This is The Mechanic, where Alex Wiltshire invites developers to discuss the difficult journeys they’ve taken to make their games. This time, Warhammer: Vermintide 2 [official site].

In designing Vermintide II’s melee combat, Mats Andersson ran through the same preset level 50 times a day for two years. This hodgepodge of the game’s most distinctive areas, enemies and swarms makes no sense and it looks terrible, but playing it about 100,000 times was what it took to ensure face-to-face brawling would be rich in heft and detail.

Andersson knew how fast he could clear that level, how much damage he should take, how many kills he should be getting; yardsticks by which he could measure each run, and it’s how clicking to swing your hammer feels like it’s caving a skull in, and why your sword feels like it can split a rat’s stringy carcass in two. “It’s very much home to me,” he says.

Developer Fatshark was no stranger to melee combat when it began to make Warhammer End Times: Vermintide, which it released in 2015. It had made 2012’s War of the Roses and 2014 followup War of the Vikings, which are both all about melee combat. But while those two games are thirdperson, Vermintide would be firstperson. “And at the same time it had to have this visceral Warhammer feeling, the meatiness of the combat,” says Andersson. “They wanted to take the War of the Roses stuff and make it more in your face and feel less mechanical.” Joining Fatshark as Vermintide hit its first alpha, making this happen was the first big challenge he faced.

His second big challenge was that, like the War Of games, Vermintide would be multiplayer, with four players cooperating against a vast swarm of enemies, sometimes 50 or 60 at a time. Traditional techniques of delivering a sense of impact, such as slowdowns and frame control of animations, were impossible because they’d cause the four players to go out of sync with each other.

Solving these challenges was a matter of piecing the combat together as the team figured out what did and didn’t work. And one of the principal concepts that emerged was the idea that when you make a strike, the game changes your movement speed. So as you swing your weapon up, your movement speed slows, then you speed up slightly as you swing down, slow again on impact, and then speed up again as you follow through.

“If you’re standing still it won’t happen, but depending on which way you move and which swing you’re in, you’ll get a different sense of tempo or cadence for each attack,” Andersson says, explaining that the little curves of speed are timed precisely to the frame to translate the distinct physical embodiment that he and his team wanted.

Vermintide’s melee combat model is very much stripped down from the one in War of the Roses, offering just a standard hit, a charged heavy hit, a block and a shove. Breaking it down in this way was a response to Vermintide’s nature as a cooperative game about managing swarms of enemies, as opposed to War of the Roses’ skill-based game about individuals facing each other in mortal duels.

”We wanted to make sure the combat puts a limit on the strain it puts on the human brain when it comes to challenges,” says Andersson. “Since we want to put a lot of challenge in cooperation, we cannot put as much into actually playing the game.” He wants players to be thinking not about a dainty feint to the left and a parry, but hitting five rats with a sweep of their sword, and then shoving another two back into the crazed path of their Slayer buddy.

To formulate these interplays, Andersson went academic. He developed a list of ‘gestalts’ or player profiles, each imagining a specific motivation of a different kind of player, from those who get a kick out of holding the line to the ‘smiters’, and tying them directly to game mechanics.

Smiters are the players who like to wield the most damaging weapons and feel like the hero. “When they click on something, it’s going to fucking die and they feel awesome.” They need heavy weapons, and they need enemies deserving of them: single targets which can take a lot of damage. Then these ideas needed to be built into the cooperative setting.

One expression of this is the Stormvermin, armoured Skaven which can take a lot more damage than the usual Clanrats. “Stormvermin are going to fuck it up for everyone else because they break the chain of control over the mass of 50 rats that the team has. So the smiter comes in. They’ve not been doing a lot because until now they’ve only been killing one rat at a time, but they get to kill this Stormvermin who’s a huge problem for the rest of the team. And that’s even though all they did was to go up and click.”

Vermintide’s sound design plays a big role, too. As well as the splatters and crunches of moment-to-moment melee, Andersson stresses the importance of background sounds and music, which help to build up the anticipation of a swarm hitting the party. For the close-up detail, though, the combat team includes a sound designer who will work on a new weapon from its earliest conception, defining the patterns of swooshes and impact sounds that mark a spiked mace as different from a mace, and supporting the gestalt it’s designed to satisfy.

On top of this, the game also remixes the sound, changing the pitch of each element, according to such factors as the intensity of combat, how much damage the player has taken, whether the enemy is targeting you or a friend, if they’re in the middle of an attack, and whether you’re behind them.

Gestalts informed the entire game, from the weapons to the level topology: smiters will get into big trouble if they find themselves facing a horde in an open space, and for Andersson that’s great: it means they’ll need the rest of the team to survive. He’s really proud that these complex interplays naturally bubble up through mechanics, not through the game tutorialising them.

The big challenge that Vermintide II imposed on Andersson and his team was adding a whole new faction in the form of Chaos. The game was originally designed around the Skaven, which naturally provide a innumerable, squishy, swarming foe. But Chaos are the opposite because you shouldn’t be able to mow them down, 20 at a time. “We wanted the combat to feel the same but different at the same time, and better,” says Andersson. “How the fuck are we going to do that?”

Solving Chaos got right to the heart of Vermintide’s delicate combat systems. Chaos Warriors and infantry are full-sized human figures, so they take up more space than Skaven and they’re taller. Player weapons now had to work for hitting both little rats and burly men who fill more of the screen, all while remaining readable in the throng so players can continue to play the fundamental game of grouping enemies together and controlling them.

One of the answers was in crafting appropriate hit reactions. Many weapons affect multiple enemies, which all react differently. Skaven were hand-key animated so they’d appear skittery and animal-like, and the Chaos faction are fully motion-captured because they’re humanoid, and both factions have large libraries of staggers and flinches for the game to choose from.

“We have quite tricky algorithms behind everything, these huge lists,” says Andersson. “If you hit with this type of weapon at this angle on this enemy then it should react like this.” These lists comprise numbers upon numbers of vectors and angles, but since he’s been working with them for four years now, he’s developed an intuitive grasp of the effect of turning a 120 into an 75. “We know the thresholds by heart by playing the same game over and over, and grind it to a fine point.”

It helps, too, that the Vermintide games go heavy on simulation, tracking the full sweep of their weapons. While other games might simply instantiate a wide hitbox for the duration of an attack, Vermintide follows the blade itself as it swings. “If we do it this way, as the weapon is hitting the head or the neck of the guy, we get the timing right.” The timing, that is, to lop a head off. And because you’ll be looking directly at the neck as the weapon passes, the decapitation is beautifully framed for you. “And that’s the key thing,” says Andersson. “What you want to do is to create a game where the core mechanics and the challenge reward you for playing in a way that looks good.

“The point is, if you create a solid simulation with rules the player can actually learn, and they’re predictable and can be mastered, and they cater towards making the game look nice, you have a sorted game. It just takes a lot of effort and 57 runs through the combat level every day for two years.” And do you know what? He claims he still does it for fun.