How Rain World Keeps the Slugcat Dream Alive With Mods

Making a game is hard. Getting anyone to care might be harder. That's why Unity launched the Indie Survival Guide – an evolving archive of Q&As, VODs, and livestreams from developers and industry folks. There’s no guaranteed playbook for success, but hearing how others navigated design, business, and getting by can give you better odds.

Today’s article spotlights a game that really embodies the spirit of “indie survival”: Rain World, created by Videocult and published by Akupara Games. Originally released in 2017, Rain World quickly garnered a dedicated fanbase and a cult following, and its enduring popularity isn’t accidental. Read on to learn how Videocult and Akupara have kept the Rain World experience fresh for players by opening up the game to modders.

Building popularity and cultivating a fanbase

Why do you think Rain World developed such a cult following? What keeps players coming back? 

James Primate, Creative Director, Videocult: That’s a really, really good question, and I think a lot of people would like to know the answer, myself included! The discourse on it ranges from “we are sigma geniuses” to “untapped market for complex themes” to “cat game cute,” and all are perfectly valid takes. 

As an idealistic creator with an agenda, my perspective is that Rain World was the result of the universe giving two artists 10 years of carte blanche development. We had ideas that we were super interested in exploring, and were able to go after them with no thought of market forces or gaming trends or whether anyone else would even like them. And the result of that is something that’s unique, and complex, and strongly of its own character, and some people like that kind of stuff!

The community aspect I definitely have an opinion on, though, and that is that we always thought of Rain World as a kind of narrative sandbox for everybody. Since it’s a largely wordless experience, much of the game is thematic and up to interpretation, so we always considered the fans’ interpretation to be as valid as our own and tried to champion their visions as much as possible, whether it’s fan art or modding or theories. And I think that’s exciting because it allows for discussion and debate and for voices from the community to be celebrated. 

Creating player-driven DLC

Rain World’s DLC, The Watcher, is a collaboration between Videocult, Akupara, and the game’s modding community, while the previous DLC, Downpour, was primarily built by the modding community. What led to the more direct collaboration this time around?

James: So this needs some context. After Rain World was initially released, we were in this bizarre situation where our publisher was being shuttered and sold off. We had fans and player interest, but didn’t have the rights or access to platforms, so we were dead in the water. We despaired and worked on other projects, and maybe sneakily made as many of Rain World’s development tools and assets available to the fans as we could to sort of keep the dream alive in the underground.

Eventually, with the help of Akupara Games and years of lawyers, we reclaimed our rights, but in the vacuum of our absence, a thriving modding community had developed, as well as some very high-quality new stories set in the Rain World universe. The favorite of ours was a collection called More Slugcats Mod, made by AndrewFM. It absolutely deserved to be published, and that was the basis of what became Rain World: Downpour. Akupara hired Andrew as lead developer, and we collaborated to bring these stories to align with our vision of the canon and the level of polish expected for a release. I’m super proud of how it turned out!

For Watcher, it was our opportunity to combine the best of both worlds: a team built of the original creators, Andrew, and all these talented new modders. And it’s been an awesome experience! Imagine being able to hire a team of people who know all your stuff as well as you do? Where basically every idea is right on the money from the start? It’s been a dream! 

Modding: Technical implementation in Unity

From a high level, how did you set up your Unity project to enable modding in Rain World?

Andrew, Development Lead, Akupara Games: Almost all the game’s assets are placed in StreamingAssets rather than within Asset Bundles, so that they remain exposed and uncompressed in the final build, and are easily accessible for viewing and editing to the modders through the game's files. The game is compiled with Mono rather than IL2CPP, and with copy PDB files set in the build settings, to support modders that are using .NET decompilers. We also gave the community access to all of our own proprietary dev tools (like Rain World’s proprietary level editor), so that they can utilize many of the same tools that were actually used in the development of the game.

What’s a technical challenge you encountered while implementing Rain World’s modding system, and how did you overcome it?

Andrew: One challenge was how to resolve conflicts when multiple different mods try to modify the same file. By default, in our modding system, when a mod changes one of the game’s files, the entire contents of the file will be replaced by the mod’s modified version. This obviously creates poor compatibility between mods. We created two systems to combat this. One is a concept of a “modification file,” which is a file with special proprietary syntax that lets the modders specify specific modification actions to perform on the file rather than replacing its contents entirely. For example, appending lines to the file, doing regex find and replace operations, etc. Another tool available to deal with conflicts is that mods can be reordered in the installed mods list, so that if two mods do end up conflicting, the player can choose to give priority to one mod over the other in resolving the conflicts.

Modding: Game design impact

How have mods influenced Rain World’s trajectory? What new ideas or gameplay mechanics moved the game in directions you didn’t anticipate?

James: The ones that have been the most impactful, in my opinion, are the ones that are products of people with skillsets or interests totally different from ours. A perfect example of this is Jolly Co-op by Garrakx, which we adapted for Downpour. This is something that’s obviously an awesome idea, but the technical implementation is completely at odds with the fundamental design loop of Rain World. I don’t think we could hire some random dev to make something like this, it basically had to be someone who just really, really wanted to see this feature and had the skills and patience to do it. It had to be Garrakx. And that’s what I love about bringing these modders on board, we can add strength to strength.

Staying aligned on the vision

Were there any issues balancing your own vision for Rain World with your community’s ideas of what the game should be?

James: It probably won’t surprise the community to hear me say this, but I personally don’t consider that stuff at all. As a creator, the greatest value that I can give to fans is in presenting a pure vision. Weighing an audience’s expectations is creating from a position of anxiety or fear and compromises what you're trying to do. I attribute the lasting success of Rain World to it being developed without compromise, and so I totally take that as a mandate. 

How did you and the modding community work together to ensure everyone felt represented creatively in The Watcher?

James: Other than that the development team for The Watcher is made up of modders, not at all. We just focused on building an authentic new direction that would be exciting and take the game to new places. I think it was less of an issue because the meat of it is genuinely new territory; technically, geographically, narratively, etc. Watcher was intended to be Rain World for people who have already played Rain World, where that feeling of surprise and discovery is fresh. In that, there is no “other side.” 

Parting thoughts

What advice would you give to other developers looking to add the modding options to their games?

James: Death of the author! It’s theirs now, let them loose! I do think a lot of creators have control issues, and they don’t like to see their baby lead its own life outside of their own narrow vision. But that’s just limiting what it’s capable of.

Rain World: The Watcher is available now on PC, and will be coming to console platforms on September 25th. Wishlist the DLC on Steam, or dive deeper into the Indie Survival Guide for more hard-earned advice from devs who’ve been there.