As of 00:01 GMT this Friday, Valve's spectacularly-popular zombie shooter Left 4 Dead will be made free to download over the company's Steam digital delivery service.

Yes, instead of spending $40 on the game, you can spend $0. The catch? The offer's only good for a 24-hour period, and once that 24 hours is up, the "free" game will be locked, and you'll need to pay up to play up.

If your connection is slow and you're worried you'll spend 23 of those 24 hours downloading the game, don't worry, you can pre-load it now and then just flip the switch on Friday morning.

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