Swapping out the engine underneath a game with a decade of accumulated mods and a famously devoted modding community is the kind of move most studios would never risk. Ludeon Studios is doing it anyway, and the early numbers suggest it might actually pay off.

What’s changing

Ludeon announced on October 13 that RimWorld update 1.7 moves the colony sim off Unity and onto Waylith Engine, a proprietary engine the studio built in-house. According to Ludeon’s own announcement, the game looks and plays identically to before, but the studio’s internal testing shows performance improvements of roughly 2 to 4 times over the Unity version — a substantial jump for a game whose late-game slowdowns, driven by large colonies and heavy simulation loads, have long been a known pain point for players. As PC Gamer and Rock Paper Shotgun both reported, the switch was paired with a teaser that Ludeon is already building a second, unannounced game on top of Waylith, suggesting the engine isn’t a one-off project scoped just for RimWorld.

How the rollout works

Update 1.7 is live now, but only through RimWorld’s “unstable” beta branch on Steam, accessible via the game’s Properties menu under the Betas tab. The default, stable release stays on version 1.6 for the time being, giving Ludeon room to work out issues before pushing Waylith to everyone. Save files carry over cleanly from 1.6 to 1.7, according to the studio, and the “vast majority” of existing mods are expected to keep working — some may be flagged as “potentially unsupported” simply because the version number changed, not because they’re actually broken. One real constraint: Ludeon says PCs older than roughly a decade may not be able to run the new engine at all, a tradeoff of chasing modern performance gains.

Why this is a bigger deal than one indie update

RimWorld’s move lands squarely in the shadow of Unity’s September 2023 “Runtime Fee” controversy, when Unity announced a planned per-installation charge — up to $0.20 per install under some license tiers — that would have hit developers retroactively on already-shipped games. The backlash was immediate and severe: developers warned the policy was unenforceable and openly abusable, and critics like Garry Newman of Facepunch Studios said the plan made installation tracking “not feasible” without inviting fraud. Unity apologized and significantly walked back the fee within about ten days, but the damage to developer trust lingered — plenty of studios said publicly at the time that they’d start evaluating alternative engines, including building their own.

Three years on, RimWorld following through on that threat, and doing so for a commercially successful, mod-dependent game with an enormous existing install base, makes it one of the more concrete examples of that 2023 trust collapse actually reshaping a studio’s technical roadmap rather than just producing angry forum posts. It’s also a reminder that “switch engines” doesn’t have to mean a years-long rebuild from scratch with broken saves and dead mods — Ludeon’s approach, keeping the Unity-era asset pipeline and data formats compatible, is a template other mid-size studios weighing the same move will likely study closely.

What to watch next

The real test is whether Waylith holds up once it leaves the unstable branch and reaches RimWorld’s full player base, mods and all. If the performance gains hold and compatibility stays as clean as promised, it strengthens the case for other Unity-reliant indie and mid-size studios — still stinging from 2023 — to consider the same path, rather than treating an in-house engine as something only AAA studios can afford to build.

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For more on how trust issues with major platforms are reshaping smaller studios’ decisions, see our coverage of Steam’s discoverability crisis. And for another indie success story navigating its own growth, check out our piece on Dave the Diver crossing 10 million copies sold.