A zombie apocalypse. You've run through the scenario a hundred times in your head. A baseball bat, light machine gun, two revolvers, and a big hunting knife are all you need to handle the horde. But when you're in that situation, a walker only a few steps away, panic runs over you. In a last-ditch effort to stay alive, you take your knife and go for the zombie's head. It goes in cleanly, but you can't pull it out. The situation just got a whole lot worse. 

"You have to design around panic," The Walking Dead: Saints & Sinners game director Todd Adamson told Gamasutra. Panic is one of the main things people fear when hopping into Skydance Interactive's virtual reality survival horror game. Losing a knife in a zombie's head represents the peak of that horror.

"The sticking in the head mechanic was the result of us needing to have combat penalties--an issue I see from VR is there are no penalties for player action," Adamson said. "Which is the key to pushing the player to make good intellectual decisions."

The Walking Dead: Saints & Sinners is a first-person survival horror VR experience set in New Orleans where players follow a narrative about warring factions of remaining humans. Players will need to climb, explore, and dig through environments to scavenge for weapons in order to fight both the living and the dead within a deep Boneworks-like physics engine.

Adamson and the team had to take precautions in order to make sure the head stabbing feature worked, even as players panicked in their living rooms. The development team took a few precautions: they don't let stabbings happen offscreen, because they would completely confuse the player. "People [who] playtested would flail their hands around," he said. "It confused them when their knife just disappeared."

Once Skydance Interactive knew they were turning their Walking Dead game into first-person survival horror, they wanted to focus on two things: fear and choice. "We wanted to make the game about your intellectual decisions, not your physical ones," Adamson said. Those choices need to be wrapped in fear. "We wanted you to be on the razor's edge of death at all times, that's what makes survival horror good."

Instead of creating a game plan to kill hundreds of zombies with full VR melee action, Adamson wanted players to consider the consequences of their actions. Do they have enough time to loot that next house? Should they risk firing a gun? The game was about learning to survive, not learning how to fight. 

Saints & Sinners originally started as a walking simulator, closer to Telltale's take on the classic comic book-turned AMC television show. But soon after beginning development, Adamson and his team decided to focus on more action-oriented gameplay with physics-based combat.

"You have to do melee combat with The Walking Dead in VR," Adamson said. "It's a daunting prospect but when it came down to actually wielding the weapon it felt so cheesy to not have any weight. It broke the immersion. We started looking that way. Most VR games prior to this, your hands didn't have any collision. You could put them through anything in the environment."

When Adamson started development on Saints & Sinners, there wasn't much proof of concept for physics-based combat in VR games. Games like Boneworks hadn't been released yet, so they were jumping into new waters. He believed the common mentality in VR was that you couldn't break the one-to-one connection between the player's hands and what was happening in-game. Multiple games, including Saints & Sinners, have proven that it's possible to break that rule and be successful. Adamson wanted to go further. 

Unlike Boneworks, where players are only limited by their own actual energy levels, Saints & Sinners limits how much players can swing with an in-game stamina meter. "One thing about designing for VR is [considering] players' different levels of physical ability and coordination," Adamson said. "It's a new challenge since everyone presses a button in the same way; it's binary. In VR, you have to account for that. We wanted everyone to be able to play."

"We didn't want to make the game physically difficult," he added. "You're going to more of an exercise game if you do that."

The choice had the unintended consequence of adding more fear and anxiety to short play sessions of Saints & Sinners. If a player becomes surrounded by zombies, they wouldn't be able to just swing their way out of it. They'd need to think of a better plan. 

That better plan also needed to fit into the span of 30 minutes. That's how long players had to explore levels in Saints & Sinners before an in-game bell rang (the story justification is the bells are used to corral and control zombies), triggering a flood of zombies into the area players were walking around in. "We thought it was good in VR generally when you're doing a lot of physical stuff, and it's scary, to give people a clear play session," Adamson said. "We also used it as a mechanism to build tension."

The stamina system and short play sessions both add to the feeling of tension when you're stuck in a fight with multiple zombies. Even more so when your knife gets lodged into a walker's head, and you're stuck trying to catch your breath. "The genesis of the idea came from simulating weight and resistance in VR. In reality, physics are the cornerstone of it," Adamson said. "[It's] an intricate system of animation and other means to achieve the results."

Skydance Interactive had to juggle complex zombie AI, player motion control affecting everything on the screen, and putting walker NPCs into a complex animation state in order to make the head stabbing mechanic work. "The way the knife goes in is curved based, we're authoring an animation curve for depth," he said. "You can stab the walker on any point in the head."

It's a stressful situation that was far more stressful during development. "We tried once putting a half-second delay to pull the knife out," Adamson said. "It would completely fuck you."

Zombies can also cling onto your arms, restricting your movement and hurting you. Two zombies can latch onto you in the final release version of the game, but an earlier version let three attack you at once. "Walker AI, we have a whole system where walkers are chasing you they are positioning themselves on you, deciding who grabs you on which arm," Adamson said. "[There was] one that would latch onto your neck in the middle, but we found that to be too much for the player."

After a certain point, when several of the developers had become skilled at taking out zombies, Adamson realized the game had become too difficult. They needed to focus on making things simpler so players could get through tough situations, even when they were panicked. 

"It was about pacing it, let people adjust to it," he said. "Making things like shaking a walker off your grappled arm simple to do and clearly explained."

Through playtesting, Adamson found that no matter what the game taught players, most of it went out the window when fear set in. "When the situation is overwhelming they just completely forget," he said. Saints & Sinners was originally tougher, throwing players into the fire much quicker than it does in the final version of the game. 

One of the biggest pieces of feedback Skydance Interactive got was to implement a casual mode, and that's a big reason why they pulled back on some ideas that might make the zombie apocalypse more unlivable. But most decisions, including the original ones, were made to prepare the player to handle an onslaught of zombies all on their own, without panicking.

"We wanted players to get good at it," Adamson said. "And by the end of the game, when they get to the katana, they could take on the hoard of walkers."