Valve may be known for Half-Life, which the company says has sold around 10 million copies since its release a decade ago, but it has also built a reputation for delivering some great multiplayer games. Counter-Strike began as a third-party mod to the original Half-Life, but it was so popular that Valve hired the developers and brought them into the fold. Early during Half-Life's development Valve hired the makers of the popular Team Fortress mod for Quake. That resulted in Team Fortress Classic for Half-Life and last year's memorable Team Fortress 2. And last month, Valve delivered Left 4 Dead, a thrilling co-op multiplayer experience that lets you and three others battle a modern day zombie apocalypse.
It's worth taking a look at Left 4 Dead and Team Fortress 2 as these two multiplayer games were released a year apart and are based on Valve's signature Source engine. What do these games tell us about Valve? It turns out plenty, when you break it down.