'Complexity is not welcome on the iPod'

Foster looked back on the development Harmonix's iPod music game Phase - on which he was designer and programmer - to outline key lessons the MTV-owned studio learnt in making one of the first original new IP titles to be sold via iTunes.

Phase uses the music tracks stored on players' iPod hard drivers to generate levels. The game was released last year - to good sales, said Foster.

But people playing games on iPod don't fit the 'gamer' label, he said.

"The audience for iPod is different to that of the PSP and DS. The iPod user is not necessarily a gamer. Complexity is not welcome on the iPod.

"The user of an iPod would not necessarily invest in fun," he added, pointing out that iPod users are more likely to spend money on music tracks than games.

He added: "iPod users are listeners first and players second. No one will play on an iPod for an hour - maybe 10 minutes or just three for a single song while they wait for the Metro."

These principles were crucial when it came to designing a game for the iPod, he added:

"Embrace your platform's limitations and audience. Don't try to cram in ideas that are not suitable," he said, pointing out that much of the success of Phase's gameplay came no from its clever use of using players' music, but from designing something that took advantage of ""the pleasantly tactile" scrollwheel on the iPod.

He added: "Design is making bad decisions in pursuit of good ones. It's about making a bad decision and sticking with it until you get to the right one. It can be emotionally draining, but that's what leads you to the things that are good, unique and right."