Rain World audio design stories: Part 2 - Side House


Rain World

We delve into the collaborative Rain World modding scene following the release of the base game, as contributors broke ground in expanding the horizons of Videocult's influential survival platformer.

By Jerry Jeriaska (The Ongaku)

If you haven't already, be sure to read Part 1 - 'Maze Runner'.

Rain World arose from humble origins as the solo project of a Swedish developer Joar Jakobsson.

Initially codenamed "Maze Runner," the prototype was announced on the TIGSource forums, generating buzz within the burgeoning indie gaming scene. Chiptune-inspired band Bright Primate joined the development, with bandmember James Therrien (aka James Primate) composing the soundtrack, mapping out additional levels, and crafting the adaptive "threat music." The other bandmember, Lydia Esrig, collaborated on the music score and gave voice to iconic characters, from ferocious lizards to reclusive lantern mice.

The runaway success of the base game, coinciding with the accidental leakage of the source code, prompted a passionate band of volunteer modders and sound designers to reverse engineer their own customized maps and redesigned slugcats. Among these unauthorized devs was AndrewFM, a coder capable of delving into the inner workings of his favorite software.

However, as weeks of innovating on Rain World mods stretched into years of commitment, and a ragtag band of devs expanded into dozens of contributors, the question of whether this was time well spent became impossible for Andrew to ignore. Was the Rain World modding community stuck in a Sisyphean loop, akin to that of the in-game player character? Was this journey prompted by curiosity predestined to end in disappointment?

Rain World

Rain World Release Promo by Del Northern

Unique data pearls

While the origins of Rain World can be attributed to a single individual toiling away at a desk in Sweden, the moment graphic designer Jakobsson took to TIGSource, a daisy-chain of collaborators began unfolding, magnifying the scope of the his vision.

James began searching the internet for an illustration style that could complement Jakobsson's crumbling vistas and properly capture the personality of the enigmatic protagonist. He happened upon the DeviantArt page of an illustrator named Allegra "Del" Northern posting Pokémon fan art.

"She had a bunch of these cat creatures with weird, big open eyes," James recalls. "This was so obviously related to the character that we were making — perfect."

Songs and Rhythms by James Therrien & Lydia Esrig feat. artwork by Del

Del's renderings of the slugcats were featured in the intro to the game, and pop up as flashbacks while hibernating. These momentary story sequences help draw the player into the deep lore underlying the mysterious post-industrial landscape.

Because the crowdfunded budget was finite, and only so much information could be conveyed through static images, Videocult required a complementary method of lore-building. To broaden the narrative, the devs came up with the innovative solution of presenting the player with rare collectible items termed "unique data pearls."

"The lore bits are distributed through these pearls that you find throughout the game," James says, "and you can bring them to one of the characters in the endgame. She will tell you what is on these pearls."

Valuing the teamwork that made Rain World's creation a success, it only made sense that the developers should seek to encourage players to form their own social communities organized around the game. Collecting data pearls would incentivize players to pool their collective knowledge and foster discussions on why the Ancients abandoned the grounds the player forages for sustenance.

"The pearls themselves are somewhat randomized," James explains. "You can't really get all of the lore in one playthough. We never had the idea that anyone would ever be going through and collecting all the pearls."

As it turned out, quite a few players went about collecting all the pearls.

"We definitely never thought of it as this completionist thing, where people would spend a thousand hours in the game getting every bit of lore through multiple playthroughs," James says. "That wound up happening, which is mind-blowing to me."

Rain World
Monk attempts to rescue Survivor, illustration by Del Northern

Side House

The first custom region mod for Rain World was undertaken by programmer AndrewFM, a recent Masters degree graduate in the field of computer science, with a focus in artificial intelligence.

"I was lucky to get into Rain World very shortly after the game came out," AndrewFM recalls. "I started playing a couple weeks after it first released and joined the Discord server not too long after that... At that point, it was so early on that we didn't have access to a level editor or anything."

Modding the Rain World base game was the programmer's first sustained effort developing in Unity, and what he found was that the leaked source code turned out to be something of a red herring. Upon being compiled and exported, assets are typically packaged in a single compressed file, leaving you with an inscrutable nugget comparable to an encrypted zip file.

"The way that Rain World packaged their game that was very useful for modding is all of the assets, images, music, sound effects were included as raw files in the game folder. That, more than the source code, was useful in picking apart the game."

Described as a tech demo for manifesting a custom region, the "Side House" mod was the first to stitch together unused maps included in the base game's deliverables. It also broke new ground by introducing a custom iteration of threat music, composed in layers just as Joar and James had pioneered in the source material.

To achieve these ends, Side House needed its own audio engineer. Volunteering for the task was Connor Skidmore, a modder with a background in producing dance music, techno, and other drum-focused styles. Contributing under the handle "12LBS," Connor set about reverse engineering the percussive threat music feature. It helped that AndrewFM appreciated the role of music in game design, as evidenced by the programmer's piano covers of Super Mario World and EarthBound themes, uploaded to his YouTube account.

"Rain World's threat music was always interesting to me, because the way it's structured is like variations on a theme," Connor explains. "They're all unique, but they share a lot of similarities as well, in a way. It tickled my logic brain to try to break them down and understand how they worked."

When the Rain World modders migrated from Discord to a community-driven portal dubbed "RainDB," more volunteers began hacking and playtesting each others' uploads.


"Side House" served as a proof of concept for modding a custom region and proved popular among the RainDB community. The next logical step was to pad out the roster of player characters. AndrewFM proposed the idea of "More Slugcats," a mod seeking to add five new breeds, each with their own save slots and custom campaigns.

