Nintendo 3DS to launch in March -

The much-hyped Nintendo 3DS will launch on March 27, costing $249 in the US - in Europe, Nintendo says neatly, it's anyone's guess, as retailers will set the price.

The form factor's much like the DSi. At the massive but rather chaotic European launch, Jonathan Woss posed the question we were all waiting to ask: "The screen - am I right in thinking it's bigger than the smaller screen?" (Answer: yes.)

The 3D effect is controlled by a depth slider, letting users calibrate the precise level of headache they want. Also new is a Circle Pad control, allowing a full 360 degrees of direction, and there's a built-in motion sensor and gyro sensor.

A new StreetPass feature swaps game information with other 3DSs nearby - stuff like Mii character data, maps for games or high scores.

"It automatically exchanges game information with people you pass in the street. You don't even need a game to be inserted for that to happen," says European marketing director Laurent Fischer. "You will find out what country they're from, what the last software was they used, you can even have head to head battles."

SpotPass allows the machine to connect via public hotspots or home Wifi to receive new content and updates.

There are three cameras, one pointing at the user, and two outward, which take photos in 3D. When the two outer cameras are pointed at one of six augmented reality cards, they superimpose images and animations onto the scene.

The new Nintendo eShop will offer access to downloadable games, including Nintendo DSiWare and games specifically made for the 3DS. Ordinary DS games also work.

But this is where Nintendo's got a slight marketing problem with the 3DS; while the platform's generally most popular with, shall we say, the more compact members of the species, the company is warning that it shouldn't be used by under-sixes.

However, the 30-odd games available at launch include Animal Crossing and Nintendogs (now with the addition of cats!) - which most sprogs attempt to trade in for violent or tarty games at just about this age.

It seems likely that the reason for the age warning is simply fear of litigation. Nintendo can't say just where it got the idea that six was a good cut-off point - with good reason, says optometrist Nathan Bonilla-Warford of VSP.

"Those of us who are optometrists and who work with children have had a lot of discussion about the Nintendo warning. There certainly is a reason to be cautious when thinking about children and 3D technology," he says.

"30 percent of children may have underlying visual problems which the Nintendo DS might - not cause exactly - but exacerbate. A lot of children may have symptoms and then get this device, then have headaches or blurry vision, and the 3D be making it worse."

The problem is that two sets of muscles control vision - one set for focus and the other for convergence. It takes infants a while to synchronise the two, which is why you're wasting your time smiling at a small baby from any further than a foot or so away. Watching 3D breaks that link.

"What we don't know is when the association is established. Is it in the first year of your life, by two, by four, by six? At what point don't you have to worry any more?" asks Neil Dodgson, 3D senior lecturer in Cambridge University's computer lab.

"Are you going to do research on kids under five? There's no way you can run an ethical test."

For this reason, he says, Nintendo is unlikely to have issued its warning on the basis of any reliable research.

"They do not want to be affected by a lawsuit in ten years' time. It's maybe hypercautious but in a very litigious environment, they're worried there might be a problem at some point," he says.

"Until there's medical evidence - which ain't gonna happen for decades - they're being really cautious."