting cliché - Sonic Unleashed is a game of two halves. After seventeen years, someone has pointed out to the developers Sonic Team that hedgehogs are indeed a nocturnal species, and in an effort to claw back some respect from animal lovers everywhere, they've included night stages.

Presumably then, after satisfying several people who cared about the accurate portrayal of animals in video games, Sonic Team realised that they were in danger of losing the popular vote, so they've made poor Sonic morph into a "werehog" during the hours of darkness. I wish I were making this up.

I'm not sure about anyone else, but upon starting a Sonic game, you expect fast-paced flawless action. You expect to see that hedgehog defying all known laws of motion as he rips through a level, bouncing off platforms, flying through the air and generally doing the exact opposite of what a real hedgehog does, which is to move slowly and spread disease. Sonic Team have captured this brilliantly in the daytime levels; there are moments of sheer wonder as you progress at high speed, unobstructed, through amazingly cinematic scenery and flawless vistas. The controls are responsive, the framerate stable, and there's a huge amount of fun to be had as the sun shines.

Unfortunately, the werehog levels are terrible. I don't know what Sonic Team were thinking - at what stage did they come up with the decision to switch off the lights, slow the game to a crawl and introduce tedious combat? At what point did they decide to make the same mistake inherent in every Sonic title since Adventure, and introduce needlessly repetitive and irrelevant gameplay that makes watching rocks erode seem like a preferable form of entertainment? Seeing a developer snatch defeat from the jaws of victory time and time again is nothing short of painful.

Sonic makes his way around these poorly constructed night levels by moving from one badly placed checkpoint to another. For some reason, his arms are now elastic, allowing him to stretch to reach ledges. A nice feature, one might assume, until it becomes obvious that much like a cheap tow-rope, the elasticity is variable, and whilst one ledge may be accessible, trying to reach to a similarly placed ledge later on will result in failure. Fortunately, those people who buy a video game specifically to test out the checkpoint system and observe death sequences will enjoy figuring out which is which.

The storyline that has inspired this supernatural silliness isn't much to write home about either - Dr. Eggman has hatched some new plan for world domination, and rather than calling in pest control to prevent Sonic from stopping him, he's decided to go all high-tech and split the planet up with a laser. Somehow this laser has created Sonic's alter-ego - a slow, lumbering beast that prefers combat over finesse, lethargy over litheness, and in a rather transparent outcome analogous to the laser itself, it's split the game in half entirely.

You might think that after humiliating Sonic with a dose of lycanthropic lunacy they'd leave well enough alone and round out the title with relatively conventional Sonic flair. You'd be wrong. Sonic is also submitted to the embarrassment of talking to townsfolk in some kind of weak RPG inspired side-questing which seems to serve no purpose other than to pad out the game.

This hub-town activity is completely out of place, irrelevant and hugely frustrating - most of the townsfolk haven't a clue as to how to help you, and even if they did you just don't care anymore. Especially not after listening to your nauseating side-kick "Chip" for more than a few seconds - a note for Sonic Team, if I wanted to watch an annoying animated character, I'd get a Nickelodeon subscription. Chip may have an integral part in the story, but he's about as welcome as a fork to the colon.

Despite huge flaws in this title, there are moments of absolute joy to be had. The sun-baked levels are a sight to behold, and a true return to the inspiration we all experienced with the first Sonic games. I love the speed of the new Hedgehog Engine, the artistry, and the obvious care and attention to detail that's been embedded. I really wish I could simply rate this game on the daytime levels alone, because it'd be dangerously close to 9/10.

So, who should buy this game? You really need to be a fan of Sonic to be able to tolerate the bad in order to get to the good. If you enjoyed the last two Sonic titles, you actually might find Unleashed to be an improvement.

There's another option to consider however; most people out there are going to have friends over, or meet with relatives this Christmas. What you need to do is buy Sonic Unleashed, find a gullible relation and get them to slog through the night levels, leaving you to enjoy the otherwise fantastic day ones.

Tell them that if they don't like it, they can go and hang out with their family instead.