tony-kun wrote:Valve likes to release games for free, then sell a more polished version of the game if it becomes popular.
See: Team Fortress Classic, Day of Defeat, Counterstrike, Ricochet
Day of Defeat and Counterstrike were originally mods that were not created by Valve. Team Fortress Classic was a port/update of the original Quake mod. Ricochet was originally going to have frequent free content updates similar to TF2, but that never happened as the game was
terrible a masterpiece.
Alien Swarm is more like Team Fortress Classic in that it is a port/update of a previous mod.