How Arkane built a roguelike atop an immersive sim with Prey's Mooncrash DLC

Last summer the team at Arkane Studios released Mooncrash, a DLC pack for their critically-acclaimed 2017 immersive sim Prey that wrapped its systems into a roguelike game of five survivors escaping from a secret moon base.

It was a fresh and innovative spin on the immersive sim, a genre of game Arkane has helped advance and define (through both Prey and the Dishonored series) -- and today at GDC, lead level designer Richard Wilson took the stage to explain how (and why) it was built.

According to him, Mooncrash has a common origin story: a number of Prey developers were set up to work on some DLC while others moved on to other projects, and they decided to try something outside their comfort zone as a way of stretching their legs, creatively.

“When you go from project to project in triple-A, a lot of the time you’re solving the exact same problems every time,” said Wilson. “This doesn’t offer much in the way of creative growth...sometimes this can even cause people to jump ship between projects.”

The team decided to have an internal game jam using Prey’s system and assets, and some of the results (which include everything from a Typhon dance party to a tentacle grenade to a working basketball game) made it into what became Mooncrash.

How some scrapped Prey elements and an internal game jam led to Mooncrash

“The experience was really valuable. A lot of the team members got to play with new tools, and step outside of their box a little bit,” said Wilson. “Everyone embraced this spirit of exploration.”

It turns out a lot of the design team were already playing a lot of roguelikes in their spare time anyway, so Mooncrash was pitched from the jump as a roguelike “cross-genre exploration” built out from some features cut from the original game.

"We explored some ideas for random level elements in Prey that ended up getting cut for scope, so we took that and leaned more heavily into that," said WIlson. "[Mooncrash] seemed like a natural extension of those ideas."

Since the team was short on roguelike design experience, they began studying landmark games in the genre to understand how to think about design problems like progression and world persistence between player deaths.

“Games like Spelunky, Rogue Legacy and Risk of Rain, they were basically masterclasses in these other spheres of thought that we hadn’t explored yet,” Wilson admitted.

Arkane also worked to deconstruct the “immersive sim” genre to try and figure out what the component parts are (vents, snippy emails to read, etc.) and whether they could work well in a roguelike framework. 

“Character skill trees, for example; this was something we had on the block when we were looking at it, and we decided to keep it,” said Wilson. "A linear, beat-by-beat narrative? That was something we examined and decided it didn't belong in the DLC."

While sorting out what to include in Mooncrash Wilson says the studio also tried to preserve as much of what made Prey successful as possible, like Arkane’s penchant for effective environmental storytelling.

“The bulk of our storytelling happens in the environment,” said Wilson. “This worked really well in Mooncrash because it takes place in a defined location, and the main character’s job is to find out what happened there.”

"We wanted the fresh start of a roguelike, where you can try new things without the fear of mistakes"

Player agency was also a key concern for the Arkane team, and Wilson admits that while the “high-level” agency available in Mooncrash is less than what’s possible in Prey (given the size and space restrictions), a lot of work went into ensuring the “low-level” agency players have (to say, choose how to move through an area or bypass an enemy) is about the same.

WIlson also noted that since systemic game design is one of the core pillars of Arkane's design philosophy, the team tried to fill Mooncrash with new design elements (like the hackable, progress-blocking “Typhon Gates” sprinkled throughout the base) for players to mess with in interesting ways.

This is something Wilson says Arkane's audience expects, but this approach to design also has the side benefit of keeping the game feeling fresher for longer as players progress through multiple playthroughs.

Wilson provided this visualization of how a player might progress through a big game like Prey, seeing a significant chunk (but far from all) of the expensive assets (shown here as dollars) on each playthrough 

“It may look like there are a thousand ways to get around these things, but in truth the player only has one or two ways in the beginning,” added Wilson. “Then they gain more tools as they progress through the game. So it sort of means that as a player gets tired of dealing with Typhon Gates, they gain more tools for dealing with the Gates, and that creates a sense of progression.” 

Here Wilson tries to sum up the design of Mooncrash in a similar slide, as the restrictions on what a player can accomplish in a given run ensure they'll see more of the game in shorter playthroughs

Arkane’s process of fitting the framework of immersive sim design around a cast of five playable characters (players start with access to just one and unlock the rest during play) was also tricky, as one of the core selling points of a game like Prey is a player’s ability to customize their abilities to suit their playstyle.

In Mooncrash each character has a much narrower set of unlockable skills, a design decision Wilson says was made in order to help players quickly grasp what a character does and how.

“Each character was focused so the player could make informed decisions,” said WIlson. “All the smaller trees, they have enough wiggle room for the player to express themselves, but they were also heavily themed so the player could make informed decisions.”

The studio also hoped that providing multiple playable characters with narrow proficiencies would encourage players to try out different playstyles. Wilson gave a quick shoutout to Suspicious Developments’ Heat Signature as a great example of a game that does this well.

“We wanted the fresh start of a roguelike, where you can try new things without the fear of mistakes,” said Wilson. “So we introduced this concept of resetting the simulation.”

