Update: Valve has extended the free trial until 1pm EDT / 10am PDT on Saturday.

Original: With the full version of Left 4 Dead free-to-play until 7:59 PM EDT / 4:59 PM PDT today, developer Valve has kicked off a weekend-long 40% off sale on the PC edition.

That brings the price of the cooperative zombie shooter down to $23.99 in the United States. Thanks to a recent price drop, that means it's cheaper than ever before on Steam, with a previous $24.99 sale having brought about a 3000% sales increase.

The studio also announced that a new statistics page is available via Steam Community, enabling players to glimpse a multitude of gameplay-related figures, including weapon usage, accuracy, pill consumption, and damage dealt to teammates.

Thanks to Shacker ajvitaly for the tip.