San Francisco - Apple has expanded its iPod lineup in time for the Christmas season with flatter, more colourful models and even more features.

Steve Jobs, Apple's chief executive, rolled out the fourth generation iPod nano and a retooled iPod touch recently. He also presented a new music software platform dubbed Genius, designed to help users compile playlists.

Flat and colorful best describe the new iPod nano, which will now be available in silver, purple, blue, green, orange, yellow, pink, red and black. It will also be the flattest iPod yet, said Jobs. This version will be more rectangular than its almost square-shaped predecessors.

Similar to the iPhone, the iPod nano now comes with a motion sensor, which allows screen contents to rotate when the iPod is turned 90 degrees. The new sensor allows the iPod to play random selections and users just have to give it a good shake.

Even though there's barely room for a battery in the new, flatter housing, the iPod nano is able to play up to 24 hours of music or four hours of video without recharge. An 8 gigabyte (GB) model will cost 149 euros (212 dollars). A larger, 16 GB version will cost 199 euros.

There have been fewer outer changes to the second generation iPod touch. It's also a little flatter and now has a built-in miniature loudspeaker. The biggest change is that, with hundreds of game titles now available via the iTunes App Store, Apple is now marketing the iPod touch as a gaming console instead of a music and video player.

Phil Schiller, head of Apple's marketing division, demonstrated two new iPod touch games in San Francisco: Spore Origins by Electronic Arts and Real Football 2009 from Gameloft. The new iPod touches come with either eight, 16 or 32 GB which cost 209 euros, 279 euros, and 369 euros respectively.

Along with the new iPod rollouts and the introduction of iTunes 8, an updated version of its music software, Apple introduced its new Genius program. It uses a new algorithm written by Apple's programmers to help iTunes users find songs to be stored in playlists.

"Genius will help music fans to rediscover their favorite songs in their iTunes music library," said Jobs.

Apple will also release new Version 2.1 software for the iPhone and iPod touch. The free update should improve the network stability of the iPhone and help it achieve longer battery life.

Experts said the new technology was not particularly revolutionary. "There were no sensations here, but a lot of improvements," said Matthias Kremp of Germany's Spiegel Online. Brad Stone of the New York Times noted: "New iPods, but no surprises." (dpa)