Remember how in the original Borderlandsthe combat felt stiff and repetitive? Enemy AI was predictable, andmost could be dealt with by simply chewing away at their health with whatever gun you happened to have equipped at that particular moment. Well, in Borderlands 2, it's a completely different story. Enemies are now smart and vicious and have some fiendishly clever tricks up their sleeves to force you to play tactically. This makes the co-operative experience - which is, let's be honest, the main reason to play Borderlands - even more rewarding. "We call it the AI ecosystem," says Gearbox Software's Steve Gibson. "The idea is that not only are enemies more reactive and more aggressive, but they can co-operate." We see this frightening prospect in action during our hands-on. We're fighting a pack of Skags, the feral dog-like creatures from the original game. Only this time they've become trickier to negotiate, tougher to bring down. One special breed of Skag has the ability to rally its weaker companions, which sets them on fire and makes them just that bit more dangerous. "This is just one example of the AI working together," says Gibson. "In battle, you now have to prioritise more than just who's closest to you. We want all the combat to feel richer and more tactical." FIVE STAR There are five character classes in total: four brand new (and one returning class), with familiar faces from the previous game serving as quest-givers. First up we have the Siren, Maya. The first game's Siren, Lilith could use the Phase Walk ability to turn invisible and sneak up on enemies; Maya's power is the Phase Lock. "She can grab an enemy and trap them in a floating bubble," says Gibson. "This can be upgraded too. The Routing add-on, for example, will freeze any enemies near your bubble." Then there's the Assassin, which is a stealth class. "He's good at finding critical points on enemies, and can create a copy of himself to distract his foes," Gibson tells us. "The Gunzerker is self-explanatory. He can dual-wield weapons and blow stuff up twice as fast." This is the class we played in our hands-on. Dual-wield power only lasts a few seconds (you can increase this with upgrades), and places another weapon in your left hand, doubling damage. Whenever we found ourselves backed into a corner, activating it would gave us the extra punch to fight our way out. Finally, there's the Commando. "He's an evolution of the Soldier from the first game. He has a turret he can deploy, which has a lot of really cool upgrades. You can place multiple turrets, or unlock the Longbow turret, which can be placed anywhere in the world, even if it's out of reach." Hang on, didn't we say five new classes? The fifth is the Mechromancer. Part pigtailed girl, part mech her special ability is control over a huge robot called Deathtrap. The catch? She's only available as day one DLC. The new classes have been designed to interact with each other. "Through upgrades the Siren can actually remotely resurrect another player, even if they're way across the map," Gibson explains. SHOOT IT YOU SLAG Adding yet another layer of tactics to combat is a new element - the unfortunately named slag. A weapon infused with this unseemly purple gunk will reduce an enemy's stats, making them weaker. "This works well for the Gunzerker. If you're dual-wielding a weapon with slag, and maybe a weapon with the lightning element, you're really going to do some damage. The idea behind including this was to reward the role-playing guys; the guys who think about all the stats and number-crunching." The hour we spent with the game was impressive. The combat feels much more dynamic, and missions have branching paths and unpredictable structures - a far cry from the fetch and carry quests of the original. Guns are also more satisfying to use, with enemies reacting to every shot in a far more readable way. Gibson also assures us that Gearbox are making the game friendlier for solo players, with a more involving story. Borderlands 2 is a radical improvement over its predecessor, and feels like the game the great, but flawed original threatened to be.