You weren’t done opening presents, were you? Because Valve has one more for you to unwrap… but only if you are fast enough.If there’s one thing you own that could always stand to be just a little bit bigger, it’s your Steam game library. Whether you’ve just finished binging on one of Valve’s infamous sales or taking advantage of yet another Humble Bundle, it never hurts to see a few more titles in the list. In celebration of the holiday, and to demonstrate thanks to the community, Valve has made Left 4 Dead 2 available for free as long as you install it before 10 am Pacific.All you need to do is head to the Steam Store and give it the order to install L4D2 on your PC. The game will be 100% free and you’ll own it just as if you had purchased it. If you try to install it after 10AM (1PM here on the East coast), thee game will revert back to its regular price and you’ll miss out.Since the Left 4 Dead series is made by Valve, and the most recent version of the game has been one of the benchmark titles for Steam on Linux, it’s not shocking to see Valve offer this game up to as many people as possible.This coming year is going to have a heavy focus on Steam Machines and Steam OS for Valve, and if everyone has at least one game that plays in that environment already it can’t hurt to check it out and see what all the fuss is about right?