Killzone 2 is a science fiction first person shooter developed by Guerilla Games for the PlayStation 3. It is the third in its line, coming after Killzone, for the PlayStation 2, and Killzone: LIberation, for the PlayStation Portable. The game was announced at the 2005 Electronic Entertainment Expo so its development period has spanned several years. Killzone 2 is set on the planet Helghan, the homeworld of the Helghast, who invaded the Interplanetary Strategic Alliance colony. This follows after the events of the two previous games, a great strategy to resonate with fans and encourage first time players to buy the previous two games to get the full plot line of the series. Since this is a first person shooter, it is targeted towards a particular portion of the population and is not a game that can be given to just anyone as a present. The recepient has to like first person shooters, and not just games in general. However, it is very popular, with pre-orders of the game rocketing above 1.1 million units in the European sector by itself.