Back in 2006 Guerilla Games released a top-down, isometric shooter on the PSP called Killzone: Liberation. The game received middling reviews, but proved the series had potential on handheld platforms. Now Guerilla Cambridge is developing Killzone: Mercenary for the PlayStation Vita, a full-fledged FPS that feels more like a true Killzone experience. During a pre-E3 event this week in Santa Monica, California, I got my hands on the game’s single- and multiplayer modes. Mercenary follows a gun-for-hire that pledges no allegiance to the valorous ISA or insidious Helghast. Players fight along...