Vodafone has launched a new interactive online game, which will offer participants a chance to win an N97 Mini handset every week.

The "N97 Mini Pick-A-Pixel" game requires registration, at which point each participant is awarded five pixels for registering.

More pixels can then be earned for each friend they get to join in, then every week, a pixel will be randomly selected and the lucky owner rewarded with a shiny new Nokia N97 Mini.

There's also a daily competition for £100 worth of Christmas Shopping Vouchers, by guessing what lies behind an obscured picture.

To play the N97 Mini Mystery, tweet your guess and include the hash-tag #n97mini.

Both competitions start 1 December and will run until midnight on 20 December 2009.