Q I’m assuming the glasses-free 3D display on the Nintendo 3DS game system has a sweet spot. How big is it, and what happens when I move outside it?

A You’re right. The glasses-free (or autostereoscopic, if you want to be fancy about it) display on the new Nintendo 3DS is a minor technological miracle, but its sweet spot is more of a viewfinder than an IMAX screen. I’ve been testing the portable device, and have found that tilting your head or hand even a fraction of a centimetre is enough to make the screen go dark or turn into a blur. This doesn’t necessarily make you dizzy or nauseous (even though Nintendo does advise users to rest their eyes with a whopping 10-minute break for every 30 minutes they spend staring at the screen) – it just kind of takes you out of the game, and could prove problematic for tasks that depend on precise hand-eye co-ordination.

One annoying result: the device could require hyperkinetic players, who may be used to dramatically dipping and diving their hands during excited gaming, to train themselves to cool their horses. I have also found that the 3D makes it very difficult for friends to comfortably watch a game over your shoulder.

Fortunately, failing all else, the system has a dial that lets players turn down the 3D effect – or shut it off altogether. But, seriously, if you’re going to do that, doesn’t it kind of defeat the whole purpose of this thing?