Left 4 Dead 2’s new features have had to be rather carefully thought out, as altering the original’s gameplay was always going to be a difficult process. It’d be a travesty to ruin the fastidiously balanced feel of the matches so loved by the original game’s fanbase, and it would certainly prove rather unpopular.

We’re in Seattle and have been given the chance to have a go at new campaigns Swamp Fever and Dark Carnival today, and it’s proved to make for a rather intense experience. The maps are just as full of jumpy and suspenseful moments, as they were the first time round and regularly inspire that feeling of panic that such a dynamic game so effortlessly delivers.

There are three new Special Infected in L4D2, all with their own unique and terrifying tactics. The Spitter is a horrible and powerful zombie, who is a very real danger to you and your team, capable of causing serious amounts of damage with the green goo she spews from her mouth. She’s a much quieter zombie, which makes it a lot more difficult to locate her than the other Specials.

The Charger is a massive Special Infected that will run like a bull at a particular player and grab a Survivor charging through anything in its path, including other Survivors. He’ll then keep hold of a Survivor and repeatedly beat them into the ground till one of them is dead and done.

The third new Special Infected we see is the Jockey, which we’ve not had a chance to play against before. He’s a hideous monstrosity with a hunchback that will pounce on a Survivor before riding them into the distance. This presents a double whammy of difficulty as it stops the player from doing much and will often quite effectively split up the group.

Left 4 Dead 2’s Special Infected will work together, using a combination of their techniques to bring down your team. The Jockey will regularly ride a player into a pool of The Spitter’s toxic goo or send them hurtling into a waiting Tank. Maybe the Tank will send you flying to the ground as a Spitter gets ready to vomit its vile puke on you or something equally as sneaky. It’s clearly a team effort this time round from both sides, AI or not.

We’ve been told on several occasions that the new game will consistently demand new tactics from players in order to keep even the hardest Left 4 Dead veterans guessing. The existing Special Infected have been toyed with a little in order to keep players on their toes so it’s not even an option to treat them how you might’ve done before.

Come daylight and the now Wandering Witch will amble around the map and stumble into unsuspecting Survivors, making her a tougher cookie to crumble. The Spitter will mercilessly spy camping players and attack accordingly, while the Charger will hurl himself towards the most proficient players bringing the team’s combined capability way down.

There’s a new range of zombies known as the “uncommon commons”, and each map boasts its own version. While they’re nowhere near as powerful as the Special Infected they’re more than capable of causing some serious problems for your team, each boasting their own special move and defensive feature. The riot cop zombies can get back up the first time you knock them down while infected clowns will alert any nearby enemies to your presence with a comical squeak of their oversized shoes.

Hillbilly zombies are found scampering about in deep mud and will spit the stuff in your eyes leaving you temporarily hindered with a mucky screen. Each of the uncommons bring about another instance in which players have to apply specific tactics, perhaps being fireproof like the hazmat zombies, or resistant to bullets from the front like the riot Infected.

The common zombies are still the primary type of enemy you’ll encounter, their major obvious upgrade being their destructibility. You can now target a specific limb or two and knock it flying, maybe blasting off a zombie’s legs as they hurtle at you or whacking off a head with one of the new melee weapons.

Indeed the melee weapons are quite the game-changer, as where before it’d be key to keep the zombies as far away as possible, with these it’s now an option to knock down an enemy right up close. The frying pan had been an instant hit (no pun intended) with fans as soon as it was shown in promotional artwork and has been just as popular with those lucky enough to have a go at these kinds of sessions.

It’s hilarious to use, bringing rather slapstick moments to the table and with it comes a whole range of other quite frankly silly melee tools. There’s an axe, an electric guitar, a night-stick, a cricket bat and a katana (great for decapitations). Each of these melee tools has its own special and unique use, for instance, the axe is the single weapon capable of killing a witch from behind with a solitary hit.

Also new to the game are the day/night effects, a larger range of guns and an improved AI Director. The new Director is capable of doing a lot more, including physically altering the layout of the map in some major ways. It can bring about weather effects on demand that’ll summon swarms of Infected, often altering the pace drastically depending on how well the team’s doing.

The new levels boast a real sense of place, which couples perfectly with the ever-increasing amounts of character exuded by the stars of the show via fresh and quick-witted remarks. It’s noticeable immediately that level design has been generally improved and you’ll spot some very close attention to detail in the form of ruined buildings and scattered miscellaneous tattered objects right away.

There’s a whole host of instances in Left 4 Dead 2 that’ll keep players guessing: gauntlet moments sending players down tight pathways with nowhere to hide and set-pieces with smoke-spilling jet fighters and collapsing bridges. There’s barely a moment to catch your breath and repeating your tactics just isn’t an option whilst progressing through a map. And of course, despite the “set-pieces”, the game’s still different with every play.

While the formula has largely stayed the same, it’s the little changes that make all the difference. Subtle refinements make for an experience that keeps with the original’s distinctive style of gameplay while the more drastic additions, like the inclusion of a grenade launcher or the fact that whole sections will change around with every play bring some very new experiences to a familiar but altered game.