On May 1, 2009, the game was released freely via Steam as a one-day trial called "Freaky Free Friday". The trial was then extended to end on Saturday. [57] Survival: a timed challenge where the Survivors are trapped in a section of the campaign maps, and try to survive as long as possible against an unending onslaught of Infected.

McWhertor, Michael (2009-11-09). "Left 4 Dead Campaigns Now (Unofficially) Work In Left 4 Dead 2". Kotaku. Archived from the original on 2010-05-28 . Retrieved 2010-07-08. Cook, Dave (28 September 2012). "Valve interview: 'I just told Gabe he was full of shit' ". VG247. Archived from the original on December 7, 2022 . Retrieved December 21, 2022.

Valve (2008). Left 4 Dead (PC). Level/area: No Mercy: The Subway (developer commentary). Elan Ruskin: Each survivor has a large database of lines to choose from based on their present activity and a variety of factors, such as their health, stress level, kind of special infected seen so far, and many others. Versus: up to four other human players take control of various Special Infected to try and prevent the Survivors from completing a stage. Special Infected are randomly assigned to Infected players; they cannot control the Witch or any Common Infected. Occasionally, as determined by the AI Director, certain players will become the Tank. The two teams swap sides once per stage, and are scored based on their stage progress as Survivors. If both teams make it to the saferoom with all four Survivors, a 25-point tiebreaker is awarded to the team that dealt the most combined damage as Special Infected. Kollar, Phil (July 27, 2010). "Valve Apologizes For Mistakenly Banning 12,000 Modern Warfare 2 Players". Game Informer. Archived from the original on July 28, 2021 . Retrieved December 21, 2022. Microsoft. "Left 4 Dead". Xbox.com. Archived from the original on June 27, 2008 . Retrieved July 8, 2008.

The Hunter is an agile enemy that can pounce a survivor from long distances, tearing at them until he is pushed off or killed. a b c d e Kuchera, Ben (2009-06-04). "Before its time? Valve explains Left 4 Dead sequel to Ars". Ars Technica. Archived from the original on 2012-05-06 . Retrieved 2009-06-04. To promote the game and provide basic training to players before starting the game, Valve chose to develop a pre-rendered intro movie. This movie was released on Halloween [51] and shows events prior to the beginning of the "No Mercy" campaign. [52] Valve chose an intro movie over in-game training mechanics because they wanted the players to be immediately dropped into a zombie apocalypse. Valve later detailed in their official Left 4 Dead blog how they designed the movie, from a basic animatic in July 2008 to the final result for the launch of the game. [52] a b Pigna, Kris (2009-06-17). "Valve Changed Left 4 Dead 2 Cover to Appease ESRB". 1UP.com. Archived from the original on 2012-11-06 . Retrieved 2009-06-17. Elston, Brett (2009-11-17). "Left 4 Dead 2 Review". GamesRadar. pp.1–4. Archived from the original on 2017-04-05 . Retrieved 2017-03-31.Left 4 Dead Available at Retail Worldwide". Valve. November 21, 2008. Archived from the original on October 10, 2012 . Retrieved November 25, 2008. A prequel to "The Passing", titled "The Sacrifice", was released on October 5, 2010, as an add-on for both Left 4 Dead and Left 4 Dead 2. This prequel ties up the story of the original game, showing the events leading to the meeting of the two groups of survivors in "The Passing" from the point of the Left 4 Dead characters. However, players can choose which character will sacrifice themselves for the others to safely continue on and not just the canonical choice of Bill. [103] Valve also provided the full "No Mercy" campaign from Left 4 Dead as a Left 4 Dead 2 campaign, which is playable with the original Survivors from Left 4 Dead. Though the maps are nearly identical to their appearance in Left 4 Dead, No Mercy in Left 4 Dead 2 contains all of the enhancements of the sequel, including the new Special Infected, Uncommon Infected, melee weapons, additional guns, and the ability to use the new game modes, including Mutations and Scavenge mode. [103] Valve (July 2008). "How Valve Connects Art Direction to Gameplay" (PDF). Archived from the original (PDF) on December 29, 2009 . Retrieved August 2, 2008.