But there’s still a level of persistence between simulation resets, in the form of “simulation score” points the player earns while playing which can then be spent to modify the simulation in future runs. Wilson says Arkane fell in love with this aspect of roguelike design, in part because of the sense of “playing a co-op game with yourself” that it can foster in Mooncrash.

As you might expect, he also notes that Mooncrash wound up being much easier than Prey for players to jump into and out of or play through multiple times. 

“When you look at a game that’s 15 hours long, and there are choices to be made in the middle...it’s possible the player can come back to that game without remembering what those choices were,” said Wilson. “If you’ve got a shorter game, players are more likely to remember those choices in the time it takes to get back to that choice, and they’re more likely to play your game more times to see those different outcomes.”

However he cautions that if the choices are too subtle and organic (something Wilson says Arkane struggled with on the Dishonored games), players can often barge through them without realizing they’ve made a significant choice at all.

Keeping the game feeling fresh run after run after run after...

“To address these issues in Mooncrash we adopted a more roguelike approach, and so we wanted to shorten the replay loops,” said Wilson. “One problem this model can cause, however, is boredom from repetition.”

To deal with that, Arkane built multiple starting locations into the game, “so when a new character started, they’d start in a different location than a previous character, but in the same level.”

This helped keep level load times low during runs, but also wound up helping players feel more familiar and comfortable with the game during character shifts.

To keep players from getting bored of seeing the same areas and enemies time after time, Wilson says "we dipped our toes into random content generation...but rather than focusing on the amount of variability we could offer, we tried to focus on meaningful variability.”

“In Mooncrash, one of the ways we tackled this is through what we called hazard channels,” he explained. The team created five different “hazard channel” states (irradiated, on fire, etc.) which could be assigned (in mix-n-match chunks) to random parts of the level, and even layered atop each other, when the simulation resets.

“The spaces can be recontextualized meaningfully for the player,” Wilson explained. “Now you have to decide if you want to find another way around, or use your tools.”

These hazard channels also had the welcome side effect of injecting variety into the game’s look and design, helping the moon base feel less stale as players progress through the game.

If you’re interested in building levels like this, Wilson cautions that Arkane found that “chunkiness” in Mooncrash’s randomization systems would lead to boring, “same-y” level layouts. 

Another slide from Wilson illustrating how randomizing systems that output levels and other assets in small, homogenous "chunks" can give you a lot of levels that feel same-y, even though they're totally unique

“Another way to add variety to the game was the corruption meter,” said Wilson. “This kept the player from hanging around in the game, and pushes them to accomplish their goals.”

It was inspired partly by the way Risk of Rain's difficulty steadily increases over time, as well as the ghost that appears when players spend too long on a stage of Spelunky.

“We like how….it pushes the player forward to reach their goals,” said WIlson. “This was one of the more contentious decisions we made, actually; a lot of people felt it went against the explorability of our games.”

Arkane tried to temper the pressure of the corruption meter by adding in a consumable item players can use to reset the meter, but Wilson said it was still a contentious system to implement.

Why DLC is a great opportunity for your team to experiment and expand on ideas

“One of the first drafts of Mooncrash was basically just opening up the Talos space station map form the first game and adding escape routes,” said Wilson. “Mooncrash ended up being much more lightweight, but the base concept of an escape game appealed to us.”

There are a number of different escape routes in the game, some of which require multiple characters to “work together” between playthroughs to unlock them. 

“The differences add very deliberate choices for the player,” said Wilson. “There are lots of choices the player has to deal with, and not only do you have to decide which escape route is most opportune for the character you’re currently playing, you have to think of the characters down the line.”

Once Arkane had this in place Wilson says the studio decided to add in a reward for players who get all five characters off the base without resetting, in order to further tie together the various roguelike elements into a larger puzzle.

“We wanted to incorporate this because it turns the game into this puzzle box, where you have to consider the strength of the characters, the complexity of the escapes, and the order you want to perform them in...as well as the difficulty ratcheting up as the player spends more time in the simulation.”

“Our big takeaway from this project is that you should be willing to break from tradition, if you're given the opportunity. DLC is a fertile ground for that, and even if you’re not successful, if your studio is still oen, you can bring some of the lessons learned back to your next core project.”

“I don’t think, at the end of the day, that Mooncrash is the future of immersive sims,’ Wilson concluded. “But I do think it’s a future for immersive sims.”

BONUS Q&A 

Asked after the panel about any regrets he had about Mooncrash, Wilson added that "If we had had the budget, I think it would have been cool to redo the moon base for every different character's vignette; that would've been cool. If we had the budget."

When another GDC attendee asked about how Arkane decides what systems, mechanics, and items to build into its games, Wilson said "in general, the mechanics, the game objects, we look to see how many systems they can interact with themselves...and then a lot of the time stuff bubbles up through iteration." 

"There are some rare cases where like okay, these two things interact in a way we can't support because there are then expectations that cascade out of this, so we have to cut it off," he added. "But in general, the more the merrier. QA loves that."