Boss battles are quite common in games. Usually equipped with a sequence of rules, they give you the opportunity to face a gargantuan challenge in search of closure or progression. So what happens when you open this ideology up and create a game that’s a constant non-scripted, unpredictable, and intense boss fight? Well, Turtle Rock – the Californian developer that's best known for maintaining the Counter Strike series and creating Left 4 Dead – has attempted to answer that question with its latest endeavour, Evolve.

Set on a hostile alien planet known simply as Shear, human colonists have discovered an undesirable collection of monstrous creatures living alongside them. As such, Hunters are called in via dropships to tackle these enormous beings using an array of weapons and tactics to get the job done. While four players assume the roles of said soldiers, a single player also takes the reins of the monster that they’re hunting in an epic four-versus-one fight for survival. During our hands-on with the title’s pre-alpha build, we were introduced to one of the local beasts and four of the warriors that are sent out to dispatch these pesky foes.

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In essence, the Hunters are a group of perfectly equipped humans whose sole job on Shear is to take down the mighty fiends that roam the settlements and environments. We handled all four of the playable characters that each come with their own unique skill sets, as well as trusty jet packs which are used to scale the large maps. When used in harmony, these tools offer more than enough options to tackle the monsters, which results in an incredibly balanced gameplay experience.

The first of the humans is Griffin, a tracker who’s designed to locate and capture the monster. He’s equipped with sound spikes, which alert the team to the creature’s location on the map, a harpoon gun that restricts the monster's movement, and the mobile arena, which forms a massive dome that traps the prey inside with your team, allowing you to co-ordinate a four-pronged attack or serve yourself up as a light snack.

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Meanwhile, Val is the medic, and arguably the most important component of the foursome, as her job is to keep the team alive and kicking. She is armed with a medgun to directly treat team mates, a healing burst that restores the group’s health within a small radius, and a tranquilliser to expose and slow the beast. She also has an anti-material rifle, which is used to pierce the monster’s tough skin at long range, exposing weak points that her allies can take full advantage of to cause extra damage.

Elsewhere, the support aspect of the team comes from Hank, who provides a tactical advantage in both offence and defence. He’s got a laser cutter to deal damage, a shield gun to protect buddies under heavy attack, and even a cloaking device to make both him and nearby allies invisible. Best of all, however, is his access to an orbital barrage, a highly effective shock-and-awe air strike that can deal extreme damage to the menace with a direct hit.

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Last but not least, there’s the pain inflictor Markov. His main task is to cause as much damage as possible utilising his close range lightning gun, his long range assault rifle, and his tactical and electrically charged arc mines. Thankfully, he is also equipped with a personal shield that helps him to avoid damage when he goes in for a sucker punch.

Despite all of these tools, it’s worth nothing that the Hunters are easy prey for the predatory monstrosity when alone, so you’ll need to work as a team in order to survive the ordeal, fell the behemoth, and subsequently win the match. And although we only got to see one set of Hunters, we were told that several other groups will feature in the final build, almost certainly bringing with them more skills and unique weaponry.

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On the other side of the food chain, the monster that we played as was called Goliath, a huge beast that favours brutality, rock throwing, and fire breathing to eradicate its enemies. This physically imposing biped also has the ability to leap great distances and climb almost all aspects of Shear’s environment thanks to its impressive strength. Initially, you have access to only one skill – we went for rock throwing – and are more susceptible to Hunter attacks. However, after feeding on indigenous wildlife, you’ll be able to evolve. This strengthens the beast, alters his appearance with ferocious spines, and unlocks the choice of a subsequent skill. This is repeated until you reach stage three, the ultimate and strongest form, which enables you to destroy an objective or wipe out your pesky pursuers entirely. More monster varieties are assured for the full release, and although their form and abilities are yet to be revealed, we’d bet that stealth-based and speed-based varieties are on the cards.

The monsters and Hunters aren’t the only things that you’ll have to think about, though, as the environments of Shear are out to get you just as much as your competitors. Man-eating plants, giant mutant crocodiles, and dinosaur-like creatures all inhabit the Forest Ruins map that we explored. These offensive animals and carnivorous plants can be used to your advantage, as luring the beast into a crocodile's lair or leading enthusiastic humans down a path filled with hungry plants can change the tide of play in an instant.

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Alongside the offensive aspects of the forest, there are also numerous tactical advantages to be exploited in the tropical setting. Many of the animals are neutral and act as a food source for the monster, replenishing its health and charging it up so that it can evolve to the next stage, but alternatively, the Hunters can mercilessly murder these peaceful inhabitants to inhibit their foe’s ability to grow in strength and regain its all-important energy. Indicator birds are another tactical advantage found on Shear: when disturbed, they scatter into the sky, revealing the location of the creature to the eager humans, helping to push the two factions closer together.

Surprisingly, even at this early stage, it feels brilliantly balanced. Fresh from the success of Left 4 Dead’s co-op component, Turtle Rock has sought to refine the experience with this innovative asymmetrical foundation. There’s no doubt that balance was an issue in the zombie shooter, and as a result it’s been at the forefront of every team member’s mind during Evolve’s development. The game is reportedly play tested every day, and this rigorous regime shows in the silky smooth gameplay that’s already shaping up very nicely in its pre-alpha state. Perhaps most impressive is that it seems endlessly replayable, with different strategies and tactics throwing up unique experiences. Considering that additional modes are planned for the game, we reckon that this is going to end up consuming quite a lot of your time.

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And with no current-gen counterpart in sight, it’s going to look the part on the PlayStation 4, too. Even in its pre-alpha state, we were impressed by the title’s implementation of the CryEngine, which puts many current releases to shame. Still, it’s worth mentioning that this will be an online-only affair, with no single player component to speak of. The artificial intelligence will take over if a team mate drops out, but don’t go expecting a bombastic solo campaign to complement the co-op action.

Nevertheless, the initial signs for this team-based romp are more than positive, and we’ve got our fingers crossed that the developer can maintain the all-important balance required to sustain an experience such as this. With a strong studio at the helm, though, and many more monster types, Hunters, and even more stomping grounds to come, this could redefine the co-operative gaming genre just like its predecessor. And that’s something that you probably won’t want to miss out on.

Is your trigger finger itching to take out some hulking beasts? Are you a fan of team-based gameplay, or do you consider yourself something of a lone wolf? Gun us down before we evolve in the comments section below.