Compensating for the assisted aiming is a solid and intuitive cover system, evolved from the one developed for Syphon Filter. Approach any wall or object and Grayson immediately takes cover, without being glued to the item in question. You're then free to sidle left to right, while the fire button pops you out to shoot. The structure of the game is fairly rigid - you're essentially moving through a series of staged encounters in arena-like rooms and corridors - but given the style of game being attempted, the trade-off is acceptable.
Unfortunately, having come up with a control scheme that makes fast, frantic run-and-gun action workable on the PSP controls, Sony Bend then take two steps back with a new enemy type that leaves your fingers tied in knots whenever they appear. They're "boilers", female Chimera with grotesque distended heads. Let them get too close and they detonate their skulls, taking off huge chunks of health. To stop them you must shoot them in the face, but since the auto-aiming isn't up to the job, you need to quickly tap up and then use the face buttons to find your target. Boilers move fast, however, and the time between spotting them and plucking bits of bone from your lacerated flesh is tight. The game is generous with health packs, but moments like this undo a lot of the good work that the otherwise thoughtful design has done.
Also deserving criticism is the wonky save system which doesn't seem to allow for the fact that Retribution is a portable game. Checkpoints are actually reasonable and fair, but the game doesn't save at each one. Switching off having reached the first big boss battle, I found that I had to replay a sizeable chunk of the level again the next time I played. With no option to save at will, it's a bizarre restriction for a game that will likely be played on buses and trains, or in lunch-breaks.
Rounding out Retribution is a solid multiplayer option, which offers everything you'd expect from a console release, even if it can't repeat the innovative and addictive co-op play of Resistance 2. All the usual modes are included, but most interesting is Assimilation, which succeeds by marrying traditional multiplayer action with a concept that ties directly into the game's story. It gives the team playing the aliens a wonderfully unfair advantage - any human players killed are converted to their side. If you're the last human remaining, it's about as tense and horrific as online gaming gets - a truly claustrophobic and panic-inducing experience that will hopefully be teased out in future instalments of the main series.
Much like Resistance 2, Retribution is more than the sum of its parts. The single-player campaign may be linear and stagey, but it's also effortlessly fun and incredibly polished. The multiplayer doesn't contain many surprises, but it does a better job of matching the online modes of "proper" consoles better than most rivals in its genre. Annoyances are minor and fleeting in nature, and the game punches above its weight with a substantial and coherent feel that too many handheld offerings lack. The PSP has been starved of beefy first-party games for so long that something this confident was always going to look special. Retribution isn't quite the saviour the PSP needs, but it's close enough to come highly recommended.