Ninety per cent of a game's source code can now be shared between an Xbox, a PC and a phone - assuming one wants an Xbox game on a three-inch screen.

The demonstration, performed at Microsoft's tech•ed conference, shows a platform game transitioning from an Xbox to a Windows Phone 7 Series, and finally to a PC. All three versions exist as a single Visual Studio project, and share 90 per cent of the source code - not to mention cloud-based state storage that allows continued gameplay between platforms.

Microsoft isn't the first to suggest that punters might want to take their gaming experience with them: Nokia's last pitch for N-Gage was as a cross-platform gaming environment that only managed one game ("Reset Generation"), which was enough to demonstrate that applying the limitations of a mobile phone to a desktop game doesn't make any sense.

N-Gage also promised cloud-based storage, allowing the user to pick up from where they left off, but even while demonstrating a game doing exactly that Microsoft's spokesman admits that it's probably not games that are going to benefit from such cross-platform-cloud-based application development.

Microsoft reckons that its combination of platforms enable all kinds of applications across three screens - with e-government and social networking being specifically mentioned. So far convergence has mainly been about accessing the same content on different devices: few people are using instant messaging on a TV, or word processing on a telephone, which is what true convergence should bring.

Quite how far convergence should go is open to debate: and Apple is headed the same way with the iPhone/iPad combination, with applications being binary-compatible between different form factors. Still, anything that reduces the amount of code one has to write is to be applauded. ®