Guerrilla to reflect the style of its new parent company. The developer soon began work on its two titles: Killzone (in development for Sony Computer Entertainment for the PlayStation 2) and Shellshock: Nam '67 (in development for Eidos Interactive for the PlayStation 2, Xbox and Microsoft Windows). Both titles would be released the following year to mixed reception, however Killzone enjoyed pre-release hype and anticipation, and despite some backfire effect due to the media hype, Killzone went on to sell over a million copies worldwide, earning Greatest Hits and Platinum status in North America and Europe respectively. Guerrilla signed an exclusive development agreement with Sony Computer Entertainment in March 2004, that would see future development solely for Sony's line of video game consoles, the PlayStation 2, PlayStation Portable and PlayStation 3. By late 2005, many companies, like Eidos Interactive, eyed purchasing Guerrilla; ultimately, Sony Computer Entertainment bought out the entirety of Guerrilla in December 2005. Guerrilla went on to release Killzone: Liberation for the PlayStation Portable in October 2006, Killzone 2 for the PlayStation 3 in February 2009, and Killzone 3 for the PlayStation 3 in February 2011. By February 2012, co-founder Brussee had left the studio to join Visceral Games. As of June 2018, Guerrilla employs 250 people in its Amsterdam offices; it planned to move into a new building on Nieuwezijds Voorburgwal in early 2019 and expand to at least 400 employees in this new location. In November 2019, Hulst was appointed the head of Worldwide Studios and Angie Smets, Jan-Bart van Beek and Michiel van der Leeuw became joint studio heads in his place. During the 2015 E3 conference, Guerrilla unveiled a new intellectual property, Horizon Zero Dawn described as a "post-apocalyptic open world action role-playing game that follows the story of Aloy, a young huntress who inhabits a world that is overrun by machines, and attempts to journey across several lands to uncover her past." In 2017, Guerrilla released Horizon Zero Dawn on the PlayStation 4. The game received widespread positive acclaim from various critics. An expansion, The Frozen Wilds, was released in November 2017. By February 2018, over 7.6 million copies had been sold, increasing to over 10 million a year later, making it one of the best-selling PlayStation 4 games. In March 2020, Hermen Hulst confirmed in an interview that Horizon Zero Dawn would receive a PC port. The PC version was released on