*PSP Favorites cover art*
From Wikipedia: Killzone: Liberation is a run and gun video game for the PlayStation Portable, developed by Guerrilla Games, and is the sequel to Killzone. Killzone: Liberation was released on October 31, 2006, in North America, November 3, 2006, in Europe and November 8, 2006, in Australia. The game chronologically continues two months after where the first game ended. Killzone: Liberation is the only PSP installment in the series, and was followed by Killzone: Mercenary on the PlayStation Vita.