When Attack on Titan hit the anime airwaves in 2013, it became an instant phenomenon. Originally a manga by Hajime Isayama, its popularity spawned several spin-off series, light novels, an upcoming live-action film, and even a rather creative photography trend. With intense action and a dystopian, post-apocalyptic setting, it's not surprising that a video game adaptation also followed suit, and now Atlus is bringing Spike Chunsoft's 3DS take on the series Westward with Attack on Titan: Humanity in Chains. It's not a masterpiece, but it is good fun, and players willing to overlook its shortcomings will find Titan hunting a thrill like nothing else.

The world of Attack on Titan is a bleak one: after mysterious, massive humanoid monsters known as Titans devoured most of the human race, the few survivors were forced to shelter in a walled settlement and eke out an existence in circumstantially-imposed captivity. After a century or so of relative calm, the Titans have returned, and as a member of humanity's last line of defence - the speedy, sword-wielding Scout Regiment - it's up to you and your allies to fight them off and protect the last remnants of your kind.

The Titans are the sickening stars of the show here - enormous, wide-eyed and resembling naked, grotesquely-proportioned men, women, and children, they're determined to lay waste to the city and will happily chow down on any humans they can get their hands on. Your battle with these beasts is as gruesome as it sounds, and the game carries its 'M' rating for a reason - expect plenty of disturbing violence and the kind of genuinely unsettling feeling that follows naturally from being tasked with slicing up smiling humanoids the size of skyscrapers.

The main Story Mode features campaigns for five different characters, and, like the anime, unfolds from multiple points of view. Playing one character's missions will unlock new missions for others, and you'll get to spend time with each of the cadets as you go. The narrative - which retreads the major points of the show - is told through a combination of cut-scenes and short, still-frame vignettes before each mission, and while it's a fine recap for fans, it doesn't quite feel like enough context if this is your first brush with the series. Without some prior knowledge, you'll get the feeling you're missing out on a good portion of what makes the world and characters so interesting - but thankfully, you can certainly enjoy the gameplay without a full grasp of the series lore.

After a few well-integrated tutorial missions, saving the world is the order of the day, and you'll do so by leading a team of four Scouts into third-person, 3D battles, making use of their signature Omni-directional Mobility gear - ODM for short. This hip-mounted grappling-hook-cum-jet-pack is what gives the fighters their impressive agility; by holding 'R', you can arc around the levels Spider-Man-style, or press 'Y' to latch onto a faraway landmark and reel yourself in at lightning speed. It's easy to get the hang of, and it feels amazing - as in many of the best action games, movement in Attack on Titan is a joy.

Your ODM is also the best way to start slashing away at those oversized monsters terrorizing humanity. Taking full advantage of the Scouts' unique kit, Attack on Titan's combat involves locking onto various contact points of an enemy with 'Y', flying towards them, swords drawn, with 'X', and timing a final button press to execute a precision cut. As soon as you start your approach, a red circle appears on the screen, along with another blue ring shrinking towards it from the edges - hit the 'X' button again when the blue ring is inside the red one and you'll nail a critical hit, doing much more damage in the process. Normal attacks leave you open to Titan retaliation, but if you hold the Circle Pad to the left or right as you're locked on, you can perform a Rotating Slash; these cyclone slices shield you from attack, but they also make the red critical circle significantly smaller, and require near-perfect timing to pull off.

Thanks to the massive speed and size differentials between your character and the Titans, slicing up enemies feels great, but Attack on Titan approaches a zen-like level of flow when you start chaining attacks together. Every technique at your disposal can be performed from the air, and a generous hang time after each hit makes it easy to take down multiple foes without ever touching the ground. Once you settle into an aerial groove, combat becomes a beautiful cycle of careening towards an enemy, bouncing back after an attack, and regrouping mid-air before hurtling towards the next target. It feels a bit like a cross between the free-falling acrobatics of Gravity Rush and the snappy precision of Sonic Adventure's homing attack, and it's absolutely exhilarating.

Taking down Titans will make you feel like a hero, but it isn't all about flash. Though the AI is predictable and plodding - perfectly believable for the Titans, whether intentional or not - there's still some strategy required in bringing these behemoths down. You can target Titans from the ankles, knees, or nape of the neck, and while the latter is a guaranteed weak-spot, it's often more efficient - not to mention safer - to immobilize the lower half before going in for the kill. Your blades will also lose their sharpness as you attack, and even break entirely with too much abuse, and so you'll have to take a moment to rearm yourself (by using items from the touchscreen inventory) from time to time.

Most of the time, your missions will revolve around taking out all attacking Titans or defending an area for a certain amount of time, but there are a variety of secondary mission types as well. Some of these work better than others; escort missions and rescue efforts add tons of tension and a sense of purpose to the action, while the less frequent fetch quests feel like padding of the worst kind. An early mission for Sasha, for instance, promises to have you "stealing meat" to sate her voracious appetite. In gameplay terms, that apparently translates into running around an utterly empty map, looking for four glowing generic item markers, with no enemies to get in your way or make things interesting - a truly pointless exercise.

