Valve has today announced that Left 4 Dead 2, sequel to last year's Left 4 Dead, has shipped to retail and will be available later this week. PC Gamers, however, will be able to purchase the game and download it through Steam starting today.

Available on the Xbox 360 and PC, L4D2 is set to continue the co-operative action of the original title. This time around, Valve has added additional melee weapons, including chainsaws, frying pans, axes, baseball bats, and more. Valve has also added addtional gameplay modes, zombies, weapons, and items that gamers can use in one of several new gameplay modes.

"With the AI Director 2.0, L4D's dynamic gameplay is taken to the next level by giving the Director the ability to procedurally change weather effects, world objects, and pathways in addition to tailoring the enemy population, effects, and sounds to match the players' performance. The result is a unique game session custom fitted to provide a satisfying and uniquely challenging experience each time the game is played."

For more information, visit www.l4d.com.