When I heard my teammate’s character cry out “Potions here!” during a mission, I just had to laugh. While games frequently borrow broad design ideas from their influences, developer Fat Shark’s Warhammer: End Times — Vermintide apes even the smallest details of Valve’s classic first-person shooter Left 4 Dead. Swap “potions” for “pills,” for example, and many gamers will hear Francis’s gruff voice echo through their brains.

And the similarities don’t stop there: the special enemy types, the glowing silhouettes of your allies, even the fly-by camera that zooms into the back of your character’s head at the start of each mission are all lifted straight from Left 4 Dead. It’s pretty shameless, but it’s also not such a bad thing. What worked about Left 4 Dead’s frantic cooperative gameplay works here as well. Plus, Vermintide builds on its predecessor’s formula in a few meaningful ways that capitalize on the grimy, medieval feel of Warhammer’s End Times lore.

In place of Left 4 Dead’s zombies, Vermintide uses humanoid rats, but to similar effect. Four players (or, if absolutely necessary, AI-controlled allies) select one of five available characters and battle their way through a collection of 13 discrete, replayable missions in an effort to quell the rodent scourge. There’s no plot to speak of, but the game provides enough context for the world to feel deep and the action to feel purposeful. The slick yet succinct opening sets the stage, each mission is prefaced by a brief voice-acted overview, and characters banter back and forth during missions. All this, combined with Vermintide’s richly detailed visuals, creates a palpable atmosphere that’s more than adequate for a multiplayer-only experience.

In keeping with this dour high fantasy world, each of the five characters relies on both ranged and melee weapons. There’s very little nuance to the melee mechanics since there’s only one attack button and you’re unable to direct your strikes beyond simply pointing the camera, but the action finds other ways to feel satisfying in spite of its relative mindlessness. The sanguine sound effects and blood-spattered screen makes cutting through wave after wave of foes feel convincingly gruesome. Luring enemies into a bottleneck for easy slaughtering or decimating a pack with a rare but glorious grenade generally elicits demented joy. And strategically swapping between your ranged and melee options to control the spacing between your party and the vermin adds a surprising amount of tactical depth.

Vermintide uses character banter to subtly guide players through its dense, occasionally confusing levels.

Perhaps most importantly, each character offers unique weapons and abilities that function in distinct ways, which represents a welcome departure from Left 4 Dead’s mechanically identical avatars. The fire-wielding Bright Wizard, for example, must occasionally “vent” the heat that builds up in her body or she’ll literally explode. The elven Waywatcher not only moves faster than her allies but can zoom in while aiming down the sight of her bow. None of these talents are hugely exciting or original–a cooldown function and sniper aiming are nothing new–but at the same time, none of the characters feel boring or underpowered, which means they add tangible variety and replayability to the experience.

Building on its individualized characters, Vermintide also includes loot and upgrade systems–another welcome tweak to the Left 4 Dead formula. Every time you complete a mission, you get to roll a set of dice. The strength of that roll determines the rarity of the item you unlock. You’ll always have some basic dice, but you can add additional, more powerful dice by locating them in the game world or by finding and carrying a “Tome” in your inventory’s lone medical supply slot. Encouraging players to risk exploration or sacrifice healing in hopes of unlocking better loot is not only deviously clever, it also incentivizes teamwork: If any player finishes a level with a Tome, every player gets an extra die.

The loot system’s by no means perfect, though. This whole setup can seem a little unfair when you go out of your way to locate the bonus dice but still end up with a low roll, but the bigger problem is a simple lack of items. When I unlocked a flaming sword for the Bright Wizard early on, I was thrilled. When I unlocked my third generic broad sword just a short while later, I started to question the depth of the loot system. You can combine unwanted items to create random new gear at the mission hub’s weapons forge, but this yields repeat items just as often as the dice. Ultimately, the loot system provides some extra motivation, but without more varied and plentiful unlocks, that motivation steadily wanes the more you play.

Encouraging players to risk exploration or sacrifice healing in hopes of unlocking better loot is not only deviously clever, it also incentivizes teamwork.

Vermintide’s missions also grow a little tired over time, though there’s actually enough inventiveness to keep players invested through at least a couple difficulty levels. Most missions challenge players to make it from point A to point B while facing consistent waves of enemies, and nearly all contain obligatory objectives that stand between you and the finish line. While these objectives are uniformly predictable–detonate the three exploding barrels, protect the six magic staves, and so on–the diverse level designs help pick up the slack: A massive shipyard becomes a sort of vertical maze. An abandoned graveyard provides a creepy, slower-paced experience. An eccentric wizard’s tower confuses when its walls and ceilings suddenly flip.

The diversity is memorable, and generally speaking, levels offer a strong mix of claustrophobic hallways and complex open areas, with the occasional hidden pathway thrown in. Outside of those short, optional side areas, though, the route from A to B will always be the same. Given that you’ll be playing the same 13 missions over and over again, alternate pathways would have certainly helped to keep the experience fresh. Fortunately, Vermintide uses random item spawns and dynamic enemy placement to keep the gameplay from getting too predictable. Just because you faced a Gutter Runner and a Pack Master (Vermintide’s versions of the Hunter and Smoker zombies) around a particular corner last time doesn’t mean you’ll find them there again in the future.

New weapons aren’t always better, per se, but they often open up new strategies.

At higher difficulty levels, this unpredictability creates dread and tension that propel the game forward and lead to intense gratification when your team survives against seemingly impossible odds. But the key word there is “team.” Vermintide’s AI is unreliable at best and comically inept at worst, so if you don’t have three friends you can drag into the End Times with you, you’ll probably end up screaming at your allies to revive you while they run off chasing…who the hell knows. You might get lucky and connect with a friendly, helpful group of Steam players, but that’s not a guaranteed solution.

Plus, Vermintide suffers from other issues beyond its braindead AI. The game doesn’t tutorialize anything, so prepare to be embarrassed as you slowly learn the ropes. Movement feels just slightly too slow, and in the face of frenetic action, it can actually feel frustratingly lethargic. And most importantly, Vermintide offers no alternate game modes. Where Left 4 Dead innovated with an asymmetrical versus mode that put half its players in control of the zombie horde, Vermintide fails to branch out in any direction.

Still, the bread and butter co-op experience shines just bright enough to compensate for this relative lack of content. Though the action is mostly mindless, it’s gruesome details and varied characters still make for satisfying gameplay. The loot system, while not as deep as it could have been, proves an intelligent addition to the Left 4 Dead formula. And the 13 levels provide enough variety that, with the right team, Vermintide remains entertaining for a solid handful of hours. I also didn’t experience any noticeable server, match-making, or technical issues during my time with the game–which does support Xbox One controllers. Vermintide is still a shameless imitation of a seven year old game, but it is, if nothing else, a creative, well-executed, and enjoyable imitation.