Formula fun: The custom chip in Sega's Virtua Reality racing game sets it apart from other driving experiences. Rupert Goodwins went for a spin

Virtua Racing is a racing car game that's superficially like any other. But no, Sega cries. Look closely. It's virtually real virtual reality.

It's all done with polygons. You might remember polygons from primary school experiments with brightly-coloured cartridge paper, safety scissors and Gloy: well, Virtua Racing is the computerised equivalent. The cars, road, buildings and scenery are seemingly composed of flat pieces of polychromatic cardboard, carefully scored, bent and glued together before being propelled across the screen at unfeasible speed.

Computer scientists salivate over this sort of thing. Ordinary computer games have the elements of their pictures stored like so many frames of animation: the game producers have to draw every possible view of each item, and this limits flexibility. With Virtua Racing, an extra computer chip in the cartridge itself works out different angles by assembling the polygons from a different viewpoint. Instead of a picture of the racing car, it's got a model which, with the right maths, it can display how it likes.

Freed from the need to have every picture worked out in advance, the game can have an infinite number of camera angles. It's supposed to be - and is far more realistic. This is the stuff that virtual reality itself will be made of in a couple of years' time, once they've got the technology cheap and fast enough to be more convincing than this - real anoraks won't need to play the game at all; just watching the title sequence is enough.

For non-computer buffs, the game offers more of a mixture of pleasures. The graphics are indeed attention-grabbing: fast, smoothly animated and colourful, they're crude but recognisable facsimiles of those in the arcade game. There's a two-player option, practice runs and an instant replay option that relives those hair-raising manoeuvres.

But that's about the depth of it. There are only three courses, compared to the 20 or so found in other games. And the controls are seemingly designed by a silicon Marquis de Sade: how else to explain that button A is for Brake and B is for Accelerate? You can choose between an automatic or manual gearbox, but different gear ratios or engine profiles aren't on the menu, and the engine sonics are more bluebottle in a milk bottle than the mighty roar of internal combustion.

Lost opportunities like this abound. Since Sega has spent years and countless millions of yen on producing a game that can support an infinite number of camera angles, why limit the choice to four? You can watch from the car's cockpit, from a spotter aircraft high in the sky or from two other positions above and behind the driver. Like the cartridge itself - twice the size of other cartridges, but only half-full of circuit board - the game looks portentous but doesn't have that much under the skin.

Virtua Racing shows its arcade heritage. It's designed for a fast and frantic few minutes of visceral pleasure, not for hours of careful strategy. If that's your bag, then you'll love the extra speed and feeling of being there that the polygon-based graphics provide. If you want something more meaty to sink your cerebellum in, it probably won't satisfy.

This isn't the most auspicious time to be launching a racing car game. But then, this isn't really a racing car game. It's a technology demonstration, and once you've got over the novelty of the silicon chips there's not much more to do than take a spin. That's a shame, since the custom chip is clearly capable of wonderful things. It'll appear again before long with something more substantial wrapped around it. Meanwhile, if you're into fast and flashy racing, Virtua will fit the bill.

(Photograph omitted)

Sega Megadrive, pounds 69.99