The PlayStation Vita is a powerful machine, but few games thus far have actually managed to leverage the hardware into providing anything technically mindblowing. The only other one I can really think of is Uncharted: Golden Abyss. Killzone: Mercenary is one of those rare games that makes me think twice before saying "It looks good... for a portable game." The gap has never been this small, and though the impending arrival of next-gen hardware will pry it wide once again, this game's visuals should age marvelously well. All of Killzone's moody military-industrial complex environments and textures are replicated extraordinarily well in Mercenary; the world of Helghan is oppressive and hostile, from the violent gales of corrupted atmosphere to the trademark glowing red eyes of the Helghast. There aren't really any surprises for anyone who's played Killzone 2 and Killzone 3, but it's a real treat for the eyes.
Portable games always have the odds stacked against them when it comes to sound; regardless of an artist's skill, the hardware is inevitably going to hold the results back. And so it is with Killzone: Mercenary. Headphones are always recommended for immersion, depth, and sheer power, though none of it will match up to a killer sound system to complement the platform's output. But on its own, Mercenary sounds good. Voice acting is hammy, which is fairly standard for the series, for better or worse. All Helghast have the same deep, Cockney accent and the ISA forces are generic hero types. But let's be fair: the action is the star of the show, not the characters. Guns and explosions are ferocious as ever, and now each kill is punctuated by the electronic chirp that is usually reserved for multiplayer.