The first slugcat attempted levied the color scheme and unique abilities of a RainDB mod called "Grapecat," a purple-furred combatant capable of wielding three spears.

The Grapecat mod could be loaded into the original campaign, but at the cost of losing access to the Survivor player character. Receiving permission to port Grapecat's design, Andrew's task was to code for a discrete save slot and leverage the critter's spear-wielding capabilities. Thus, "Spearmaster" was born.

Rain World

Spearmaster art by character portrait illustrator AnnoyingFlower.

The initial "More Slugcats" mod allowed for alternate avatars. "Other than that," AndrewFM says, "it was exactly the same game."

Connor adds, "We didn't have any level editor, so most content additions were out of the question. This led to my [first full] project with Andrew, where he and I worked together to try to reverse engineer the game's level format, with the end goal of making our own unofficial level editor."

Connor already had ideas in mind for a mod called "Eastward Expansion" that would incorporate custom-built areas. RainDB was making gradual inroads, but not without frustrating setbacks in turn. When Videocult caught wind of it, the developers realized the modders were in need of assistance. They intervened by packaging the Rain World 1.5 update, released in late 2017, with an official level editor.

The introduction of this tool represented a critical step forward in bootstrapping the proliferation of user-generated content housed on RainDB. According to Conner, "Suddenly a lot of the ideas we had that seemed super far-fetched became much more feasible."

Alphas, Gems and Junk offers a glimpse of early Rain World audio experiments

The 1.5 update added two new slugcats, called The Monk and the Hunter, providing a wider array of difficulty settings. The new characters also expanded on the lore by revealing events taking place before and after the Survivor campaign.

"With the release of that new version of Rain World, a lot of the mods broke," AndrewFM recalls. "Everyone had to port their mods to this new version." Modders were delving back into their code at the same time that new maps were possible, and the content update was providing a blueprint for how to situate newcomers like Spearmaster within their own campaigns.

"Let's make maps that are purpose-built for these different slugcats," became the driver. The "More Slugcats" prototype had already gained traction. The concept of a more elaborate expansion resonated with users on RainDB.

More slugcats

Behind the scenes, the publisher that had picked up the rights to the IP following the Kickstarter campaign was falling out of contact with Videocult, leaving no clear protocol in place for publicizing user-generated content. Del's final contribution to Rain World would be encapsulated in the 1.5 update, jeopardizing the future of development.

Despite official development on Rain World seemingly drawing to a close, the gravitational pull of "More Slugcats" attracted a wider array of collaborators.

"One of the main artists who did a lot of the hibernation and character selection screen art was someone named AnnoyingFlower," says AndrewFM. The contributor studied Del's art, eventually publishing a style guide. "All the other artists that we brought on, we gave them that style guide. That was to keep as many of the illustrations as visually consistent as we could, despite having a lot of different artists working on it."

Much of the Eastward Expansion's team soon joined development on "More Slugcats," while Connor revised and implemented his music track "Onto A New Dawn," repurposed from his own mod.

"Andrew's plans were well-organized and he had a strong vision for the project," Connor says. "I poured over the TIGSource devlog thread to try to understand where James and Joar were coming from when they originally made the game, and try to reflect that spirit as authentically as possible."

12 Lands, Boundless Space · RW 75 - Onto A New Dawn

Inspired by Videocult's Hunter and Monk characters, the modded slugcats would also explore the world at different points in the timeline. In the earliest time period, the structures built by the Ancients have yet to collapse into disrepair, revealing painted frescoes on the brick walls approaching the Shoreline.

The waste disposal system, fueled by pools of corrosive liquid, introduce perilous new platforming challenges. The reason for these structures' collapse becomes apparent upon the completion of Spearmaster's campaign. Broadcast satellite dishes remain standing, though inbound messages go unanswered by the inhabitants of the Iterator superstructures.

Another cue taken from the 1.5 update was the modification of enemy AI. The base game's Hunter protagonist presented players with a more challenging difficulty option, populating maps with aggressive predators. In designing "More Slugcats," the devs contextualized this gameplay challenge. From the get-go, Spearmaster encounters hostile lizards leaping at the player and spewing projectiles from their mouths. Taken together, the two campaigns suggest that the Shoreline's predators become pacified as the timeline progresses.

Rain World's "More Slugcats" expansion was taking on its own creative identity. However, whether it would ever reach an audience was thrown into question the more time elapsed.

Andrew says of the expansion, "The original plan was for this to be a little mod that we released on RainDB and probably no one would see it outside of the people who frequented the Rain World Discord. It was almost like the further we got into development, the more it started to bother me."

"It was like the project increased in scope so much and the number of people getting involved in it was getting so big, it started feeling disappointing that we spent five years of our lives with forty different people working on this project and barely anyone was going to see it. It would be this obscure little mod that gets released on this website that no one really knows about."

The publisher sitting on Rain World's intellectual property eventually severed ties with Videocult, as the former was acquired by a separate corporate entity. The murky legal status of the IP suggested that the acquisition signaled the terminus of the franchise.

"Our [original publisher] basically got eaten by another company and we were in legal limbo for years," says James. "We thought Rain World was over."

To be concluded...

James Primate is a video game composer – brightprimate.bandcamp.com | Twitter @BRIGHTPRIMATE | Spotify artist page

AndrewFM is a video game developer - Ko-fi | Twitter @AndrewFM

Connor Skidmore is a video game composer - SoundCloud