Later missions mix things up in much more interesting ways, with horseback riding across open plains and through close-quartered forests changing the way you look at both your ODM and angles of attack. Story Mode won't last long - clocking in at somewhere around a half-dozen hours for most - but it's a fun ride while it does, and after a few hours of play, you'll unlock the other half of the game: World Mode.

In World Mode, you'll create a cadet from scratch, and take them through a series of challenge missions, levelling up, upgrading your weapons and ODM, and earning Steel Coins as you go. There's a town to develop, lore-packed Scout Reports to find, and a StreetPass function that allows you to recruit other players' characters as AI allies. The character editor is a bit bare bones at first, but completing missions will unlock new faces, hairstyles, and clothing to use in crafting your cadet.

World Mode adds a huge amount of longevity to an otherwise brief experience, and while you can play through solo, it's at its best when tackled with up to three other players, either locally or over the internet. Players who fall in love with the acrobatic combat will have a blast slicing their way through it all, pouring stat points into different categories to create their perfect warrior, developing new weapons and gear, and teaming up with other Titan hunters online. Story Mode is definitely a nice warm up, but World Mode feels like the real heart of the game.

Whether solo or with friends, Humanity in Chains is a lot of fun, and captures the feeling of the anime surprisingly well. Even so, it's not without issues - chief among them the camera. Camera control is awkwardly (if necessarily) relegated to the D-Pad on the original 3DS, though there's Circle Pad Pro and New 3DS C-stick support for players with access to those devices. In the absence of a second stick, we found that frequent tapping of the 'L' button for snap-to-centre was the best way to keep the camera in line - but even so, it moves a bit slowly for our liking, even on the fastest setting. Most of the time it's not a huge problem, but for missions which require more precision - taking out specific Titans, or protecting an ally, for instance - the uncooperative camera can really frustrate. We failed one escort mission nearly a dozen times simply because we couldn't consistently trust the camera to target the Titans closest to our charge, and when we finally did clear the level, it felt like pure luck - we had no clue what we were attacking when they finally made it to safety in time.

The headaches carry over into navigation as well. The samey environments - which heavily reuse assets and feature very few landmarks - combined with the nearly-invisible and always smaller than expected boundary lines within each stage can make it maddeningly tough to get your bearings at times. It also doesn't help that the mini-map is locked into an absolute orientation - an option for the map to follow your character's viewpoint instead would offer a welcome, more useful alternative.

These problems are frustrating precisely because they trip up the sense of flow that the game has in its best moments. When you're soaring around the city, hopping from Titan to Titan, zooming towards weak spots and landing critical hits, Attack on Titan feels incredible. But when you're slamming into invisible walls, trying desperately to target a specific enemy, or running away from the action just to have a few seconds to fix your camera, it's almost embarrassingly clumsy.

Unfortunately, this double-edged quality extends to the presentation as well. The animated cut-scenes are crisp and high-quality (though they're lifted directly from the anime, so they're neither new nor in 3D), the Titans are appropriately creepy looking, and smart use of blur and slow-motion effects contribute to the thrilling sense of speed that characterizes combat. On the whole, however, Humanity in Chains is a visually underwhelming experience. Character models are passable but inexpressive, environments are bland and uniform, and the astoundingly sombre colour palette - while certainly true to the source material - is dull and uninspiring. The 3D effect looks great, but turning up the stereoscopic slider does a number on the frame-rate, which isn't exactly stellar to begin with. A few thoughtful touches - like blood and blur creeping in from the sides of the screen when your character's hurt - provide impressive moments, but they're balanced out by a general lack of polish that makes Attack on Titan feel like a rushed effort.

Surprisingly, that also includes the translation; Atlus has a legendary localization team, but they were absolutely out to lunch for this one. The dialogue, story summaries, and mission descriptions are marked by awkward word choice and unnatural syntax that distract from the drama at hand, as in this wonky recap: "In the rearguard Mikasa has been aiding the refuge of the residents. Mikasa hears the bell signaling the sheltering completion, and goes to help Eren's vanguard". It's far from unintelligible, but quite a few sentences took us a few passes to parse, and it's a disappointing departure from the publisher's usually excellent standards.

Audio, happily, is Attack on Titan's saving grace in terms of presentation. The soundtrack fires on all cylinders with vocal rock and metal, orchestral themes, and martial choral works, while Japanese voice acting and soundbytes lifted right from the anime give the action an authentic feel.

Conclusion

Fantastic and frustrating in turn, Attack on Titan: Humanity in Chains is a fun game that's held back from greatness by several smaller issues. If you're a fan of the anime or manga and don't mind some rough edges, it's well worth checking out; the beautifully breathless combat is incredibly exciting, arcing around town with your ODM will make you feel like a superhero, and World Mode provides plenty to play with once you've relived the anime storyline - and if you can gather a few recruits to fight alongside you online, all the better. An underwhelming presentation and an unwieldily camera make it a tougher sell for non-fans, but if you're willing to overlook those flaws, unchaining humanity can be a blast.