joshsymonds Working on RimWorld
Architecture
Two components: a C# Harmony mod (pushes colony state via WebSocket) and a Go WASM reference module (8 computation modules in one binary). Design doc: docs/rimworld.md.
Reference module pattern: Same as D2R — generated Go struct literals from game data, computation logic in Go, compiled to WASM. No D1 database.
.reference/RimWorldDefs/ # XML Defs (SCP'd from Steam Deck, gitignored)
.reference/RimWorldDecompiled-v16/ # Fresh decompile (gitignored)
plugins/rimworld/tools/datagen/ # XML parser + Go code generator
plugins/rimworld/reference/data/ # Generated *_gen.go files
plugins/rimworld/reference/ # WASM entry point + 8 computation packages
Verification
View changes require just build-views + committing views.gen.ts. See working-on-views skill for details. CI does not rebuild views — forgetting this ships stale HTML.
go test ./plugins/rimworld/... # All RimWorld tests
go run ./plugins/rimworld/tools/datagen # Regenerate from XML
GOOS=wasip1 GOARCH=wasm go build -o ref.wasm ./plugins/rimworld/reference # Build WASM (<5MB)
just test-go # Full Go suite
Datagen: XML Inheritance Resolver
The datagen tool parses 1,558 XML Def files across Core + 5 DLCs. RimWorld uses ParentName attribute inheritance — child defs override parent fields, inheriting everything else.
Key design decision: The resolver namespaces byDefName by defType:defName to prevent cross-type collisions (e.g., ThingDef "MultiAnalyzer" vs ResearchProjectDef "MultiAnalyzer").
Name matching: All handlers use matchDef() — exact match → prefix match → substring match. Never first-hit substring.
Formula-to-Module Mapping
Each module's computation comes from specific decompiled C# types. When verifying after a patch, check these types:
| Module | Decompiled Types | Key Formula |
|---|---|---|
| Surgery | SurgeryOutcomeEffectDef (XML), SurgeryOutcomeComp_* |
quality = surgeon × bed × medicine_curve × difficulty × inspired, clamp(0, 0.98) |
| Crops | Plant.GrowthRate, PlantUtility.GrowthRateFactorFor_* |
rate = fertility × temperature × light × (NoxiousHaze) × (Drought) |
| Combat (ranged) | VerbProperties |
DPS = damage × burst / (warmup + cooldown + burst_delay) × accuracy |
| Combat (melee) | StatWorker_MeleeAverageDPS, VerbProperties.AdjustedMeleeSelectionWeight |
weight = damage², trueDPS = Σ(damage³) / Σ(damage² × cooldown) |
| Combat (armor) | ArmorUtility.ApplyArmor |
ea = max(rating - AP, 0); zones: deflect (<ea/2), half (<ea), full |
| Materials | StatPart_Quality (XML StatDefs) |
final = base × material_factor × quality_factor |
| Drugs | CompProperties_Drug (XML) |
Data-driven: market value, addictiveness, ingredients |
| Raids | StorytellerUtility.DefaultThreatPointsNow |
Piecewise curves: PointsPerWealthCurve, PointsPerColonistByWealthCurve |
| Genes | GeneDef (XML, Verse namespace) |
Data-driven: complexity, metabolism, exclusion tags |
| Research | ResearchProjectDef (XML, Verse namespace) |
Chain traversal + tribal tech level multipliers (medieval 1.5×, industrial+ 2×) |
Critical v1.6 change: Surgery was refactored from hardcoded C# to a comp system (SurgeryOutcomeEffectDef in XML). The formula is identical but the architecture changed completely. The 98% cap and medicine curve (0,0.7),(1,1),(2,1.3) are now in Core/RecipeDefs/SurgeryOutcomeEffectDefs.xml.
Melee DPS trap: Selection weight is damage², NOT damage/cooldown. This was wrong in our initial implementation and corrected via v1.6 decompile verification.
Patch-Day Verification
When Ludeon ships a RimWorld update:
1. Extract fresh data from Steam Deck
# SSH: deck@172.31.0.39, password in memory
nix-shell -p sshpass --run 'sshpass -p "..." scp -r deck@172.31.0.39:"~/.steam/steam/steamapps/common/RimWorld/Data/*/Defs" .reference/RimWorldDefs/'
nix-shell -p sshpass --run 'sshpass -p "..." scp -r deck@172.31.0.39:"~/.steam/steam/steamapps/common/RimWorld/RimWorldLinux_Data/Managed/" .reference/RimWorldDLLs/Managed/'
2. Decompile formula-relevant types
The decompiler runs via a temporary dotnet project in /tmp/ilspy-decompile/:
nix-shell -p dotnet-sdk_8 --run 'cd /tmp/ilspy-decompile && dotnet run -- \
.reference/RimWorldDLLs/Managed/Assembly-CSharp.dll \
.reference/RimWorldDLLs/Managed \
.reference/RimWorldDecompiled-v16'
The project uses ICSharpCode.Decompiler NuGet package. It needs the full Managed/ directory (102 DLLs) as reference assemblies — without them, ILSpy fails to resolve Unity dependencies.
Namespace gotcha: Some types are in Verse not RimWorld: GeneDef, ResearchProjectDef, ArmorUtility, DamageWorker, VerbProperties.
3. Diff and verify
Compare decompiled output against previous version. Focus on the types in the formula mapping table above. If any formula changed:
- Update the Go computation package
- Update tests with new expected values
- Regenerate data:
go run ./plugins/rimworld/tools/datagen - Run full test suite
4. Regenerate and test
go run ./plugins/rimworld/tools/datagen # Regenerate from fresh XML
go test ./plugins/rimworld/... # Verify all modules
Data Sources
| Source | Location | Contents |
|---|---|---|
| XML Defs | .reference/RimWorldDefs/{Core,Royalty,Ideology,Biotech,Anomaly,Odyssey}/ |
All game data (ThingDefs, GeneDefs, RecipeDefs, StatDefs, etc.) |
| v1.6 decompile | .reference/RimWorldDecompiled-v16/ |
Formula-relevant C# types |
| Old decompile | .reference/RimWorldDecompiled/ |
v1.2.2753, pre-Biotech — do not trust for current formulas |
| Reference DLLs | .reference/RimWorldDLLs/Managed/ |
Full Managed directory for ILSpy reference resolution |