Free game demos are nothing new, but Valve has just upped the ante by allowing PC gamers with a Steam account to download the excellent (and terrifying) zombie shooter Left4Dead in its entirety for FREE.

If this is a gift-horse it’s only saddled by the fact that this is a limited time offer. Interested parties, and we’re guessing that’ll be many of you, have until midnight tonight to download the game. After that you’ve got 24 short hours to play the heck out of it before the trial period comes to an end and you’re required to fork out the full asking price in order to continue - or not, as the case may be. 24 hours should be more than enough to play through the single-player game, although co-op/online multiplayer is where the long-term action is.

So that’s your heads-up for a remarkable freebie – see valvesoftware.com if you don’t have a Steam account.