Any developer working on a mascot kart racing game knows that there's one title their game will always be compared to. That isn't to say that Mario Kart is untouchable; merely that it represents the genre benchmark, the standard that all others have to aspire to. Sonic and SEGA All-Stars Racing made a decent fist of taking Nintendo head-on two years ago: though it fell just short, the game proved popular enough for its struggling publisher to bankroll a sequel. SEGA & All-Stars Racing Transformed is its name, it's coming later this year, and we spent a bit of time putting it through its paces at Sumo Digital's Sheffield home.

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If the game was unlikely to escape Mario Kart comparisons in the first place, its new central mechanic makes it impossible not to discuss the similarities. As with Mario Kart 7, Transformed doesn't just restrict its vehicles to the track, instead sending them skidding across water and soaring into the sky. Sumo's game had already been conceived before Nintendo's E3 conference, and the developer watched in horror at the airborne and aquatic sequences in the trailer. SEGA had been all but gazumped by its former rival.In practice, however, the two games play quite differently. In fact Transformed has the edge in one very obvious regard. In Mario Kart 7, plunging beneath the waves made little meaningful difference to how the game played; this was merely a cosmetic change. Similarly, gliding, while more involved than underwater racing, wasn't so much about flying as falling with style. Hit the water here, however, and you'll immediately notice tweaks to the handling – it's closer to something like Hydro Thunder Hurricane than a land-based arcade racer. And on the occasions you zoom above the track, there's a fully-fledged flight model, as you guide your now-winged vehicle through floating boost gates. Better still, there's a brief pause and satisfying mechanical whirrs and clunks as your kart morphs into its new form, in a manner reminiscent of a certain Hasbro toy franchise. Robotniks in disguise, anyone?Whether you're travelling across land or sea, or through the air, there's a robust and convincing physics model that generates a sense of weight all too rare among racers of this kind. Handling is still that same blend of Mario Kart and OutRun, but with a little more heft to it – perhaps down to the involvement of lead designer Gareth Wilson, who worked on Blur and Project Gotham Racing during his time at Bizarre Creations. The water may not cause you as many problems as in something like Wave Race – in fact, occasionally you'll be able to trick off waves for a boost - but you'll still need to watch out for whirlpools that can slow you down or drag you under.Indeed, it isn't just the vehicles to which the Transformed of the title refers, as roads you raced on in the first lap may have crumbled into the water by the second, while elsewhere terrain steepens to form ramps that send you skyward. These scripted events aren't a match for the explosive destruction of something like Split/Second, but they help keep you on your toes, and the effect further invigorates the already smartly-designed tracks.The two stages we played through were packed with shortcuts and alternative routes. A Panzer Dragoon-themed course naturally has you spending a fair bit of time in the air, while the Monkey Ball track allows you the choice of winding, narrow, barrier-free strips of track up above, or the wider stretches below that are slower but easier to negotiate. One particularly neat touch is a shortcut which sends you leaping onto a numbered target lifted from the Monkey Target mini-game. Sumo has been careful to ensure that the tracks fit the IP, though in the case of Monkey Ball, the studio had to get special permission from SEGA Japan to include water, before then entering into discussions about how water should behave in the Monkey Ball universe. It's heartening to witness that kind of meticulous focus on fine detail, and Sumo's near-fanboyish enthusiasm for the characters and worlds featured here show that these SEGA favourites are in safe hands.If the track design is easy to admire, the graphical overhaul is even more attention-grabbing. Sumo is using a bespoke engine for Transformed, and the improvements over its predecessor are startling. It still has those same glorious SEGA blue skies, but there's much more detail in both environments and vehicles, while the whole thing runs at an exhilarating pace. Even in its unfinished state, this demonstrates surprisingly strong production values for a kart racer, and the graphics can only improve between now and its autumn release.As for the soundtrack, popular composer Richard Jacques has contributed a number of tracks that remix classic SEGA tunes from yesteryear, while some players will be delighted to learn that the polarising commentator from the first game has been removed. Instead, an announcer only occasionally interjects to relay the most important race information, while crowds clap, cheer and chant the name of their favourite racer.Which brings us to the character roster, and there are a few surprise names on there. Naturally, there are some familiar faces, too – Sonic obviously returns, though this time he's driving a Koenigsegg-style supercar, part of a conscious decision by Sumo to make the vehicles a little cooler. But Dreamcast owners will be particular thrilled to see Skies of Arcadia's Vyse, in a vehicle based on the Delphinus. Golden Axe's Gilius Thunderhead – who was originally planned for inclusion in the original – gets to ride a Ray Harryhausen-esque bronze creature that morphs into a turtle and an eagle. We're sworn to secrecy on the later stages, but suffice to say anyone who didn't think the first game was enough of a SEGA love-in is in for a treat. The fan service here is phenomenal, and the final unlockable in particular is one that will delight long-term Sega acolytes.Other aspects have been refined, so now instead of SEGA miles you earn points for your chosen character that feed into a levelling system, unlocking various trinkets and vehicle mods. Though the focus is still on split-screen multiplayer, there are now online races, supporting up to eight players, with a range of modes and options to customise your race experience. For lone players, there's an extensive Story mode with 16 new tracks spread across a number of different SEGA worlds, represented here by floating islands. Four favourites from the original game also return, including Jet Set Radio Future's Shibuya and the Death Egg track which was released as downloadable content.There are plenty more secrets to be revealed, no doubt, but even at this stage, Transformed is bigger and better-looking than the original and with a neat central hook that has a significant impact on the way the game plays. If rest can live up to what we've seen so far, then Mario might finally have a genuine challenger to his karting crown.

Chris Schilling is a freelance contributor to IGN and loves video games more than life itself. Keep track of Chris's passions onand keep get the latest game updates on