Since the appearance on the Portal 2 website of a mysterious countdown clock, speculation was rife as to what it all meant. The timer has now reached zero, but, contrary to suggestions that it might, Portal 2 hasn't been released early, but there is still a chance.

Instead, Valve have challenged Steam gamers to play various indie titles, specifically 13 titles that include the likes of Super Meat Boy, Bit.Trip Beat and Audiosurf, until enough hours have been logged worldwide to trigger Portal 2's release, this "Potato sack" of games include some of the finest Indie titles on Steam. Some of the Potato Sack games have also had some special Portal 2 features added, such as Bit.Trip Beat having Portal 2 themed stage to play from the main menu.

In other Valve news, the company recently released a new update for Team Fortress 2 entitled 'Hatless'. The patch adds a player coaching system, new voting rules, reworked maps, and, of course, no hats whatsoever, although should you buy the Potato Sack you'll get a Potato Hat for TF2.

Portal 2 is released on April 19th in North America and April 21st for Europe, so for any European PC gamers out there you could potentially get to play Portal 2 much earlier than it's offical release, however sadly PS3 and Xbox 360 owners will have to wait until the official street dates.

You can pick up The Potato Sack for £27.22, or you could always buy it with Portal 2 and save an extra 10% off the usual price costing £51.21 in total.